Write release notes for v0.19.0

artifact_ownership_contract_test.go

@@ -0,0 +1,43 @@
+package promptkit_test
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"testing"
+
+	"go.maximumdirect.net/configkit"
+	"go.maximumdirect.net/promptkit"
+)
+
+type independentArtifactReader struct{}
+
+func (independentArtifactReader) Read(_ context.Context, ref promptkit.ArtifactRef) (*promptkit.Artifact, error) {
+	return &promptkit.Artifact{Body: []byte(ref.Body), Hash: ref.Body}, nil
+}
+
+func TestConcurrentPreparationWithTransferredArtifacts(t *testing.T) {
+	input := configkit.Input{Source: configkit.Mapping("ownership", map[string]any{
+		"profiles": []any{map[string]any{"id": "profile", "endpoint": "https://example.invalid/v1", "model": "model"}},
+		"prompts":  []any{map[string]any{"id": "prompt", "default_profile": "profile", "inputs": []any{map[string]any{"name": "document", "required": true}}, "messages": []any{map[string]any{"role": "user", "content": `{{input "document"}}`}}, "output": map[string]any{"format": "text", "validation_mode": "none"}}},
+	})}
+	engine, err := promptkit.NewEngine(promptkit.Config{Sources: promptkit.ConfigurationSources{Main: &input}}, promptkit.WithArtifactReader(independentArtifactReader{}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	var group sync.WaitGroup
+	for i := range 24 {
+		group.Go(func() {
+			value := fmt.Sprintf("body-%d", i)
+			prepared, err := engine.Prepare(context.Background(), promptkit.RunRequest{PromptID: "prompt", Inputs: map[string]promptkit.ArtifactRef{"document": promptkit.Inline(value)}})
+			if err != nil {
+				t.Errorf("prepare: %v", err)
+				return
+			}
+			if len(prepared.Messages) != 1 || prepared.Messages[0].Content != value || prepared.InputHashes["document"] != value {
+				t.Errorf("prepared = %+v", prepared)
+			}
+		})
+	}
+	group.Wait()
+}

backends.go

@@ -78,7 +78,8 @@ type AuthenticationProbeConfig struct {
 // It encodes fields without validating them; NewEngine validates the final
 // effective configuration after all selected source layers are combined.
 // Mapping captures a copy of supported input values at creation; unsupported
-// values fail when the source is loaded.
+// values fail when the source is loaded. ExtraParams must use ConfigKit Mapping
+// input forms; callers must explicitly convert numbers or containers as needed.
 func BackendSource(label string, backends []BackendConfig) configkit.Source {
 	definitions := make([]any, 0, len(backends))
 	for _, config := range backends {
@@ -96,7 +97,7 @@ func BackendSource(label string, backends []BackendConfig) configkit.Source {
 			fields["queue_capacity"] = *config.QueueCapacity
 		}
 		if config.ExtraParams != nil {
-			fields["extra_params"] = providerMapForMapping(config.ExtraParams)
+			fields["extra_params"] = config.ExtraParams
 		}
 		if config.SmokeTests != nil {
 			smokeTests := make(map[string]any)

bundled_composition_contract_test.go

@@ -2,8 +2,8 @@ package promptkit_test
 
 import (
 	"context"
-	"fmt"
-	"strings"
+	"reflect"
+	"slices"
 	"testing"
 
 	"go.maximumdirect.net/configkit"
@@ -58,11 +58,10 @@ func TestBundledCompositionReplacementAndInheritance(t *testing.T) {
 	if target := inspect("openrouter/profile"); target.BackendID != "openrouter/local" || target.Model != "collection-model" {
 		t.Fatalf("collection = %+v", target)
 	}
-	for _, tier := range []string{"low", "medium", "high", "xhigh", "max"} {
-		target := inspect("auto-" + tier)
-		if target.BackendID != "other" || target.Model != "other-model" || !strings.Contains(fmt.Sprint(target.ExtraParams), "cost_tier:"+tier) || !strings.Contains(fmt.Sprint(target.ExtraParams), "id:auto-router") {
-			t.Errorf("tier %s = %+v", tier, target)
-		}
+	target := inspect("auto-low")
+	wantPlugins := map[string]any{"plugins": []any{map[string]any{"id": "auto-router", "cost_tier": "low"}}}
+	if target.BackendID != "other" || target.Model != "other-model" || !reflect.DeepEqual(target.ExtraParams, wantPlugins) {
+		t.Errorf("inherited tier = %+v", target)
 	}
 }
 
@@ -70,11 +69,11 @@ func TestBundledCompositionSequenceModes(t *testing.T) {
 	for _, test := range []struct {
 		name, mode, id string
 		wantErr        bool
-		count          int
+		hasAuto        bool
 	}{
-		{"duplicate append", "append", "auto", true, 0},
-		{"distinct append", "append", "custom", false, 18},
-		{"replace", "replace", "custom", false, 1},
+		{"duplicate append", "append", "auto", true, false},
+		{"distinct append", "append", "custom", false, true},
+		{"replace", "replace", "custom", false, false},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			input := configkit.Input{Source: configkit.Mapping("sequence", map[string]any{
@@ -92,7 +91,7 @@ func TestBundledCompositionSequenceModes(t *testing.T) {
 				t.Fatal(err)
 			}
 			profiles, err := engine.ListProfiles(context.Background())
-			if err != nil || len(profiles) != test.count {
+			if err != nil || !slices.Contains(profiles, "custom") || slices.Contains(profiles, "auto") != test.hasAuto {
 				t.Fatalf("profiles = %v, %v", profiles, err)
 			}
 		})

bundled_execution_contract_test.go

@@ -51,8 +51,7 @@ func TestBundledProfilePreparationAndExecution(t *testing.T) {
 func TestBundledProfileHTTPPayloads(t *testing.T) {
 	t.Setenv("OPENROUTER_API_KEY", "synthetic-key")
 	for _, test := range []struct{ id, model, tier string }{
-		{"auto-low", "openrouter/auto", "low"}, {"auto-medium", "openrouter/auto", "medium"}, {"auto-high", "openrouter/auto", "high"}, {"auto-xhigh", "openrouter/auto", "xhigh"}, {"auto-max", "openrouter/auto", "max"},
-		{"auto", "openrouter/auto", ""}, {"free", "openrouter/free", ""}, {"gpt-luna-latest", "~openai/gpt-luna-latest", ""},
+		{"auto-low", "openrouter/auto", "low"}, {"gpt-luna-latest", "~openai/gpt-luna-latest", ""},
 	} {
 		t.Run(test.id, func(t *testing.T) {
 			var body map[string]any

bundled_openrouter_contract_test.go

@@ -51,23 +51,16 @@ func TestBundledOpenRouterOptionsAndInventory(t *testing.T) {
 			if err != nil {
 				t.Fatal(err)
 			}
-			want := 0
-			if test.enabled {
-				want = 17
-			}
-			if len(profiles) != want || len(backends) != boolCount(test.enabled) || len(prompts) != 0 || len(collections) != 0 {
+			if (len(profiles) > 0) != test.enabled || len(backends) != boolCount(test.enabled) || len(prompts) != 0 || len(collections) != 0 {
 				t.Fatalf("inventories: %v %v %v %v", profiles, backends, prompts, collections)
 			}
 			if test.enabled {
-				wantProfiles := []string{"auto", "auto-high", "auto-low", "auto-max", "auto-medium", "auto-xhigh", "claude-fable-latest", "claude-haiku-latest", "claude-opus-latest", "claude-sonnet-latest", "free", "gemini-flash-latest", "gemini-pro-latest", "gpt-astra-latest", "gpt-luna-latest", "gpt-sol-latest", "gpt-terra-latest"}
-				if !reflect.DeepEqual(profiles, wantProfiles) || !reflect.DeepEqual(backends, []string{"openrouter"}) {
+				if !reflect.DeepEqual(backends, []string{"openrouter"}) {
 					t.Fatalf("bundle inventory: %v %v", profiles, backends)
 				}
-				for id, model := range map[string]string{"auto": "openrouter/auto", "auto-max": "openrouter/auto", "gpt-luna-latest": "~openai/gpt-luna-latest", "free": "openrouter/free"} {
-					profile, err := engine.InspectProfile(context.Background(), id)
-					if err != nil || profile.EffectiveModelParams.Model != model || profile.EffectiveModelParams.BackendID != "openrouter" {
-						t.Fatalf("profile %s = %+v, %v", id, profile, err)
-					}
+				profile, err := engine.InspectProfile(context.Background(), "auto")
+				if err != nil || profile.EffectiveModelParams.BackendID != "openrouter" {
+					t.Fatalf("bundle profile = %+v, %v", profile, err)
 				}
 				view, err := engine.InspectConfiguration()
 				if err != nil {

bundled_smoke_contract_test.go

@@ -3,6 +3,7 @@ package promptkit_test
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"io"
 	"net/http"
 	"reflect"
@@ -13,6 +14,45 @@ import (
 	"go.maximumdirect.net/promptkit"
 )
 
+type cancelingAuthenticationBody struct {
+	remaining int
+	cancel    context.CancelFunc
+	closed    bool
+}
+
+func (b *cancelingAuthenticationBody) Read(p []byte) (int, error) {
+	n := min(len(p), b.remaining)
+	for i := range p[:n] {
+		p[i] = 'x'
+	}
+	b.remaining -= n
+	if b.remaining == 0 {
+		b.cancel()
+		return n, context.Canceled
+	}
+	return n, nil
+}
+func (b *cancelingAuthenticationBody) Close() error { b.closed = true; return nil }
+
+func TestAuthenticationReadCancellationWinsOverOverflow(t *testing.T) {
+	for _, size := range []int{1024, (1 << 20) + 1} {
+		ctx, cancel := context.WithCancel(context.Background())
+		body := &cancelingAuthenticationBody{remaining: size, cancel: cancel}
+		engine, err := promptkit.NewEngine(promptkit.Config{HTTPClient: &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
+			return &http.Response{StatusCode: 200, Header: make(http.Header), Body: body}, nil
+		})}})
+		if err != nil {
+			cancel()
+			t.Fatal(err)
+		}
+		report, err := engine.SmokeTest(ctx, promptkit.SmokeTestRequest{Kind: promptkit.SmokeTestAuthentication, BackendID: "openrouter"})
+		cancel()
+		if !errors.Is(err, context.Canceled) || report == nil || report.Completed || report.Failure != promptkit.ExecutionFailureCanceled || report.Facts.CredentialsAccepted != nil || report.Facts.ResponseReceived == nil || !*report.Facts.ResponseReceived || !body.closed {
+			t.Fatalf("size %d: report=%+v error=%v closed=%v", size, report, err, body.closed)
+		}
+	}
+}
+
 func TestBundledSmokeHTTPDefaults(t *testing.T) {
 	t.Setenv("OPENROUTER_API_KEY", "synthetic-key")
 	var urls []string
@@ -125,3 +165,17 @@ func TestBundledSmokeSelectionUsesEffectiveConfiguration(t *testing.T) {
 		}
 	}
 }
+
+func TestBundledSmokeAuthenticationResponseOverflow(t *testing.T) {
+	transport := roundTripFunc(func(*http.Request) (*http.Response, error) {
+		return &http.Response{StatusCode: 200, Header: make(http.Header), Body: io.NopCloser(strings.NewReader(strings.Repeat("x", (1<<20)+1)))}, nil
+	})
+	engine, err := promptkit.NewEngine(promptkit.Config{HTTPClient: &http.Client{Transport: transport}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	report, err := engine.SmokeTest(context.Background(), promptkit.SmokeTestRequest{Kind: promptkit.SmokeTestAuthentication, BackendID: "openrouter", APIKey: "private-key-marker"})
+	if err != nil || report == nil || !report.Completed || report.Reason != promptkit.SmokeTestReasonAuthenticationResponseLimitExceeded || report.Failure != promptkit.ExecutionFailureOther || report.Facts.CredentialsAccepted != nil {
+		t.Fatalf("overflow = %+v, %v", report, err)
+	}
+}

convert.go

@@ -2,7 +2,6 @@ package promptkit
 
 import (
 	"fmt"
-	"reflect"
 	"unicode/utf8"
 
 	"go.maximumdirect.net/promptkit/internal/domain"
@@ -395,88 +394,10 @@ func copyAnyMap(src map[string]any) map[string]any {
 	if src == nil {
 		return nil
 	}
-	out := make(map[string]any, len(src))
-	for k, v := range src {
-		out[k] = copyAny(v)
-	}
-	return out
+	return jsonvalue.CloneTrusted(src).(map[string]any)
 }
 
-func copyAny(value any) any {
-	if value == nil {
-		return nil
-	}
-	switch v := value.(type) {
-	case map[string]any:
-		return copyAnyMap(v)
-	case []any:
-		out := make([]any, len(v))
-		for i, item := range v {
-			out[i] = copyAny(item)
-		}
-		return out
-	case []string:
-		return copyStringSlice(v)
-	case []byte:
-		return copyBytes(v)
-	default:
-		return copyReflectValue(reflect.ValueOf(value)).Interface()
-	}
-}
-
-func copyReflectValue(value reflect.Value) reflect.Value {
-	if !value.IsValid() {
-		return value
-	}
-
-	switch value.Kind() {
-	case reflect.Interface:
-		if value.IsNil() {
-			return reflect.Zero(value.Type())
-		}
-		copied := copyReflectValue(value.Elem())
-		if copied.IsValid() && copied.Type().AssignableTo(value.Type()) {
-			return copied
-		}
-		out := reflect.New(value.Type()).Elem()
-		out.Set(copied)
-		return out
-	case reflect.Pointer:
-		if value.IsNil() {
-			return reflect.Zero(value.Type())
-		}
-		out := reflect.New(value.Type().Elem())
-		out.Elem().Set(copyReflectValue(value.Elem()))
-		return out
-	case reflect.Map:
-		if value.IsNil() {
-			return reflect.Zero(value.Type())
-		}
-		out := reflect.MakeMapWithSize(value.Type(), value.Len())
-		iter := value.MapRange()
-		for iter.Next() {
-			out.SetMapIndex(copyReflectValue(iter.Key()), copyReflectValue(iter.Value()))
-		}
-		return out
-	case reflect.Slice:
-		if value.IsNil() {
-			return reflect.Zero(value.Type())
-		}
-		out := reflect.MakeSlice(value.Type(), value.Len(), value.Cap())
-		for i := 0; i < value.Len(); i++ {
-			out.Index(i).Set(copyReflectValue(value.Index(i)))
-		}
-		return out
-	case reflect.Array:
-		out := reflect.New(value.Type()).Elem()
-		for i := 0; i < value.Len(); i++ {
-			out.Index(i).Set(copyReflectValue(value.Index(i)))
-		}
-		return out
-	default:
-		return value
-	}
-}
+func copyAny(value any) any { return jsonvalue.CloneTrusted(value) }
 
 func copyStringSlice(src []string) []string {
 	if src == nil {

docs/consumers/configuration-migration.md

@@ -139,8 +139,10 @@ and diffs expose resolved values, recorded normalization and provenance.
 can apply further overrides, so the views are not promised to be identical.
 
 Remove `PromptVersion` and `PromptIdentity.Version` uses and the corresponding
-`prompt_version` JSON members. Prompt hashes are opaque equality values and may
-change when the removed field no longer participates in hashing.
+`prompt_version` JSON members. Prompt definition hashes are opaque equality
+values and may also change because redundant captured fields were removed.
+Invalidate persisted caches or comparisons that span this change; hashes from
+inspection and preparation of the same captured definition still agree.
 
 ## Identity Mapping
 

docs/consumers/pkg-promptkit.md

@@ -178,7 +178,12 @@ input := configkit.Input{Source: document}
 ```
 
 `ProfileSource` and `BackendSource` are smaller typed conveniences when null
-is not needed. Backend and profile definitions are supplied by the caller;
+is not needed. Their provider maps use ConfigKit Mapping input forms: built-in
+scalars, `[]any`, and `map[string]any` recursively. Convert `json.Number` or
+typed containers explicitly to an appropriate supported value, choosing numeric
+precision for your application. Mapping captures supported values immediately;
+unsupported or cyclic values are reported when loaded. Runtime override values
+follow their separate rules. Backend and profile definitions are supplied by the caller;
 there is no registration-only backend namespace.
 
 When configuration or message files change, build and validate a new engine,
@@ -714,18 +719,19 @@ if err != nil {
 }
 
 target := inspection.EffectiveModelParams
+if inspection.APIKeyRequired {
+	// Arrange a usable direct or configured environment credential.
+}
 if target.APIKeyEnv != "" {
-	// This is a configured optional environment lookup source.
-} else if inspection.APIKeyRequired {
-	// Arrange a direct credential before later execution.
+	// This is the configured environment lookup source, not its value.
 }
 ```
 
 Use this configuration-time boundary when only the profile and its target need
 checking. Use `Prepare` when the application also needs prompt, input, schema,
 or rendering work; use prepared execution when that work must remain tied to a
-later execution. A reported `APIKeyEnv` is a configured optional source, while
-`APIKeyRequired` is the explicit local requirement. The
+later execution. A reported `APIKeyEnv` identifies a configured source, while
+`APIKeyRequired` is the explicit requirement; both may be present. The
 [credential format reference](../formats.md#credentials) and the method's
 [GoDoc](../../engine.go) own the exact precedence, timing, result, and error
 contracts.
@@ -879,6 +885,12 @@ secret-handling policies.
 
 ## Extension Interfaces
 
+JSON Schema validation and native structured output use a self-contained root
+document. Internal references are supported; references to other files or
+network resources fail during preparation. `WithSchemaFile` selects one root
+file, while `WithSchemaFS` and `SchemaDir` select a root source. Prepared
+executions retain their captured schema even if the source later changes.
+
 Inject an [`LLMClient` or `ArtifactReader`](../../types.go) when the built-in
 behavior does not fit the application. Their GoDoc defines concurrent use,
 context handling, ownership of copied values, nil responses, and preservation
@@ -886,6 +898,11 @@ of collaborator errors. Implementations must honor cancellation, safely manage
 copies they retain, avoid unsafe logging of content or credentials, and enforce
 the application policy that motivated the injection.
 
+A successful `ArtifactReader.Read` transfers the returned artifact and mutable
+body storage to Promptkit. Readers that previously reused a returned buffer
+must instead return independent storage and stop mutating it after return;
+private scratch buffers may still be reused when the returned bytes are copied.
+
 ## Handle Errors
 
 Use `errors.Is` with the

docs/development.md

@@ -58,6 +58,14 @@ exist.
 
 ## Maintainer Validation
 
+Use the newest Go installation already available locally for ordinary
+development checks. Put its `bin` directory first on `PATH` and set
+`GOTOOLCHAIN=local` to keep that toolchain selected. For repository-isolated
+checks, set `GOWORK=off`; consumers may use their own workspaces. The selected
+validation patch does not by itself change the module's consumer minimum. See
+the [release toolchain policy](policy/release.md#consumer-minimum-and-release-toolchain)
+and [release procedure](release.md#prepare-the-candidate) for release selection.
+
 For ordinary work, select validation proportionate to the change. Do not repeat
 successful checks for unchanged content merely to create a commit. During
 development, run relevant Go tests and vet, format changed Go files, and execute

docs/formats.md

@@ -418,11 +418,17 @@ generic inheritance and layer mechanics, consult
 ## Schemas
 
 Schemas are JSON documents selected by a prompt or request `schema_path`.
-Directory and `fs.FS` schema paths resolve within the configured root;
-referenced nested schemas resolve relative to the owning schema document.
+Directory and `fs.FS` schema paths resolve within the configured root. Each
+schema must be self-contained: in-document references, IDs, and anchors are
+supported, but references requiring another file or network resource fail.
+References must also work without the source filename as a base; use fragment
+references or explicit schema IDs rather than relying on that filename.
 `WithSchemaFile` exposes one schema under its base name. An unreadable,
 invalid, or unresolvable schema causes an operational validation error.
 Valid JSON that fails the schema instead yields a failed validation result.
+Schema documents are detached without applying the provider extra-parameter
+copy limits; this does not change the schema decoder, compiler, or
+self-contained-resource rules.
 
 ## Credentials
 

docs/integrations/openai-compatible-chat.md

@@ -16,14 +16,13 @@ Generation sends an HTTP `POST` with `Content-Type: application/json`.
 Before the client is called, the engine resolves framework, backend, profile,
 and request values into one execution target. Endpoint configuration is trimmed
 and must be an absolute HTTP or HTTPS URL with a host and without user
-information, a query, or a fragment. A non-empty endpoint from the target
-overrides the client's configured base URL. The final selected endpoint is
-validated again before transport.
+information, a query, or a fragment. The target's endpoint is validated again
+before transport.
 
 The completion URL is composed through parsed URL path operations. Nested base
 paths are retained, repeated trailing slashes are normalized, and the result
 has exactly one appended `/chat/completions` suffix. Generation fails before
-sending when neither source supplies a valid endpoint.
+sending when the target does not supply a valid endpoint.
 
 The target's backend ID is routing metadata for prepared values, results, and
 injected clients. The built-in client does not derive the URL from that ID and
@@ -70,7 +69,9 @@ and numeric `usage`; unrelated fields and account limits are ignored. This is
 only a minimal identifying subset of OpenRouter's documented
 [current-key response](https://github.com/OpenRouterTeam/docs/blob/main/api_reference/limits.mdx#checking-your-limits),
 not validation of the full account document. Other statuses and unrecognized
-200 responses do not establish acceptance.
+200 responses do not establish acceptance. A 200 response exceeding the bounded
+recognition allowance reports `authentication_response_limit_exceeded`, leaving
+credential acceptance unknown; see the [public reason](../../smoke_diagnostics.go).
 
 Diagnostic HTTP evidence describes the last request observed at Promptkit's
 RoundTripper boundary and any response associated with it. It includes the
@@ -87,8 +88,7 @@ transport for HTTP-only diagnostics.
 ## Request Body
 
 The request body always contains `model` and `messages`. The execution
-target's model takes precedence over the client's configured model, and one
-must be available.
+target's model must be available.
 
 Each ordinary message contains its `role` and string `content`. A
 cache-controlled message instead uses a text content block containing `type`,
@@ -115,9 +115,10 @@ The client conditionally includes:
   strict flag, and schema document. Plain JSON validation does not add an
   object-only response constraint.
 
-The engine resolves backend, profile, and request extra-parameter maps by
-whole-map replacement rather than key merging. The resulting effective map is
-merged into the top-level body. Empty keys, values that cannot be encoded, and
+Configured profile maps recursively overlay backend defaults, while a nonempty
+runtime override replaces the complete configured map. The [format reference](../formats.md#defaults-and-overrides)
+owns these resolution rules. The resulting effective map is merged into the
+top-level body. Empty keys, values that cannot be encoded, and
 collisions with these reserved fields are rejected before any provider call:
 
 - `model`

docs/internal/capacity.md

@@ -68,9 +68,8 @@ Preparation and validation never hold an active permit.
 
 The manager's `Acquire` operation owns that active-permit acquisition and
 returns an idempotent release function. The coordinator uses it around
-individual attempts. The earlier one-shot wrapper still delegates to the same
-operation for focused internal callers and tests, but engine assembly no
-longer uses it. There is one queue and one active limit per limited backend pool.
+individual attempts. There is one queue and one active limit per limited backend
+pool.
 
 When all active permits are occupied, calls join a mutex-protected FIFO waiter
 list. Releasing a permit transfers it directly to the oldest remaining waiter
@@ -121,7 +120,7 @@ validation, bounded admission, idempotent release, context handling, and
 unlimited admission. The
 [client tests](../../internal/capacity/client_test.go) own peak enforcement,
 FIFO transfer, canceled-waiter removal, grant/cancel races, independent pools,
-unlimited calls, passthrough behavior, and panic release.
+unlimited calls, and panic release using test-only one-shot calls.
 
 The [runner tests](../../internal/usecase/runner_test.go) own ordinary early
 admission, lease lifetime, failure release, and shared initial/repair

docs/internal/llm.md

@@ -26,10 +26,9 @@ client uses its endpoint, credential metadata, generation fields, and extra
 parameters. `BackendID` remains routing metadata
 for the generation boundary and is not mapped into the provider payload.
 
-Construction trims and validates a nonempty configured base URL and clones any
-supplied `http.Client` so Promptkit can apply its timeout default without
-mutating the caller's client. An empty configured base remains valid because a
-resolved request target may supply the endpoint. Generation preparation then:
+Construction clones any supplied `http.Client` so Promptkit can apply its
+timeout default without mutating the caller's client. Generation preparation
+then:
 
 1. validates shared execution-setting invariants and the final selected base
    endpoint;
@@ -42,6 +41,10 @@ resolved request target may supply the endpoint. Generation preparation then:
    the complete-request failure remains a request failure;
 6. resolves authentication and freezes the URL, body, and optional credential.
 
+Provider values are detached with trusted copying before encoding. Custom JSON
+encoding methods and per-value encoding-failure diagnostics operate on those
+private copies rather than retained prepared or diagnostic metadata.
+
 Each execution of that prepared request creates a fresh HTTP request, body
 reader, and attempt timeout context. It closes the response body and returns
 the HTTP status, decoded response or error, reported token values and presence,
@@ -77,7 +80,8 @@ not retain headers, credentials, raw request or response bodies, or a redirect
 trace. These are observations at Promptkit's RoundTripper boundary, not proof
 that bytes reached a peer or that a custom transport did no hidden dispatch.
 Reachability and named authentication probes use the same configured built-in
-client but discard their response bodies after local recognition. The
+client. The OpenRouter adapter owns endpoint derivation, bounded account-response
+recognition, and body closure; the smoke coordinator interprets its evidence. The
 [integration contract](../integrations/openai-compatible-chat.md#explicit-smoke-diagnostics)
 owns their observable HTTP semantics.
 
@@ -105,14 +109,13 @@ public ownership and redaction semantics belong to the
 
 ## Failure Categories
 
-The package preserves distinct error identities for invalid client
-configuration, invalid generation requests, request execution failures,
-non-success provider statuses, and malformed successful responses. Provider
-response bodies are never exposed in raw form through non-success errors.
+The package preserves distinct error identities for invalid generation
+requests, request execution failures, non-success provider statuses, and
+malformed successful responses. Provider response bodies are never exposed in
+raw form through non-success errors.
 
-Invalid nonempty configured endpoints are configuration failures. A missing or
-invalid final selected endpoint is an invalid generation request and is
-rejected before transport.
+A missing or invalid final selected endpoint is an invalid generation request
+and is rejected before transport.
 
 Authentication resolves a trimmed direct key before a trimmed configured
 environment value. Optional missing, empty, or whitespace-only sources do not

docs/internal/observation.md

@@ -10,6 +10,10 @@ lifecycle instrumentation spans the facade and runner boundaries.
 Prepared execution starts only after its private payload is atomically claimed;
 the facade receives that invocation's recorder privately and emits the terminal
 event after public error mapping. Failed claims and preparation emit nothing.
+The public projection retains private operation-owner metadata separately from
+inspectable child causes. Terminal classification uses that owner, preserving
+context precedence and generation-specific transport/provider details rather
+than mistaking a collaborator's nested lookup error for the parent's operation.
 
 The facade masks inherited recorder and prepared-claim state when entering
 preparation or execution. Delegated calls from an injected collaborator retain

docs/internal/overview.md

@@ -23,7 +23,7 @@ contributor workflow and validation.
 | `internal/generation` | Coordinates frozen built-in HTTP attempts and one-shot injected calls through active backend permits, including bounded status retries, cancellable backoff, ordinary attempt observations, and invocation-local evidence for diagnostics. | [Internal generation coordination](generation.md) |
 | `internal/defaults` | Defines application-neutral framework constants and constructs the default execution target. It contains no CLI, server, or inbound HTTP limits. | [Framework defaults](../../internal/defaults/defaults.go) |
 | `internal/filecatalog` | Provides deterministic YAML discovery and path helpers for operating-system filesystems and `fs.FS` sources. | [File catalog](../../internal/filecatalog/catalog.go) |
-| `internal/jsonvalue` | Validates and deeply copies bounded JSON-compatible extra-parameter and prepared-schema trees while preserving supported concrete value types and rejecting cycles or excessive depth and work. | [JSON values](../../internal/jsonvalue/jsonvalue.go) |
+| `internal/jsonvalue` | Validates and deeply copies bounded JSON-compatible provider values, and detaches previously accepted values without repeating validation. | [JSON values](../../internal/jsonvalue/jsonvalue.go) |
 | `internal/promptdef` | Provides a narrow captured-prompt lookup contract, not-found identity, and execution-ready definition hash. | [Prompt lookup](../../internal/promptdef/repository.go), [framework formats](../formats.md) |
 | `internal/profile` | Provides a narrow captured-profile lookup contract and not-found identity. | [Profile lookup](../../internal/profile/repository.go), [framework formats](../formats.md) |
 | `internal/prompt` | Renders prompt messages from Go templates with artifact, variable, session, and cache-control data, and conservatively enumerates dependencies from captured template syntax. | [Go-template renderer](../../internal/prompt/go_renderer.go), [requirement discovery](../../internal/prompt/requirements.go) |

docs/internal/runner.md

@@ -42,10 +42,11 @@ Ordinary preparation selects the full prompt definition and construction-time
 hash. It retains its early request-ID check before direct-session
 normalization. Referenced message content and static template syntax were
 captured when the engine was built.
+Rendering uses those captured parses, cloning them per call to bind request
+input helpers; it does not parse templates during execution.
 
-`InspectPrompt` selects captured metadata through an optional repository
-capability, falling back to the full definition and existing hash resolution
-for internal repositories without it. It returns owned metadata without
+`InspectPrompt` selects captured metadata directly from the repository. It
+returns owned metadata without
 rendering templates or touching profile, artifact, schema, renderer, validator,
 admission, or model collaborators. The root
 [`Engine.InspectPrompt`](../../engine.go) GoDoc owns the public operation's
@@ -57,8 +58,7 @@ snapshot by the selected prompt ID. The analyzer receives only
 those identity fields rather than an execution definition. It analyzes the
 snapshot with the supplied caller variables and normalized direct-session
 bypass; it does not resolve target readiness or enter the preparation
-pipeline. Missing snapshot capability is a prompt-load failure rather than a
-source fallback. The root
+pipeline. An unavailable captured snapshot is a prompt-load failure. The root
 [`Engine.InspectRequirements`](../../requirements.go) GoDoc owns the public
 operation's exact contract.
 
@@ -142,11 +142,10 @@ one execution-precedence and error-ordering implementation while allowing a
 full backend pool to reject work before expensive schema, artifact, and
 rendering operations. `Prepare` discards the plan after returning its public
 metadata. `Run` retains the plan through initial and repaired-output validation
-and discards it when the operation ends. Prepared execution transfers the
-completed preparation's owned message, input-hash, and copied-schema values
-into its private payload, while deep-copying mutable provider extras and
-creating an independent details snapshot. Claim completion or discard clears
-the execution payload without removing the details snapshot.
+and discards it when the operation ends. Prepared execution retains one
+immutable, redacted metadata snapshot shared by execution and internal details.
+The facade detaches mutable public details. Claim completion or discard clears
+execution-only payload references without modifying the retained metadata.
 
 The root facade's `Engine.ValidateRequest` uses the same complete preparation
 path as `Prepare` and discards the resulting internal prepared value without
@@ -176,7 +175,7 @@ encoding of that session, every role and content value, and cache-control
 presence and values; its hexadecimal value is opaque.
 
 The configuration snapshot is read-only after engine construction. Concurrent
-`Prepare` and `Run` calls copy their resolved targets and keep all invocation
+`Prepare` and `Run` calls use detached captured targets and keep invocation
 state local.
 
 ## Run Flow

docs/internal/sources.md

@@ -85,6 +85,8 @@ returning and retains no source capability for public inspection.
 
 Prompt materialization shares a lazy metadata snapshot across root and collection
 resources during construction, avoiding a full metadata copy per collection.
+Input metadata, message content and templates, and output contracts are captured
+separately before the definition, inspection, and hash are assembled.
 
 Normalization and defaults are recorded at individual resolved field paths,
 including message roles and cache controls. List indexes identify fields for
@@ -146,8 +148,8 @@ change rendering behavior.
 ConfigKit resolves profile inheritance before the handoff. Within a collection,
 `extends: {id: parent}` names a sibling local ID; it is not a cross-collection reference.
 The configuration adapter validates final effective resource references and
-field values, then builds target
-snapshots with backend defaults and presence/suppression state. A profile can
+field values, then captures backend definitions and profile target snapshots
+with backend defaults and presence/suppression state. A profile can
 remain partial until runtime overrides complete it. `InspectProfile` selects
 that captured target without prompt, artifact, schema, credential lookup, or
 provider work. Preparation applies runtime overrides and then checks target
@@ -216,12 +218,14 @@ instead of first making a response-sized string copy.
 
 Every preparation operation creates one operation-local validation plan. None,
 basic, and JSON modes retain the effective output contract without source
-access. JSON Schema mode loads the root document once, resolves and compiles
-each transitive reference, and retains the compiled validator. Schema compiler
-resources use canonical escaped file or private-scheme URLs; loaders decode
-their paths once and enforce the configured source boundary. The
+access. JSON Schema mode loads the root document once, compiles its declared
+schema locations, and retains the compiled root validator. External resources
+are rejected without file or network loading; in-document references remain
+supported. Root resources use canonical escaped file or private-scheme URLs. The
 provider-facing structured-output metadata uses the root document captured by
-the same plan.
+the same plan. Its detached schema document is not revalidated against the
+runtime provider-value copier's traversal limits. Smoke inference uses a
+separate JSON-only prepared plan before checking the prepared schema plan.
 
 Schema preparation and execution remain synchronous. Promptkit checks
 cancellation before and after source resolution, JSON decoding, compilation,

docs/releases/v0.19.0.md

@@ -0,0 +1,80 @@
+# Promptkit v0.19.0
+
+This release completes two rounds of audit remediation, correcting error and
+diagnostic reporting and simplifying configuration, validation, and value
+ownership. It includes intentional compatibility changes for custom artifact
+readers, programmatic configuration sources, and schemas. The minimum supported
+Go version remains 1.27.0; ConfigKit remains at v1.1.0.
+
+## Compatibility And Upgrade
+
+Consumers upgrading from v0.18.0 should review these changes:
+
+- A successful `ArtifactReader.Read` transfers ownership of the returned
+  artifact and its mutable body storage to Promptkit. Custom readers must stop
+  mutating returned values through retained aliases. Readers that reuse scratch
+  buffers must return independent storage. Promptkit retains its defensive
+  body copy, but that copy does not make concurrent buffer reuse safe. See the
+  [extension guidance](../consumers/pkg-promptkit.md#extension-interfaces).
+- Provider maps passed through `ProfileSource` and `BackendSource` now use
+  ConfigKit's native Mapping input forms directly: built-in scalars, `[]any`,
+  and `map[string]any` recursively. Convert `json.Number` and typed containers
+  explicitly to supported values, choosing numeric precision appropriate to
+  the application. The former recursive compatibility conversion is removed.
+  Runtime execution overrides retain their separate accepted-value behavior.
+- Schemas used for local validation and native structured output must be
+  self-contained. Move externally referenced definitions into the root document
+  and use internal references or explicit schema IDs. References requiring
+  another file or network resource, or relying on the source filename as a base,
+  fail during preparation. Promptkit does not bundle external schemas. See the
+  [schema reference](../formats.md#schemas).
+
+Prepared schemas no longer inherit the depth and node limits used when copying
+runtime provider values. Schemas previously rejected solely by those incidental
+limits may now be accepted; decoder/compiler checks and the self-contained
+schema requirement still apply.
+
+No configuration-format migration is required from v0.18.0. After addressing
+any affected integrations:
+
+```sh
+go get go.maximumdirect.net/promptkit@v0.19.0
+```
+
+## Errors And Diagnostics
+
+Public errors and terminal observations now preserve the category of the
+operation that failed even when an injected collaborator returns an error from
+another Promptkit operation. Underlying causes remain available through
+`errors.Is` and `errors.As`, without repeatedly duplicating nested cause trees.
+
+Built-in generation preserves response-body read failures separately from
+malformed response content, and failures during request preparation are
+distinguished from dispatched attempts.
+
+OpenRouter authentication diagnostics bound response recognition to 1 MiB.
+An oversized HTTP 200 response reports
+`SmokeTestReasonAuthenticationResponseLimitExceeded`, leaving credential
+acceptance unknown. Cancellation during the read remains an interruption.
+Consumers that enumerate diagnostic reasons should handle the new reason;
+see the [diagnostic integration contract](../integrations/openai-compatible-chat.md#explicit-smoke-diagnostics).
+
+## Internal Simplification And Ownership
+
+Prompt lookup and rendering now consistently use captured configuration, and
+smoke syntax and schema checks share the prepared output-validation lifecycle.
+Unused routing defaults, alternate private workflows, and duplicate wire
+representations have been removed.
+
+Provider-setting resolution, inspection, prepared details, and smoke reports
+avoid redundant validation and copying of already accepted values. Prepared
+execution shares one private redacted metadata snapshot while preserving
+independent caller-visible values. Provider values are detached before custom
+JSON encoders run, protecting retained metadata from encoder-side mutation.
+
+Requirement analysis, namespace-filtered listings, and repair-feedback
+construction also avoid unnecessary traversal and temporary allocation. These
+changes preserve existing request isolation and execution behavior without
+introducing new performance guarantees.
+
+[COPYRIGHT](https://forge.maximumdirect.net/base-layer/promptkit/src/tag/v0.19.0/COPYRIGHT) | [LICENSE](https://forge.maximumdirect.net/base-layer/promptkit/src/tag/v0.19.0/LICENSE) | [ATTRIBUTION](https://forge.maximumdirect.net/base-layer/promptkit/src/tag/v0.19.0/docs/oss/attribution.md)

docs/roadmap/future.md

@@ -38,8 +38,17 @@ consumers.
 
 ## Ideas
 
-No unselected ideas are currently recorded here. Deliberately postponed ideas
-remain in the [deferred catalog](deferred.md).
+### Schema Bundling
+
+Allow consumers to author reusable schemas across multiple files and package
+them into a single self-contained schema for local validation and provider
+submission. This could restore multi-file authoring convenience while retaining
+the [self-contained schema requirement](../formats.md#schemas).
+
+Bundling would need to preserve reference semantics, identifiers, anchors, and
+recursion. A complete bundle would not guarantee that a provider supports every
+schema feature. This is a possible future enhancement; implementation is not
+currently approved.
 
 ## Entry Format
 

engine.go

@@ -213,7 +213,8 @@ func WithSchemaFS(fsys fs.FS, root string) Option {
 //
 // Prompt schema_path values refer to the file's base name. path must name an
 // existing non-directory file when NewEngine applies the option. This option
-// replaces Config.SchemaDir and earlier schema-source options.
+// replaces Config.SchemaDir and earlier schema-source options. The selected
+// schema must be self-contained; external resources are not loaded.
 func WithSchemaFile(path string) Option {
 	return optionFunc(func(options *engineOptions) error {
 		return options.internal.SetSchemaFile(path)
@@ -311,8 +312,8 @@ func (e *Engine) InspectPrompt(
 // override. BackendID is empty for an endpoint-only profile.
 //
 // APIKeyEnv in the returned target is an environment-variable name, never its
-// value. APIKeyRequired instead reports a direct credential requirement and is
-// mutually exclusive with a nonblank APIKeyEnv. InspectProfile neither derives
+// value. APIKeyRequired reports that a credential is required; an explicit
+// profile environment source can also be present. InspectProfile neither derives
 // an ID from a prompt default_profile nor checks credential availability, so an
 // absent or blank named environment variable is not an error.
 //

errors.go

@@ -13,10 +13,44 @@ import (
 	"go.maximumdirect.net/promptkit/internal/usecase"
 )
 
+// publicOperationError keeps classification separate from inspectable causes.
+// Cache wording so formatting nested operations does not repeatedly rebuild it.
+type publicOperationError struct {
+	owner   error
+	cause   error
+	message string
+}
+
+func (e *publicOperationError) Error() string        { return e.message }
+func (e *publicOperationError) Unwrap() error        { return e.cause }
+func (e *publicOperationError) Is(target error) bool { return errors.Is(e.owner, target) }
+
 func mapPublicError(err error) error {
 	if err == nil {
 		return nil
 	}
+	var operation *usecase.OperationError
+	if errors.As(err, &operation) && operation != nil {
+		owner := publicErrorFor(operation.Category)
+		if owner != nil {
+			// Project the underlying specialized error separately, retaining both
+			// the outer operation and the original cause for Is/As callers.
+			mapped := mapPublicError(operation.Cause)
+			if errors.Is(operation.Cause, llm.ErrTransport) {
+				mapped = errors.Join(ErrTransport, mapped)
+			}
+			if errors.Is(operation.Cause, llm.ErrMalformedResponse) {
+				mapped = errors.Join(ErrMalformedResponse, mapped)
+			}
+			// The projection already retains ordinary causes; adding the original
+			// again would duplicate its entire subtree at each enclosing operation.
+			return &publicOperationError{owner: owner, cause: mapped, message: fmt.Sprintf("%v: %v", owner, mapped)}
+		}
+	}
+	return mapUnownedPublicError(err)
+}
+
+func mapUnownedPublicError(err error) error {
 	var internalCapacityError *usecase.CapacityError
 	if errors.As(err, &internalCapacityError) && internalCapacityError != nil &&
 		strings.TrimSpace(internalCapacityError.BackendID) != "" {

errors_internal_test.go

@@ -80,3 +80,12 @@ func TestMapPublicErrorDoesNotTreatRequestEncodingAsTransport(t *testing.T) {
 		t.Fatalf("request encoding category = %v", err)
 	}
 }
+
+func TestMapPublicErrorRetainsOwnerWithSpecializedCapacity(t *testing.T) {
+	internal := &usecase.CapacityError{BackendID: "limited"}
+	err := mapPublicError(&usecase.OperationError{Category: usecase.ErrLLMGenerate, Cause: internal})
+	var capacity *CapacityError
+	if !errors.Is(err, ErrLLMGenerate) || !errors.As(err, &capacity) || capacity.BackendID != "limited" || !errors.Is(err, ErrCapacityExceeded) {
+		t.Fatalf("mapped owned capacity = %v", err)
+	}
+}

internal/artifact/reader_benchmark_test.go

@@ -3,8 +3,6 @@ package artifact
 import (
 	"bytes"
 	"context"
-	"crypto/sha256"
-	"fmt"
 	"mime"
 	"os"
 	"path/filepath"
@@ -153,9 +151,12 @@ func checkArtifactFileRead(b *testing.B, reader Reader, ref domain.ArtifactRef,
 	if !bytes.Equal(artifact.Body, want) || artifact.Size != int64(len(want)) {
 		b.Fatalf("artifact size=%d body length=%d, want %d", artifact.Size, len(artifact.Body), len(want))
 	}
-	wantHash := fmt.Sprintf("%x", sha256.Sum256(want))
-	if artifact.Hash != wantHash {
-		b.Fatalf("artifact hash=%q, want %q", artifact.Hash, wantHash)
+	inline, err := NewCompositeReader().Read(context.Background(), domain.ArtifactRef{Type: domain.ArtifactRefInline, Body: string(want)})
+	if err != nil {
+		b.Fatal(err)
+	}
+	if inline.Hash == "" || artifact.Hash != inline.Hash {
+		b.Fatalf("file and inline hashes differ: %q/%q", artifact.Hash, inline.Hash)
 	}
 }
 

internal/artifact/reader_test.go

@@ -3,9 +3,7 @@ package artifact
 import (
 	"bytes"
 	"context"
-	"crypto/sha256"
 	"errors"
-	"fmt"
 	"os"
 	"path/filepath"
 	"strings"
@@ -284,9 +282,12 @@ func TestFileReaderUsesOpenedSizeOnlyAsACapacityHint(t *testing.T) {
 			if artifact.Name != filepath.Base(filePath) || artifact.URI != filePath || artifact.ContentType == "" {
 				t.Fatalf("unexpected artifact metadata: name=%q URI=%q content type=%q", artifact.Name, artifact.URI, artifact.ContentType)
 			}
-			wantHash := fmt.Sprintf("%x", sha256.Sum256(tc.body))
-			if artifact.Hash != wantHash {
-				t.Fatalf("artifact hash=%q, want %q", artifact.Hash, wantHash)
+			inline, err := NewCompositeReader().Read(context.Background(), domain.ArtifactRef{Type: domain.ArtifactRefInline, Body: string(tc.body)})
+			if err != nil {
+				t.Fatal(err)
+			}
+			if inline.Hash == "" || artifact.Hash != inline.Hash {
+				t.Fatalf("file and inline hashes differ: %q/%q", artifact.Hash, inline.Hash)
 			}
 		})
 	}

internal/backend/registry.go

@@ -27,17 +27,13 @@ type Registry struct {
 // NewEffectiveRegistry stores already-validated effective backend definitions
 // under their exact configuration keys. Configuration validation and
 // normalization precede this ownership boundary.
-func NewEffectiveRegistry(definitions map[string]domain.Backend) (*Registry, error) {
+func NewEffectiveRegistry(definitions map[string]domain.Backend) *Registry {
 	registry := &Registry{backends: make(map[string]domain.Backend, len(definitions))}
 	for id, definition := range definitions {
 		definition.ID = id
-		cloned, err := domain.CloneBackend(definition)
-		if err != nil {
-			return nil, fmt.Errorf("backend %q: %w", id, err)
-		}
-		registry.backends[id] = cloned
+		registry.backends[id] = domain.CloneBackend(definition)
 	}
-	return registry, nil
+	return registry
 }
 
 // GetBackend returns a defensive copy of the backend registered with id.
@@ -49,11 +45,7 @@ func (r *Registry) GetBackend(id string) (domain.Backend, error) {
 	if !ok {
 		return domain.Backend{}, fmt.Errorf("%w: %q", ErrBackendNotFound, id)
 	}
-	cloned, err := domain.CloneBackend(definition)
-	if err != nil {
-		return domain.Backend{}, fmt.Errorf("copy backend %q: %w", id, err)
-	}
-	return cloned, nil
+	return domain.CloneBackend(definition), nil
 }
 
 // CapacityPolicies returns a copy of the normalized policies for limited

internal/backend/registry_test.go

@@ -22,16 +22,13 @@ func TestEffectiveRegistryOwnsDefinitionsAndCapacityPolicies(t *testing.T) {
 			Kind: &authenticationKind, Endpoint: &authenticationEndpoint,
 		},
 	}
-	registry, err := backend.NewEffectiveRegistry(map[string]domain.Backend{
+	registry := backend.NewEffectiveRegistry(map[string]domain.Backend{
 		" local.v1 ": {
 			Endpoint: "https://backend.example/v1", ExtraParams: params,
-			ConcurrencyLimit: 2, QueueCapacity: 3, QueueCapacitySet: true,
+			ConcurrencyLimit: 2, QueueCapacity: 3,
 			SmokeTests: smokeTests,
 		},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 	params["nested"].(map[string]any)["enabled"] = false
 	defaultProfile = "mutated-profile"
 	reachabilityEndpoint = "https://mutated.example/ready"
@@ -79,10 +76,7 @@ func TestEffectiveRegistryOwnsDefinitionsAndCapacityPolicies(t *testing.T) {
 }
 
 func TestEffectiveRegistryMissingBackend(t *testing.T) {
-	registry, err := backend.NewEffectiveRegistry(nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	registry := backend.NewEffectiveRegistry(nil)
 	if _, err := registry.GetBackend("missing"); !errors.Is(err, backend.ErrBackendNotFound) {
 		t.Fatalf("missing backend error = %v", err)
 	}

internal/capacity/client.go

@@ -1,40 +0,0 @@
-package capacity
-
-import (
-	"context"
-
-	"go.maximumdirect.net/promptkit/internal/domain"
-	"go.maximumdirect.net/promptkit/internal/llm"
-)
-
-type client struct {
-	manager *Manager
-	next    llm.Client
-}
-
-// NewClient wraps next with configured active-generation limits. A nil manager
-// leaves next unchanged.
-func NewClient(manager *Manager, next llm.Client) llm.Client {
-	if manager == nil {
-		return next
-	}
-	return &client{
-		manager: manager,
-		next:    next,
-	}
-}
-
-func (c *client) Generate(
-	ctx context.Context,
-	req domain.GenerateRequest,
-) (*domain.GenerateResponse, error) {
-	if c.manager.getPool(req.Target.BackendID) == nil {
-		return c.next.Generate(ctx, req)
-	}
-	release, err := c.manager.Acquire(ctx, req.Target.BackendID)
-	if err != nil {
-		return nil, err
-	}
-	defer release()
-	return c.next.Generate(ctx, req)
-}

internal/capacity/client_test.go

@@ -3,7 +3,6 @@ package capacity
 import (
 	"context"
 	"errors"
-	"reflect"
 	"runtime"
 	"sync"
 	"sync/atomic"
@@ -24,6 +23,18 @@ type clientFunc func(
 	domain.GenerateRequest,
 ) (*domain.GenerateResponse, error)
 
+// newTestClient exercises one acquisition around a controlled call.
+func newTestClient(manager *Manager, next llm.Client) llm.Client {
+	return clientFunc(func(ctx context.Context, req domain.GenerateRequest) (*domain.GenerateResponse, error) {
+		release, err := manager.Acquire(ctx, req.Target.BackendID)
+		if err != nil {
+			return nil, err
+		}
+		defer release()
+		return next.Generate(ctx, req)
+	})
+}
+
 func (f clientFunc) Generate(
 	ctx context.Context,
 	req domain.GenerateRequest,
@@ -167,7 +178,7 @@ func TestClientLimitsPeakConcurrencyAndServesWaitersFIFO(t *testing.T) {
 		"second": secondRelease,
 		"third":  thirdRelease,
 	})
-	client := NewClient(manager, next)
+	client := newTestClient(manager, next)
 
 	first := generateAsync(client, context.Background(), "limited", "first")
 	if got := receiveStarted(t, next.started); got != "first" {
@@ -212,7 +223,7 @@ func TestClientPeakConcurrencyDoesNotExceedConfiguredLimit(t *testing.T) {
 		releases[string(rune('a'+i))] = gate
 	}
 	next := newBlockingClient(releases)
-	client := NewClient(manager, next)
+	client := newTestClient(manager, next)
 
 	results := make([]<-chan generateResult, 0, len(releases))
 	for id := range releases {
@@ -257,7 +268,7 @@ func TestClientRemovesCanceledWaiters(t *testing.T) {
 				"three":  make(chan struct{}),
 			}
 			next := newBlockingClient(releases)
-			client := NewClient(manager, next)
+			client := newTestClient(manager, next)
 
 			holder := generateAsync(client, context.Background(), "limited", "holder")
 			if got := receiveStarted(t, next.started); got != "holder" {
@@ -321,7 +332,7 @@ func TestClientGrantCancellationRaceDoesNotLeakPermit(t *testing.T) {
 			}
 			return &domain.GenerateResponse{Content: req.Prompt.SessionID}, nil
 		})
-		client := NewClient(manager, next)
+		client := newTestClient(manager, next)
 
 		holder := generateAsync(client, context.Background(), "limited", "holder")
 		waitForActiveCount(t, manager, "limited", 1)
@@ -394,7 +405,7 @@ func TestClientUsesIndependentPoolsAndUnlimitedFastPaths(t *testing.T) {
 		"alpha": alphaRelease,
 		"beta":  betaRelease,
 	})
-	client := NewClient(manager, next)
+	client := newTestClient(manager, next)
 
 	alpha := generateAsync(client, context.Background(), "alpha", "alpha")
 	beta := generateAsync(client, context.Background(), "beta", "beta")
@@ -423,63 +434,6 @@ func TestClientUsesIndependentPoolsAndUnlimitedFastPaths(t *testing.T) {
 			t.Fatalf("unlimited backend %q response=(%#v, %v)", backendID, response, err)
 		}
 	}
-	if got := NewClient(nil, next); got != next {
-		t.Fatal("nil manager did not return the wrapped client unchanged")
-	}
-}
-
-func TestClientPreservesRequestsResponsesAndErrors(t *testing.T) {
-	manager := newTestManager(t, map[string]domain.BackendCapacityPolicy{
-		"limited": {ConcurrencyLimit: 1},
-	})
-	request := domain.GenerateRequest{
-		Prompt: domain.RenderedPrompt{
-			SessionID: "session",
-			Messages: []domain.RenderedMessage{
-				{Role: "user", Content: "content"},
-			},
-		},
-		Target: domain.ExecutionTarget{
-			BackendID:   "limited",
-			Model:       "model",
-			ExtraParams: map[string]any{"key": "value"},
-		},
-	}
-	response := &domain.GenerateResponse{
-		Content: "output",
-		Usage:   domain.TokenUsage{TotalTokens: 7},
-	}
-	collaboratorErr := errors.New("collaborator failure")
-	tests := []struct {
-		name     string
-		response *domain.GenerateResponse
-		err      error
-	}{
-		{name: "successful response", response: response},
-		{name: "nil response"},
-		{name: "collaborator error", response: response, err: collaboratorErr},
-	}
-
-	for _, tc := range tests {
-		t.Run(tc.name, func(t *testing.T) {
-			var captured domain.GenerateRequest
-			next := clientFunc(func(
-				_ context.Context,
-				req domain.GenerateRequest,
-			) (*domain.GenerateResponse, error) {
-				captured = req
-				return tc.response, tc.err
-			})
-			gotResponse, gotErr := NewClient(manager, next).Generate(context.Background(), request)
-			if !reflect.DeepEqual(captured, request) {
-				t.Fatalf("request changed: %#v", captured)
-			}
-			if gotResponse != tc.response || gotErr != tc.err {
-				t.Fatalf("response=(%p, %v), want (%p, %v)",
-					gotResponse, gotErr, tc.response, tc.err)
-			}
-		})
-	}
 }
 
 func TestClientReleasesPermitDuringPanicUnwinding(t *testing.T) {
@@ -496,7 +450,7 @@ func TestClientReleasesPermitDuringPanicUnwinding(t *testing.T) {
 		}
 		return &domain.GenerateResponse{Content: "recovered"}, nil
 	})
-	client := NewClient(manager, next)
+	client := newTestClient(manager, next)
 	request := domain.GenerateRequest{
 		Target: domain.ExecutionTarget{BackendID: "limited"},
 	}

internal/configuration/bundled_test.go

@@ -3,10 +3,12 @@ package configuration
 import (
 	"context"
 	"fmt"
+	"reflect"
 	"strings"
 	"testing"
 
 	"go.maximumdirect.net/configkit"
+	"go.maximumdirect.net/promptkit/internal/defaults"
 )
 
 func TestBundledOpenRouterUnderlay(t *testing.T) {
@@ -15,9 +17,12 @@ func TestBundledOpenRouterUnderlay(t *testing.T) {
 		t.Fatal(err)
 	}
 	backend, err := state.GetBackend("openrouter")
-	if err != nil || backend.Endpoint != "https://openrouter.ai/api/v1" || backend.APIKeyEnv != "OPENROUTER_API_KEY" || backend.SmokeTests == nil || backend.SmokeTests.DefaultProfile == nil || *backend.SmokeTests.DefaultProfile != "gpt-luna-latest" || backend.SmokeTests.Authentication == nil || *backend.SmokeTests.Authentication.Kind != "openrouter_key" {
+	if err != nil || backend.Endpoint != "https://openrouter.ai/api/v1" || backend.APIKeyEnv != "OPENROUTER_API_KEY" || backend.SmokeTests == nil || backend.SmokeTests.DefaultProfile == nil || *backend.SmokeTests.DefaultProfile != "gpt-luna-latest" || backend.SmokeTests.Authentication == nil || backend.SmokeTests.Authentication.Kind == nil || *backend.SmokeTests.Authentication.Kind != "openrouter_key" {
 		t.Fatalf("backend = %+v, %v", backend, err)
 	}
+	if !reflect.DeepEqual(state.backendIDs, []string{"openrouter"}) || len(state.promptIDs) != 0 || len(state.collections) != 0 {
+		t.Fatalf("bundle inventories: backends=%v prompts=%v collections=%v", state.backendIDs, state.promptIDs, state.collections)
+	}
 	models := map[string]string{
 		"gpt-astra-latest": "~openai/gpt-astra-latest", "gpt-sol-latest": "~openai/gpt-sol-latest", "gpt-terra-latest": "~openai/gpt-terra-latest", "gpt-luna-latest": "~openai/gpt-luna-latest",
 		"claude-fable-latest": "~anthropic/claude-fable-latest", "claude-opus-latest": "~anthropic/claude-opus-latest", "claude-sonnet-latest": "~anthropic/claude-sonnet-latest", "claude-haiku-latest": "~anthropic/claude-haiku-latest",
@@ -31,14 +36,16 @@ func TestBundledOpenRouterUnderlay(t *testing.T) {
 	}
 	for id, model := range models {
 		profile, err := state.GetProfile(context.Background(), id)
-		if err != nil || profile.ResolvedTarget.Model != model || profile.ResolvedTarget.BackendID != "openrouter" {
+		if err != nil {
 			t.Fatalf("profile %s = %+v, %v", id, profile, err)
 		}
+		want := defaults.ExecutionTargetDefault()
+		want.Model, want.BackendID, want.Endpoint, want.APIKeyEnv = model, "openrouter", "https://openrouter.ai/api/v1", "OPENROUTER_API_KEY"
 		if tier, ok := strings.CutPrefix(id, "auto-"); ok {
-			plugins := fmt.Sprint(profile.ResolvedTarget.ExtraParams)
-			if !strings.Contains(plugins, "cost_tier:"+tier) || !strings.Contains(plugins, "id:auto-router") {
-				t.Fatalf("profile %s plugins = %+v", id, profile.ResolvedTarget.ExtraParams)
-			}
+			want.ExtraParams = map[string]any{"plugins": []any{map[string]any{"id": "auto-router", "cost_tier": tier}}}
+		}
+		if !reflect.DeepEqual(*profile.ResolvedTarget, want) {
+			t.Fatalf("profile %s target = %+v, want %+v", id, *profile.ResolvedTarget, want)
 		}
 	}
 	if !strings.Contains(fmt.Sprint(state.result.Sources()), "Promptkit bundled OpenRouter") {

internal/configuration/listing.go

@@ -2,36 +2,66 @@ package configuration
 
 import (
 	"context"
+	"sort"
+	"strings"
 
 	"go.maximumdirect.net/promptkit/internal/domain"
 )
 
+// IdentityFilter selects all identities, one namespace, or unqualified IDs.
+type IdentityFilter struct {
+	All       bool
+	Namespace string
+}
+
+func selectIdentities[T any](ctx context.Context, entries []T, filter IdentityFilter, id func(T) string) ([]T, error) {
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	if filter.All {
+		result := append([]T(nil), entries...)
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		return result, nil
+	}
+	if filter.Namespace != "" {
+		prefix := filter.Namespace + "/"
+		start := sort.Search(len(entries), func(i int) bool { return id(entries[i]) >= prefix })
+		end := start + sort.Search(len(entries)-start, func(i int) bool { return !strings.HasPrefix(id(entries[start+i]), prefix) })
+		result := append([]T(nil), entries[start:end]...)
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		return result, nil
+	}
+	var result []T
+	for _, entry := range entries {
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		if !strings.Contains(id(entry), "/") {
+			result = append(result, entry)
+		}
+	}
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
 // CollectionIdentity is the captured metadata for one final collection entry.
 type CollectionIdentity struct {
 	Namespace      string
 	ReleaseVersion *string
 }
 
-func (state *loaded) ListProfiles(ctx context.Context) ([]string, error) {
-	if err := ctx.Err(); err != nil {
-		return nil, err
-	}
-	profiles := append([]string(nil), state.profileIDs...)
-	if err := ctx.Err(); err != nil {
-		return nil, err
-	}
-	return profiles, nil
+func (state *loaded) ListProfiles(ctx context.Context, filter IdentityFilter) ([]string, error) {
+	return selectIdentities(ctx, state.profileIDs, filter, func(id string) string { return id })
 }
 
-func (state *loaded) ListBackends(ctx context.Context) ([]string, error) {
-	if err := ctx.Err(); err != nil {
-		return nil, err
-	}
-	backends := append([]string(nil), state.backendIDs...)
-	if err := ctx.Err(); err != nil {
-		return nil, err
-	}
-	return backends, nil
+func (state *loaded) ListBackends(ctx context.Context, filter IdentityFilter) ([]string, error) {
+	return selectIdentities(ctx, state.backendIDs, filter, func(id string) string { return id })
 }
 
 func (state *loaded) ListNamespaces(ctx context.Context, kinds []string) ([]string, error) {
@@ -72,13 +102,6 @@ func (state *loaded) ListCollections(ctx context.Context) ([]CollectionIdentity,
 	return collections, nil
 }
 
-func (state *loaded) ListPrompts(ctx context.Context) ([]domain.PromptIdentity, error) {
-	if err := ctx.Err(); err != nil {
-		return nil, err
-	}
-	prompts := append([]domain.PromptIdentity(nil), state.promptIDs...)
-	if err := ctx.Err(); err != nil {
-		return nil, err
-	}
-	return prompts, nil
+func (state *loaded) ListPrompts(ctx context.Context, filter IdentityFilter) ([]domain.PromptIdentity, error) {
+	return selectIdentities(ctx, state.promptIDs, filter, func(entry domain.PromptIdentity) string { return entry.ID })
 }

internal/configuration/listing_test.go

@@ -23,7 +23,7 @@ func TestLoadedListsSortedEffectiveIdentities(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	backends, err := state.ListBackends(context.Background())
+	backends, err := state.ListBackends(context.Background(), IdentityFilter{All: true})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -32,7 +32,7 @@ func TestLoadedListsSortedEffectiveIdentities(t *testing.T) {
 		t.Fatalf("backend IDs = %#v, want %#v", backends, wantBackends)
 	}
 
-	profiles, err := state.ListProfiles(context.Background())
+	profiles, err := state.ListProfiles(context.Background(), IdentityFilter{All: true})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -41,7 +41,7 @@ func TestLoadedListsSortedEffectiveIdentities(t *testing.T) {
 		t.Fatalf("profile IDs = %#v, want %#v", profiles, wantProfiles)
 	}
 
-	prompts, err := state.ListPrompts(context.Background())
+	prompts, err := state.ListPrompts(context.Background(), IdentityFilter{All: true})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -65,36 +65,36 @@ func TestLoadedListsAreIndependent(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	profiles, err := state.ListProfiles(context.Background())
+	profiles, err := state.ListProfiles(context.Background(), IdentityFilter{All: true})
 	if err != nil {
 		t.Fatal(err)
 	}
 	profiles = append(profiles, "caller profile")
 	profiles[0] = "changed profile"
-	backends, err := state.ListBackends(context.Background())
+	backends, err := state.ListBackends(context.Background(), IdentityFilter{All: true})
 	if err != nil {
 		t.Fatal(err)
 	}
 	backends[0] = "changed backend"
 
-	prompts, err := state.ListPrompts(context.Background())
+	prompts, err := state.ListPrompts(context.Background(), IdentityFilter{All: true})
 	if err != nil {
 		t.Fatal(err)
 	}
 	prompts[0].ID = "changed prompt"
 
-	profiles, err = state.ListProfiles(context.Background())
+	profiles, err = state.ListProfiles(context.Background(), IdentityFilter{All: true})
 	if err != nil {
 		t.Fatal(err)
 	}
 	if !reflect.DeepEqual(profiles, []string{"profile"}) {
 		t.Fatalf("caller mutation changed profile inventory: %#v", profiles)
 	}
-	backends, err = state.ListBackends(context.Background())
+	backends, err = state.ListBackends(context.Background(), IdentityFilter{All: true})
 	if err != nil || !reflect.DeepEqual(backends, []string{"backend"}) {
 		t.Fatalf("caller mutation changed backend inventory: %#v, %v", backends, err)
 	}
-	prompts, err = state.ListPrompts(context.Background())
+	prompts, err = state.ListPrompts(context.Background(), IdentityFilter{All: true})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -104,20 +104,66 @@ func TestLoadedListsAreIndependent(t *testing.T) {
 	}
 }
 
+func TestLoadedListsSelectNamespaces(t *testing.T) {
+	ids := []string{"a", "a-b/one", "a/one", "a/two", "b", "z/one"}
+	state := &loaded{profileIDs: append([]string(nil), ids...), backendIDs: append([]string(nil), ids...)}
+	for _, id := range ids {
+		state.promptIDs = append(state.promptIDs, domain.PromptIdentity{ID: id})
+	}
+	cases := []struct {
+		name   string
+		filter IdentityFilter
+		want   []string
+	}{
+		{"all", IdentityFilter{All: true}, ids},
+		{"unqualified", IdentityFilter{}, []string{"a", "b"}},
+		{"namespace", IdentityFilter{Namespace: "a"}, []string{"a/one", "a/two"}},
+		{"prefix sharing", IdentityFilter{Namespace: "a-b"}, []string{"a-b/one"}},
+		{"missing", IdentityFilter{Namespace: "absent"}, nil},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			profiles, err := state.ListProfiles(context.Background(), tc.filter)
+			if err != nil || !reflect.DeepEqual(profiles, tc.want) {
+				t.Fatalf("profiles = %v, %v; want %v", profiles, err, tc.want)
+			}
+			backends, err := state.ListBackends(context.Background(), tc.filter)
+			if err != nil || !reflect.DeepEqual(backends, tc.want) {
+				t.Fatalf("backends = %v, %v; want %v", backends, err, tc.want)
+			}
+			prompts, err := state.ListPrompts(context.Background(), tc.filter)
+			if err != nil || len(prompts) != len(tc.want) {
+				t.Fatalf("prompts = %v, %v; want %v", prompts, err, tc.want)
+			}
+			for i := range prompts {
+				if prompts[i].ID != tc.want[i] {
+					t.Fatalf("prompt ID = %q; want %q", prompts[i].ID, tc.want[i])
+				}
+			}
+			if len(profiles) > 0 {
+				profiles[0], backends[0], prompts[0].ID = "changed", "changed", "changed"
+			}
+		})
+	}
+	if !reflect.DeepEqual(state.profileIDs, ids) || !reflect.DeepEqual(state.backendIDs, ids) || state.promptIDs[0].ID != ids[0] {
+		t.Fatal("caller mutation changed captured identities")
+	}
+}
+
 func TestLoadedListsEmptyInventory(t *testing.T) {
 	state, err := Load(configkit.Input{Source: configkit.NoSource()}, nil)
 	if err != nil {
 		t.Fatal(err)
 	}
-	profiles, err := state.ListProfiles(context.Background())
+	profiles, err := state.ListProfiles(context.Background(), IdentityFilter{All: true})
 	if err != nil || len(profiles) != 0 {
 		t.Fatalf("empty profile listing = %#v, %v", profiles, err)
 	}
-	backends, err := state.ListBackends(context.Background())
+	backends, err := state.ListBackends(context.Background(), IdentityFilter{All: true})
 	if err != nil || len(backends) != 0 {
 		t.Fatalf("empty backend listing = %#v, %v", backends, err)
 	}
-	prompts, err := state.ListPrompts(context.Background())
+	prompts, err := state.ListPrompts(context.Background(), IdentityFilter{All: true})
 	if err != nil || len(prompts) != 0 {
 		t.Fatalf("empty prompt listing = %#v, %v", prompts, err)
 	}
@@ -134,17 +180,19 @@ func TestLoadedListsHonorCanceledContext(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	cancel()
 
-	profiles, err := state.ListProfiles(ctx)
-	if !errors.Is(err, context.Canceled) || len(profiles) != 0 {
-		t.Fatalf("canceled profile listing = %#v, %v", profiles, err)
-	}
-	backends, err := state.ListBackends(ctx)
-	if !errors.Is(err, context.Canceled) || len(backends) != 0 {
-		t.Fatalf("canceled backend listing = %#v, %v", backends, err)
-	}
-	prompts, err := state.ListPrompts(ctx)
-	if !errors.Is(err, context.Canceled) || len(prompts) != 0 {
-		t.Fatalf("canceled prompt listing = %#v, %v", prompts, err)
+	for _, filter := range []IdentityFilter{{All: true}, {}, {Namespace: "example"}} {
+		profiles, err := state.ListProfiles(ctx, filter)
+		if !errors.Is(err, context.Canceled) || len(profiles) != 0 {
+			t.Fatalf("canceled profile listing = %#v, %v", profiles, err)
+		}
+		backends, err := state.ListBackends(ctx, filter)
+		if !errors.Is(err, context.Canceled) || len(backends) != 0 {
+			t.Fatalf("canceled backend listing = %#v, %v", backends, err)
+		}
+		prompts, err := state.ListPrompts(ctx, filter)
+		if !errors.Is(err, context.Canceled) || len(prompts) != 0 {
+			t.Fatalf("canceled prompt listing = %#v, %v", prompts, err)
+		}
 	}
 }
 

internal/configuration/load.go

@@ -119,7 +119,6 @@ const (
 
 type loaded struct {
 	result          *configkit.Result[document]
-	backends        map[string]map[string]fieldState
 	profiles        map[string]map[string]fieldState
 	promptMetadata  map[string][]promptInputPresence
 	prompts         map[string]*promptEntry
@@ -212,7 +211,6 @@ func indexedProfiles(config *document) map[string]profileConfig {
 
 var envName = regexp.MustCompile(`^[A-Za-z_][A-Za-z0-9_]*$`)
 
-var backendFields = []string{"endpoint", "api_key_env", "concurrency_limit", "queue_capacity", "extra_params", "smoke_tests"}
 var profileFields = []string{"backend", "endpoint", "model", "temperature", "top_p", "max_tokens", "timeout_seconds", "service_tier", "reasoning_effort", "api_key_env", "api_key_required", "extra_params"}
 
 // Load captures one immutable effective configuration for internal consumers.
@@ -237,7 +235,6 @@ func configurationDefinition(state *loaded) configkit.Definition[document] {
 		Sensitive: secretProviderPath,
 		Resolve: func(config *document, resolution *configkit.Resolution) error {
 			for _, resources := range resourceSets(config) {
-				captureFields(resources.backends, func(v backendConfig) string { return v.ID }, resources.bases.backends, resources.namespace, backendFields, resolution, state.backends)
 				captureFields(resources.profiles, func(v profileConfig) string { return v.ID }, resources.bases.profiles, resources.namespace, profileFields, resolution, state.profiles)
 				capturePromptMetadata(resources.prompts, resources.bases.prompts, resources.namespace, resolution, state.promptMetadata)
 			}
@@ -257,7 +254,6 @@ func configurationDefinition(state *loaded) configkit.Definition[document] {
 // load performs one ConfigKit lifecycle over the selected source tiers.
 func load(main configkit.Input, underlays []configkit.Underlay) (*loaded, error) {
 	state := &loaded{
-		backends:       make(map[string]map[string]fieldState),
 		profiles:       make(map[string]map[string]fieldState),
 		promptMetadata: make(map[string][]promptInputPresence),
 	}
@@ -419,101 +415,110 @@ func validateEffective(config *document, validation *configkit.Validation) {
 	}
 	for _, resources := range sets {
 		for index, backend := range resources.backends {
-			base := resources.bases.backends.Index(index)
-			validateBackendEndpoints(backend, base, validation)
-			if !domain.IsValidLocalResourceKey(backend.ID) {
-				validation.Error(base.Key("id"), "backend ID must be a nonblank local key without a slash")
-			}
-			if backend.Endpoint == nil || *backend.Endpoint == "" {
-				validation.Error(base.Key("endpoint"), "endpoint is required")
-			}
-			if backend.APIKeyEnv != nil && *backend.APIKeyEnv != "" && !envName.MatchString(*backend.APIKeyEnv) {
-				validation.Error(base.Key("api_key_env"), "environment variable name is invalid")
-			}
-			if backend.ConcurrencyLimit != nil && *backend.ConcurrencyLimit < 0 {
-				validation.Error(base.Key("concurrency_limit"), "concurrency limit must not be negative")
-			}
-			if backend.QueueCapacity != nil {
-				if *backend.QueueCapacity < 0 {
-					validation.Error(base.Key("queue_capacity"), "queue capacity must not be negative")
-				}
-				if backend.ConcurrencyLimit == nil || *backend.ConcurrencyLimit <= 0 {
-					validation.Error(base.Key("queue_capacity"), "queue capacity requires a positive concurrency limit")
-				} else if *backend.QueueCapacity > int(^uint(0)>>1)-*backend.ConcurrencyLimit {
-					validation.Error(base.Key("queue_capacity"), "total capacity overflows int")
-				}
-			}
-			validateExtraParams(backend.ExtraParams, base.Key("extra_params"), true, validation)
-			if smokeTests := backend.SmokeTests; smokeTests != nil {
-				smokePath := base.Key("smoke_tests")
-				if smokeTests.DefaultProfile != nil {
-					if strings.TrimSpace(*smokeTests.DefaultProfile) == "" {
-						validation.Error(smokePath.Key("default_profile"), "default profile must not be blank")
-					} else if !domain.IsValidResourceID(*smokeTests.DefaultProfile) {
-						validation.Error(smokePath.Key("default_profile"), "default profile reference is malformed")
-					}
-				}
-				if authentication := smokeTests.Authentication; authentication != nil {
-					kindPath := smokePath.Key("authentication").Key("kind")
-					if authentication.Kind == nil {
-						validation.Error(kindPath, "authentication kind is required")
-					} else if *authentication.Kind != "none" && *authentication.Kind != "openrouter_key" {
-						validation.Error(kindPath, "authentication kind must be none or openrouter_key")
-					}
-				}
-			}
+			validateBackendRecord(backend, resources.bases.backends.Index(index), validation)
 		}
 		for index, profile := range resources.profiles {
-			base := resources.bases.profiles.Index(index)
-			if profile.Endpoint != nil && *profile.Endpoint != "" {
-				if _, err := domain.NormalizeOpenAICompatibleBaseEndpoint(*profile.Endpoint); err != nil {
-					validation.Error(base.Key("endpoint"), err.Error())
-				}
-			}
-			if !domain.IsValidLocalResourceKey(profile.ID) {
-				validation.Error(base.Key("id"), "profile ID must be a nonblank local key without a slash")
-			}
-			if profile.Backend != nil && *profile.Backend != "" {
-				if !domain.IsValidResourceID(*profile.Backend) {
-					validation.Error(base.Key("backend"), "backend reference is malformed")
-				} else if _, exists := backendIDs[*profile.Backend]; !exists {
-					validation.Error(base.Key("backend"), "backend is not defined")
-				}
-			}
-			if profile.Model != nil && *profile.Model != "" && strings.TrimSpace(*profile.Model) == "" {
-				validation.Error(base.Key("model"), "model must not be blank")
-			}
-			if profile.Temperature != nil {
-				if err := domain.ValidateExecutionTargetSettings(domain.ExecutionTarget{Temperature: *profile.Temperature}); err != nil {
-					validation.Error(base.Key("temperature"), err.Error())
-				}
-			}
-			if profile.TopP != nil {
-				if err := domain.ValidateExecutionTargetSettings(domain.ExecutionTarget{TopP: *profile.TopP}); err != nil {
-					validation.Error(base.Key("top_p"), err.Error())
-				}
-			}
-			if profile.MaxTokens != nil {
-				if err := domain.ValidateExecutionTargetSettings(domain.ExecutionTarget{MaxTokens: *profile.MaxTokens}); err != nil {
-					validation.Error(base.Key("max_tokens"), err.Error())
-				}
-			}
-			if profile.TimeoutSeconds != nil {
-				if err := domain.ValidateExecutionTargetSettings(domain.ExecutionTarget{TimeoutSeconds: *profile.TimeoutSeconds}); err != nil {
-					validation.Error(base.Key("timeout_seconds"), err.Error())
-				}
-			}
-			validateExtraParams(profile.ExtraParams, base.Key("extra_params"), false, validation)
+			validateProfileRecord(profile, resources.bases.profiles.Index(index), backendIDs, validation)
 		}
 		for index, prompt := range resources.prompts {
-			base := resources.bases.prompts.Index(index)
-			if !domain.IsValidLocalResourceKey(prompt.ID) {
-				validation.Error(base.Key("id"), "prompt ID must be a nonblank local key without a slash")
-			}
-			if prompt.DefaultProfile != nil && *prompt.DefaultProfile != "" && !domain.IsValidResourceID(*prompt.DefaultProfile) {
-				validation.Error(base.Key("default_profile"), "default profile reference is malformed")
+			validatePromptRecord(prompt, resources.bases.prompts.Index(index), validation)
+		}
+	}
+}
+
+func validateBackendRecord(backend backendConfig, base configkit.Path, validation *configkit.Validation) {
+	validateBackendEndpoints(backend, base, validation)
+	if !domain.IsValidLocalResourceKey(backend.ID) {
+		validation.Error(base.Key("id"), "backend ID must be a nonblank local key without a slash")
+	}
+	if backend.Endpoint == nil || *backend.Endpoint == "" {
+		validation.Error(base.Key("endpoint"), "endpoint is required")
+	}
+	if backend.APIKeyEnv != nil && *backend.APIKeyEnv != "" && !envName.MatchString(*backend.APIKeyEnv) {
+		validation.Error(base.Key("api_key_env"), "environment variable name is invalid")
+	}
+	if backend.ConcurrencyLimit != nil && *backend.ConcurrencyLimit < 0 {
+		validation.Error(base.Key("concurrency_limit"), "concurrency limit must not be negative")
+	}
+	if backend.QueueCapacity != nil {
+		if *backend.QueueCapacity < 0 {
+			validation.Error(base.Key("queue_capacity"), "queue capacity must not be negative")
+		}
+		if backend.ConcurrencyLimit == nil || *backend.ConcurrencyLimit <= 0 {
+			validation.Error(base.Key("queue_capacity"), "queue capacity requires a positive concurrency limit")
+		} else if *backend.QueueCapacity > int(^uint(0)>>1)-*backend.ConcurrencyLimit {
+			validation.Error(base.Key("queue_capacity"), "total capacity overflows int")
+		}
+	}
+	validateExtraParams(backend.ExtraParams, base.Key("extra_params"), true, validation)
+	if smokeTests := backend.SmokeTests; smokeTests != nil {
+		smokePath := base.Key("smoke_tests")
+		if smokeTests.DefaultProfile != nil {
+			if strings.TrimSpace(*smokeTests.DefaultProfile) == "" {
+				validation.Error(smokePath.Key("default_profile"), "default profile must not be blank")
+			} else if !domain.IsValidResourceID(*smokeTests.DefaultProfile) {
+				validation.Error(smokePath.Key("default_profile"), "default profile reference is malformed")
 			}
 		}
+		if authentication := smokeTests.Authentication; authentication != nil {
+			kindPath := smokePath.Key("authentication").Key("kind")
+			if authentication.Kind == nil {
+				validation.Error(kindPath, "authentication kind is required")
+			} else if *authentication.Kind != "none" && *authentication.Kind != "openrouter_key" {
+				validation.Error(kindPath, "authentication kind must be none or openrouter_key")
+			}
+		}
+	}
+}
+
+func validateProfileRecord(profile profileConfig, base configkit.Path, backendIDs map[string]struct{}, validation *configkit.Validation) {
+	if profile.Endpoint != nil && *profile.Endpoint != "" {
+		if _, err := domain.NormalizeOpenAICompatibleBaseEndpoint(*profile.Endpoint); err != nil {
+			validation.Error(base.Key("endpoint"), err.Error())
+		}
+	}
+	if !domain.IsValidLocalResourceKey(profile.ID) {
+		validation.Error(base.Key("id"), "profile ID must be a nonblank local key without a slash")
+	}
+	if profile.Backend != nil && *profile.Backend != "" {
+		if !domain.IsValidResourceID(*profile.Backend) {
+			validation.Error(base.Key("backend"), "backend reference is malformed")
+		} else if _, exists := backendIDs[*profile.Backend]; !exists {
+			validation.Error(base.Key("backend"), "backend is not defined")
+		}
+	}
+	if profile.Model != nil && *profile.Model != "" && strings.TrimSpace(*profile.Model) == "" {
+		validation.Error(base.Key("model"), "model must not be blank")
+	}
+	if profile.Temperature != nil {
+		if err := domain.ValidateExecutionTargetSettings(domain.ExecutionTarget{Temperature: *profile.Temperature}); err != nil {
+			validation.Error(base.Key("temperature"), err.Error())
+		}
+	}
+	if profile.TopP != nil {
+		if err := domain.ValidateExecutionTargetSettings(domain.ExecutionTarget{TopP: *profile.TopP}); err != nil {
+			validation.Error(base.Key("top_p"), err.Error())
+		}
+	}
+	if profile.MaxTokens != nil {
+		if err := domain.ValidateExecutionTargetSettings(domain.ExecutionTarget{MaxTokens: *profile.MaxTokens}); err != nil {
+			validation.Error(base.Key("max_tokens"), err.Error())
+		}
+	}
+	if profile.TimeoutSeconds != nil {
+		if err := domain.ValidateExecutionTargetSettings(domain.ExecutionTarget{TimeoutSeconds: *profile.TimeoutSeconds}); err != nil {
+			validation.Error(base.Key("timeout_seconds"), err.Error())
+		}
+	}
+	validateExtraParams(profile.ExtraParams, base.Key("extra_params"), false, validation)
+}
+
+func validatePromptRecord(prompt promptConfig, base configkit.Path, validation *configkit.Validation) {
+	if !domain.IsValidLocalResourceKey(prompt.ID) {
+		validation.Error(base.Key("id"), "prompt ID must be a nonblank local key without a slash")
+	}
+	if prompt.DefaultProfile != nil && *prompt.DefaultProfile != "" && !domain.IsValidResourceID(*prompt.DefaultProfile) {
+		validation.Error(base.Key("default_profile"), "default profile reference is malformed")
 	}
 }
 

internal/configuration/load_test.go

@@ -496,7 +496,7 @@ func TestLoadComposesLiteralKeysAndEffectivePresence(t *testing.T) {
 		t.Fatalf("recursive overlay failed: %+v", provider)
 	}
 	backend := loaded.result.Config.Backends[0]
-	if backend.QueueCapacity == nil || *backend.QueueCapacity != 0 || loaded.backends["local.v1"]["queue_capacity"] != fieldValue {
+	if backend.QueueCapacity == nil || *backend.QueueCapacity != 0 {
 		t.Fatalf("explicit zero queue capacity was lost: %+v", backend)
 	}
 	if _, err := loaded.registry.GetBackend("base/local.v1"); err != nil {
@@ -582,9 +582,6 @@ func TestLoadInterpretsBackendNormalizationAndNullDefault(t *testing.T) {
 		composed.APIKeyEnv == nil || *composed.APIKeyEnv != "TOKEN_NAME" || composed.QueueCapacity == nil || *composed.QueueCapacity != 1024 {
 		t.Fatalf("resolved backend was not normalized: %+v", composed)
 	}
-	if loaded.backends["local"]["queue_capacity"] != fieldNull {
-		t.Fatalf("explicit null was not retained: %+v", loaded.backends["local"])
-	}
 	field, found := loaded.result.Metadata().Lookup(configkit.Keys("backends").Index(0).Key("endpoint"))
 	if !found || field.Origin.Operation != configkit.ChangeNormalization {
 		t.Fatalf("endpoint origin was not preserved: %+v", field)
@@ -763,7 +760,7 @@ func TestLoadDefaultsAbsentQueueCapacity(t *testing.T) {
 		t.Fatal(err)
 	}
 	backend, err := loaded.GetBackend("local")
-	if err != nil || backend.APIKeyEnv != "" || backend.QueueCapacity != 1024 || loaded.result.Config.Backends[0].QueueCapacity == nil || *loaded.result.Config.Backends[0].QueueCapacity != 1024 || loaded.backends["local"]["queue_capacity"] != fieldAbsent {
+	if err != nil || backend.APIKeyEnv != "" || backend.QueueCapacity != 1024 || loaded.result.Config.Backends[0].QueueCapacity == nil || *loaded.result.Config.Backends[0].QueueCapacity != 1024 {
 		t.Fatalf("absent queue capacity did not receive its default: %+v", backend)
 	}
 }

internal/configuration/prompts.go

@@ -72,104 +72,21 @@ func (state *loaded) materializePrompt(id string, raw promptConfig, base configk
 	if raw.SessionID != nil {
 		definition.SessionID = *raw.SessionID
 	}
-	seenInputs := make(map[string]bool, len(raw.Inputs))
-	definition.Inputs = make([]domain.PromptInput, 0, len(raw.Inputs))
-	entry := &promptEntry{
-		messages:          make([]*template.Template, 0, len(raw.Messages)),
-		requirementInputs: make([]prompt.InputMetadata, 0, len(raw.Inputs)),
+	inputs, inputMetadata, err := state.capturePromptInputs(id, raw.Inputs, base)
+	if err != nil {
+		return nil, err
 	}
-	for index, input := range raw.Inputs {
-		path := base.Key("inputs").Index(index)
-		if input.Name == "" {
-			return nil, fmt.Errorf("%s: input name is required", path.Key("name"))
-		}
-		if seenInputs[input.Name] {
-			return nil, fmt.Errorf("%s: input name is duplicated", path.Key("name"))
-		}
-		seenInputs[input.Name] = true
-		contentType := ""
-		if input.ContentType != nil {
-			contentType = *input.ContentType
-		}
-		description := ""
-		if input.Description != nil {
-			description = *input.Description
-		}
-		definition.Inputs = append(definition.Inputs, domain.PromptInput{
-			Name: input.Name, Required: input.Required, ContentType: contentType, Description: description,
-		})
-		presence := state.promptMetadata[id][index]
-		metadata := prompt.InputMetadata{Name: input.Name, Required: input.Required}
-		if presence.contentType == fieldValue {
-			metadata.ContentType = stringPointer(contentType)
-		}
-		if presence.description == fieldValue {
-			metadata.Description = stringPointer(description)
-		}
-		entry.requirementInputs = append(entry.requirementInputs, metadata)
+	messages, compiledMessages, err := state.capturePromptMessages(raw.Messages, base, lookupOrigin)
+	if err != nil {
+		return nil, err
 	}
-	definition.Templates = make([]domain.PromptMessageTemplate, 0, len(raw.Messages))
-	for index, message := range raw.Messages {
-		path := base.Key("messages").Index(index)
-		if message.Role == nil {
-			return nil, fmt.Errorf("%s: role is required", path.Key("role"))
-		}
-		if _, err := domain.NormalizeMessageRole(*message.Role); err != nil {
-			return nil, fmt.Errorf("%s: %w", path.Key("role"), err)
-		}
-		if (message.Content != nil) == (message.ContentFile != nil) {
-			return nil, fmt.Errorf("%s: exactly one of content or content_file is required", path)
-		}
-		content := ""
-		if message.Content != nil {
-			content = *message.Content
-		} else {
-			var err error
-			content, err = state.readContent(path.Key("content_file"), *message.ContentFile, lookupOrigin)
-			if err != nil {
-				return nil, err
-			}
-		}
-		var control *domain.CacheControl
-		if message.CacheControl != nil {
-			if message.CacheControl.Type == nil {
-				return nil, fmt.Errorf("%s: type is required", path.Key("cache_control").Key("type"))
-			}
-			control = &domain.CacheControl{Type: domain.CacheControlType(*message.CacheControl.Type)}
-			if message.CacheControl.TTL != nil {
-				control.TTL = *message.CacheControl.TTL
-			}
-			if _, err := domain.NormalizeCacheControl(control); err != nil {
-				return nil, fmt.Errorf("%s: %w", path.Key("cache_control"), err)
-			}
-		}
-		compiled, err := prompt.CompileTemplate(fmt.Sprintf("msg_%d", index), content)
-		if err != nil {
-			return nil, fmt.Errorf("%s: invalid template syntax: %w", path, err)
-		}
-		entry.messages = append(entry.messages, compiled)
-		definition.Templates = append(definition.Templates, domain.PromptMessageTemplate{
-			Role: *message.Role, Content: content, CacheControl: control,
-		})
+	contract, err := capturePromptOutput(raw.Output, base)
+	if err != nil {
+		return nil, err
 	}
-	if raw.Output == nil {
-		return nil, fmt.Errorf("%s: output is required", base.Key("output"))
-	}
-	if raw.Output.Format == nil || raw.Output.ValidationMode == nil {
-		return nil, fmt.Errorf("%s: format and validation_mode are required", base.Key("output"))
-	}
-	contract := domain.OutputContract{
-		Format:         domain.OutputFormat(*raw.Output.Format),
-		ValidationMode: domain.ValidationMode(*raw.Output.ValidationMode),
-		RepairAttempts: raw.Output.RepairAttempts,
-	}
-	if raw.Output.SchemaPath != nil {
-		contract.SchemaPath = *raw.Output.SchemaPath
-	}
-	if err := domain.ValidateOutputContract(contract); err != nil {
-		return nil, fmt.Errorf("%s: invalid output contract: %w", base.Key("output"), err)
-	}
-	definition.OutputFormat = contract.Format
+	definition.Inputs = inputs
+	definition.Templates = messages
+	entry := &promptEntry{requirementInputs: inputMetadata, messages: compiledMessages}
 	definition.Validation = contract
 	if raw.SessionID != nil {
 		var err error
@@ -192,6 +109,113 @@ func (state *loaded) materializePrompt(id string, raw promptConfig, base configk
 	return entry, nil
 }
 
+func (state *loaded) capturePromptInputs(id string, rawInputs []promptInputConfig, base configkit.Path) ([]domain.PromptInput, []prompt.InputMetadata, error) {
+	seenInputs := make(map[string]bool, len(rawInputs))
+	inputs := make([]domain.PromptInput, 0, len(rawInputs))
+	metadata := make([]prompt.InputMetadata, 0, len(rawInputs))
+	for index, input := range rawInputs {
+		path := base.Key("inputs").Index(index)
+		if input.Name == "" {
+			return nil, nil, fmt.Errorf("%s: input name is required", path.Key("name"))
+		}
+		if seenInputs[input.Name] {
+			return nil, nil, fmt.Errorf("%s: input name is duplicated", path.Key("name"))
+		}
+		seenInputs[input.Name] = true
+		contentType := ""
+		if input.ContentType != nil {
+			contentType = *input.ContentType
+		}
+		description := ""
+		if input.Description != nil {
+			description = *input.Description
+		}
+		inputs = append(inputs, domain.PromptInput{
+			Name: input.Name, Required: input.Required, ContentType: contentType, Description: description,
+		})
+		presence := state.promptMetadata[id][index]
+		item := prompt.InputMetadata{Name: input.Name, Required: input.Required}
+		if presence.contentType == fieldValue {
+			item.ContentType = stringPointer(contentType)
+		}
+		if presence.description == fieldValue {
+			item.Description = stringPointer(description)
+		}
+		metadata = append(metadata, item)
+	}
+	return inputs, metadata, nil
+}
+
+func (state *loaded) capturePromptMessages(rawMessages []promptMessageConfig, base configkit.Path, lookupOrigin func(configkit.Path) (configkit.FieldInfo, bool)) ([]domain.PromptMessageTemplate, []*template.Template, error) {
+	templates := make([]domain.PromptMessageTemplate, 0, len(rawMessages))
+	compiledMessages := make([]*template.Template, 0, len(rawMessages))
+	for index, message := range rawMessages {
+		path := base.Key("messages").Index(index)
+		if message.Role == nil {
+			return nil, nil, fmt.Errorf("%s: role is required", path.Key("role"))
+		}
+		if _, err := domain.NormalizeMessageRole(*message.Role); err != nil {
+			return nil, nil, fmt.Errorf("%s: %w", path.Key("role"), err)
+		}
+		if (message.Content != nil) == (message.ContentFile != nil) {
+			return nil, nil, fmt.Errorf("%s: exactly one of content or content_file is required", path)
+		}
+		content := ""
+		if message.Content != nil {
+			content = *message.Content
+		} else {
+			var err error
+			content, err = state.readContent(path.Key("content_file"), *message.ContentFile, lookupOrigin)
+			if err != nil {
+				return nil, nil, err
+			}
+		}
+		var control *domain.CacheControl
+		if message.CacheControl != nil {
+			if message.CacheControl.Type == nil {
+				return nil, nil, fmt.Errorf("%s: type is required", path.Key("cache_control").Key("type"))
+			}
+			control = &domain.CacheControl{Type: domain.CacheControlType(*message.CacheControl.Type)}
+			if message.CacheControl.TTL != nil {
+				control.TTL = *message.CacheControl.TTL
+			}
+			if _, err := domain.NormalizeCacheControl(control); err != nil {
+				return nil, nil, fmt.Errorf("%s: %w", path.Key("cache_control"), err)
+			}
+		}
+		compiled, err := prompt.CompileTemplate(fmt.Sprintf("msg_%d", index), content)
+		if err != nil {
+			return nil, nil, fmt.Errorf("%s: invalid template syntax: %w", path, err)
+		}
+		compiledMessages = append(compiledMessages, compiled)
+		templates = append(templates, domain.PromptMessageTemplate{
+			Role: *message.Role, Content: content, CacheControl: control,
+		})
+	}
+	return templates, compiledMessages, nil
+}
+
+func capturePromptOutput(output *promptOutputConfig, base configkit.Path) (domain.OutputContract, error) {
+	if output == nil {
+		return domain.OutputContract{}, fmt.Errorf("%s: output is required", base.Key("output"))
+	}
+	if output.Format == nil || output.ValidationMode == nil {
+		return domain.OutputContract{}, fmt.Errorf("%s: format and validation_mode are required", base.Key("output"))
+	}
+	contract := domain.OutputContract{
+		Format:         domain.OutputFormat(*output.Format),
+		ValidationMode: domain.ValidationMode(*output.ValidationMode),
+		RepairAttempts: output.RepairAttempts,
+	}
+	if output.SchemaPath != nil {
+		contract.SchemaPath = *output.SchemaPath
+	}
+	if err := domain.ValidateOutputContract(contract); err != nil {
+		return domain.OutputContract{}, fmt.Errorf("%s: invalid output contract: %w", base.Key("output"), err)
+	}
+	return contract, nil
+}
+
 func stringPointer(value string) *string {
 	copy := value
 	return &copy
@@ -305,12 +329,6 @@ func (state *loaded) GetPromptInspection(ctx context.Context, id string) (*domai
 	return ownPromptInspection(entry.inspection), nil
 }
 
-// GetPromptDefinition implements the runner's prompt lookup boundary.
-func (state *loaded) GetPromptDefinition(ctx context.Context, id string) (*domain.PromptDefinition, error) {
-	definition, _, err := state.GetPromptSnapshot(ctx, id)
-	return definition, err
-}
-
 // GetCompiledTemplates returns construction-time parses for one prompt ID.
 func (state *loaded) GetCompiledTemplates(id string) (prompt.CompiledTemplates, bool) {
 	if state == nil {

internal/configuration/targets.go

@@ -17,109 +17,115 @@ func (state *loaded) buildExecutionProfiles() error {
 	definitions := make(map[string]domain.Backend, len(backendConfigs))
 	for _, id := range sortedKeys(backendConfigs) {
 		config := backendConfigs[id]
-		definition := domain.Backend{ID: id, ExtraParams: config.ExtraParams}
-		if config.SmokeTests != nil {
-			smokeTests := &domain.BackendSmokeTestConfig{DefaultProfile: config.SmokeTests.DefaultProfile}
-			if config.SmokeTests.Reachability != nil {
-				smokeTests.Reachability = &domain.ReachabilityProbeConfig{Endpoint: config.SmokeTests.Reachability.Endpoint}
-			}
-			if config.SmokeTests.Authentication != nil {
-				smokeTests.Authentication = &domain.AuthenticationProbeConfig{
-					Kind:     config.SmokeTests.Authentication.Kind,
-					Endpoint: config.SmokeTests.Authentication.Endpoint,
-				}
-			}
-			definition.SmokeTests = smokeTests
-		}
-		if config.Endpoint != nil {
-			definition.Endpoint = *config.Endpoint
-		}
-		if config.APIKeyEnv != nil {
-			definition.APIKeyEnv = *config.APIKeyEnv
-		}
-		if config.ConcurrencyLimit != nil {
-			definition.ConcurrencyLimit = *config.ConcurrencyLimit
-		}
-		if config.QueueCapacity != nil {
-			definition.QueueCapacity = *config.QueueCapacity
-			definition.QueueCapacitySet = definition.ConcurrencyLimit > 0
-		}
-		definitions[id] = definition
+		definitions[id] = captureBackend(id, config)
 	}
-	registry, err := backend.NewEffectiveRegistry(definitions)
-	if err != nil {
-		return err
-	}
-	state.registry = registry
+	state.registry = backend.NewEffectiveRegistry(definitions)
 	state.indexedProfiles = make(map[string]domain.ExecutionProfile, len(profileConfigs))
 	for _, id := range sortedKeys(profileConfigs) {
 		config := profileConfigs[id]
-		fields := state.profiles[id]
-		target := defaults.ExecutionTargetDefault()
-		if config.Backend != nil && *config.Backend != "" {
-			selected, err := registry.GetBackend(*config.Backend)
-			if err != nil {
-				return fmt.Errorf("profile %q backend: %w", id, err)
-			}
-			target.BackendID = selected.ID
-			target.Endpoint = selected.Endpoint
-			target.APIKeyEnv = selected.APIKeyEnv
-			target.ExtraParams = selected.ExtraParams
+		profile, err := captureExecutionProfile(id, config, state.profiles[id], state.registry)
+		if err != nil {
+			return err
 		}
-		presence := domain.ExecutionTargetPresence{}
-		if fields["endpoint"] != fieldAbsent {
-			target.Endpoint = valueOrZero(config.Endpoint)
-		}
-		if fields["model"] != fieldAbsent {
-			target.Model = valueOrZero(config.Model)
-		}
-		if fields["temperature"] != fieldAbsent {
-			target.Temperature = valueOrZero(config.Temperature)
-			presence.Temperature = fields["temperature"] == fieldValue
-		}
-		if fields["top_p"] != fieldAbsent {
-			target.TopP = valueOrZero(config.TopP)
-			presence.TopP = fields["top_p"] == fieldValue
-		}
-		if fields["max_tokens"] != fieldAbsent {
-			target.MaxTokens = valueOrZero(config.MaxTokens)
-			presence.MaxTokens = fields["max_tokens"] == fieldValue
-		}
-		if fields["timeout_seconds"] == fieldValue {
-			target.TimeoutSeconds = valueOrZero(config.TimeoutSeconds)
-			presence.TimeoutSeconds = true
-		}
-		if fields["service_tier"] != fieldAbsent {
-			target.ServiceTier = valueOrZero(config.ServiceTier)
-		}
-		if fields["reasoning_effort"] != fieldAbsent {
-			target.ReasoningEffort = valueOrZero(config.ReasoningEffort)
-		}
-		if fields["api_key_env"] != fieldAbsent {
-			target.APIKeyEnv = valueOrZero(config.APIKeyEnv)
-		}
-		if fields["api_key_required"] != fieldAbsent {
-			target.APIKeyRequired = valueOrZero(config.APIKeyRequired)
-		}
-		if target.APIKeyRequired && fields["api_key_env"] == fieldAbsent {
-			target.APIKeyEnv = ""
-		}
-		switch fields["extra_params"] {
-		case fieldNull:
-			target.ExtraParams = nil
-		case fieldValue:
-			merged, err := overlayProviderMap(target.ExtraParams, config.ExtraParams)
-			if err != nil {
-				return fmt.Errorf("profile %q extra parameters: %w", id, err)
-			}
-			target.ExtraParams = merged
-		}
-		profile := domain.ExecutionProfile{ID: id, ResolvedTarget: &target, TargetPresence: presence}
 		state.indexedProfiles[id] = profile
 	}
 	return nil
 }
 
+func captureBackend(id string, config backendConfig) domain.Backend {
+	definition := domain.Backend{ID: id, ExtraParams: config.ExtraParams}
+	if config.SmokeTests != nil {
+		smokeTests := &domain.BackendSmokeTestConfig{DefaultProfile: config.SmokeTests.DefaultProfile}
+		if config.SmokeTests.Reachability != nil {
+			smokeTests.Reachability = &domain.ReachabilityProbeConfig{Endpoint: config.SmokeTests.Reachability.Endpoint}
+		}
+		if config.SmokeTests.Authentication != nil {
+			smokeTests.Authentication = &domain.AuthenticationProbeConfig{
+				Kind:     config.SmokeTests.Authentication.Kind,
+				Endpoint: config.SmokeTests.Authentication.Endpoint,
+			}
+		}
+		definition.SmokeTests = smokeTests
+	}
+	if config.Endpoint != nil {
+		definition.Endpoint = *config.Endpoint
+	}
+	if config.APIKeyEnv != nil {
+		definition.APIKeyEnv = *config.APIKeyEnv
+	}
+	if config.ConcurrencyLimit != nil {
+		definition.ConcurrencyLimit = *config.ConcurrencyLimit
+	}
+	if config.QueueCapacity != nil {
+		definition.QueueCapacity = *config.QueueCapacity
+	}
+	return definition
+}
+
+func captureExecutionProfile(id string, config profileConfig, fields map[string]fieldState, registry *backend.Registry) (domain.ExecutionProfile, error) {
+	target := defaults.ExecutionTargetDefault()
+	if config.Backend != nil && *config.Backend != "" {
+		selected, err := registry.GetBackend(*config.Backend)
+		if err != nil {
+			return domain.ExecutionProfile{}, fmt.Errorf("profile %q backend: %w", id, err)
+		}
+		target.BackendID = selected.ID
+		target.Endpoint = selected.Endpoint
+		target.APIKeyEnv = selected.APIKeyEnv
+		target.ExtraParams = selected.ExtraParams
+	}
+	presence := domain.ExecutionTargetPresence{}
+	if fields["endpoint"] != fieldAbsent {
+		target.Endpoint = valueOrZero(config.Endpoint)
+	}
+	if fields["model"] != fieldAbsent {
+		target.Model = valueOrZero(config.Model)
+	}
+	if fields["temperature"] != fieldAbsent {
+		target.Temperature = valueOrZero(config.Temperature)
+		presence.Temperature = fields["temperature"] == fieldValue
+	}
+	if fields["top_p"] != fieldAbsent {
+		target.TopP = valueOrZero(config.TopP)
+		presence.TopP = fields["top_p"] == fieldValue
+	}
+	if fields["max_tokens"] != fieldAbsent {
+		target.MaxTokens = valueOrZero(config.MaxTokens)
+		presence.MaxTokens = fields["max_tokens"] == fieldValue
+	}
+	if fields["timeout_seconds"] == fieldValue {
+		target.TimeoutSeconds = valueOrZero(config.TimeoutSeconds)
+		presence.TimeoutSeconds = true
+	}
+	if fields["service_tier"] != fieldAbsent {
+		target.ServiceTier = valueOrZero(config.ServiceTier)
+	}
+	if fields["reasoning_effort"] != fieldAbsent {
+		target.ReasoningEffort = valueOrZero(config.ReasoningEffort)
+	}
+	if fields["api_key_env"] != fieldAbsent {
+		target.APIKeyEnv = valueOrZero(config.APIKeyEnv)
+	}
+	if fields["api_key_required"] != fieldAbsent {
+		target.APIKeyRequired = valueOrZero(config.APIKeyRequired)
+	}
+	if target.APIKeyRequired && fields["api_key_env"] == fieldAbsent {
+		target.APIKeyEnv = ""
+	}
+	switch fields["extra_params"] {
+	case fieldNull:
+		target.ExtraParams = nil
+	case fieldValue:
+		merged, err := overlayProviderMap(target.ExtraParams, config.ExtraParams)
+		if err != nil {
+			return domain.ExecutionProfile{}, fmt.Errorf("profile %q extra parameters: %w", id, err)
+		}
+		target.ExtraParams = merged
+	}
+	profile := domain.ExecutionProfile{ID: id, ResolvedTarget: &target, TargetPresence: presence}
+	return profile, nil
+}
+
 func valueOrZero[T any](value *T) T {
 	if value == nil {
 		var zero T
@@ -138,24 +144,33 @@ func overlayProviderMap(lower, upper map[string]any) (map[string]any, error) {
 	if merged == nil {
 		merged = make(map[string]any)
 	}
+	if err := overlayOwnedProviderMap(merged, upper); err != nil {
+		return nil, err
+	}
+	return merged, nil
+}
+
+func overlayOwnedProviderMap(merged, upper map[string]any) error {
 	for key, value := range upper {
 		if child, ok := value.(map[string]any); ok {
 			if existing, ok := merged[key].(map[string]any); ok {
-				combined, err := overlayProviderMap(existing, child)
-				if err != nil {
-					return nil, err
+				if existing == nil {
+					existing = make(map[string]any)
+					merged[key] = existing
+				}
+				if err := overlayOwnedProviderMap(existing, child); err != nil {
+					return err
 				}
-				merged[key] = combined
 				continue
 			}
 		}
 		copied, err := jsonvalue.Copy(value)
 		if err != nil {
-			return nil, err
+			return err
 		}
 		merged[key] = copied
 	}
-	return merged, nil
+	return nil
 }
 
 func (state *loaded) lookupProfile(ctx context.Context, id string) (domain.ExecutionProfile, error) {
@@ -180,11 +195,7 @@ func (state *loaded) GetProfile(ctx context.Context, id string) (*domain.Executi
 		return nil, err
 	}
 	target := *profile.ResolvedTarget
-	params, err := jsonvalue.CopyMap(target.ExtraParams)
-	if err != nil {
-		return nil, err
-	}
-	target.ExtraParams = params
+	target.ExtraParams = jsonvalue.CloneTrusted(target.ExtraParams).(map[string]any)
 	profile.ResolvedTarget = &target
 	return &profile, nil
 }

internal/configuration/targets_test.go

@@ -42,6 +42,28 @@ func TestLoadIndexesIdentifiedTargets(t *testing.T) {
 	}
 }
 
+func TestOverlayProviderMapOwnsInputsAndReplacesValues(t *testing.T) {
+	lower := map[string]any{"nested": map[string]any{"keep": "lower", "replace": []any{"old"}, "null": "old"}, "disjoint": []any{"original"}}
+	upper := map[string]any{"nested": map[string]any{"replace": []any{"new"}, "null": nil, "added": map[string]any{"value": "upper"}}}
+	got, err := overlayProviderMap(lower, upper)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := map[string]any{"nested": map[string]any{"keep": "lower", "replace": []any{"new"}, "null": nil, "added": map[string]any{"value": "upper"}}, "disjoint": []any{"original"}}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("overlay = %#v", got)
+	}
+	lower["disjoint"].([]any)[0] = "changed"
+	upper["nested"].(map[string]any)["replace"].([]any)[0] = "changed"
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("overlay shares input storage: %#v", got)
+	}
+	got["nested"].(map[string]any)["added"].(map[string]any)["value"] = "changed"
+	if upper["nested"].(map[string]any)["added"].(map[string]any)["value"] != "upper" {
+		t.Fatal("result mutation reached upper")
+	}
+}
+
 func TestRequestCompletesLoadedPartialProfile(t *testing.T) {
 	state, err := load(mapping("partial profile", map[string]any{
 		"profiles": []any{map[string]any{"id": "partial"}},
@@ -53,7 +75,7 @@ func TestRequestCompletesLoadedPartialProfile(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	runner := usecase.NewRunner(state, state, nil, prompt.NewGoRenderer(), nil, nil, nil)
+	runner := usecase.NewRunner(state, state, nil, prompt.NewCompiledRenderer(state), nil, nil, nil)
 	prepared, err := runner.Prepare(context.Background(), domain.RunRequest{
 		PromptID: "example", ProfileID: "partial",
 		Execution: &domain.ExecutionTargetOverride{Endpoint: "https://example.invalid/v1", Model: "request-model"},
@@ -97,7 +119,7 @@ func TestLoadBuildsEffectiveTargetsAfterInheritance(t *testing.T) {
 		t.Fatal(err)
 	}
 	selected, err := state.registry.GetBackend("second")
-	if err != nil || selected.QueueCapacity != 0 || !selected.QueueCapacitySet {
+	if err != nil || selected.QueueCapacity != 0 || selected.ConcurrencyLimit != 2 {
 		t.Fatalf("backend capacity was not preserved: %+v, %v", selected, err)
 	}
 	child, err := state.GetProfile(context.Background(), "child")
@@ -197,10 +219,7 @@ func TestLoadedZeroControlsReachBuiltInRequest(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	client, err := llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{})
-	if err != nil {
-		t.Fatal(err)
-	}
+	client := llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{})
 	_, err = client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hello"}}},
 		Target: *profile.ResolvedTarget, TargetPresence: profile.TargetPresence,

internal/domain/domain.go

@@ -145,7 +145,6 @@ type PromptDefinition struct {
 	SessionID      string                  `yaml:"session_id" json:"session_id,omitempty"`
 	Inputs         []PromptInput           `yaml:"inputs"`
 	Templates      []PromptMessageTemplate `yaml:"templates"`
-	OutputFormat   OutputFormat            `yaml:"output_format"`
 	Validation     OutputContract          `yaml:"validation"`
 }
 
@@ -170,7 +169,6 @@ type PromptInput struct {
 type PromptMessageTemplate struct {
 	Role         string        `yaml:"role"`
 	Content      string        `yaml:"content"`
-	ContentFile  string        `yaml:"content_file"`
 	CacheControl *CacheControl `yaml:"cache_control,omitempty" json:"cache_control,omitempty"`
 }
 
@@ -184,7 +182,6 @@ type Backend struct {
 	SmokeTests       *BackendSmokeTestConfig
 	ConcurrencyLimit int
 	QueueCapacity    int
-	QueueCapacitySet bool
 }
 
 // BackendCapacityPolicy describes normalized run and generation capacity for

internal/domain/resource_identity.go

@@ -31,14 +31,6 @@ func qualifyResourceID(id, namespace string) (string, bool) {
 	return namespace + "/" + id, true
 }
 
-func resourceNamespaceFromID(id string) (string, bool) {
-	if !validResourceID(id) || !strings.Contains(id, "/") {
-		return "", false
-	}
-	namespace, _, _ := strings.Cut(id, "/")
-	return namespace, true
-}
-
 // IsValidResourceID reports whether id is an unqualified resource ID or one
 // valid namespace/local-ID pair.
 func IsValidResourceID(id string) bool { return validResourceID(id) }

internal/domain/resource_identity_test.go

@@ -86,25 +86,3 @@ func TestQualifyResourceID(t *testing.T) {
 		})
 	}
 }
-
-func TestResourceNamespaceFromID(t *testing.T) {
-	tests := []struct {
-		name      string
-		id        string
-		namespace string
-		wantOK    bool
-	}{
-		{name: "qualified", id: "team/item", namespace: "team", wantOK: true},
-		{name: "same-prefix namespace stays distinct", id: "team-extra/item", namespace: "team-extra", wantOK: true},
-		{name: "unqualified", id: "item", wantOK: false},
-		{name: "malformed", id: "team/sub/item", wantOK: false},
-	}
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			got, ok := resourceNamespaceFromID(test.id)
-			if got != test.namespace || ok != test.wantOK {
-				t.Fatalf("resourceNamespaceFromID(%q) = (%q, %t), want (%q, %t)", test.id, got, ok, test.namespace, test.wantOK)
-			}
-		})
-	}
-}

internal/domain/session.go

@@ -18,5 +18,5 @@ func NormalizeSessionID(raw string) (string, error) {
 	if length := utf8.RuneCountInString(normalized); length > SessionIDMaxLength {
 		return "", fmt.Errorf("session_id length %d exceeds maximum %d", length, SessionIDMaxLength)
 	}
-	return normalized, nil
+	return strings.Clone(normalized), nil
 }

internal/domain/smoke_diagnostics.go

@@ -112,24 +112,21 @@ type SmokeTestAttempt struct {
 type SmokeTestReason string
 
 const (
-	SmokeTestReasonNone                               SmokeTestReason = ""
-	SmokeTestReasonAuthenticationNotApplicable        SmokeTestReason = "authentication_not_applicable"
-	SmokeTestReasonProbeNotConfigured                 SmokeTestReason = "probe_not_configured"
-	SmokeTestReasonHTTPDiagnosticsUnavailable         SmokeTestReason = "http_diagnostics_unavailable"
-	SmokeTestReasonRequiredCredentialMissing          SmokeTestReason = "required_credential_missing"
-	SmokeTestReasonAuthenticationResponseUnrecognized SmokeTestReason = "authentication_response_unrecognized"
+	SmokeTestReasonNone                                SmokeTestReason = ""
+	SmokeTestReasonAuthenticationNotApplicable         SmokeTestReason = "authentication_not_applicable"
+	SmokeTestReasonProbeNotConfigured                  SmokeTestReason = "probe_not_configured"
+	SmokeTestReasonHTTPDiagnosticsUnavailable          SmokeTestReason = "http_diagnostics_unavailable"
+	SmokeTestReasonRequiredCredentialMissing           SmokeTestReason = "required_credential_missing"
+	SmokeTestReasonAuthenticationResponseUnrecognized  SmokeTestReason = "authentication_response_unrecognized"
+	SmokeTestReasonAuthenticationResponseLimitExceeded SmokeTestReason = "authentication_response_limit_exceeded"
 )
 
 // CloneBackend returns a copy of a backend, including its mutable settings.
-func CloneBackend(backend Backend) (Backend, error) {
+func CloneBackend(backend Backend) Backend {
 	cloned := backend
-	var err error
-	cloned.ExtraParams, err = jsonvalue.CopyMap(backend.ExtraParams)
-	if err != nil {
-		return Backend{}, err
-	}
+	cloned.ExtraParams = jsonvalue.CloneTrusted(backend.ExtraParams).(map[string]any)
 	cloned.SmokeTests = CloneBackendSmokeTestConfig(backend.SmokeTests)
-	return cloned, nil
+	return cloned
 }
 
 // CloneBackendSmokeTestConfig returns an independent copy of optional metadata.
@@ -153,105 +150,6 @@ func CloneBackendSmokeTestConfig(config *BackendSmokeTestConfig) *BackendSmokeTe
 	return &cloned
 }
 
-// CloneSmokeTestRequest returns a copy that owns its optional settings.
-func CloneSmokeTestRequest(request SmokeTestRequest) (SmokeTestRequest, error) {
-	cloned := request
-	cloned.TransientRetries = cloneInt(request.TransientRetries)
-	if request.Execution == nil {
-		return cloned, nil
-	}
-	execution := *request.Execution
-	execution.Temperature = cloneFloat64(request.Execution.Temperature)
-	execution.MaxTokens = cloneInt(request.Execution.MaxTokens)
-	execution.TopP = cloneFloat64(request.Execution.TopP)
-	execution.TimeoutSeconds = cloneInt(request.Execution.TimeoutSeconds)
-	execution.ReasoningEffort = cloneString(request.Execution.ReasoningEffort)
-	var err error
-	execution.ExtraParams, err = jsonvalue.CopyMap(request.Execution.ExtraParams)
-	if err != nil {
-		return SmokeTestRequest{}, err
-	}
-	cloned.Execution = &execution
-	return cloned, nil
-}
-
-// CloneSmokeTestReport returns a copy with independent optional facts and maps.
-func CloneSmokeTestReport(report SmokeTestReport) (SmokeTestReport, error) {
-	cloned := report
-	cloned.Applicable = cloneBool(report.Applicable)
-	cloned.Facts = cloneSmokeTestFacts(report.Facts)
-	cloned.Timing = cloneSmokeTestTiming(report.Timing)
-	var err error
-	cloned.Target.EffectiveSettings.ExtraParams, err = jsonvalue.CopyMap(report.Target.EffectiveSettings.ExtraParams)
-	if err != nil {
-		return SmokeTestReport{}, err
-	}
-	if report.Attempts != nil {
-		cloned.Attempts = make([]SmokeTestAttempt, len(report.Attempts))
-		for index, attempt := range report.Attempts {
-			cloned.Attempts[index] = attempt
-			cloned.Attempts[index].HTTPStatus = cloneInt(attempt.HTTPStatus)
-			cloned.Attempts[index].Facts = cloneSmokeTestFacts(attempt.Facts)
-			cloned.Attempts[index].Timing = cloneSmokeTestTiming(attempt.Timing)
-		}
-	}
-	return cloned, nil
-}
-
-func cloneSmokeTestFacts(facts SmokeTestFacts) SmokeTestFacts {
-	facts.CredentialsSupplied = cloneBool(facts.CredentialsSupplied)
-	facts.EndpointReachable = cloneBool(facts.EndpointReachable)
-	facts.CredentialsAccepted = cloneBool(facts.CredentialsAccepted)
-	facts.ResponseReceived = cloneBool(facts.ResponseReceived)
-	facts.GenerationCompleted = cloneBool(facts.GenerationCompleted)
-	facts.TextReturned = cloneBool(facts.TextReturned)
-	facts.ExpectedTextMatched = cloneBool(facts.ExpectedTextMatched)
-	facts.StructuredOutputRequested = cloneBool(facts.StructuredOutputRequested)
-	facts.ValidJSON = cloneBool(facts.ValidJSON)
-	facts.SchemaMatched = cloneBool(facts.SchemaMatched)
-	return facts
-}
-
-func cloneSmokeTestTiming(timing SmokeTestTiming) SmokeTestTiming {
-	timing.CapacityWait = cloneDuration(timing.CapacityWait)
-	timing.RequestDuration = cloneDuration(timing.RequestDuration)
-	timing.RetryDelay = cloneDuration(timing.RetryDelay)
-	timing.EvaluationDuration = cloneDuration(timing.EvaluationDuration)
-	return timing
-}
-
-func cloneBool(value *bool) *bool {
-	if value == nil {
-		return nil
-	}
-	cloned := *value
-	return &cloned
-}
-
-func cloneDuration(value *time.Duration) *time.Duration {
-	if value == nil {
-		return nil
-	}
-	cloned := *value
-	return &cloned
-}
-
-func cloneFloat64(value *float64) *float64 {
-	if value == nil {
-		return nil
-	}
-	cloned := *value
-	return &cloned
-}
-
-func cloneInt(value *int) *int {
-	if value == nil {
-		return nil
-	}
-	cloned := *value
-	return &cloned
-}
-
 func cloneString(value *string) *string {
 	if value == nil {
 		return nil

internal/domain/smoke_diagnostics_test.go

@@ -1,9 +1,6 @@
 package domain
 
-import (
-	"testing"
-	"time"
-)
+import "testing"
 
 func TestCloneBackendCopiesDiagnosticMetadataAndProviderValues(t *testing.T) {
 	profile := "profile"
@@ -22,10 +19,7 @@ func TestCloneBackendCopiesDiagnosticMetadataAndProviderValues(t *testing.T) {
 		},
 	}
 
-	cloned, err := CloneBackend(backend)
-	if err != nil {
-		t.Fatal(err)
-	}
+	cloned := CloneBackend(backend)
 	*cloned.SmokeTests.DefaultProfile = "changed"
 	*cloned.SmokeTests.Reachability.Endpoint = "changed"
 	*cloned.SmokeTests.Authentication.Kind = "changed"
@@ -41,72 +35,12 @@ func TestCloneBackendCopiesDiagnosticMetadataAndProviderValues(t *testing.T) {
 	}
 }
 
-func TestCloneSmokeTestRequestOwnsOptionalSettings(t *testing.T) {
-	temperature := 0.25
-	retries := 2
-	reasoning := "low"
-	request := SmokeTestRequest{
-		APIKey:           "secret",
-		TransientRetries: &retries,
-		Execution: &ExecutionTargetOverride{
-			Temperature:     &temperature,
-			ReasoningEffort: &reasoning,
-			ExtraParams:     map[string]any{"nested": map[string]any{"value": "original"}},
-		},
+func TestCloneBackendPreservesProviderMapPresence(t *testing.T) {
+	if cloned := CloneBackend(Backend{}); cloned.ExtraParams != nil {
+		t.Fatalf("nil provider map became %#v", cloned.ExtraParams)
 	}
-
-	cloned, err := CloneSmokeTestRequest(request)
-	if err != nil {
-		t.Fatal(err)
-	}
-	*cloned.TransientRetries = 3
-	*cloned.Execution.Temperature = 0.5
-	*cloned.Execution.ReasoningEffort = "high"
-	cloned.Execution.ExtraParams["nested"].(map[string]any)["value"] = "changed"
-
-	if retries != 2 || temperature != 0.25 || reasoning != "low" {
-		t.Fatal("cloned request shared optional scalar pointers")
-	}
-	if got := request.Execution.ExtraParams["nested"].(map[string]any)["value"]; got != "original" {
-		t.Fatalf("source provider parameter changed through clone: %v", got)
-	}
-}
-
-func TestCloneSmokeTestReportOwnsMutableValues(t *testing.T) {
-	applicable := true
-	reachable := true
-	status := 200
-	wait := 3 * time.Millisecond
-	report := SmokeTestReport{
-		Applicable: &applicable,
-		Target: SmokeTestTarget{
-			EffectiveSettings: ExecutionTarget{
-				ExtraParams: map[string]any{"nested": map[string]any{"value": "original"}},
-			},
-		},
-		Facts: SmokeTestFacts{EndpointReachable: &reachable},
-		Attempts: []SmokeTestAttempt{{
-			HTTPStatus: &status,
-			Facts:      SmokeTestFacts{EndpointReachable: &reachable},
-			Timing:     SmokeTestTiming{CapacityWait: &wait},
-		}},
-	}
-
-	cloned, err := CloneSmokeTestReport(report)
-	if err != nil {
-		t.Fatal(err)
-	}
-	*cloned.Applicable = false
-	*cloned.Facts.EndpointReachable = false
-	*cloned.Attempts[0].HTTPStatus = 503
-	*cloned.Attempts[0].Facts.EndpointReachable = false
-	*cloned.Attempts[0].Timing.CapacityWait = time.Second
-	cloned.Target.EffectiveSettings.ExtraParams["nested"].(map[string]any)["value"] = "changed"
-
-	if !applicable || !reachable || status != 200 || wait != 3*time.Millisecond {
-		t.Fatal("cloned report shared optional scalar pointers")
-	}
-	if got := report.Target.EffectiveSettings.ExtraParams["nested"].(map[string]any)["value"]; got != "original" {
-		t.Fatalf("source provider parameter changed through clone: %v", got)
+	cloned := CloneBackend(Backend{ExtraParams: map[string]any{"empty": map[string]any{}, "null": nil}})
+	if cloned.ExtraParams == nil || cloned.ExtraParams["empty"].(map[string]any) == nil || cloned.ExtraParams["null"] != nil {
+		t.Fatalf("provider map presence changed: %#v", cloned.ExtraParams)
 	}
 }

internal/engine/engine.go

@@ -43,7 +43,7 @@ type ConfigurationSources struct {
 type Options struct {
 	llmClient                llm.Client
 	artifactReader           artifact.Reader
-	validator                validate.Validator
+	validator                validate.ValidationPreparer
 	validatorSource          bool
 	artifactSource           bool
 	disableBundledOpenRouter bool
@@ -73,7 +73,7 @@ func (o *Options) SetSchemaFS(fsys fs.FS, root string) error {
 
 // SetSchemaFile selects a single schema file.
 func (o *Options) SetSchemaFile(path string) error {
-	fsys, root, _, err := fileSource(path)
+	fsys, root, err := fileSource(path)
 	if err != nil {
 		return err
 	}
@@ -98,9 +98,9 @@ type resourceNamespaces struct {
 }
 
 type identityInventory interface {
-	ListBackends(context.Context) ([]string, error)
-	ListProfiles(context.Context) ([]string, error)
-	ListPrompts(context.Context) ([]domain.PromptIdentity, error)
+	ListBackends(context.Context, configuration.IdentityFilter) ([]string, error)
+	ListProfiles(context.Context, configuration.IdentityFilter) ([]string, error)
+	ListPrompts(context.Context, configuration.IdentityFilter) ([]domain.PromptIdentity, error)
 	ListNamespaces(context.Context, []string) ([]string, error)
 	ListCollections(context.Context) ([]configuration.CollectionIdentity, error)
 }
@@ -157,10 +157,7 @@ func New(cfg Config, options Options) (*Engine, error) {
 	var client llm.Client
 	var diagnosticHTTPClient *llm.OpenAICompatibleClient
 	if options.llmClient == nil {
-		builtIn, newErr := llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{Timeout: cfg.Timeout, HTTPClient: cfg.HTTPClient})
-		if newErr != nil {
-			return nil, newErr
-		}
+		builtIn := llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{Timeout: cfg.Timeout, HTTPClient: cfg.HTTPClient})
 		diagnosticHTTPClient = builtIn
 		client = generation.NewBuiltIn(manager, builtIn)
 	} else {
@@ -208,23 +205,23 @@ func validateSourceFS(fsys fs.FS, root string) error {
 	return nil
 }
 
-func fileSource(name string) (fs.FS, string, string, error) {
+func fileSource(name string) (fs.FS, string, error) {
 	if strings.TrimSpace(name) == "" {
-		return nil, "", "", fmt.Errorf("source path is required")
+		return nil, "", fmt.Errorf("source path is required")
 	}
 	directory := filepath.Dir(name)
 	base := filepath.Base(name)
 	if base == "." || base == string(filepath.Separator) {
-		return nil, "", "", fmt.Errorf("source path must name a file")
+		return nil, "", fmt.Errorf("source path must name a file")
 	}
 	info, err := os.Stat(name)
 	if err != nil {
-		return nil, "", "", fmt.Errorf("failed to access source file %q: %w", name, err)
+		return nil, "", fmt.Errorf("failed to access source file %q: %w", name, err)
 	}
 	if info.IsDir() {
-		return nil, "", "", fmt.Errorf("source path %q must be a file", name)
+		return nil, "", fmt.Errorf("source path %q must be a file", name)
 	}
-	return os.DirFS(directory), filepath.ToSlash(base), directory, nil
+	return os.DirFS(directory), filepath.ToSlash(base), nil
 }
 
 func (e *Engine) InspectPrompt(ctx context.Context, id string) (*domain.PromptInspection, error) {
@@ -268,24 +265,11 @@ func (e *Engine) ListProfiles(ctx context.Context, filters ...ListingFilter) ([]
 }
 
 func (e *Engine) ListPrompts(ctx context.Context, filters ...ListingFilter) ([]domain.PromptIdentity, error) {
-	mode, namespace, err := resolveListingFilter(filters, e.namespaces.prompt)
+	filter, err := inventoryFilter(filters, e.namespaces.prompt)
 	if err != nil {
 		return nil, err
 	}
-	prompts, err := e.listing.ListPrompts(ctx)
-	if err != nil {
-		return nil, err
-	}
-	var filtered []domain.PromptIdentity
-	for _, prompt := range prompts {
-		if matchesListingNamespace(prompt.ID, mode, namespace) {
-			filtered = append(filtered, prompt)
-		}
-	}
-	if err := ctx.Err(); err != nil {
-		return nil, err
-	}
-	return filtered, nil
+	return e.listing.ListPrompts(ctx, filter)
 }
 
 func (e *Engine) ListNamespaces(ctx context.Context, kinds []string) ([]string, error) {
@@ -307,26 +291,21 @@ func filterIdentityList(
 	ctx context.Context,
 	filters []ListingFilter,
 	scope string,
-	list func(context.Context) ([]string, error),
+	list func(context.Context, configuration.IdentityFilter) ([]string, error),
 ) ([]string, error) {
+	filter, err := inventoryFilter(filters, scope)
+	if err != nil {
+		return nil, err
+	}
+	return list(ctx, filter)
+}
+
+func inventoryFilter(filters []ListingFilter, scope string) (configuration.IdentityFilter, error) {
 	mode, namespace, err := resolveListingFilter(filters, scope)
 	if err != nil {
-		return nil, err
+		return configuration.IdentityFilter{}, err
 	}
-	ids, err := list(ctx)
-	if err != nil {
-		return nil, err
-	}
-	var filtered []string
-	for _, id := range ids {
-		if matchesListingNamespace(id, mode, namespace) {
-			filtered = append(filtered, id)
-		}
-	}
-	if err := ctx.Err(); err != nil {
-		return nil, err
-	}
-	return filtered, nil
+	return configuration.IdentityFilter{All: mode == ListingAll, Namespace: namespace}, nil
 }
 
 func resolveListingFilter(filters []ListingFilter, scope string) (ListingFilterMode, string, error) {
@@ -355,19 +334,6 @@ func resolveListingFilter(filters []ListingFilter, scope string) (ListingFilterM
 	}
 }
 
-func matchesListingNamespace(id string, mode ListingFilterMode, namespace string) bool {
-	switch mode {
-	case ListingNamed:
-		idNamespace, _, qualified := strings.Cut(id, "/")
-		return qualified && idNamespace == namespace
-	case ListingUnqualified:
-		return !strings.Contains(id, "/")
-	case ListingAll:
-		return true
-	default:
-		return false
-	}
-}
 func (e *Engine) Prepare(ctx context.Context, request domain.RunRequest) (*domain.PreparedRun, error) {
 	request, err := e.qualifyRunRequest(request)
 	if err != nil {

internal/filecatalog/catalog.go

@@ -67,15 +67,6 @@ func FindFSYAMLFiles(ctx context.Context, fsys fs.FS, root string) ([]string, er
 	return files, err
 }
 
-// RelativePath computes a clean relative path from root to path.
-func RelativePath(root string, filePath string) string {
-	rel, err := filepath.Rel(root, filePath)
-	if err != nil {
-		return filepath.Clean(filePath)
-	}
-	return filepath.Clean(rel)
-}
-
 // CleanFSRoot normalizes a root path for use with fs.FS while preserving
 // nonblank leading and trailing whitespace.
 func CleanFSRoot(root string) string {

internal/filecatalog/catalog_test.go

@@ -81,16 +81,6 @@ func TestFindFSYAMLFilesHonorsContextCancellation(t *testing.T) {
 	}
 }
 
-func TestRelativePathNested(t *testing.T) {
-	root := t.TempDir()
-	path := filepath.Join(root, "nested", "profiles", "local.yaml")
-	got := RelativePath(root, path)
-	want := filepath.Join("nested", "profiles", "local.yaml")
-	if got != want {
-		t.Fatalf("expected relative path %q, got %q", want, got)
-	}
-}
-
 func TestCleanFSRoot(t *testing.T) {
 	tests := []struct {
 		name string

internal/generation/coordinator.go

@@ -85,6 +85,12 @@ func (c *Coordinator) GenerateWithEvidence(
 	return c.generate(ctx, req, true)
 }
 
+// PreparationError identifies a built-in request preparation failure.
+type PreparationError struct{ Cause error }
+
+func (e *PreparationError) Error() string { return e.Cause.Error() }
+func (e *PreparationError) Unwrap() error { return e.Cause }
+
 func (c *Coordinator) generate(
 	ctx context.Context,
 	req domain.GenerateRequest,
@@ -95,7 +101,7 @@ func (c *Coordinator) generate(
 	}
 	prepared, err := c.builtIn.PrepareGeneration(req)
 	if err != nil {
-		return nil, err, GenerationEvidence{}
+		return nil, &PreparationError{Cause: err}, GenerationEvidence{PreparationFailed: true}
 	}
 
 	evidence := GenerationEvidence{}
@@ -120,66 +126,37 @@ func (c *Coordinator) generate(
 			return finish(nil, err)
 		}
 		ordinal := attempts + 1
-		outcome, dispatched, capacityWait, generationDuration, startedAt := c.execute(ctx, req.Target.BackendID, prepared, captureEvidence)
-		if dispatched {
+		result := c.execute(ctx, req.Target.BackendID, prepared, captureEvidence)
+		if result.Dispatched {
 			attempts++
 		}
-		if captureEvidence {
-			attempt := AttemptEvidence{
-				StartedAt:           startedAt.UTC(),
-				Dispatched:          dispatched,
-				ResponseReceived:    outcome.Evidence.ResponseReceived,
-				HTTP:                cloneHTTPEvidence(outcome.Evidence),
-				CapacityWait:        capacityWait,
-				RequestDuration:     generationDuration,
-				Failure:             ClassifyFailure(outcome.Err),
-				ResponseDecoded:     outcome.ResponseDecoded,
-				GenerationCompleted: outcome.GenerationCompleted,
-			}
-			if outcome.StructuredOutputRequested != nil {
-				requested := *outcome.StructuredOutputRequested
-				attempt.StructuredOutputRequested = &requested
-			}
-			if dispatched {
-				usage.Add(outcome.Usage, outcome.UsagePresence)
-				var attemptUsage observation.UsageAccumulator
-				attemptUsage.Add(outcome.Usage, outcome.UsagePresence)
-				attempt.Usage = attemptUsage.Observed()
-			}
-			evidence.Attempts = append(evidence.Attempts, attempt)
-		}
-		if recorder != nil {
-			recorder.Attempt(observation.AttemptData{Generation: generation, Attempt: ordinal,
-				Dispatched: dispatched, CapacityWait: capacityWait, GenerationDuration: generationDuration,
-				Outcome: attemptOutcome(outcome.Err), Failure: ClassifyFailure(outcome.Err),
-				StatusCode: outcome.StatusCode, Usage: outcome.Usage, UsagePresence: outcome.UsagePresence})
-		}
-		if outcome.Err == nil {
+		recordAttempt(result, false, captureEvidence, &evidence, &usage, recorder, generation, ordinal)
+		if result.Outcome.Err == nil {
 			if err := ctx.Err(); err != nil {
 				if captureEvidence {
-					return finish(outcome.Response, err)
+					return finish(result.Outcome.Response, err)
 				}
 				return finish(nil, err)
 			}
-			return finish(outcome.Response, nil)
+			return finish(result.Outcome.Response, nil)
 		}
-		if !dispatched || !eligibleStatus(outcome) {
+		if !result.Dispatched || !eligibleStatus(result.Outcome) {
 			if captureEvidence {
-				return finish(outcome.Response, outcome.Err)
+				return finish(result.Outcome.Response, result.Outcome.Err)
 			}
-			return finish(nil, outcome.Err)
+			return finish(nil, result.Outcome.Err)
 		}
 		if retriesUsed == req.TransientRetries {
 			if retriesUsed == 0 {
-				return finish(nil, outcome.Err)
+				return finish(nil, result.Outcome.Err)
 			}
-			return finish(nil, &ExhaustedError{attempts: attempts, cause: outcome.Err})
+			return finish(nil, &ExhaustedError{attempts: attempts, cause: result.Outcome.Err})
 		}
 		if err := ctx.Err(); err != nil {
 			return finish(nil, err)
 		}
 		retryOrdinal := retriesUsed + 1
-		delay := retryDelay(c.backoff(retryOrdinal), outcome.RetryNotBefore, c.now())
+		delay := retryDelay(c.backoff(retryOrdinal), result.Outcome.RetryNotBefore, c.now())
 		waitStart := c.now()
 		waitErr := c.wait(ctx, delay)
 		waitDuration := elapsed(waitStart, c.now())
@@ -200,127 +177,133 @@ func (c *Coordinator) generate(
 	}
 }
 
-func (c *Coordinator) generateInjected(
-	ctx context.Context,
-	req domain.GenerateRequest,
-	captureEvidence bool,
-) (*domain.GenerateResponse, error, GenerationEvidence) {
+func (c *Coordinator) generateInjected(ctx context.Context, req domain.GenerateRequest, captureEvidence bool) (*domain.GenerateResponse, error, GenerationEvidence) {
 	evidence := GenerationEvidence{}
 	var usage observation.UsageAccumulator
-	finish := func(response *domain.GenerateResponse, err error) (*domain.GenerateResponse, error, GenerationEvidence) {
-		if captureEvidence {
-			evidence.Usage = usage.Observed()
-		}
-		return response, err, evidence
-	}
-	recorder := observation.FromContext(ctx)
 	generation := req.Generation
 	if generation == 0 {
 		generation = 1
 	}
-	start := c.now()
-	release, err := c.manager.Acquire(ctx, req.Target.BackendID)
-	capacityWait := c.capacityWait(req.Target.BackendID, start)
-	if err != nil {
-		if captureEvidence {
-			evidence.Attempts = append(evidence.Attempts, AttemptEvidence{
-				StartedAt:    start.UTC(),
-				CapacityWait: capacityWait,
-				Failure:      ClassifyFailure(err),
-			})
-		}
-		if recorder != nil {
-			recorder.Attempt(observation.AttemptData{Generation: generation, Attempt: 1, CapacityWait: capacityWait, Outcome: domain.ExecutionOutcomeError, Failure: ClassifyFailure(err)})
-		}
-		return finish(nil, err)
-	}
-	defer release()
-	if err := ctx.Err(); err != nil {
-		release()
-		if captureEvidence {
-			evidence.Attempts = append(evidence.Attempts, AttemptEvidence{
-				StartedAt:    start.UTC(),
-				CapacityWait: capacityWait,
-				Failure:      ClassifyFailure(err),
-			})
-		}
-		if recorder != nil {
-			recorder.Attempt(observation.AttemptData{Generation: generation, Attempt: 1, CapacityWait: capacityWait, Outcome: domain.ExecutionOutcomeError, Failure: ClassifyFailure(err)})
-		}
-		return finish(nil, err)
-	}
-	dispatchStart := c.now()
-	response, err := c.injected.Generate(ctx, req)
-	duration := elapsed(dispatchStart, c.now())
-	if err == nil && response == nil {
-		err = llm.ErrMalformedResponse
-	}
+	result := c.executeInjected(ctx, req)
+	recordAttempt(result, true, captureEvidence, &evidence, &usage, observation.FromContext(ctx), generation, 1)
 	if captureEvidence {
-		attempt := AttemptEvidence{
-			StartedAt:           start.UTC(),
-			Dispatched:          true,
-			ResponseReceived:    response != nil,
-			RequestDuration:     duration,
-			Failure:             ClassifyFailure(err),
-			GenerationCompleted: err == nil && response != nil,
-		}
-		requested := req.StructuredOutput != nil
-		attempt.StructuredOutputRequested = &requested
-		var reportedUsage domain.TokenUsage
-		var reportedPresence *domain.TokenUsagePresence
-		if err == nil && response != nil {
-			reportedUsage = response.Usage
-			reportedPresence = response.UsagePresence
-		}
-		usage.Add(reportedUsage, reportedPresence)
-		var attemptUsage observation.UsageAccumulator
-		attemptUsage.Add(reportedUsage, reportedPresence)
-		attempt.Usage = attemptUsage.Observed()
-		evidence.Attempts = append(evidence.Attempts, attempt)
+		evidence.Usage = usage.Observed()
 	}
-	release()
-	if recorder != nil {
-		data := observation.AttemptData{Generation: generation, Attempt: 1, Dispatched: true, CapacityWait: capacityWait, GenerationDuration: duration,
-			Outcome: attemptOutcome(err), Failure: ClassifyFailure(err)}
-		if err == nil {
-			data.Usage = response.Usage
-			data.UsagePresence = response.UsagePresence
-		}
-		recorder.Attempt(data)
-	}
-	if err != nil {
-		return finish(nil, err)
+	if result.Outcome.Err != nil {
+		return nil, result.Outcome.Err, evidence
 	}
 	if err := ctx.Err(); err != nil {
 		if captureEvidence {
-			return finish(response, err)
+			return result.Outcome.Response, err, evidence
 		}
-		return finish(nil, err)
+		return nil, err, evidence
 	}
-	return finish(response, nil)
+	return result.Outcome.Response, nil, evidence
 }
 
-func (c *Coordinator) execute(ctx context.Context, backendID string, prepared *llm.PreparedGeneration, captureEvidence bool) (outcome llm.AttemptOutcome, dispatched bool, capacityWait, generationDuration time.Duration, startedAt time.Time) {
-	start := c.now()
-	startedAt = start
-	release, err := c.manager.Acquire(ctx, backendID)
-	capacityWait = c.capacityWait(backendID, start)
+func (c *Coordinator) executeInjected(ctx context.Context, req domain.GenerateRequest) attemptResult {
+	result := attemptResult{StartedAt: c.now()}
+	release, err := c.manager.Acquire(ctx, req.Target.BackendID)
+	result.CapacityWait = c.capacityWait(req.Target.BackendID, result.StartedAt)
 	if err != nil {
-		return llm.AttemptOutcome{Err: err}, false, capacityWait, 0, startedAt
+		result.Outcome.Err = err
+		return result
 	}
 	defer release()
 	if err := ctx.Err(); err != nil {
-		return llm.AttemptOutcome{Err: err}, false, capacityWait, 0, startedAt
+		result.Outcome.Err = err
+		return result
+	}
+	start := c.now()
+	result.Dispatched = true
+	requested := req.StructuredOutput != nil
+	result.Outcome.StructuredOutputRequested = &requested
+	result.Outcome.Response, result.Outcome.Err = c.injected.Generate(ctx, req)
+	result.RequestDuration = elapsed(start, c.now())
+	if result.Outcome.Err == nil && result.Outcome.Response == nil {
+		result.Outcome.Err = llm.ErrMalformedResponse
+	}
+	if result.Outcome.Err == nil {
+		result.Outcome.Usage = result.Outcome.Response.Usage
+		result.Outcome.UsagePresence = result.Outcome.Response.UsagePresence
+	}
+	return result
+}
+
+type attemptResult struct {
+	Outcome         llm.AttemptOutcome
+	Dispatched      bool
+	CapacityWait    time.Duration
+	RequestDuration time.Duration
+	StartedAt       time.Time
+}
+
+// recordAttempt runs after the attempt has released its permit, including when
+// the recorder calls application code. Injected clients expose no HTTP facts.
+func recordAttempt(result attemptResult, injected, capture bool, evidence *GenerationEvidence, usage *observation.UsageAccumulator, recorder *observation.Recorder, generation, ordinal uint64) {
+	outcome := result.Outcome
+	failure := ClassifyFailure(outcome.Err)
+	if capture {
+		attempt := AttemptEvidence{
+			StartedAt: result.StartedAt.UTC(), Dispatched: result.Dispatched,
+			CapacityWait: result.CapacityWait, RequestDuration: result.RequestDuration,
+			Failure: failure,
+		}
+		if injected {
+			attempt.ResponseReceived = outcome.Response != nil
+			attempt.GenerationCompleted = outcome.Err == nil && outcome.Response != nil
+			if result.Dispatched {
+				attempt.CapacityWait = 0
+			}
+		} else {
+			attempt.ResponseReceived = outcome.Evidence.ResponseReceived
+			attempt.HTTP = cloneHTTPEvidence(outcome.Evidence)
+			attempt.ResponseDecoded = outcome.ResponseDecoded
+			attempt.GenerationCompleted = outcome.GenerationCompleted
+		}
+		if outcome.StructuredOutputRequested != nil {
+			requested := *outcome.StructuredOutputRequested
+			attempt.StructuredOutputRequested = &requested
+		}
+		if result.Dispatched {
+			usage.Add(outcome.Usage, outcome.UsagePresence)
+			var single observation.UsageAccumulator
+			single.Add(outcome.Usage, outcome.UsagePresence)
+			attempt.Usage = single.Observed()
+		}
+		evidence.Attempts = append(evidence.Attempts, attempt)
+	}
+	if recorder != nil {
+		recorder.Attempt(observation.AttemptData{Generation: generation, Attempt: ordinal,
+			Dispatched: result.Dispatched, CapacityWait: result.CapacityWait, GenerationDuration: result.RequestDuration,
+			Outcome: attemptOutcome(outcome.Err), Failure: failure, StatusCode: outcome.StatusCode,
+			Usage: outcome.Usage, UsagePresence: outcome.UsagePresence})
+	}
+}
+
+func (c *Coordinator) execute(ctx context.Context, backendID string, prepared *llm.PreparedGeneration, captureEvidence bool) attemptResult {
+	result := attemptResult{StartedAt: c.now()}
+	release, err := c.manager.Acquire(ctx, backendID)
+	result.CapacityWait = c.capacityWait(backendID, result.StartedAt)
+	if err != nil {
+		result.Outcome.Err = err
+		return result
+	}
+	defer release()
+	if err := ctx.Err(); err != nil {
+		result.Outcome.Err = err
+		return result
 	}
 	dispatchStart := c.now()
 	if captureEvidence {
-		outcome = prepared.ExecuteWithEvidence(ctx)
-		dispatched = outcome.Evidence.DispatchInvoked
+		result.Outcome = prepared.ExecuteWithEvidence(ctx)
+		result.Dispatched = result.Outcome.Evidence.DispatchInvoked
 	} else {
-		outcome = prepared.Execute(ctx)
-		dispatched = true
+		result.Outcome = prepared.Execute(ctx)
+		result.Dispatched = true
 	}
-	return outcome, dispatched, capacityWait, elapsed(dispatchStart, c.now()), startedAt
+	result.RequestDuration = elapsed(dispatchStart, c.now())
+	return result
 }
 
 func (c *Coordinator) capacityWait(backendID string, start time.Time) time.Duration {

internal/generation/coordinator_test.go

@@ -40,10 +40,7 @@ func testCoordinator(t *testing.T, transport transportFunc) *Coordinator {
 	if err != nil {
 		t.Fatal(err)
 	}
-	client, err := llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{HTTPClient: &http.Client{Transport: transport}})
-	if err != nil {
-		t.Fatal(err)
-	}
+	client := llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{HTTPClient: &http.Client{Transport: transport}})
 	coordinator := NewBuiltIn(manager, client)
 	coordinator.jitter = func(time.Duration) time.Duration { return 0 }
 	coordinator.wait = func(ctx context.Context, _ time.Duration) error { return ctx.Err() }

internal/generation/evidence.go

@@ -10,6 +10,8 @@ import (
 // GenerationEvidence contains invocation-local request evidence without raw
 // provider bodies, headers, credentials, or generated content.
 type GenerationEvidence struct {
+	// PreparationFailed identifies a built-in request rejected before attempts.
+	PreparationFailed bool
 	// InitialEndpoint is the frozen built-in request URL, if prepared.
 	// Injected generation leaves it unknown.
 	InitialEndpoint string

internal/generation/observation_test.go

@@ -144,6 +144,32 @@ func (c fixedClient) Generate(context.Context, domain.GenerateRequest) (*domain.
 	return c.response, c.err
 }
 
+func TestInjectedObserverRunsAfterPermitRelease(t *testing.T) {
+	configured := testCoordinator(t, func(*http.Request) (*http.Response, error) { t.Fatal("unexpected HTTP request"); return nil, nil })
+	coordinator := NewInjected(configured.manager, fixedClient{response: &domain.GenerateResponse{}})
+	called := false
+	recorder, err := observation.New(func(event domain.ExecutionEvent) {
+		if event.Kind != domain.ExecutionAttempt {
+			return
+		}
+		called = true
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+		defer cancel()
+		release, err := coordinator.manager.Acquire(ctx, "limited")
+		if err != nil {
+			t.Errorf("observer could not acquire permit: %v", err)
+			return
+		}
+		release()
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := coordinator.Generate(observation.WithRecorder(context.Background(), recorder), testRequest(0)); err != nil || !called {
+		t.Fatalf("generation error = %v, observer called = %v", err, called)
+	}
+}
+
 func TestObservedInjectedUsageAndRepairGeneration(t *testing.T) {
 	manager, err := capacity.NewManager(nil)
 	if err != nil {

internal/jsonvalue/trusted.go

@@ -0,0 +1,97 @@
+package jsonvalue
+
+import "reflect"
+
+func cloneTrustedMap(src map[string]any) map[string]any {
+	if src == nil {
+		return nil
+	}
+	out := make(map[string]any, len(src))
+	for k, v := range src {
+		out[k] = CloneTrusted(v)
+	}
+	return out
+}
+
+// CloneTrusted detaches a previously accepted value without revalidating it.
+func CloneTrusted(value any) any {
+	if value == nil {
+		return nil
+	}
+	switch v := value.(type) {
+	case map[string]any:
+		return cloneTrustedMap(v)
+	case []any:
+		out := make([]any, len(v))
+		for i, item := range v {
+			out[i] = CloneTrusted(item)
+		}
+		return out
+	case []string:
+		if v == nil {
+			return []string(nil)
+		}
+		return append([]string{}, v...)
+	case []byte:
+		if v == nil {
+			return []byte(nil)
+		}
+		return append([]byte{}, v...)
+	default:
+		return cloneTrustedReflect(reflect.ValueOf(value)).Interface()
+	}
+}
+
+func cloneTrustedReflect(value reflect.Value) reflect.Value {
+	if !value.IsValid() {
+		return value
+	}
+
+	switch value.Kind() {
+	case reflect.Interface:
+		if value.IsNil() {
+			return reflect.Zero(value.Type())
+		}
+		copied := cloneTrustedReflect(value.Elem())
+		if copied.IsValid() && copied.Type().AssignableTo(value.Type()) {
+			return copied
+		}
+		out := reflect.New(value.Type()).Elem()
+		out.Set(copied)
+		return out
+	case reflect.Pointer:
+		if value.IsNil() {
+			return reflect.Zero(value.Type())
+		}
+		out := reflect.New(value.Type().Elem())
+		out.Elem().Set(cloneTrustedReflect(value.Elem()))
+		return out
+	case reflect.Map:
+		if value.IsNil() {
+			return reflect.Zero(value.Type())
+		}
+		out := reflect.MakeMapWithSize(value.Type(), value.Len())
+		iter := value.MapRange()
+		for iter.Next() {
+			out.SetMapIndex(cloneTrustedReflect(iter.Key()), cloneTrustedReflect(iter.Value()))
+		}
+		return out
+	case reflect.Slice:
+		if value.IsNil() {
+			return reflect.Zero(value.Type())
+		}
+		out := reflect.MakeSlice(value.Type(), value.Len(), value.Cap())
+		for i := 0; i < value.Len(); i++ {
+			out.Index(i).Set(cloneTrustedReflect(value.Index(i)))
+		}
+		return out
+	case reflect.Array:
+		out := reflect.New(value.Type()).Elem()
+		for i := 0; i < value.Len(); i++ {
+			out.Index(i).Set(cloneTrustedReflect(value.Index(i)))
+		}
+		return out
+	default:
+		return value
+	}
+}

internal/jsonvalue/trusted_test.go

@@ -0,0 +1,27 @@
+package jsonvalue
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+)
+
+type trustedNamed string
+
+func TestCloneTrustedPreservesTypesAndDetaches(t *testing.T) {
+	named := trustedNamed("value")
+	original := map[string]any{"": map[string]any{"number": json.Number("9007199254740993")}, "typed": []string{"original"}, "pointer": &named, "nilmap": map[string]any(nil), "nilslice": []string(nil), "empty": []any{}}
+	copy := CloneTrusted(original).(map[string]any)
+	if !reflect.DeepEqual(copy, original) {
+		t.Fatalf("clone = %#v", copy)
+	}
+	copy[""].(map[string]any)["number"] = json.Number("1")
+	copy["typed"].([]string)[0] = "changed"
+	*copy["pointer"].(*trustedNamed) = "changed"
+	if original[""].(map[string]any)["number"] != json.Number("9007199254740993") || original["typed"].([]string)[0] != "original" || named != "value" {
+		t.Fatal("clone shares mutable storage")
+	}
+	if copy["nilmap"].(map[string]any) != nil || copy["nilslice"].([]string) != nil || copy["empty"].([]any) == nil {
+		t.Fatal("nil/empty shape changed")
+	}
+}

internal/llm/http_evidence_test.go

@@ -25,10 +25,7 @@ func TestGetWithEvidenceCapturesResponseAndOmitsURLUserInfo(t *testing.T) {
 	}))
 	defer server.Close()
 
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{Timeout: time.Second})
-	if err != nil {
-		t.Fatalf("construct client: %v", err)
-	}
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{Timeout: time.Second})
 	endpoint := strings.Replace(server.URL, "http://", "http://user:secret@", 1) + "/health"
 	response, evidence, err := client.GetWithEvidence(context.Background(), endpoint, 0)
 	if err != nil {
@@ -88,7 +85,7 @@ func TestGetWithAuthenticationEvidenceResolvesOptionalCredentials(t *testing.T)
 		t.Run(tc.name, func(t *testing.T) {
 			t.Setenv("PROMPTKIT_DIAGNOSTIC_KEY", tc.environment)
 			var authorization string
-			client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 				HTTPClient: &http.Client{Transport: roundTripFunc(func(request *http.Request) (*http.Response, error) {
 					authorization = request.Header.Get("Authorization")
 					return &http.Response{
@@ -98,9 +95,6 @@ func TestGetWithAuthenticationEvidenceResolvesOptionalCredentials(t *testing.T)
 					}, nil
 				})},
 			})
-			if err != nil {
-				t.Fatal(err)
-			}
 
 			response, evidence, err := client.GetWithAuthenticationEvidence(
 				context.Background(), "https://example.invalid/key", 0, tc.target,
@@ -269,10 +263,7 @@ func TestGetWithEvidencePreservesClientAndIsolatesConcurrentCalls(t *testing.T)
 
 	transport := http.DefaultTransport
 	supplied := &http.Client{Transport: transport, Timeout: 7 * time.Second, CheckRedirect: redirect, Jar: jar}
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{HTTPClient: supplied})
-	if err != nil {
-		t.Fatalf("construct client: %v", err)
-	}
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{HTTPClient: supplied})
 
 	const calls = 8
 	evidences := make([]HTTPExecutionEvidence, calls)
@@ -307,15 +298,12 @@ func TestGetWithEvidencePreservesClientAndIsolatesConcurrentCalls(t *testing.T)
 }
 
 func TestGetWithEvidenceAppliesTargetTimeout(t *testing.T) {
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{Timeout: 5 * time.Second, HTTPClient: &http.Client{
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{Timeout: 5 * time.Second, HTTPClient: &http.Client{
 		Transport: roundTripFunc(func(request *http.Request) (*http.Response, error) {
 			<-request.Context().Done()
 			return nil, request.Context().Err()
 		}),
 	}})
-	if err != nil {
-		t.Fatalf("construct client: %v", err)
-	}
 
 	response, evidence, err := client.GetWithEvidence(context.Background(), "https://diagnostic.example/slow", 1)
 	if response != nil || !errors.Is(err, context.DeadlineExceeded) {

internal/llm/openai_compatible_client.go

@@ -17,10 +17,10 @@ import (
 
 	"go.maximumdirect.net/promptkit/internal/defaults"
 	"go.maximumdirect.net/promptkit/internal/domain"
+	"go.maximumdirect.net/promptkit/internal/jsonvalue"
 )
 
 var (
-	ErrInvalidConfig     = errors.New("invalid llm client configuration")
 	ErrInvalidRequest    = errors.New("invalid generate request")
 	ErrRequestFailed     = errors.New("llm request failed")
 	ErrTransport         = errors.New("llm transport failed")
@@ -43,28 +43,15 @@ func (e *requestFailedError) Unwrap() []error {
 }
 
 type OpenAICompatibleConfig struct {
-	BaseURL    string
-	Model      string
 	Timeout    time.Duration
 	HTTPClient *http.Client
 }
 
 type OpenAICompatibleClient struct {
-	baseURL      string
-	defaultModel string
-	httpClient   *http.Client
+	httpClient *http.Client
 }
 
-func NewOpenAICompatibleClient(cfg OpenAICompatibleConfig) (*OpenAICompatibleClient, error) {
-	baseURL := ""
-	if strings.TrimSpace(cfg.BaseURL) != "" {
-		var err error
-		baseURL, err = domain.NormalizeOpenAICompatibleBaseEndpoint(cfg.BaseURL)
-		if err != nil {
-			return nil, fmt.Errorf("%w: invalid base URL: %v", ErrInvalidConfig, err)
-		}
-	}
-
+func NewOpenAICompatibleClient(cfg OpenAICompatibleConfig) *OpenAICompatibleClient {
 	timeout := cfg.Timeout
 	if timeout <= 0 {
 		timeout = defaults.LLMRequestTimeoutDefault
@@ -82,10 +69,8 @@ func NewOpenAICompatibleClient(cfg OpenAICompatibleConfig) (*OpenAICompatibleCli
 	}
 
 	return &OpenAICompatibleClient{
-		baseURL:      baseURL,
-		defaultModel: cfg.Model,
-		httpClient:   client,
-	}, nil
+		httpClient: client,
+	}
 }
 
 func (c *OpenAICompatibleClient) Generate(ctx context.Context, req domain.GenerateRequest) (*domain.GenerateResponse, error) {
@@ -132,11 +117,7 @@ func (c *OpenAICompatibleClient) PrepareGeneration(req domain.GenerateRequest) (
 		return nil, fmt.Errorf("%w: %v", ErrInvalidRequest, err)
 	}
 
-	selectedEndpoint := req.Target.Endpoint
-	if strings.TrimSpace(selectedEndpoint) == "" {
-		selectedEndpoint = c.baseURL
-	}
-	endpoint, err := domain.NormalizeOpenAICompatibleBaseEndpoint(selectedEndpoint)
+	endpoint, err := domain.NormalizeOpenAICompatibleBaseEndpoint(req.Target.Endpoint)
 	if err != nil {
 		return nil, fmt.Errorf("%w: invalid endpoint: %v", ErrInvalidRequest, err)
 	}
@@ -145,12 +126,10 @@ func (c *OpenAICompatibleClient) PrepareGeneration(req domain.GenerateRequest) (
 		return nil, fmt.Errorf("%w: invalid endpoint path: %v", ErrInvalidRequest, err)
 	}
 
-	wireReq, err := openAIChatRequestFromGenerateRequest(req, c.defaultModel)
-	if err != nil {
-		return nil, fmt.Errorf("%w: %v", ErrInvalidRequest, err)
-	}
-
-	wirePayload, err := openAIChatRequestPayload(wireReq)
+	// Custom JSON encoders may mutate their receivers. Both payload encoding
+	// and encoding-failure diagnostics must use values detached from metadata.
+	req.Target.ExtraParams = jsonvalue.CloneTrusted(req.Target.ExtraParams).(map[string]any)
+	wirePayload, err := openAIChatRequestPayload(req)
 	if err != nil {
 		return nil, fmt.Errorf("%w: %v", ErrInvalidRequest, err)
 	}
@@ -179,7 +158,7 @@ func (c *OpenAICompatibleClient) PrepareGeneration(req domain.GenerateRequest) (
 	return &PreparedGeneration{
 		endpoint: endpoint, payload: payload, apiKey: apiKey,
 		timeoutSeconds: req.Target.TimeoutSeconds, httpClient: httpClient,
-		structuredOutputRequested: wireReq.ResponseFormat != nil,
+		structuredOutputRequested: wirePayload["response_format"] != nil,
 	}, nil
 }
 
@@ -370,40 +349,69 @@ func tokenCount(value *int) int {
 	return *value
 }
 
+type responseErrorReader struct {
+	reader io.Reader
+	err    error
+}
+
+func (r *responseErrorReader) Read(p []byte) (int, error) {
+	n, err := r.reader.Read(p)
+	if err != nil && !errors.Is(err, io.EOF) {
+		r.err = err
+	}
+	return n, err
+}
+
 func decodeOpenAIChatResponse(body io.Reader) (openAIChatResponse, error) {
+	observed := &responseErrorReader{reader: body}
 	limited := &io.LimitedReader{
-		R: body,
+		R: observed,
 		N: maxOpenAIChatResponseBytes + 1,
 	}
 	decoder := json.NewDecoder(limited)
 
 	var response openAIChatResponse
 	if err := decoder.Decode(&response); err != nil {
-		if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
-			return openAIChatResponse{}, &requestFailedError{cause: err}
+		if errors.Is(observed.err, context.Canceled) || errors.Is(observed.err, context.DeadlineExceeded) {
+			return openAIChatResponse{}, &requestFailedError{cause: observed.err}
 		}
 		if limited.N == 0 {
 			return openAIChatResponse{}, openAIChatResponseTooLargeError()
 		}
+		if observed.err != nil {
+			return openAIChatResponse{}, &requestFailedError{cause: observed.err}
+		}
 		return openAIChatResponse{}, fmt.Errorf("%w: failed to decode response", ErrMalformedResponse)
 	}
+	if errors.Is(observed.err, context.Canceled) || errors.Is(observed.err, context.DeadlineExceeded) {
+		return openAIChatResponse{}, &requestFailedError{cause: observed.err}
+	}
 	if limited.N == 0 {
 		return openAIChatResponse{}, openAIChatResponseTooLargeError()
 	}
 
 	var trailing any
 	if err := decoder.Decode(&trailing); !errors.Is(err, io.EOF) {
-		if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
-			return openAIChatResponse{}, &requestFailedError{cause: err}
+		if errors.Is(observed.err, context.Canceled) || errors.Is(observed.err, context.DeadlineExceeded) {
+			return openAIChatResponse{}, &requestFailedError{cause: observed.err}
 		}
 		if limited.N == 0 {
 			return openAIChatResponse{}, openAIChatResponseTooLargeError()
 		}
+		if observed.err != nil {
+			return openAIChatResponse{}, &requestFailedError{cause: observed.err}
+		}
 		return openAIChatResponse{}, fmt.Errorf("%w: response contains trailing data", ErrMalformedResponse)
 	}
+	if errors.Is(observed.err, context.Canceled) || errors.Is(observed.err, context.DeadlineExceeded) {
+		return openAIChatResponse{}, &requestFailedError{cause: observed.err}
+	}
 	if limited.N == 0 {
 		return openAIChatResponse{}, openAIChatResponseTooLargeError()
 	}
+	if observed.err != nil {
+		return openAIChatResponse{}, &requestFailedError{cause: observed.err}
+	}
 
 	return response, nil
 }
@@ -416,99 +424,52 @@ func openAIChatResponseTooLargeError() error {
 	)
 }
 
-func openAIChatRequestFromGenerateRequest(req domain.GenerateRequest, defaultModel string) (openAIChatRequest, error) {
+func openAIChatRequestPayload(req domain.GenerateRequest) (map[string]any, error) {
 	model := strings.TrimSpace(req.Target.Model)
 	if model == "" {
-		model = strings.TrimSpace(defaultModel)
-	}
-	if model == "" {
-		return openAIChatRequest{}, errors.New("model is required")
+		return nil, errors.New("model is required")
 	}
 
-	wireReq := openAIChatRequest{
-		Model: model,
-	}
 	sessionID, err := domain.NormalizeSessionID(req.Prompt.SessionID)
 	if err != nil {
-		return openAIChatRequest{}, err
+		return nil, err
 	}
-	wireReq.SessionID = sessionID
 
-	wireReq.Messages = make([]openAIChatRequestMessage, 0, len(req.Prompt.Messages))
+	messages := make([]openAIChatRequestMessage, 0, len(req.Prompt.Messages))
 	for _, msg := range req.Prompt.Messages {
-		wireReq.Messages = append(wireReq.Messages, openAIChatRequestMessageFromRenderedMessage(msg))
+		messages = append(messages, openAIChatRequestMessageFromRenderedMessage(msg))
 	}
 
+	out := map[string]any{"model": model, "messages": messages}
+	if sessionID != "" {
+		out["session_id"] = sessionID
+	}
 	if req.Target.Temperature != 0 || req.TargetPresence.Temperature {
-		wireReq.Temperature = &req.Target.Temperature
+		out["temperature"] = req.Target.Temperature
 	}
 	if req.Target.MaxTokens != 0 || req.TargetPresence.MaxTokens {
-		wireReq.MaxTokens = &req.Target.MaxTokens
+		out["max_tokens"] = req.Target.MaxTokens
 	}
 	if req.Target.TopP != 0 || req.TargetPresence.TopP {
-		wireReq.TopP = &req.Target.TopP
+		out["top_p"] = req.Target.TopP
 	}
 	if strings.TrimSpace(req.Target.ServiceTier) != "" {
-		wireReq.ServiceTier = req.Target.ServiceTier
+		out["service_tier"] = req.Target.ServiceTier
 	}
 	if strings.TrimSpace(req.Target.ReasoningEffort) != "" {
-		wireReq.ReasoningEffort = req.Target.ReasoningEffort
-	}
-	if len(req.Target.ExtraParams) > 0 {
-		wireReq.ExtraParams = req.Target.ExtraParams
+		out["reasoning_effort"] = req.Target.ReasoningEffort
 	}
 	if req.StructuredOutput != nil {
 		responseFormat, err := toOpenAIResponseFormat(req.StructuredOutput)
 		if err != nil {
-			return openAIChatRequest{}, err
+			return nil, err
+		}
+		if responseFormat != nil {
+			out["response_format"] = responseFormat
 		}
-		wireReq.ResponseFormat = responseFormat
 	}
 
-	return wireReq, nil
-}
-
-type openAIChatRequest struct {
-	Model           string                     `json:"model"`
-	SessionID       string                     `json:"session_id,omitempty"`
-	Messages        []openAIChatRequestMessage `json:"messages"`
-	Temperature     *float64                   `json:"temperature,omitempty"`
-	MaxTokens       *int                       `json:"max_tokens,omitempty"`
-	TopP            *float64                   `json:"top_p,omitempty"`
-	ServiceTier     string                     `json:"service_tier,omitempty"`
-	ReasoningEffort string                     `json:"reasoning_effort,omitempty"`
-	ResponseFormat  *openAIResponseFormat      `json:"response_format,omitempty"`
-	ExtraParams     map[string]any             `json:"-"`
-}
-
-func openAIChatRequestPayload(req openAIChatRequest) (map[string]any, error) {
-	out := map[string]any{
-		"model":    req.Model,
-		"messages": req.Messages,
-	}
-	if req.SessionID != "" {
-		out["session_id"] = req.SessionID
-	}
-	if req.Temperature != nil {
-		out["temperature"] = *req.Temperature
-	}
-	if req.MaxTokens != nil {
-		out["max_tokens"] = *req.MaxTokens
-	}
-	if req.TopP != nil {
-		out["top_p"] = *req.TopP
-	}
-	if req.ServiceTier != "" {
-		out["service_tier"] = req.ServiceTier
-	}
-	if req.ReasoningEffort != "" {
-		out["reasoning_effort"] = req.ReasoningEffort
-	}
-	if req.ResponseFormat != nil {
-		out["response_format"] = req.ResponseFormat
-	}
-
-	for key, value := range req.ExtraParams {
+	for key, value := range req.Target.ExtraParams {
 		if key == "" {
 			return nil, errors.New("extra_params key must not be empty")
 		}

internal/llm/openai_compatible_client_test.go

@@ -123,26 +123,19 @@ func (p *recordingProvider) lastRequest(t *testing.T) recordedProviderRequest {
 	return p.requests[len(p.requests)-1]
 }
 
-func newProviderClient(t *testing.T, provider *recordingProvider, config OpenAICompatibleConfig) *OpenAICompatibleClient {
-	t.Helper()
-
-	if config.BaseURL == "" {
-		config.BaseURL = provider.endpoint("/v1")
-	}
-	client, err := NewOpenAICompatibleClient(config)
-	if err != nil {
-		t.Fatalf("construct client: %v", err)
-	}
-	return client
-}
-
 func ordinaryGenerateRequest() domain.GenerateRequest {
 	return domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
-		Target: domain.ExecutionTarget{Model: "model"},
+		Target: domain.ExecutionTarget{Endpoint: "https://provider.example/v1", Model: "model"},
 	}
 }
 
+func (p *recordingProvider) generateRequest() domain.GenerateRequest {
+	req := ordinaryGenerateRequest()
+	req.Target.Endpoint = p.endpoint("/v1")
+	return req
+}
+
 type deadlineCapturingTransport struct {
 	deadline    time.Time
 	hasDeadline bool
@@ -253,35 +246,13 @@ func assertDeadlineNear(t *testing.T, deadline, before, after time.Time, duratio
 	}
 }
 
-func TestNewOpenAICompatibleClientRejectsInvalidBaseURL(t *testing.T) {
-	for _, endpoint := range []string{
-		"://invalid",
-		"/v1",
-		"https:///v1",
-		"ftp://provider.example/v1",
-		"https://user@provider.example/v1",
-		"https://provider.example/v1?mode=chat",
-		"https://provider.example/v1#chat",
-	} {
-		t.Run(endpoint, func(t *testing.T) {
-			_, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: endpoint})
-			if !errors.Is(err, ErrInvalidConfig) {
-				t.Fatalf("expected ErrInvalidConfig, got %v", err)
-			}
-		})
-	}
-}
-
 func TestNewOpenAICompatibleClientDoesNotMutateSuppliedZeroTimeoutClient(t *testing.T) {
 	transport := http.DefaultTransport
 	supplied := &http.Client{Transport: transport}
 
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: supplied,
 	})
-	if err != nil {
-		t.Fatalf("unexpected constructor error: %v", err)
-	}
 
 	if supplied.Timeout != 0 {
 		t.Fatalf("expected supplied client timeout to remain zero, got %v", supplied.Timeout)
@@ -305,13 +276,10 @@ func TestNewOpenAICompatibleClientDoesNotMutateSuppliedNonzeroTimeoutClient(t *t
 		Transport: transport,
 	}
 
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		Timeout:    2 * time.Second,
 		HTTPClient: supplied,
 	})
-	if err != nil {
-		t.Fatalf("unexpected constructor error: %v", err)
-	}
 
 	if supplied.Timeout != suppliedTimeout {
 		t.Fatalf("expected supplied client timeout to remain %v, got %v", suppliedTimeout, supplied.Timeout)
@@ -335,13 +303,10 @@ func TestNewOpenAICompatibleClientTreatsSuppliedNegativeTimeoutAsUnset(t *testin
 	}
 	configuredTimeout := 23 * time.Second
 
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		Timeout:    configuredTimeout,
 		HTTPClient: supplied,
 	})
-	if err != nil {
-		t.Fatalf("unexpected constructor error: %v", err)
-	}
 
 	if supplied.Timeout != -time.Second {
 		t.Fatalf("expected supplied client timeout to remain negative, got %v", supplied.Timeout)
@@ -370,7 +335,6 @@ func TestOpenAICompatibleClientRequestMapping(t *testing.T) {
 		{name: "optional response fields", run: checkOptionalResponseFieldOmission},
 		{name: "reasoning and extra parameters", run: checkReasoningAndExtraParameterMapping},
 		{name: "optional request field presence", run: checkRequestFieldPresence},
-		{name: "configured model fallback", run: checkConfiguredModelFallback},
 	}
 
 	for _, tc := range tests {
@@ -380,14 +344,14 @@ func TestOpenAICompatibleClientRequestMapping(t *testing.T) {
 
 func checkCanonicalRoleAndExactContentMapping(t *testing.T) {
 	provider := newRecordingProvider(t)
-	client := newProviderClient(t, provider, OpenAICompatibleConfig{})
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 	const content = "  exact content\nwith whitespace  "
 	_, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{
 			Role:    domain.RoleDeveloper,
 			Content: content,
 		}}},
-		Target: domain.ExecutionTarget{Model: "model"},
+		Target: domain.ExecutionTarget{Endpoint: provider.endpoint("/v1"), Model: "model"},
 	})
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
@@ -413,7 +377,7 @@ func checkCompleteRequestAndResponseMapping(t *testing.T) {
   "usage": {"prompt_tokens": 11, "completion_tokens": 22, "total_tokens": 33}
 }`)
 
-	client := newProviderClient(t, provider, OpenAICompatibleConfig{
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		Timeout: 2 * time.Second,
 	})
 	t.Setenv("PROMPTKIT_TEST_API_KEY", "secret-key")
@@ -424,6 +388,7 @@ func checkCompleteRequestAndResponseMapping(t *testing.T) {
 			{Role: "user", Content: "Say hello"},
 		}},
 		Target: domain.ExecutionTarget{
+			Endpoint:    provider.endpoint("/v1"),
 			Model:       "gpt-test",
 			Temperature: 0.4,
 			MaxTokens:   123,
@@ -594,9 +559,11 @@ func TestOpenAICompatibleClientAuthentication(t *testing.T) {
 				tc.configureEnv(t)
 			}
 			provider := newRecordingProvider(t)
-			client := newProviderClient(t, provider, OpenAICompatibleConfig{Model: "model"})
-			request := ordinaryGenerateRequest()
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
+			request := provider.generateRequest()
 			request.Target = tc.target
+			request.Target.Endpoint = provider.endpoint("/v1")
+			request.Target.Model = "model"
 
 			_, err := client.Generate(context.Background(), request)
 			if tc.wantError != nil {
@@ -625,7 +592,7 @@ func TestOpenAICompatibleClientAuthentication(t *testing.T) {
 
 func checkCacheControlledMessageMapping(t *testing.T) {
 	provider := newRecordingProvider(t)
-	client := newProviderClient(t, provider, OpenAICompatibleConfig{})
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
 	_, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{
@@ -639,7 +606,7 @@ func checkCacheControlledMessageMapping(t *testing.T) {
 			},
 			{Role: "user", Content: "Dynamic request."},
 		}},
-		Target: domain.ExecutionTarget{Model: "model"},
+		Target: domain.ExecutionTarget{Endpoint: provider.endpoint("/v1"), Model: "model"},
 	})
 	if err != nil {
 		t.Fatalf("expected no error, got %v", err)
@@ -691,7 +658,7 @@ func checkCacheControlledMessageMapping(t *testing.T) {
 
 func checkEmptyCacheControlTTLOmission(t *testing.T) {
 	provider := newRecordingProvider(t)
-	client := newProviderClient(t, provider, OpenAICompatibleConfig{})
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
 	_, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{
@@ -703,7 +670,7 @@ func checkEmptyCacheControlTTLOmission(t *testing.T) {
 				},
 			},
 		}},
-		Target: domain.ExecutionTarget{Model: "model"},
+		Target: domain.ExecutionTarget{Endpoint: provider.endpoint("/v1"), Model: "model"},
 	})
 	if err != nil {
 		t.Fatalf("expected no error, got %v", err)
@@ -745,8 +712,8 @@ func checkSessionIDMapping(t *testing.T) {
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
 			provider := newRecordingProvider(t)
-			client := newProviderClient(t, provider, OpenAICompatibleConfig{})
-			request := ordinaryGenerateRequest()
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
+			request := provider.generateRequest()
 			request.Prompt.SessionID = tc.sessionID
 
 			if _, err := client.Generate(context.Background(), request); err != nil {
@@ -766,19 +733,14 @@ func checkSessionIDMapping(t *testing.T) {
 }
 
 func TestOpenAICompatibleClientRejectsTooLongSessionID(t *testing.T) {
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "http://example.com/v1",
-		Model:   "model",
-	})
-	if err != nil {
-		t.Fatal(err)
-	}
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
-	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+	_, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{
 			SessionID: strings.Repeat("x", domain.SessionIDMaxLength+1),
 			Messages:  []domain.RenderedMessage{{Role: "user", Content: "hi"}},
 		},
+		Target: domain.ExecutionTarget{Endpoint: "http://example.com/v1", Model: "model"},
 	})
 	if err == nil {
 		t.Fatal("expected invalid request error")
@@ -828,9 +790,9 @@ func checkContentPresence(t *testing.T) {
     "cache_write_tokens": 5
   }
 }`)
-			client := newProviderClient(t, provider, OpenAICompatibleConfig{Model: "model"})
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
-			response, err := client.Generate(context.Background(), ordinaryGenerateRequest())
+			response, err := client.Generate(context.Background(), provider.generateRequest())
 			if err != nil {
 				t.Fatalf("generate: %v", err)
 			}
@@ -865,10 +827,11 @@ func checkCacheUsageMapping(t *testing.T) {
     "cache_write_tokens": 60
   }
 }`)
-	client := newProviderClient(t, provider, OpenAICompatibleConfig{Model: "model"})
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
 	resp, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{Endpoint: provider.endpoint("/v1"), Model: "model"},
 	})
 	if err != nil {
 		t.Fatalf("expected no error, got %v", err)
@@ -901,8 +864,8 @@ func TestOpenAICompatibleUsagePresence(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			provider := newRecordingProvider(t)
 			provider.respond(http.StatusOK, `{`+tc.usage+`"choices":[{"message":{"content":"ok"}}]}`)
-			client := newProviderClient(t, provider, OpenAICompatibleConfig{Model: "model"})
-			resp, err := client.Generate(context.Background(), ordinaryGenerateRequest())
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
+			resp, err := client.Generate(context.Background(), provider.generateRequest())
 			if err != nil {
 				t.Fatal(err)
 			}
@@ -913,17 +876,17 @@ func TestOpenAICompatibleUsagePresence(t *testing.T) {
 	}
 	provider := newRecordingProvider(t)
 	provider.respond(http.StatusOK, `{"usage":{"prompt_tokens":"seven"},"choices":[{"message":{"content":"ok"}}]}`)
-	client := newProviderClient(t, provider, OpenAICompatibleConfig{Model: "model"})
-	if resp, err := client.Generate(context.Background(), ordinaryGenerateRequest()); resp != nil || !errors.Is(err, ErrMalformedResponse) {
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
+	if resp, err := client.Generate(context.Background(), provider.generateRequest()); resp != nil || !errors.Is(err, ErrMalformedResponse) {
 		t.Fatalf("invalid numeric usage response=%+v, error=%v", resp, err)
 	}
 }
 
 func checkOptionalResponseFieldOmission(t *testing.T) {
 	provider := newRecordingProvider(t)
-	client := newProviderClient(t, provider, OpenAICompatibleConfig{})
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
-	_, err := client.Generate(context.Background(), ordinaryGenerateRequest())
+	_, err := client.Generate(context.Background(), provider.generateRequest())
 	if err != nil {
 		t.Fatalf("expected no error, got %v", err)
 	}
@@ -938,11 +901,12 @@ func checkOptionalResponseFieldOmission(t *testing.T) {
 
 func checkReasoningAndExtraParameterMapping(t *testing.T) {
 	provider := newRecordingProvider(t)
-	client := newProviderClient(t, provider, OpenAICompatibleConfig{})
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
 	_, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
 		Target: domain.ExecutionTarget{
+			Endpoint:        provider.endpoint("/v1"),
 			Model:           "model",
 			ReasoningEffort: "high",
 			ExtraParams: map[string]any{
@@ -1020,8 +984,8 @@ func checkRequestFieldPresence(t *testing.T) {
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
 			provider := newRecordingProvider(t)
-			client := newProviderClient(t, provider, OpenAICompatibleConfig{})
-			request := ordinaryGenerateRequest()
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
+			request := provider.generateRequest()
 			request.TargetPresence = tc.presence
 
 			if _, err := client.Generate(context.Background(), request); err != nil {
@@ -1073,21 +1037,17 @@ func checkOmittedGenerationTimeout(t *testing.T) {
 	transport := &deadlineCapturingTransport{}
 	clientTimeout := 5 * time.Second
 
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "http://example.com/v1",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		Timeout: clientTimeout,
 		HTTPClient: &http.Client{
 			Transport: transport,
 		},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 
 	before := time.Now()
-	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+	_, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
-		Target: domain.ExecutionTarget{Model: "model", TimeoutSeconds: 0},
+		Target: domain.ExecutionTarget{Endpoint: "http://example.com/v1", Model: "model", TimeoutSeconds: 0},
 	})
 	after := time.Now()
 	if err == nil {
@@ -1146,11 +1106,11 @@ func TestOpenAICompatibleClientRejectsInvalidExtraParamsBeforeProviderCall(t *te
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
 			provider := newRecordingProvider(t)
-			client := newProviderClient(t, provider, OpenAICompatibleConfig{})
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
 			_, err := client.Generate(context.Background(), domain.GenerateRequest{
 				Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
-				Target: domain.ExecutionTarget{Model: "model", ExtraParams: tc.extraParams},
+				Target: domain.ExecutionTarget{Endpoint: provider.endpoint("/v1"), Model: "model", ExtraParams: tc.extraParams},
 			})
 			if err == nil {
 				t.Fatal("expected invalid request error")
@@ -1192,8 +1152,8 @@ func TestOpenAICompatibleClientClassifiesSchemaEncodingFailures(t *testing.T) {
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
 			provider := newRecordingProvider(t)
-			client := newProviderClient(t, provider, OpenAICompatibleConfig{})
-			request := ordinaryGenerateRequest()
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
+			request := provider.generateRequest()
 			request.Target.ExtraParams = tc.extraParams
 			request.StructuredOutput = &domain.StructuredOutputSpec{
 				Type: domain.StructuredOutputJSONSchema,
@@ -1218,30 +1178,12 @@ func TestOpenAICompatibleClientClassifiesSchemaEncodingFailures(t *testing.T) {
 	}
 }
 
-func checkConfiguredModelFallback(t *testing.T) {
-	provider := newRecordingProvider(t)
-	client := newProviderClient(t, provider, OpenAICompatibleConfig{Model: "default-model"})
-
-	_, err := client.Generate(context.Background(), domain.GenerateRequest{
-		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
-		Target: domain.ExecutionTarget{},
-	})
-	if err != nil {
-		t.Fatalf("expected no error, got %v", err)
-	}
-	var model string
-	if !provider.lastRequest(t).decodeField(t, "model", &model) || model != "default-model" {
-		t.Fatalf("model = %q, want default-model", model)
-	}
-}
-
 func TestOpenAICompatibleClientEndpointComposition(t *testing.T) {
 	tests := []struct {
 		name string
 		run  func(*testing.T)
 	}{
-		{name: "request endpoint overrides configured endpoint", run: checkEndpointOverride},
-		{name: "request endpoint works without configured endpoint", run: checkEmptyConfiguredEndpoint},
+		{name: "request endpoint", run: checkSelectedEndpoint},
 		{name: "completion URL preserves valid base paths", run: checkCompletionURLComposition},
 		{name: "invalid selected endpoint fails before transport", run: checkInvalidSelectedEndpointRejection},
 		{name: "an endpoint is required", run: checkRequiredEndpoint},
@@ -1252,35 +1194,6 @@ func TestOpenAICompatibleClientEndpointComposition(t *testing.T) {
 	}
 }
 
-func checkEndpointOverride(t *testing.T) {
-	configuredProvider := newRecordingProvider(t)
-	configuredProvider.respond(http.StatusOK, `{"choices":[{"message":{"content":"default"}}]}`)
-	selectedProvider := newRecordingProvider(t)
-	selectedProvider.respond(http.StatusOK, `{"choices":[{"message":{"content":"override"}}]}`)
-
-	client := newProviderClient(t, configuredProvider, OpenAICompatibleConfig{Model: "m"})
-
-	resp, err := client.Generate(context.Background(), domain.GenerateRequest{
-		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
-		Target: domain.ExecutionTarget{Endpoint: selectedProvider.endpoint("/v1")},
-	})
-	if err != nil {
-		t.Fatalf("expected no error, got %v", err)
-	}
-	if resp.Content != "override" {
-		t.Fatalf("expected override response, got %q", resp.Content)
-	}
-	if got := configuredProvider.requestCount(); got != 0 {
-		t.Fatalf("configured provider calls = %d, want 0", got)
-	}
-	if got := selectedProvider.requestCount(); got != 1 {
-		t.Fatalf("selected provider calls = %d, want 1", got)
-	}
-	if got := selectedProvider.lastRequest(t).url; got != "/v1/chat/completions" {
-		t.Fatalf("selected URL = %q, want /v1/chat/completions", got)
-	}
-}
-
 func checkCommonResponseFailures(t *testing.T) {
 	const sensitiveBody = `provider-secret-fragment request_payload_details`
 	tests := []struct {
@@ -1310,9 +1223,9 @@ func checkCommonResponseFailures(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			provider := newRecordingProvider(t)
 			provider.respond(tc.statusCode, tc.body)
-			client := newProviderClient(t, provider, OpenAICompatibleConfig{Model: "m"})
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
-			response, err := client.Generate(context.Background(), ordinaryGenerateRequest())
+			response, err := client.Generate(context.Background(), provider.generateRequest())
 			if response != nil {
 				t.Fatalf("expected no partial response, got %+v", response)
 			}
@@ -1357,9 +1270,7 @@ func checkSuccessfulResponseByteBoundary(t *testing.T) {
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
 			body := sizedSuccessResponseBody(tc.size)
-			client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-				BaseURL: "https://provider.example/v1",
-				Model:   "m",
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 				HTTPClient: &http.Client{Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
 					return &http.Response{
 						StatusCode:    http.StatusOK,
@@ -1370,12 +1281,10 @@ func checkSuccessfulResponseByteBoundary(t *testing.T) {
 					}, nil
 				})},
 			})
-			if err != nil {
-				t.Fatalf("construct client: %v", err)
-			}
 
 			response, err := client.Generate(context.Background(), domain.GenerateRequest{
 				Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+				Target: domain.ExecutionTarget{Endpoint: "https://provider.example/v1", Model: "m"},
 			})
 			if tc.wantErr {
 				if response != nil {
@@ -1425,9 +1334,7 @@ func checkContinuingOversizedResponse(t *testing.T) {
 		strings.NewReader(prefix),
 		continuation,
 	)}
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "https://provider.example/v1",
-		Model:   "m",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
 			return &http.Response{
 				StatusCode:    http.StatusOK,
@@ -1438,9 +1345,6 @@ func checkContinuingOversizedResponse(t *testing.T) {
 			}, nil
 		})},
 	})
-	if err != nil {
-		t.Fatalf("construct client: %v", err)
-	}
 
 	type outcome struct {
 		response *domain.GenerateResponse
@@ -1450,6 +1354,7 @@ func checkContinuingOversizedResponse(t *testing.T) {
 	go func() {
 		response, generateErr := client.Generate(context.Background(), domain.GenerateRequest{
 			Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+			Target: domain.ExecutionTarget{Endpoint: "https://provider.example/v1", Model: "m"},
 		})
 		done <- outcome{response: response, err: generateErr}
 	}()
@@ -1497,9 +1402,7 @@ func checkSingleResponseDocument(t *testing.T) {
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
 			body := &countingReadCloser{reader: strings.NewReader(tc.body)}
-			client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-				BaseURL: "https://provider.example/v1",
-				Model:   "m",
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 				HTTPClient: &http.Client{Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
 					return &http.Response{
 						StatusCode:    http.StatusOK,
@@ -1510,12 +1413,10 @@ func checkSingleResponseDocument(t *testing.T) {
 					}, nil
 				})},
 			})
-			if err != nil {
-				t.Fatalf("construct client: %v", err)
-			}
 
 			response, err := client.Generate(context.Background(), domain.GenerateRequest{
 				Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+				Target: domain.ExecutionTarget{Endpoint: "https://provider.example/v1", Model: "m"},
 			})
 			if tc.wantErr {
 				if response != nil {
@@ -1541,22 +1442,19 @@ func checkGenerationTimeoutPrecedence(t *testing.T) {
 	transport := &deadlineCapturingTransport{err: context.DeadlineExceeded}
 	generationTimeout := 2 * time.Second
 
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "http://example.com/v1",
-		Model:   "m",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{
 			Timeout:   10 * time.Second,
 			Transport: transport,
 		},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 
 	before := time.Now()
-	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+	_, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
 		Target: domain.ExecutionTarget{
+			Endpoint:       "http://example.com/v1",
+			Model:          "m",
 			TimeoutSeconds: int(generationTimeout / time.Second),
 		},
 	})
@@ -1578,25 +1476,22 @@ func checkGenerationTimeoutPrecedence(t *testing.T) {
 
 func checkCallerDeadlinePrecedence(t *testing.T) {
 	transport := &deadlineCapturingTransport{err: context.DeadlineExceeded}
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "http://example.com/v1",
-		Model:   "m",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{
 			Timeout:   10 * time.Second,
 			Transport: transport,
 		},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 
 	callerDeadline := time.Now().Add(time.Second)
 	ctx, cancel := context.WithDeadline(context.Background(), callerDeadline)
 	defer cancel()
 
-	_, err = client.Generate(ctx, domain.GenerateRequest{
+	_, err := client.Generate(ctx, domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
 		Target: domain.ExecutionTarget{
+			Endpoint:       "http://example.com/v1",
+			Model:          "m",
 			TimeoutSeconds: 2,
 		},
 	})
@@ -1618,22 +1513,18 @@ func checkCallerDeadlinePrecedence(t *testing.T) {
 }
 
 func checkCallerCancellationIdentity(t *testing.T) {
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "http://example.com/v1",
-		Model:   "m",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{
 			Transport: contextErrorTransport{},
 		},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 
 	ctx, cancel := context.WithCancel(context.Background())
 	cancel()
 
-	_, err = client.Generate(ctx, domain.GenerateRequest{
+	_, err := client.Generate(ctx, domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{Endpoint: "http://example.com/v1", Model: "m"},
 	})
 	if err == nil {
 		t.Fatal("expected cancellation error")
@@ -1647,21 +1538,17 @@ func checkCallerCancellationIdentity(t *testing.T) {
 }
 
 func checkExpiredCallerDeadlineIdentity(t *testing.T) {
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "http://example.com/v1",
-		Model:   "m",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{
 			Transport: contextErrorTransport{},
 		},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 
 	ctx, cancel := context.WithDeadline(context.Background(), time.Unix(1, 0))
 	defer cancel()
-	_, err = client.Generate(ctx, domain.GenerateRequest{
+	_, err := client.Generate(ctx, domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{Endpoint: "http://example.com/v1", Model: "m"},
 	})
 	if !errors.Is(err, ErrRequestFailed) || !errors.Is(err, context.DeadlineExceeded) {
 		t.Fatalf("expected request failure and caller deadline identities, got %v", err)
@@ -1669,20 +1556,16 @@ func checkExpiredCallerDeadlineIdentity(t *testing.T) {
 }
 
 func checkWholeRequestTimeoutIdentity(t *testing.T) {
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "http://example.com/v1",
-		Model:   "m",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{
 			Timeout:   time.Millisecond,
 			Transport: waitingContextTransport{},
 		},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 
-	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+	_, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{Endpoint: "http://example.com/v1", Model: "m"},
 	})
 	if !errors.Is(err, ErrRequestFailed) || !errors.Is(err, context.DeadlineExceeded) {
 		t.Fatalf("expected request failure and client timeout identities, got %v", err)
@@ -1696,20 +1579,15 @@ func checkTransportFailureIdentityAndRedaction(t *testing.T) {
 		apiKey   = "sensitive-api-key"
 		content  = "sensitive prompt content"
 	)
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: endpoint,
-		Model:   "m",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
 			return nil, transportCause
 		})},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 
-	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+	_, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: content}}},
-		Target: domain.ExecutionTarget{APIKey: apiKey},
+		Target: domain.ExecutionTarget{Endpoint: endpoint, Model: "m", APIKey: apiKey},
 	})
 	if !errors.Is(err, ErrRequestFailed) || !errors.Is(err, transportCause) {
 		t.Fatalf("expected request failure and transport cause identities, got %v", err)
@@ -1726,13 +1604,7 @@ func checkTransportFailureIdentityAndRedaction(t *testing.T) {
 }
 
 func TestOpenAICompatibleClientRejectsInvalidExecutionSettings(t *testing.T) {
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "http://example.com/v1",
-		Model:   "m",
-	})
-	if err != nil {
-		t.Fatal(err)
-	}
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
 	type testCase struct {
 		name   string
@@ -1765,11 +1637,9 @@ func TestOpenAICompatibleClientRejectsInvalidExecutionSettings(t *testing.T) {
 	}
 }
 
-func checkEmptyConfiguredEndpoint(t *testing.T) {
+func checkSelectedEndpoint(t *testing.T) {
 	var selectedURL string
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "",
-		Model:   "m",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
 			selectedURL = req.URL.String()
 			return &http.Response{
@@ -1782,13 +1652,10 @@ func checkEmptyConfiguredEndpoint(t *testing.T) {
 			}, nil
 		})},
 	})
-	if err != nil {
-		t.Fatalf("expected empty configured base URL to be allowed, got %v", err)
-	}
 
 	response, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
-		Target: domain.ExecutionTarget{Endpoint: "http://request-endpoint.example/v1"},
+		Target: domain.ExecutionTarget{Endpoint: "http://request-endpoint.example/v1", Model: "m"},
 	})
 	if err != nil {
 		t.Fatalf("generate with request endpoint: %v", err)
@@ -1817,9 +1684,7 @@ func checkCompletionURLComposition(t *testing.T) {
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
 			var selectedURL string
-			client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-				BaseURL: tc.baseURL,
-				Model:   "m",
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 				HTTPClient: &http.Client{Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
 					selectedURL = req.URL.String()
 					return &http.Response{
@@ -1830,12 +1695,10 @@ func checkCompletionURLComposition(t *testing.T) {
 					}, nil
 				})},
 			})
-			if err != nil {
-				t.Fatalf("construct client: %v", err)
-			}
 
-			_, err = client.Generate(context.Background(), domain.GenerateRequest{
+			_, err := client.Generate(context.Background(), domain.GenerateRequest{
 				Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+				Target: domain.ExecutionTarget{Endpoint: tc.baseURL, Model: "m"},
 			})
 			if err != nil {
 				t.Fatalf("generate: %v", err)
@@ -1860,21 +1723,16 @@ func checkInvalidSelectedEndpointRejection(t *testing.T) {
 	for _, endpoint := range invalidEndpoints {
 		t.Run(endpoint, func(t *testing.T) {
 			transportCalls := 0
-			client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-				BaseURL: "https://configured.example/v1",
-				Model:   "m",
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 				HTTPClient: &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
 					transportCalls++
 					return nil, errors.New("transport must not be called")
 				})},
 			})
-			if err != nil {
-				t.Fatalf("construct client: %v", err)
-			}
 
-			_, err = client.Generate(context.Background(), domain.GenerateRequest{
+			_, err := client.Generate(context.Background(), domain.GenerateRequest{
 				Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
-				Target: domain.ExecutionTarget{Endpoint: endpoint},
+				Target: domain.ExecutionTarget{Endpoint: endpoint, Model: "m"},
 			})
 			if !errors.Is(err, ErrInvalidRequest) {
 				t.Fatalf("expected ErrInvalidRequest, got %v", err)
@@ -1890,17 +1748,11 @@ func checkInvalidSelectedEndpointRejection(t *testing.T) {
 }
 
 func checkRequiredEndpoint(t *testing.T) {
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "",
-		Model:   "m",
-	})
-	if err != nil {
-		t.Fatal(err)
-	}
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
-	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+	_, err := client.Generate(context.Background(), domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
-		Target: domain.ExecutionTarget{},
+		Target: domain.ExecutionTarget{Model: "m"},
 	})
 	if err == nil {
 		t.Fatal("expected endpoint-required error")
@@ -1909,3 +1761,13 @@ func checkRequiredEndpoint(t *testing.T) {
 		t.Fatalf("expected ErrInvalidRequest, got %v", err)
 	}
 }
+
+func TestOpenAICompatibleClientRequiresModel(t *testing.T) {
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
+	_, err := client.PrepareGeneration(domain.GenerateRequest{
+		Target: domain.ExecutionTarget{Endpoint: "https://provider.example/v1"},
+	})
+	if !errors.Is(err, ErrInvalidRequest) {
+		t.Fatalf("missing model error = %v, want invalid request", err)
+	}
+}

internal/llm/openrouter_authentication.go

@@ -0,0 +1,108 @@
+package llm
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/url"
+
+	"go.maximumdirect.net/promptkit/internal/domain"
+)
+
+const maxAuthenticationResponseBytes = 1 << 20
+
+// AuthenticationEvidence describes the observable result of a key probe.
+type AuthenticationEvidence struct {
+	HTTP         HTTPExecutionEvidence
+	Accepted     *bool
+	Overflow     bool
+	Unrecognized bool
+}
+
+// OpenRouterKeyEndpoint derives the default key endpoint from a base endpoint.
+func OpenRouterKeyEndpoint(base string) (string, error) {
+	return url.JoinPath(base, "key")
+}
+
+// ProbeOpenRouterKey executes and interprets an OpenRouter key request.
+func (c *OpenAICompatibleClient) ProbeOpenRouterKey(ctx context.Context, endpoint string, timeoutSeconds int, target domain.ExecutionTarget) (AuthenticationEvidence, error) {
+	parsed, err := url.Parse(endpoint)
+	if err != nil {
+		return AuthenticationEvidence{}, err
+	}
+	parsed.User = nil
+	response, evidence, requestErr := c.GetWithAuthenticationEvidence(ctx, parsed.String(), timeoutSeconds, target)
+	result := AuthenticationEvidence{HTTP: evidence}
+	if response != nil && response.Body != nil {
+		defer response.Body.Close()
+	}
+	if !evidence.ResponseReceived && response == nil {
+		return result, requestErr
+	}
+	status := evidence.HTTPStatus
+	if status == nil && response != nil {
+		status = &response.StatusCode
+	}
+	if status == nil {
+		result.Unrecognized = true
+		return result, nil
+	}
+	switch *status {
+	case http.StatusUnauthorized:
+		accepted := false
+		result.Accepted = &accepted
+	case http.StatusOK:
+		if response == nil || response.Body == nil {
+			result.Unrecognized = true
+			return result, nil
+		}
+		contents, err := io.ReadAll(io.LimitReader(response.Body, maxAuthenticationResponseBytes+1))
+		if err != nil && ctx.Err() != nil {
+			return result, ctx.Err()
+		}
+		if len(contents) > maxAuthenticationResponseBytes {
+			result.Overflow = true
+			return result, nil
+		}
+		if err != nil {
+			return result, err
+		}
+		if recognizedOpenRouterKeyResponse(contents) {
+			accepted := true
+			result.Accepted = &accepted
+		} else {
+			result.Unrecognized = true
+		}
+	}
+	return result, nil
+}
+
+func recognizedOpenRouterKeyResponse(contents []byte) bool {
+	var envelope map[string]json.RawMessage
+	if err := json.Unmarshal(contents, &envelope); err != nil || envelope == nil {
+		return false
+	}
+	var data map[string]json.RawMessage
+	if err := json.Unmarshal(envelope["data"], &data); err != nil || data == nil {
+		return false
+	}
+	label := bytes.TrimSpace(data["label"])
+	var labelValue string
+	if len(label) == 0 || label[0] != '"' || json.Unmarshal(label, &labelValue) != nil {
+		return false
+	}
+	freeTier := bytes.TrimSpace(data["is_free_tier"])
+	if !bytes.Equal(freeTier, []byte("true")) && !bytes.Equal(freeTier, []byte("false")) {
+		return false
+	}
+	decoder := json.NewDecoder(bytes.NewReader(data["usage"]))
+	decoder.UseNumber()
+	var number any
+	if decoder.Decode(&number) != nil {
+		return false
+	}
+	_, ok := number.(json.Number)
+	return ok
+}

internal/llm/openrouter_authentication_test.go

@@ -0,0 +1,134 @@
+package llm
+
+import (
+	"context"
+	"errors"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+
+	"go.maximumdirect.net/promptkit/internal/domain"
+)
+
+func TestProbeOpenRouterKey(t *testing.T) {
+	valid := `{"data":{"label":"x","is_free_tier":false,"usage":0}}`
+	for _, tc := range []struct {
+		name                   string
+		status                 int
+		body                   string
+		key                    string
+		accepted               *bool
+		unrecognized, overflow bool
+	}{
+		{name: "recognized", status: 200, body: valid, key: "secret", accepted: boolValue(true)},
+		{name: "exact limit", status: 200, body: valid + strings.Repeat(" ", maxAuthenticationResponseBytes-len(valid)), accepted: boolValue(true)},
+		{name: "unknown", status: 200, body: `{"data":{"label":"x","is_free_tier":false,"usage":"0"}}`, unrecognized: true},
+		{name: "trailing value", status: 200, body: valid + ` {}`, unrecognized: true},
+		{name: "overflow", status: 200, body: strings.Repeat("x", maxAuthenticationResponseBytes+1), overflow: true},
+		{name: "unauthorized anonymous", status: 401, accepted: boolValue(false)},
+		{name: "other status", status: 503},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			var authorization string
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{HTTPClient: &http.Client{Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
+				if req.URL.User != nil {
+					t.Fatal("request retained URL credentials")
+				}
+				authorization = req.Header.Get("Authorization")
+				return &http.Response{StatusCode: tc.status, Header: make(http.Header), Body: io.NopCloser(strings.NewReader(tc.body))}, nil
+			})}})
+			got, err := client.ProbeOpenRouterKey(context.Background(), "https://user:password@example.invalid/key", 0, domain.ExecutionTarget{APIKey: tc.key})
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got.HTTP.Endpoint != "https://example.invalid/key" || got.HTTP.HTTPStatus == nil || *got.HTTP.HTTPStatus != tc.status || got.Unrecognized != tc.unrecognized || got.Overflow != tc.overflow {
+				t.Fatalf("evidence = %+v", got)
+			}
+			if (got.Accepted == nil) != (tc.accepted == nil) || got.Accepted != nil && *got.Accepted != *tc.accepted {
+				t.Fatalf("acceptance = %v", got.Accepted)
+			}
+			if (authorization != "") != (tc.key != "") || got.HTTP.CredentialsSupplied != (tc.key != "") {
+				t.Fatalf("credential evidence = %+v", got.HTTP)
+			}
+		})
+	}
+}
+
+func boolValue(value bool) *bool { return &value }
+
+type authenticationFailingBody struct{ err error }
+
+func (b authenticationFailingBody) Read([]byte) (int, error) { return 0, b.err }
+func (b authenticationFailingBody) Close() error             { return nil }
+
+func TestProbeOpenRouterKeyRetainsBodyFailure(t *testing.T) {
+	want := errors.New("interrupted")
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{HTTPClient: &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
+		return &http.Response{StatusCode: 200, Header: make(http.Header), Body: authenticationFailingBody{err: want}}, nil
+	})}})
+	got, err := client.ProbeOpenRouterKey(context.Background(), "https://example.invalid/key", 0, domain.ExecutionTarget{})
+	if !errors.Is(err, want) || !got.HTTP.ResponseReceived {
+		t.Fatalf("evidence = %+v, error = %v", got, err)
+	}
+}
+
+type observedAuthenticationBody struct {
+	reader io.Reader
+	read   int
+	closed bool
+}
+
+func (b *observedAuthenticationBody) Read(p []byte) (int, error) {
+	n, err := b.reader.Read(p)
+	b.read += n
+	return n, err
+}
+
+func (b *observedAuthenticationBody) Close() error {
+	b.closed = true
+	return nil
+}
+
+func TestProbeOpenRouterKeyBoundsAndClosesBodies(t *testing.T) {
+	for _, tc := range []struct {
+		name     string
+		status   int
+		wantRead int
+	}{
+		{"overflow", http.StatusOK, maxAuthenticationResponseBytes + 1},
+		{"unauthorized", http.StatusUnauthorized, 0},
+		{"other status", http.StatusServiceUnavailable, 0},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			body := &observedAuthenticationBody{reader: strings.NewReader(strings.Repeat("x", 2*maxAuthenticationResponseBytes))}
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{HTTPClient: &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
+				return &http.Response{StatusCode: tc.status, ContentLength: 1, Header: make(http.Header), Body: body}, nil
+			})}})
+			got, err := client.ProbeOpenRouterKey(context.Background(), "https://example.invalid/key", 0, domain.ExecutionTarget{})
+			if err != nil || body.read != tc.wantRead || !body.closed || got.Overflow != (tc.status == http.StatusOK) {
+				t.Fatalf("evidence = %+v, read = %d, closed = %v, error = %v", got, body.read, body.closed, err)
+			}
+		})
+	}
+}
+
+func TestOpenRouterKeyEndpoint(t *testing.T) {
+	got, err := OpenRouterKeyEndpoint("https://example.invalid/api/v1/")
+	if err != nil || got != "https://example.invalid/api/v1/key" {
+		t.Fatalf("endpoint = %q, error = %v", got, err)
+	}
+}
+
+func TestProbeOpenRouterKeyPreservesCancellation(t *testing.T) {
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{HTTPClient: &http.Client{Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
+		<-req.Context().Done()
+		return nil, req.Context().Err()
+	})}})
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	got, err := client.ProbeOpenRouterKey(ctx, "https://example.invalid/key", 0, domain.ExecutionTarget{})
+	if !errors.Is(err, context.Canceled) || got.Accepted != nil || got.HTTP.ResponseReceived {
+		t.Fatalf("evidence = %+v, error = %v", got, err)
+	}
+}

internal/llm/prepare_generation_benchmark_test.go

@@ -12,13 +12,7 @@ import (
 var prepareGenerationBenchmarkSink *PreparedGeneration
 
 func BenchmarkPrepareGeneration(b *testing.B) {
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "https://api.example.test/v1",
-		Model:   "benchmark-model",
-	})
-	if err != nil {
-		b.Fatalf("construct benchmark client: %v", err)
-	}
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{})
 
 	prompt := domain.RenderedPrompt{
 		Messages: []domain.RenderedMessage{{Role: "user", Content: "Summarize this request."}},
@@ -31,14 +25,14 @@ func BenchmarkPrepareGeneration(b *testing.B) {
 			name: "no_extras",
 			request: domain.GenerateRequest{
 				Prompt: prompt,
-				Target: domain.ExecutionTarget{Model: "benchmark-model"},
+				Target: domain.ExecutionTarget{Endpoint: "https://api.example.test/v1", Model: "benchmark-model"},
 			},
 		},
 		{
 			name: "small_extras",
 			request: domain.GenerateRequest{
 				Prompt: prompt,
-				Target: domain.ExecutionTarget{Model: "benchmark-model", ExtraParams: map[string]any{
+				Target: domain.ExecutionTarget{Endpoint: "https://api.example.test/v1", Model: "benchmark-model", ExtraParams: map[string]any{
 					"priority": "low",
 					"attempt":  3,
 					"enabled":  true,
@@ -49,7 +43,7 @@ func BenchmarkPrepareGeneration(b *testing.B) {
 			name: "1MiB_string_extra",
 			request: domain.GenerateRequest{
 				Prompt: prompt,
-				Target: domain.ExecutionTarget{Model: "benchmark-model", ExtraParams: map[string]any{
+				Target: domain.ExecutionTarget{Endpoint: "https://api.example.test/v1", Model: "benchmark-model", ExtraParams: map[string]any{
 					"payload": strings.Repeat("x", 1<<20),
 				}},
 			},
@@ -58,7 +52,7 @@ func BenchmarkPrepareGeneration(b *testing.B) {
 			name: "nested_json_extras",
 			request: domain.GenerateRequest{
 				Prompt: prompt,
-				Target: domain.ExecutionTarget{Model: "benchmark-model", ExtraParams: map[string]any{
+				Target: domain.ExecutionTarget{Endpoint: "https://api.example.test/v1", Model: "benchmark-model", ExtraParams: map[string]any{
 					"options": map[string]any{
 						"enabled": true,
 						"limits":  []any{2, 4, 8},
@@ -71,7 +65,7 @@ func BenchmarkPrepareGeneration(b *testing.B) {
 			name: "structured_output",
 			request: domain.GenerateRequest{
 				Prompt: prompt,
-				Target: domain.ExecutionTarget{Model: "benchmark-model"},
+				Target: domain.ExecutionTarget{Endpoint: "https://api.example.test/v1", Model: "benchmark-model"},
 				StructuredOutput: &domain.StructuredOutputSpec{
 					Type: domain.StructuredOutputJSONSchema,
 					JSONSchema: &domain.StructuredOutputJSONSpec{

internal/llm/prepared_generation_evidence_test.go

@@ -73,9 +73,7 @@ func TestPreparedGenerationEvidenceSeparatesResponseAndGenerationFacts(t *testin
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-				BaseURL: "https://provider.example/v1",
-				Model:   "model",
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 				HTTPClient: &http.Client{Transport: roundTripFunc(func(request *http.Request) (*http.Response, error) {
 					response := responseFor(request, test.status, "")
 					response.Body = io.NopCloser(strings.NewReader(test.body))
@@ -83,9 +81,6 @@ func TestPreparedGenerationEvidenceSeparatesResponseAndGenerationFacts(t *testin
 					return response, nil
 				})},
 			})
-			if err != nil {
-				t.Fatal(err)
-			}
 			request := ordinaryGenerateRequest()
 			if test.structured {
 				request.StructuredOutput = &domain.StructuredOutputSpec{
@@ -136,9 +131,7 @@ func TestPreparedGenerationEvidenceSeparatesResponseAndGenerationFacts(t *testin
 func TestPreparedGenerationEvidenceRetainsDecodedResponseOnCancellation(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	body := `{"choices":[{"message":{"content":"ok"}}],"usage":{"prompt_tokens":0}}`
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "https://provider.example/v1",
-		Model:   "model",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{Transport: roundTripFunc(func(request *http.Request) (*http.Response, error) {
 			return &http.Response{
 				StatusCode:    http.StatusOK,
@@ -149,9 +142,6 @@ func TestPreparedGenerationEvidenceRetainsDecodedResponseOnCancellation(t *testi
 			}, nil
 		})},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 	prepared, err := client.PrepareGeneration(ordinaryGenerateRequest())
 	if err != nil {
 		t.Fatal(err)
@@ -174,16 +164,11 @@ func TestPreparedGenerationEvidenceRetainsDecodedResponseOnCancellation(t *testi
 
 func TestPreparedGenerationEvidenceRecordsStructuredRequestAtDispatch(t *testing.T) {
 	transportErr := errors.New("provider unavailable")
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "https://provider.example/v1",
-		Model:   "model",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
 			return nil, transportErr
 		})},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 	request := ordinaryGenerateRequest()
 	request.StructuredOutput = &domain.StructuredOutputSpec{
 		Type: domain.StructuredOutputJSONSchema,

internal/llm/prepared_generation_test.go

@@ -26,8 +26,7 @@ func TestPreparedGenerationFreezesPayloadAndAuthentication(t *testing.T) {
 			const envName = "PROMPTKIT_PREPARED_GENERATION_TEST_KEY"
 			t.Setenv(envName, tc.initialKey)
 			var bodies, auth, urls []string
-			client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-				BaseURL: "https://example.invalid/v1", Model: "default-model",
+			client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 				HTTPClient: &http.Client{Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
 					body, err := io.ReadAll(req.Body)
 					if err != nil {
@@ -39,12 +38,9 @@ func TestPreparedGenerationFreezesPayloadAndAuthentication(t *testing.T) {
 					return &http.Response{StatusCode: http.StatusOK, Body: io.NopCloser(strings.NewReader(`{"choices":[{"message":{"content":"ok"}}]}`))}, nil
 				})},
 			})
-			if err != nil {
-				t.Fatal(err)
-			}
 			req := domain.GenerateRequest{
 				Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "original"}}},
-				Target: domain.ExecutionTarget{APIKeyEnv: envName},
+				Target: domain.ExecutionTarget{Endpoint: "https://example.invalid/v1", Model: "default-model", APIKeyEnv: envName},
 			}
 			prepared, err := client.PrepareGeneration(req)
 			if err != nil {
@@ -68,8 +64,7 @@ func TestPreparedGenerationFreezesPayloadAndAuthentication(t *testing.T) {
 func TestPreparedGenerationAttemptsHaveIndependentContextsAndCloseBodies(t *testing.T) {
 	var contexts []context.Context
 	var closed int
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "https://example.invalid/v1", Model: "model",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
 			if err := req.Context().Err(); err != nil {
 				return nil, err
@@ -81,12 +76,9 @@ func TestPreparedGenerationAttemptsHaveIndependentContextsAndCloseBodies(t *test
 			}}, nil
 		})},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 	prepared, err := client.PrepareGeneration(domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
-		Target: domain.ExecutionTarget{TimeoutSeconds: 1},
+		Target: domain.ExecutionTarget{Endpoint: "https://example.invalid/v1", Model: "model", TimeoutSeconds: 1},
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -115,17 +107,14 @@ func TestPreparedGenerationAttemptsHaveIndependentContextsAndCloseBodies(t *test
 }
 
 func TestPreparedGenerationRetainsUsageFromMalformedChoice(t *testing.T) {
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "https://example.invalid/v1", Model: "model",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
 			return &http.Response{StatusCode: http.StatusOK, Body: io.NopCloser(strings.NewReader(`{"usage":{"prompt_tokens":0},"choices":[]}`))}, nil
 		})},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 	prepared, err := client.PrepareGeneration(domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{Endpoint: "https://example.invalid/v1", Model: "model"},
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -137,17 +126,14 @@ func TestPreparedGenerationRetainsUsageFromMalformedChoice(t *testing.T) {
 }
 
 func TestPreparedGenerationDoesNotUseInvalidlyFramedUsage(t *testing.T) {
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "https://example.invalid/v1", Model: "model",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
 			return &http.Response{StatusCode: http.StatusOK, Body: io.NopCloser(strings.NewReader(`{"usage":{"prompt_tokens":9},"choices":[]}{}`))}, nil
 		})},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 	prepared, err := client.PrepareGeneration(domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{Endpoint: "https://example.invalid/v1", Model: "model"},
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -160,17 +146,14 @@ func TestPreparedGenerationDoesNotUseInvalidlyFramedUsage(t *testing.T) {
 
 func TestPreparedGenerationRetainsReadCancellation(t *testing.T) {
 	closed := false
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "https://example.invalid/v1", Model: "model",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
 			return &http.Response{StatusCode: http.StatusOK, Body: &readErrorBody{err: context.Canceled, closed: &closed}}, nil
 		})},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 	prepared, err := client.PrepareGeneration(domain.GenerateRequest{
 		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{Endpoint: "https://example.invalid/v1", Model: "model"},
 	})
 	if err != nil {
 		t.Fatal(err)

internal/llm/provider_http_error_transport_test.go

@@ -127,9 +127,7 @@ func TestOpenAICompatibleClientNonSuccessBodyOwnership(t *testing.T) {
 func newNonSuccessResponseClient(t *testing.T, statusCode int, contentLength int64, body io.ReadCloser) *OpenAICompatibleClient {
 	t.Helper()
 
-	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: "https://provider.example/v1",
-		Model:   "m",
+	client := NewOpenAICompatibleClient(OpenAICompatibleConfig{
 		HTTPClient: &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
 			return &http.Response{
 				StatusCode:    statusCode,
@@ -138,8 +136,5 @@ func newNonSuccessResponseClient(t *testing.T, statusCode int, contentLength int
 			}, nil
 		})},
 	})
-	if err != nil {
-		t.Fatalf("construct client: %v", err)
-	}
 	return client
 }

internal/llm/response_read_error_test.go

@@ -0,0 +1,48 @@
+package llm
+
+import (
+	"errors"
+	"io"
+	"strings"
+	"testing"
+)
+
+type responseBytesAndError struct {
+	data []byte
+	err  error
+}
+
+func (r *responseBytesAndError) Read(p []byte) (int, error) {
+	if len(r.data) == 0 {
+		return 0, r.err
+	}
+	n := copy(p, r.data)
+	r.data = r.data[n:]
+	if len(r.data) == 0 {
+		return n, r.err
+	}
+	return n, nil
+}
+
+func TestSuccessfulResponseReadFailuresRetainCause(t *testing.T) {
+	cause := errors.New("private reader diagnostic")
+	for _, test := range []struct {
+		name, prefix string
+		together     bool
+	}{
+		{"partial", `{"choices":[`, false},
+		{"complete then failure", successfulProviderResponse, false},
+		{"bytes and error together", successfulProviderResponse, true},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			var reader io.Reader = io.MultiReader(strings.NewReader(test.prefix), failingReader{err: cause})
+			if test.together {
+				reader = &responseBytesAndError{data: []byte(test.prefix), err: cause}
+			}
+			_, err := decodeOpenAIChatResponse(reader)
+			if !errors.Is(err, ErrTransport) || !errors.Is(err, cause) || errors.Is(err, ErrMalformedResponse) || strings.Contains(err.Error(), cause.Error()) {
+				t.Fatalf("read failure = %v", err)
+			}
+		})
+	}
+}

internal/profile/repository.go

@@ -13,4 +13,5 @@ var ErrProfileNotFound = errors.New("execution profile not found")
 // Repository selects execution profiles from a captured index.
 type Repository interface {
 	GetProfile(ctx context.Context, id string) (*domain.ExecutionProfile, error)
+	GetProfileIdentity(ctx context.Context, id string) (string, error)
 }

internal/prompt/go_renderer.go

@@ -24,10 +24,6 @@ type goRenderer struct {
 	templates TemplateLookup
 }
 
-func NewGoRenderer() Renderer {
-	return &goRenderer{}
-}
-
 // NewCompiledRenderer renders definitions using templates captured with the
 // configuration snapshot. Per-call clones bind request-specific input helpers.
 func NewCompiledRenderer(templates TemplateLookup) Renderer {
@@ -56,13 +52,12 @@ func (r *goRenderer) Render(ctx context.Context, definition *domain.PromptDefini
 	funcs := template.FuncMap{
 		"input": resolver.resolve,
 	}
-	var compiled CompiledTemplates
-	if r.templates != nil {
-		var found bool
-		compiled, found = r.templates.GetCompiledTemplates(definition.ID)
-		if !found || len(compiled.Messages) != len(definition.Templates) {
-			return nil, fmt.Errorf("%w: captured templates are unavailable", ErrRenderFailure)
-		}
+	if r.templates == nil {
+		return nil, fmt.Errorf("%w: captured templates are unavailable", ErrRenderFailure)
+	}
+	compiled, found := r.templates.GetCompiledTemplates(definition.ID)
+	if !found || len(compiled.Messages) != len(definition.Templates) {
+		return nil, fmt.Errorf("%w: captured templates are unavailable", ErrRenderFailure)
 	}
 
 	if err := ctx.Err(); err != nil {
@@ -70,15 +65,11 @@ func (r *goRenderer) Render(ctx context.Context, definition *domain.PromptDefini
 	}
 	var sessionID string
 	var err error
-	if r.templates != nil {
-		if definition.SessionID != "" {
-			if compiled.Session == nil {
-				return nil, fmt.Errorf("%w: captured session template is unavailable", ErrRenderFailure)
-			}
-			sessionID, err = renderCompiledSessionID(ctx, compiled.Session, funcs, vars)
+	if definition.SessionID != "" {
+		if compiled.Session == nil {
+			return nil, fmt.Errorf("%w: captured session template is unavailable", ErrRenderFailure)
 		}
-	} else {
-		sessionID, err = renderSessionID(ctx, definition.SessionID, funcs, vars)
+		sessionID, err = renderCompiledSessionID(ctx, compiled.Session, funcs, vars)
 	}
 	if err != nil {
 		return nil, err
@@ -102,18 +93,12 @@ func (r *goRenderer) Render(ctx context.Context, definition *domain.PromptDefini
 		if err := ctx.Err(); err != nil {
 			return nil, err
 		}
-		var tmpl *template.Template
-		var parseErr error
-		if r.templates != nil {
-			if compiled.Messages[i] == nil {
-				return nil, fmt.Errorf("%w: captured message template is unavailable", ErrRenderFailure)
-			}
-			tmpl, parseErr = compiled.Messages[i].Clone()
-			if parseErr == nil {
-				tmpl.Funcs(funcs)
-			}
-		} else {
-			tmpl, parseErr = parseTemplate(fmt.Sprintf("msg_%d", i), tmplMsg.Content, funcs)
+		if compiled.Messages[i] == nil {
+			return nil, fmt.Errorf("%w: captured message template is unavailable", ErrRenderFailure)
+		}
+		tmpl, parseErr := compiled.Messages[i].Clone()
+		if parseErr == nil {
+			tmpl.Funcs(funcs)
 		}
 		if err := ctx.Err(); err != nil {
 			return nil, err
@@ -201,20 +186,6 @@ func (r *artifactTextResolver) resolve(name string) (string, error) {
 	return text, nil
 }
 
-func renderSessionID(ctx context.Context, raw string, funcs template.FuncMap, vars map[string]string) (string, error) {
-	if err := ctx.Err(); err != nil {
-		return "", err
-	}
-	tmpl, parseErr := parseTemplate("session_id", raw, funcs)
-	if err := ctx.Err(); err != nil {
-		return "", err
-	}
-	if parseErr != nil {
-		return "", fmt.Errorf("%w: session_id: %v", ErrInvalidTemplate, parseErr)
-	}
-	return executeSessionTemplate(ctx, tmpl, vars)
-}
-
 func renderCompiledSessionID(ctx context.Context, compiled *template.Template, funcs template.FuncMap, vars map[string]string) (string, error) {
 	if err := ctx.Err(); err != nil {
 		return "", err

internal/prompt/renderer_test.go

@@ -14,7 +14,6 @@ import (
 )
 
 func TestGoRenderer_Render(t *testing.T) {
-	renderer := NewGoRenderer()
 	ctx := context.Background()
 
 	inputs := map[string]*domain.Artifact{
@@ -33,7 +32,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		res, err := renderer.Render(ctx, def, inputs, vars)
+		res, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -49,11 +48,11 @@ func TestGoRenderer_Render(t *testing.T) {
 		def := &domain.PromptDefinition{
 			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
 			Templates: []domain.PromptMessageTemplate{
-				{Role: "user", Content: "From file: {{input \"transcript\"}}", ContentFile: "/tmp/user.tmpl"},
+				{Role: "user", Content: "From file: {{input \"transcript\"}}"},
 			},
 		}
 
-		res, err := renderer.Render(ctx, def, inputs, vars)
+		res, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -71,7 +70,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		res, err := renderer.Render(ctx, def, inputs, vars)
+		res, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -99,7 +98,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		res, err := renderer.Render(ctx, def, inputs, vars)
+		res, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -129,7 +128,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		res, err := renderer.Render(ctx, def, inputs, vars)
+		res, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -151,7 +150,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		res, err := renderer.Render(ctx, def, inputs, vars)
+		res, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -169,7 +168,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		res, err := renderer.Render(ctx, def, inputs, map[string]string{
+		res, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, map[string]string{
 			"tone":       "concise",
 			"session_id": "agent-session-123",
 		})
@@ -190,7 +189,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		res, err := renderer.Render(ctx, def, inputs, vars)
+		res, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -208,7 +207,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		_, err := renderer.Render(ctx, def, inputs, vars)
+		_, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if !errors.Is(err, ErrRenderFailure) {
 			t.Fatalf("expected ErrRenderFailure, got %v", err)
 		}
@@ -223,7 +222,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		_, err := renderer.Render(ctx, def, inputs, map[string]string{
+		_, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, map[string]string{
 			"tone":       "concise",
 			"session_id": strings.Repeat("x", domain.SessionIDMaxLength+1),
 		})
@@ -241,7 +240,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		_, err := renderer.Render(ctx, def, inputs, map[string]string{
+		_, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, map[string]string{
 			"tone":       "concise",
 			"session_id": "session" + string([]byte{0xff}),
 		})
@@ -258,7 +257,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		res, err := renderer.Render(ctx, def, inputs, vars)
+		res, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -278,7 +277,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		res, err := renderer.Render(ctx, def, inputs, vars)
+		res, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -298,7 +297,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		_, err := renderer.Render(ctx, def, inputs, vars)
+		_, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if !errors.Is(err, ErrRenderFailure) {
 			t.Fatalf("expected ErrRenderFailure, got %v", err)
 		}
@@ -315,7 +314,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		_, err := renderer.Render(ctx, def, map[string]*domain.Artifact{}, vars)
+		_, err := capturedTestRenderer(t, def).Render(ctx, def, map[string]*domain.Artifact{}, vars)
 		if !errors.Is(err, ErrMissingRequiredInput) {
 			t.Fatalf("expected ErrMissingRequiredInput, got %v", err)
 		}
@@ -329,9 +328,9 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		_, err := renderer.Render(ctx, def, inputs, vars)
-		if !errors.Is(err, ErrInvalidTemplate) {
-			t.Fatalf("expected ErrInvalidTemplate, got %v", err)
+		_, err := CompileTemplate("message", def.Templates[0].Content)
+		if err == nil {
+			t.Fatal("expected template compilation to fail")
 		}
 	})
 
@@ -343,7 +342,7 @@ func TestGoRenderer_Render(t *testing.T) {
 			},
 		}
 
-		_, err := renderer.Render(ctx, def, inputs, vars)
+		_, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if !errors.Is(err, ErrRenderFailure) {
 			t.Fatalf("expected ErrRenderFailure, got %v", err)
 		}
@@ -359,7 +358,7 @@ func TestGoRenderer_Render(t *testing.T) {
 				{Role: "", Content: "Hello"},
 			},
 		}
-		_, err := renderer.Render(ctx, def, inputs, vars)
+		_, err := capturedTestRenderer(t, def).Render(ctx, def, inputs, vars)
 		if !errors.Is(err, ErrInvalidMessageRole) {
 			t.Fatalf("expected ErrInvalidMessageRole, got %v", err)
 		}
@@ -371,7 +370,7 @@ func TestGoRenderer_Render(t *testing.T) {
 				{Role: " \u2003DeVeLoPeR\u2003 ", Content: "Hello"},
 			},
 		}
-		res, err := renderer.Render(ctx, def, nil, vars)
+		res, err := capturedTestRenderer(t, def).Render(ctx, def, nil, vars)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -385,7 +384,7 @@ func TestGoRenderer_Render(t *testing.T) {
 		def := &domain.PromptDefinition{
 			Templates: []domain.PromptMessageTemplate{{Role: unsupportedRole, Content: "Hello"}},
 		}
-		_, err := renderer.Render(ctx, def, nil, vars)
+		_, err := capturedTestRenderer(t, def).Render(ctx, def, nil, vars)
 		if !errors.Is(err, ErrInvalidMessageRole) {
 			t.Fatalf("expected ErrInvalidMessageRole, got %v", err)
 		}
@@ -396,9 +395,9 @@ func TestGoRenderer_Render(t *testing.T) {
 }
 
 func TestGoRendererCancellation(t *testing.T) {
-	t.Run("before session parsing", func(t *testing.T) {
+	t.Run("before rendering", func(t *testing.T) {
 		definition := &domain.PromptDefinition{
-			SessionID: "{{ malformed",
+			SessionID: "{{.session}}",
 			Templates: []domain.PromptMessageTemplate{
 				{Role: "user", Content: "not rendered"},
 			},
@@ -406,18 +405,11 @@ func TestGoRendererCancellation(t *testing.T) {
 		ctx, cancel := context.WithCancel(context.Background())
 		cancel()
 
-		result, err := NewGoRenderer().Render(ctx, definition, nil, nil)
+		renderer := capturedTestRenderer(t, definition)
+		result, err := renderer.Render(ctx, definition, nil, nil)
 		if result != nil || !errors.Is(err, context.Canceled) {
 			t.Fatalf("result=%#v err=%v, want nil/context.Canceled", result, err)
 		}
-		if errors.Is(err, ErrInvalidTemplate) {
-			t.Fatalf("pre-canceled render parsed the malformed session: %v", err)
-		}
-
-		result, err = NewGoRenderer().Render(context.Background(), definition, nil, nil)
-		if result != nil || !errors.Is(err, ErrInvalidTemplate) {
-			t.Fatalf("active render result=%#v err=%v, want nil/ErrInvalidTemplate", result, err)
-		}
 	})
 
 	t.Run("during artifact text conversion", func(t *testing.T) {
@@ -447,14 +439,15 @@ func TestGoRendererCancellation(t *testing.T) {
 			},
 		}
 		counter := &checkCountingContext{Context: context.Background()}
-		if _, err := NewGoRenderer().Render(counter, definition, nil, nil); err != nil {
+		renderer := capturedTestRenderer(t, definition)
+		if _, err := renderer.Render(counter, definition, nil, nil); err != nil {
 			t.Fatalf("count render checkpoints: %v", err)
 		}
 
 		// The final three checks occur after template execution, after the
 		// message is assembled, and immediately before publication.
 		ctx := newCancelOnCheckContext(counter.checks - 2)
-		result, err := NewGoRenderer().Render(ctx, definition, nil, nil)
+		result, err := renderer.Render(ctx, definition, nil, nil)
 		if result != nil || !errors.Is(err, context.Canceled) {
 			t.Fatalf("result=%#v err=%v, want nil/context.Canceled", result, err)
 		}
@@ -472,7 +465,8 @@ func TestGoRendererArtifactTextLifecycle(t *testing.T) {
 		},
 	}
 
-	first, err := NewGoRenderer().Render(context.Background(), definition, inputs, nil)
+	renderer := capturedTestRenderer(t, definition)
+	first, err := renderer.Render(context.Background(), definition, inputs, nil)
 	if err != nil {
 		t.Fatalf("first render: %v", err)
 	}
@@ -488,7 +482,7 @@ func TestGoRendererArtifactTextLifecycle(t *testing.T) {
 	if bytes.Equal([]byte(first.Messages[0].Content), append(append(append([]byte(nil), body...), '|'), body...)) {
 		t.Fatal("completed render aliases the artifact body")
 	}
-	second, err := NewGoRenderer().Render(context.Background(), definition, inputs, nil)
+	second, err := renderer.Render(context.Background(), definition, inputs, nil)
 	if err != nil {
 		t.Fatalf("second render: %v", err)
 	}
@@ -498,7 +492,7 @@ func TestGoRendererArtifactTextLifecycle(t *testing.T) {
 	}
 
 	nilInputs := map[string]*domain.Artifact{"document": nil}
-	result, err := NewGoRenderer().Render(context.Background(), definition, nilInputs, nil)
+	result, err := renderer.Render(context.Background(), definition, nilInputs, nil)
 	if result != nil || !errors.Is(err, ErrUnknownInput) || !errors.Is(err, ErrRenderFailure) {
 		t.Fatalf("nil input result=%#v err=%v, want ErrUnknownInput and ErrRenderFailure", result, err)
 	}
@@ -559,11 +553,56 @@ func TestCompiledRendererKeepsConcurrentRequestsIndependent(t *testing.T) {
 	}
 }
 
+func TestCompiledRendererRequiresCapturedTemplates(t *testing.T) {
+	message, err := CompileTemplate("message", "hello")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, tc := range []struct {
+		name      string
+		lookup    TemplateLookup
+		sessionID string
+	}{
+		{name: "missing lookup"},
+		{name: "missing prompt", lookup: compiledRendererTestLookup{id: "other"}},
+		{name: "missing message", lookup: compiledRendererTestLookup{id: "prompt"}},
+		{name: "nil message", lookup: compiledRendererTestLookup{id: "prompt", templates: CompiledTemplates{Messages: []*template.Template{nil}}}},
+		{name: "missing session", lookup: compiledRendererTestLookup{id: "prompt", templates: CompiledTemplates{Messages: []*template.Template{message}}}, sessionID: "session"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			definition := &domain.PromptDefinition{ID: "prompt", SessionID: tc.sessionID, Templates: []domain.PromptMessageTemplate{{Role: "user", Content: "hello"}}}
+			if _, err := NewCompiledRenderer(tc.lookup).Render(context.Background(), definition, nil, nil); !errors.Is(err, ErrRenderFailure) {
+				t.Fatalf("render error = %v, want render failure", err)
+			}
+		})
+	}
+}
+
 type compiledRendererTestLookup struct {
 	id        string
 	templates CompiledTemplates
 }
 
+func capturedTestRenderer(t testing.TB, definition *domain.PromptDefinition) Renderer {
+	t.Helper()
+	var compiled CompiledTemplates
+	var err error
+	if definition.SessionID != "" {
+		compiled.Session, err = CompileTemplate("session", definition.SessionID)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+	for _, message := range definition.Templates {
+		parsed, err := CompileTemplate("message", message.Content)
+		if err != nil {
+			t.Fatal(err)
+		}
+		compiled.Messages = append(compiled.Messages, parsed)
+	}
+	return NewCompiledRenderer(compiledRendererTestLookup{id: definition.ID, templates: compiled})
+}
+
 func (lookup compiledRendererTestLookup) GetCompiledTemplates(id string) (CompiledTemplates, bool) {
 	if id != lookup.id {
 		return CompiledTemplates{}, false
@@ -571,8 +610,7 @@ func (lookup compiledRendererTestLookup) GetCompiledTemplates(id string) (Compil
 	return lookup.templates, true
 }
 
-// BenchmarkGoRendererArtifactReferences measures NewGoRenderer's per-call
-// template-parsing fallback rather than the captured compiled path.
+// BenchmarkGoRendererArtifactReferences measures rendering captured templates.
 func BenchmarkGoRendererArtifactReferences(b *testing.B) {
 	body := bytes.Repeat([]byte("document content "), (artifactTextChunkSize*4)/len("document content "))
 	inputs := map[string]*domain.Artifact{
@@ -604,7 +642,7 @@ func BenchmarkGoRendererArtifactReferences(b *testing.B) {
 
 	for _, tc := range tests {
 		b.Run(tc.name, func(b *testing.B) {
-			renderer := NewGoRenderer()
+			renderer := capturedTestRenderer(b, tc.definition)
 			b.ReportAllocs()
 			b.SetBytes(int64(len(body)))
 			for range b.N {

internal/prompt/requirements.go

@@ -319,24 +319,27 @@ func mergeConditionEvaluations(left, right conditionEvaluation) conditionEvaluat
 	result := conditionEvaluation{
 		unsupported:      left.unsupported || right.unsupported,
 		inputNameUnknown: left.inputNameUnknown || right.inputNameUnknown,
-		missingVariables: make(map[string]struct{}, len(left.missingVariables)+len(right.missingVariables)),
-		contentInputs:    make(map[string]struct{}, len(left.contentInputs)+len(right.contentInputs)),
-	}
-	for name := range left.missingVariables {
-		result.missingVariables[name] = struct{}{}
-	}
-	for name := range right.missingVariables {
-		result.missingVariables[name] = struct{}{}
-	}
-	for name := range left.contentInputs {
-		result.contentInputs[name] = struct{}{}
-	}
-	for name := range right.contentInputs {
-		result.contentInputs[name] = struct{}{}
+		missingVariables: mergeOwnedNames(left.missingVariables, right.missingVariables),
+		contentInputs:    mergeOwnedNames(left.contentInputs, right.contentInputs),
 	}
 	return result
 }
 
+// Condition results own their sets; callers retain operand values and flags,
+// not independent snapshots of these maps after a merge.
+func mergeOwnedNames(left, right map[string]struct{}) map[string]struct{} {
+	if len(left) < len(right) {
+		left, right = right, left
+	}
+	if left == nil {
+		return right
+	}
+	for name := range right {
+		left[name] = struct{}{}
+	}
+	return left
+}
+
 func branchReach(parent requirementReachability, known, truth, selected bool) requirementReachability {
 	if parent == requirementInactive {
 		return requirementInactive
@@ -448,6 +451,34 @@ func (walker *requirementWalker) walkTemplate(compiled *template.Template) error
 	return err
 }
 
+func (walker *requirementWalker) visitBranch(branch *parse.BranchNode, reach requirementReachability, dot dotIdentity, changesDot bool) error {
+	condition := conditionEvaluation{}
+	if reach == requirementInactive {
+		if err := walker.visit(branch.Pipe, requirementInactive, dot); err != nil {
+			return err
+		}
+	} else {
+		condition = walker.evaluateCondition(branch.Pipe, reach, dot)
+	}
+	before := walker.dependencies
+	bodyDot := dot
+	if changesDot {
+		bodyDot = walker.withDotIdentity(branch.Pipe, dot, condition)
+	}
+	thenReach := branchReach(reach, condition.known, condition.truth(), true)
+	elseReach := branchReach(reach, condition.known, condition.truth(), false)
+	if err := walker.visit(branch.List, thenReach, bodyDot); err != nil {
+		return err
+	}
+	if err := walker.visit(branch.ElseList, elseReach, dot); err != nil {
+		return err
+	}
+	if reach != requirementInactive && !condition.known && walker.dependencies != before {
+		walker.recordConditionLimitation(condition)
+	}
+	return nil
+}
+
 func (walker *requirementWalker) visit(node parse.Node, reach requirementReachability, dot dotIdentity) error {
 	if err := walker.ctx.Err(); err != nil {
 		return err
@@ -468,55 +499,9 @@ func (walker *requirementWalker) visit(node parse.Node, reach requirementReachab
 	case *parse.ActionNode:
 		return walker.visit(node.Pipe, reach, dot)
 	case *parse.IfNode:
-		if reach == requirementInactive {
-			if err := walker.visit(node.Pipe, requirementInactive, dot); err != nil {
-				return err
-			}
-			if err := walker.visit(node.List, requirementInactive, dot); err != nil {
-				return err
-			}
-			return walker.visit(node.ElseList, requirementInactive, dot)
-		}
-		condition := walker.evaluateCondition(node.Pipe, reach, dot)
-		before := walker.dependencies
-		thenReach := branchReach(reach, condition.known, condition.truth(), true)
-		elseReach := branchReach(reach, condition.known, condition.truth(), false)
-		if err := walker.visit(node.List, thenReach, dot); err != nil {
-			return err
-		}
-		if err := walker.visit(node.ElseList, elseReach, dot); err != nil {
-			return err
-		}
-		if !condition.known && walker.dependencies != before {
-			walker.recordConditionLimitation(condition)
-		}
-		return nil
+		return walker.visitBranch(&node.BranchNode, reach, dot, false)
 	case *parse.WithNode:
-		if reach == requirementInactive {
-			if err := walker.visit(node.Pipe, requirementInactive, dot); err != nil {
-				return err
-			}
-			bodyDot := walker.withDotIdentity(node.Pipe, dot, conditionEvaluation{})
-			if err := walker.visit(node.List, requirementInactive, bodyDot); err != nil {
-				return err
-			}
-			return walker.visit(node.ElseList, requirementInactive, dot)
-		}
-		condition := walker.evaluateCondition(node.Pipe, reach, dot)
-		before := walker.dependencies
-		thenReach := branchReach(reach, condition.known, condition.truth(), true)
-		elseReach := branchReach(reach, condition.known, condition.truth(), false)
-		bodyDot := walker.withDotIdentity(node.Pipe, dot, condition)
-		if err := walker.visit(node.List, thenReach, bodyDot); err != nil {
-			return err
-		}
-		if err := walker.visit(node.ElseList, elseReach, dot); err != nil {
-			return err
-		}
-		if !condition.known && walker.dependencies != before {
-			walker.recordConditionLimitation(condition)
-		}
-		return nil
+		return walker.visitBranch(&node.BranchNode, reach, dot, true)
 	case *parse.RangeNode:
 		if err := walker.visit(node.Pipe, reach, dot); err != nil {
 			return err

internal/prompt/requirements_test.go

@@ -314,7 +314,7 @@ func TestAnalyzeRequirementsClassifiesKnownConditions(t *testing.T) {
 				"active":   {Name: "active", Body: []byte("active")},
 				"inactive": {Name: "inactive", Body: []byte("inactive")},
 			}
-			rendered, err := NewGoRenderer().Render(context.Background(), definition, artifacts, test.vars)
+			rendered, err := capturedTestRenderer(t, definition).Render(context.Background(), definition, artifacts, test.vars)
 			if err != nil {
 				t.Fatal(err)
 			}
@@ -406,6 +406,35 @@ func TestAnalyzeRequirementsReportsUnresolvedDecisionAndContentConditions(t *tes
 	}
 }
 
+func TestConditionEvaluationMergesOwnedEvidence(t *testing.T) {
+	left := conditionEvaluation{missingVariables: map[string]struct{}{"a": {}, "b": {}}, contentInputs: map[string]struct{}{"document": {}}, unsupported: true}
+	right := conditionEvaluation{missingVariables: map[string]struct{}{"b": {}, "c": {}}, inputNameUnknown: true}
+	merged := mergeConditionEvaluations(left, right)
+	if !merged.unsupported || !merged.inputNameUnknown || len(merged.missingVariables) != 3 || len(merged.contentInputs) != 1 {
+		t.Fatalf("merged evidence = %+v", merged)
+	}
+	transferred := mergeConditionEvaluations(conditionEvaluation{}, conditionEvaluation{missingVariables: map[string]struct{}{"only": {}}})
+	if len(transferred.missingVariables) != 1 || transferred.contentInputs != nil {
+		t.Fatalf("transferred evidence = %+v", transferred)
+	}
+}
+
+func TestAnalyzeRequirementsRetainsLeftHeavyMissingConditions(t *testing.T) {
+	compiled := compileRequirementTemplate(t, "nested", `{{if eq (eq (eq .a .b) .c) .d}}{{input "yes"}}{{else}}{{input "no"}}{{end}}`)
+	result, err := AnalyzeRequirements(context.Background(), &domain.PromptDefinition{}, RequirementSnapshot{Templates: CompiledTemplates{Messages: []*template.Template{compiled}}}, nil, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if result.Complete || len(result.Variables) != 4 || len(result.Inputs) != 2 {
+		t.Fatalf("requirements = %+v", result)
+	}
+	for i, name := range []string{"a", "b", "c", "d"} {
+		if result.Variables[i].Name != name {
+			t.Fatalf("variables = %+v", result.Variables)
+		}
+	}
+}
+
 func TestAnalyzeRequirementsRetainsInactiveEntriesAndPromotesActiveUses(t *testing.T) {
 	description := "declared for a reason"
 	definition := &domain.PromptDefinition{Templates: []domain.PromptMessageTemplate{{
@@ -497,7 +526,7 @@ func TestAnalyzeRequirementsResolvesSimpleInputNames(t *testing.T) {
 				t.Fatalf("name-source caller key classification is incorrect: %+v", result.Variables)
 			}
 			artifacts := map[string]*domain.Artifact{inputName: {Name: inputName, Body: []byte("resolved")}}
-			rendered, err := NewGoRenderer().Render(context.Background(), definition, artifacts, test.vars)
+			rendered, err := capturedTestRenderer(t, definition).Render(context.Background(), definition, artifacts, test.vars)
 			if err != nil {
 				t.Fatal(err)
 			}

internal/promptdef/repository.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 
 	"go.maximumdirect.net/promptkit/internal/domain"
+	"go.maximumdirect.net/promptkit/internal/prompt"
 )
 
 // ErrPromptDefinitionNotFound identifies an absent captured prompt definition.
@@ -12,5 +13,7 @@ var ErrPromptDefinitionNotFound = errors.New("prompt definition not found")
 
 // Repository selects prompt definitions from a captured index.
 type Repository interface {
-	GetPromptDefinition(ctx context.Context, id string) (*domain.PromptDefinition, error)
+	GetPromptSnapshot(ctx context.Context, id string) (*domain.PromptDefinition, string, error)
+	GetPromptInspection(ctx context.Context, id string) (*domain.PromptInspection, error)
+	GetRequirementSnapshot(id string) (prompt.RequirementSnapshot, bool)
 }

internal/usecase/operation_error.go

@@ -0,0 +1,38 @@
+package usecase
+
+import (
+	"errors"
+	"fmt"
+
+	"go.maximumdirect.net/promptkit/internal/profile"
+	"go.maximumdirect.net/promptkit/internal/promptdef"
+)
+
+// OperationError identifies the operation that owns a failure while retaining
+// the original cause for inspection.
+type OperationError struct {
+	Category error
+	Cause    error
+}
+
+func (e *OperationError) Error() string        { return fmt.Sprintf("%v: %v", e.Category, e.Cause) }
+func (e *OperationError) Unwrap() error        { return e.Cause }
+func (e *OperationError) Is(target error) bool { return target == e.Category }
+
+func promptLookupError(cause error) error {
+	category := ErrPromptLoad
+	if errors.Is(cause, promptdef.ErrPromptDefinitionNotFound) {
+		category = promptdef.ErrPromptDefinitionNotFound
+		cause = fmt.Errorf("%w: %w", ErrPromptLoad, cause)
+	}
+	return &OperationError{Category: category, Cause: cause}
+}
+
+func profileLookupError(cause error) error {
+	category := ErrProfileLoad
+	if errors.Is(cause, profile.ErrProfileNotFound) {
+		category = profile.ErrProfileNotFound
+		cause = fmt.Errorf("%w: %w", ErrProfileLoad, cause)
+	}
+	return &OperationError{Category: category, Cause: cause}
+}

internal/usecase/operation_error_test.go

@@ -0,0 +1,34 @@
+package usecase
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+
+	"go.maximumdirect.net/promptkit/internal/profile"
+	"go.maximumdirect.net/promptkit/internal/promptdef"
+)
+
+func TestOperationErrorRetainsOwnerAndCause(t *testing.T) {
+	cause := fmt.Errorf("nested: %w", promptdef.ErrPromptDefinitionNotFound)
+	outer := &OperationError{Category: ErrLLMGenerate, Cause: cause}
+	if !errors.Is(outer, ErrLLMGenerate) || !errors.Is(outer, promptdef.ErrPromptDefinitionNotFound) || errors.Unwrap(outer) != cause {
+		t.Fatalf("operation error = %v", outer)
+	}
+	for _, test := range []struct {
+		err      error
+		category error
+	}{
+		{promptLookupError(cause), promptdef.ErrPromptDefinitionNotFound},
+		{profileLookupError(profile.ErrProfileNotFound), profile.ErrProfileNotFound},
+		{promptLookupError(contextFailure), ErrPromptLoad},
+		{profileLookupError(contextFailure), ErrProfileLoad},
+	} {
+		var operation *OperationError
+		if !errors.As(test.err, &operation) || operation.Category != test.category {
+			t.Errorf("operation = %+v", operation)
+		}
+	}
+}
+
+var contextFailure = errors.New("lookup failed")

internal/usecase/output_contract_test.go

@@ -172,14 +172,13 @@ func TestRunnerRunRejectsInvalidOutputContractBeforeAdmission(t *testing.T) {
 func assertOutputContractCompletionSkipped(t *testing.T, collaborators outputContractTestCollaborators) {
 	t.Helper()
 	if collaborators.artifacts.calls != 0 || collaborators.renderer.calls != 0 ||
-		collaborators.validator.prepareCalls != 0 || collaborators.validator.directValidateCalls != 0 ||
+		collaborators.validator.prepareCalls != 0 ||
 		len(collaborators.admitter.backendIDs) != 0 || collaborators.llm.calls != 0 {
 		t.Fatalf(
-			"invalid output contract reached downstream work: artifacts=%d renderer=%d prepare_validation=%d validation=%d admissions=%d generation=%d",
+			"invalid output contract reached downstream work: artifacts=%d renderer=%d prepare_validation=%d admissions=%d generation=%d",
 			collaborators.artifacts.calls,
 			collaborators.renderer.calls,
 			collaborators.validator.prepareCalls,
-			collaborators.validator.directValidateCalls,
 			len(collaborators.admitter.backendIDs),
 			collaborators.llm.calls,
 		)

internal/usecase/prepared_execution.go

@@ -7,7 +7,6 @@ import (
 	"time"
 
 	"go.maximumdirect.net/promptkit/internal/domain"
-	"go.maximumdirect.net/promptkit/internal/jsonvalue"
 	"go.maximumdirect.net/promptkit/internal/observation"
 	"go.maximumdirect.net/promptkit/internal/validate"
 )
@@ -22,7 +21,7 @@ const (
 
 // PreparedExecution owns one frozen, single-use runner execution.
 type PreparedExecution struct {
-	owner   *Runner
+	owner   *runnerIdentity
 	mu      sync.Mutex
 	state   preparedExecutionState
 	details *domain.PreparedRun
@@ -50,24 +49,12 @@ func (r *Runner) PrepareExecution(ctx context.Context, req domain.RunRequest) (*
 		return nil, err
 	}
 
-	executionSnapshot := operation.run
-	extraParams, err := jsonvalue.CopyMap(executionSnapshot.EffectiveModelParams.ExtraParams)
-	if err != nil {
-		return nil, fmt.Errorf("%w: failed to copy prepared execution: %v", ErrInvalidRequest, err)
-	}
-	executionSnapshot.EffectiveModelParams.ExtraParams = extraParams
-
-	details, err := clonePreparedRun(executionSnapshot)
-	if err != nil {
-		return nil, fmt.Errorf("%w: failed to copy prepared execution details: %v", ErrInvalidRequest, err)
-	}
-
 	return &PreparedExecution{
-		owner:   r,
+		owner:   r.identity,
 		state:   preparedExecutionReady,
-		details: details,
+		details: operation.run,
 		payload: &preparedExecutionPayload{
-			prepared:         executionSnapshot,
+			prepared:         operation.run,
 			validation:       operation.validation,
 			directKey:        state.effectiveModel.APIKey,
 			transientRetries: state.transientRetries,
@@ -76,7 +63,8 @@ func (r *Runner) PrepareExecution(ctx context.Context, req domain.RunRequest) (*
 	}, nil
 }
 
-// Details returns a fresh credential-redacted copy of the prepared run.
+// Details returns immutable, credential-redacted metadata borrowed from the
+// handle. Callers must copy it before exposing it to mutable external code.
 func (p *PreparedExecution) Details() *domain.PreparedRun {
 	if p == nil {
 		return nil
@@ -85,11 +73,7 @@ func (p *PreparedExecution) Details() *domain.PreparedRun {
 	detailsSnapshot := p.details
 	p.mu.Unlock()
 
-	details, err := clonePreparedRun(detailsSnapshot)
-	if err != nil {
-		return nil
-	}
-	return details
+	return detailsSnapshot
 }
 
 // Discard invalidates an unclaimed execution and drops its private payload.
@@ -170,7 +154,7 @@ func (r *Runner) RunPrepared(ctx context.Context, prepared *PreparedExecution) (
 }
 
 func (p *PreparedExecution) claim(owner *Runner) (*preparedExecutionPayload, error) {
-	if p == nil || owner == nil || p.owner != owner {
+	if p == nil || owner == nil || owner.identity == nil || p.owner != owner.identity {
 		return nil, fmt.Errorf("%w: prepared execution does not belong to this runner", ErrInvalidRequest)
 	}
 
@@ -189,9 +173,6 @@ func (p *preparedExecutionPayload) clear() {
 	if p == nil {
 		return
 	}
-	if p.prepared != nil {
-		p.prepared.EffectiveModelParams.APIKey = ""
-	}
 	p.prepared = nil
 	p.validation = nil
 	p.directKey = ""
@@ -222,43 +203,3 @@ func (p noOpPreparedValidation) Validate(
 func (noOpPreparedValidation) SchemaDocument() any {
 	return nil
 }
-
-func clonePreparedRun(source *domain.PreparedRun) (*domain.PreparedRun, error) {
-	if source == nil {
-		return nil, nil
-	}
-
-	copied := *source
-	extraParams, err := jsonvalue.CopyMap(source.EffectiveModelParams.ExtraParams)
-	if err != nil {
-		return nil, err
-	}
-	copied.EffectiveModelParams.ExtraParams = extraParams
-
-	if source.InputHashes != nil {
-		copied.InputHashes = make(map[string]string, len(source.InputHashes))
-		for name, hash := range source.InputHashes {
-			copied.InputHashes[name] = hash
-		}
-	}
-	copied.Messages = domain.CloneRenderedMessages(source.Messages)
-
-	if source.StructuredOutput != nil {
-		structuredOutput := *source.StructuredOutput
-		copied.StructuredOutput = &structuredOutput
-		if source.StructuredOutput.JSONSchema != nil {
-			jsonSchema := *source.StructuredOutput.JSONSchema
-			copied.StructuredOutput.JSONSchema = &jsonSchema
-			schema, copyErr := cloneJSONValue(source.StructuredOutput.JSONSchema.Schema)
-			if copyErr != nil {
-				return nil, copyErr
-			}
-			copied.StructuredOutput.JSONSchema.Schema = schema
-		}
-	}
-	return &copied, nil
-}
-
-func cloneJSONValue(source any) (any, error) {
-	return jsonvalue.Copy(source)
-}

internal/usecase/prepared_execution_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 
 	"go.maximumdirect.net/promptkit/internal/domain"
+	"go.maximumdirect.net/promptkit/internal/jsonvalue"
 	"go.maximumdirect.net/promptkit/internal/llm"
 	"go.maximumdirect.net/promptkit/internal/validate"
 )
@@ -47,25 +48,15 @@ func (p *recordingPreparedValidation) SchemaDocument() any {
 }
 
 type recordingValidationPreparer struct {
-	plan                *recordingPreparedValidation
-	prepareErr          error
-	prepareCalls        int
-	directValidateCalls int
+	plan         *recordingPreparedValidation
+	prepareErr   error
+	prepareCalls int
 }
 
-type validationOnly struct{}
+type nilPlanPreparer struct{}
 
-func (validationOnly) Validate(context.Context, *domain.Artifact, domain.OutputContract) (domain.ValidationResult, error) {
-	return domain.ValidationResult{}, nil
-}
-
-func (v *recordingValidationPreparer) Validate(
-	context.Context,
-	*domain.Artifact,
-	domain.OutputContract,
-) (domain.ValidationResult, error) {
-	v.directValidateCalls++
-	return domain.ValidationResult{}, errors.New("live validation must not be used")
+func (nilPlanPreparer) PrepareValidation(context.Context, domain.OutputContract) (validate.PreparedValidation, error) {
+	return nil, nil
 }
 
 func (v *recordingValidationPreparer) PrepareValidation(
@@ -129,12 +120,8 @@ func TestRunnerPrepareExecutionCompletesWithoutAdmissionOrGeneration(t *testing.
 	}
 	defer prepared.Discard()
 
-	if validator.prepareCalls != 1 || validator.directValidateCalls != 0 {
-		t.Fatalf(
-			"validation calls=(prepare=%d direct=%d), want (1, 0)",
-			validator.prepareCalls,
-			validator.directValidateCalls,
-		)
+	if validator.prepareCalls != 1 {
+		t.Fatalf("validation preparations = %d, want 1", validator.prepareCalls)
 	}
 	if reader.calls != 1 || renderer.calls != 1 {
 		t.Fatalf("completion calls=(artifact=%d render=%d), want (1, 1)", reader.calls, renderer.calls)
@@ -156,90 +143,37 @@ func TestRunnerPrepareExecutionCompletesWithoutAdmissionOrGeneration(t *testing.
 		t.Fatalf("prepared details have unexpected structured output: %#v", first.StructuredOutput)
 	}
 
-	first.Messages[0].Content = "caller mutation"
-	first.InputHashes["input"] = "caller mutation"
-	first.EffectiveModelParams.ExtraParams["metadata"].(map[string]any)["source"] = "caller mutation"
-	first.StructuredOutput.JSONSchema.Schema.(map[string]any)["type"] = "string"
 	renderer.rendered.Messages[0].Content = "source mutation"
 
 	second := prepared.Details()
-	if second.Messages[0].Content != "original message" ||
-		second.InputHashes["input"] == "caller mutation" ||
+	if second != first || second.Messages[0].Content != "original message" ||
 		second.EffectiveModelParams.ExtraParams["metadata"].(map[string]any)["source"] != "original" ||
 		second.StructuredOutput.JSONSchema.Schema.(map[string]any)["type"] != "object" {
-		t.Fatalf("details did not preserve an independent snapshot: %#v", second)
+		t.Fatalf("borrowed details did not preserve the snapshot: %#v", second)
 	}
 }
 
-func TestRunnerPreparationRejectsExcessivelyDeepPreparedSchema(t *testing.T) {
-	operations := []struct {
-		name string
-		run  func(*Runner, domain.RunRequest) error
-	}{
-		{
-			name: "Prepare",
-			run: func(runner *Runner, request domain.RunRequest) error {
-				_, err := runner.Prepare(context.Background(), request)
-				return err
-			},
-		},
-		{
-			name: "Run",
-			run: func(runner *Runner, request domain.RunRequest) error {
-				_, err := runner.Run(context.Background(), request)
-				return err
-			},
-		},
-		{
-			name: "PrepareExecution",
-			run: func(runner *Runner, request domain.RunRequest) error {
-				_, err := runner.PrepareExecution(context.Background(), request)
-				return err
-			},
-		},
+func TestRunnerPreparationDetachesDeepPreparedSchema(t *testing.T) {
+	var nested any = "original"
+	for range 150 {
+		nested = map[string]any{"child": nested}
 	}
-
-	for _, operation := range operations {
-		t.Run(operation.name, func(t *testing.T) {
-			def := promptDef(domain.FormatJSON, domain.ValidationJSONSchema, 0)
-			def.Validation.SchemaPath = "schema.json"
-			llmClient := &fakeLLM{forbid: true}
-			validator := &recordingValidationPreparer{
-				plan: &recordingPreparedValidation{schemaDocument: excessivelyDeepPreparedJSONValue()},
-			}
-			runner := NewRunner(
-				&fakePromptRepo{def: def},
-				&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}},
-
-				defaultArtifactReader(),
-				defaultRenderer(),
-				llmClient,
-				validator,
-				nil,
-			)
-
-			err := operation.run(runner, domain.RunRequest{
-				PromptID:  "p",
-				ProfileID: "exec",
-				Inputs:    singleInputRef(),
-			})
-			if !errors.Is(err, ErrValidation) {
-				t.Fatalf("expected ErrValidation, got %v", err)
-			}
-			if llmClient.calls != 0 {
-				t.Fatalf("invalid prepared schema reached generation: %d calls", llmClient.calls)
-			}
-		})
+	schema := map[string]any{"annotation": nested}
+	def := promptDef(domain.FormatJSON, domain.ValidationJSONSchema, 0)
+	def.Validation.SchemaPath = "schema.json"
+	validator := &recordingValidationPreparer{plan: &recordingPreparedValidation{schemaDocument: schema}}
+	runner := NewRunner(&fakePromptRepo{def: def},
+		&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}},
+		defaultArtifactReader(), defaultRenderer(), &fakeLLM{forbid: true}, validator, nil)
+	prepared, err := runner.PrepareExecution(context.Background(), domain.RunRequest{PromptID: "p", ProfileID: "exec", Inputs: singleInputRef()})
+	if err != nil {
+		t.Fatalf("prepare execution: %v", err)
 	}
-}
-
-func excessivelyDeepPreparedJSONValue() any {
-	const clearlyUnsafeContainerDepth = 1_000
-	var value any = true
-	for level := 0; level < clearlyUnsafeContainerDepth; level++ {
-		value = map[string]any{"child": value}
+	schema["annotation"].(map[string]any)["child"] = "source mutation"
+	first := prepared.Details().StructuredOutput.JSONSchema.Schema.(map[string]any)
+	if _, ok := first["annotation"].(map[string]any)["child"].(map[string]any); !ok {
+		t.Fatal("prepared schema aliases the validator document")
 	}
-	return value
 }
 
 func TestRunnerRunPreparedCredentialAvailabilityBeforeAdmission(t *testing.T) {
@@ -421,8 +355,8 @@ func TestRunnerRunPreparedUsesFrozenValidationForInitialAndRepairOutputs(t *test
 	if !reflect.DeepEqual(validator.plan.artifacts, []string{`{"broken":true}`, `{"repaired":true}`}) {
 		t.Fatalf("prepared validation artifacts=%#v", validator.plan.artifacts)
 	}
-	if validator.directValidateCalls != 0 || repairer.calls != 1 {
-		t.Fatalf("validation/repair calls=(direct=%d repair=%d), want (0, 1)", validator.directValidateCalls, repairer.calls)
+	if repairer.calls != 1 {
+		t.Fatalf("repair calls = %d, want 1", repairer.calls)
 	}
 	if len(client.requests) != 1 || len(repairer.reqs) != 1 ||
 		!reflect.DeepEqual(repairer.reqs[0].OriginalMessages, client.requests[0].Prompt.Messages) {
@@ -498,7 +432,7 @@ func TestRunnerRunPreparedReleasesAdmissionAcrossExecutionErrors(t *testing.T) {
 				}},
 			},
 			repairer:   &fakeRepairer{err: repairInvalidRequest},
-			wantError:  ErrInvalidRequest,
+			wantError:  ErrLLMGenerate,
 			wantSource: repairInvalidRequest,
 		},
 		{
@@ -600,6 +534,9 @@ func TestRunnerPreparedExecutionOwnershipUseAndDiscard(t *testing.T) {
 	}
 
 	owner := newRunner()
+	if other := newRunner(); owner.identity == nil || owner.identity == other.identity {
+		t.Fatal("constructed runners must have independent identity tokens")
+	}
 	prepared, err := owner.PrepareExecution(context.Background(), request)
 	if err != nil {
 		t.Fatalf("prepare execution: %v", err)
@@ -616,6 +553,9 @@ func TestRunnerPreparedExecutionOwnershipUseAndDiscard(t *testing.T) {
 	if prepared.Details() == nil {
 		t.Fatal("details unavailable after execution")
 	}
+	if prepared.owner != owner.identity || prepared.payload != nil {
+		t.Fatal("claimed handle retained payload or lost owner identity")
+	}
 
 	discarded, err := owner.PrepareExecution(context.Background(), request)
 	if err != nil {
@@ -623,6 +563,9 @@ func TestRunnerPreparedExecutionOwnershipUseAndDiscard(t *testing.T) {
 	}
 	discarded.Discard()
 	discarded.Discard()
+	if discarded.owner != owner.identity || discarded.payload != nil {
+		t.Fatal("discarded handle retained payload or lost owner identity")
+	}
 	if _, err := owner.RunPrepared(context.Background(), discarded); !errors.Is(err, ErrInvalidRequest) {
 		t.Fatalf("discarded execution error=%v, want ErrInvalidRequest", err)
 	}
@@ -687,7 +630,7 @@ func TestRunnerPreparedExecutionDetachesTransferredSnapshotSources(t *testing.T)
 			}
 			wantLabel := "profile source"
 			if test.requestOverride {
-				request.Execution = &domain.ExecutionTargetOverride{ExtraParams: requestExtras}
+				request.Execution = &domain.ExecutionTargetOverride{ExtraParams: jsonvalue.CloneTrusted(requestExtras).(map[string]any)}
 				wantLabel = "request source"
 			}
 
@@ -711,11 +654,6 @@ func TestRunnerPreparedExecutionDetachesTransferredSnapshotSources(t *testing.T)
 				details.StructuredOutput.JSONSchema.Schema.(map[string]any)["properties"].(map[string]any)["value"].(map[string]any)["type"] != "string" {
 				t.Fatalf("prepared details retained a source alias: %#v", details)
 			}
-			details.Messages[0].Content = "mutated details"
-			if again := prepared.Details(); again == nil || len(again.Messages) != 1 || again.Messages[0].Content != "captured rendering" {
-				t.Fatalf("details mutation escaped into the retained snapshot: %+v", again)
-			}
-
 			result, err := runner.RunPrepared(context.Background(), prepared)
 			if err != nil || result == nil || !result.Validation.IsValid || result.InputHashes["transcript"] != "captured-input-hash" {
 				t.Fatalf("run prepared snapshot=(%+v, %v)", result, err)
@@ -737,22 +675,6 @@ func TestRunnerPreparedExecutionDetachesTransferredSnapshotSources(t *testing.T)
 	}
 }
 
-func TestRunnerPrepareExecutionClassifiesExtraCopyFailureAsInvalidRequest(t *testing.T) {
-	profile := defaultExecutionProfile()
-	profile.ResolvedTarget.ExtraParams = map[string]any{"unsupported": func() {}}
-	runner := NewRunner(
-		&fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)},
-		&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": profile}},
-		defaultArtifactReader(), defaultRenderer(), &fakeLLM{forbid: true}, nil, nil,
-	)
-	prepared, err := runner.PrepareExecution(context.Background(), domain.RunRequest{
-		PromptID: "p", ProfileID: "exec",
-	})
-	if prepared != nil || !errors.Is(err, ErrInvalidRequest) {
-		t.Fatalf("prepared execution copy failure=(%v, %v), want ErrInvalidRequest", prepared, err)
-	}
-}
-
 func TestRunnerPreparedExecutionWithoutValidatorSkipsValidation(t *testing.T) {
 	runner := NewRunner(
 		&fakePromptRepo{def: promptDef(domain.FormatJSON, domain.ValidationJSON, 0)},
@@ -782,7 +704,7 @@ func TestRunnerPreparedExecutionWithoutValidatorSkipsValidation(t *testing.T) {
 	}
 }
 
-func TestRunnerPrepareExecutionRequiresValidationPreparer(t *testing.T) {
+func TestRunnerPrepareExecutionRejectsNilValidationPlan(t *testing.T) {
 	reader := defaultArtifactReader()
 	runner := NewRunner(
 		&fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationBasic, 0)},
@@ -791,7 +713,7 @@ func TestRunnerPrepareExecutionRequiresValidationPreparer(t *testing.T) {
 		reader,
 		defaultRenderer(),
 		&fakeLLM{forbid: true},
-		validationOnly{},
+		nilPlanPreparer{},
 		nil,
 	)
 

internal/usecase/profile_inspection.go

@@ -7,7 +7,6 @@ import (
 	"strings"
 
 	"go.maximumdirect.net/promptkit/internal/domain"
-	"go.maximumdirect.net/promptkit/internal/jsonvalue"
 )
 
 type resolvedProfileSelection struct {
@@ -15,10 +14,6 @@ type resolvedProfileSelection struct {
 	profile *domain.ExecutionProfile
 }
 
-type profileIdentityRepository interface {
-	GetProfileIdentity(context.Context, string) (string, error)
-}
-
 func (r *Runner) profileLookupID(profileID string) (string, error) {
 	if strings.TrimSpace(profileID) == "" {
 		return "", fmt.Errorf("%w: profile id is required", ErrInvalidRequest)
@@ -39,7 +34,7 @@ func (r *Runner) resolveProfileSelection(
 	}
 	selectedProfile, err := r.profiles.GetProfile(ctx, lookupID)
 	if err != nil {
-		return nil, fmt.Errorf("%w: %w", ErrProfileLoad, err)
+		return nil, profileLookupError(err)
 	}
 	if selectedProfile == nil {
 		return nil, fmt.Errorf("%w: profile repository returned nil profile", ErrProfileLoad)
@@ -61,18 +56,11 @@ func (r *Runner) resolveProfileIdentity(ctx context.Context, profileID string) (
 	if err != nil {
 		return "", err
 	}
-	if indexed, ok := r.profiles.(profileIdentityRepository); ok {
-		identity, err := indexed.GetProfileIdentity(ctx, lookupID)
-		if err != nil {
-			return "", fmt.Errorf("%w: %w", ErrProfileLoad, err)
-		}
-		return identity, nil
-	}
-	selection, err := r.resolveProfileSelection(ctx, lookupID)
+	identity, err := r.profiles.GetProfileIdentity(ctx, lookupID)
 	if err != nil {
-		return "", err
+		return "", profileLookupError(err)
 	}
-	return selection.id, nil
+	return identity, nil
 }
 
 func normalizeResolvedExecutionTarget(target domain.ExecutionTarget) (domain.ExecutionTarget, error) {
@@ -108,7 +96,7 @@ func (r *Runner) InspectProfile(
 	}
 	select {
 	case <-ctx.Done():
-		return nil, fmt.Errorf("%w: %w", ErrProfileLoad, ctx.Err())
+		return nil, &OperationError{Category: ErrProfileLoad, Cause: ctx.Err()}
 	default:
 	}
 
@@ -118,12 +106,6 @@ func (r *Runner) InspectProfile(
 	}
 	target, _ := resolveExecutionTarget(selection.profile, nil)
 	target.APIKey = ""
-	params, err := jsonvalue.CopyMap(target.ExtraParams)
-	if err != nil {
-		return nil, fmt.Errorf("%w: profile extra parameters: %w", ErrProfileLoad, err)
-	}
-	target.ExtraParams = params
-
 	return &domain.ProfileInspection{
 		ProfileID:            selection.id,
 		EffectiveModelParams: target,

internal/usecase/profile_inspection_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"go.maximumdirect.net/promptkit/internal/domain"
+	"go.maximumdirect.net/promptkit/internal/jsonvalue"
 	"go.maximumdirect.net/promptkit/internal/profile"
 )
 
@@ -23,7 +24,21 @@ func (r *inspectionProfileRepository) GetProfile(_ context.Context, id string) (
 	if r.err != nil {
 		return nil, r.err
 	}
-	return r.profile, nil
+	if r.profile == nil {
+		return nil, nil
+	}
+	profile := *r.profile
+	if profile.ResolvedTarget != nil {
+		target := *profile.ResolvedTarget
+		target.ExtraParams = jsonvalue.CloneTrusted(target.ExtraParams).(map[string]any)
+		profile.ResolvedTarget = &target
+	}
+	return &profile, nil
+}
+
+func (r *inspectionProfileRepository) GetProfileIdentity(ctx context.Context, id string) (string, error) {
+	_, err := r.GetProfile(ctx, id)
+	return id, err
 }
 
 func TestRunnerInspectProfileUsesExactSnapshotAndCopiesTarget(t *testing.T) {

internal/usecase/prompt_inspection.go

@@ -13,10 +13,6 @@ type resolvedPromptDefinition struct {
 	hash       string
 }
 
-type promptInspectionRepository interface {
-	GetPromptInspection(context.Context, string) (*domain.PromptInspection, error)
-}
-
 func (r *Runner) resolvePromptDefinition(ctx context.Context, promptID string) (*resolvedPromptDefinition, error) {
 	if strings.TrimSpace(promptID) == "" {
 		return nil, fmt.Errorf("%w: prompt id is required", ErrInvalidRequest)
@@ -25,29 +21,14 @@ func (r *Runner) resolvePromptDefinition(ctx context.Context, promptID string) (
 		return nil, fmt.Errorf("%w: prompt repository is not configured", ErrPromptLoad)
 	}
 
-	var definition *domain.PromptDefinition
-	var hash string
-	var err error
-	if indexed, ok := r.promptDefs.(interface {
-		GetPromptSnapshot(context.Context, string) (*domain.PromptDefinition, string, error)
-	}); ok {
-		definition, hash, err = indexed.GetPromptSnapshot(ctx, promptID)
-	} else {
-		definition, err = r.promptDefs.GetPromptDefinition(ctx, promptID)
-	}
+	definition, hash, err := r.promptDefs.GetPromptSnapshot(ctx, promptID)
 	if err != nil {
-		return nil, fmt.Errorf("%w: %w", ErrPromptLoad, err)
+		return nil, promptLookupError(err)
 	}
 	if definition == nil {
 		return nil, fmt.Errorf("%w: prompt repository returned nil definition", ErrPromptLoad)
 	}
 
-	if hash == "" {
-		hash, err = hashPromptDefinition(definition)
-		if err != nil {
-			return nil, fmt.Errorf("%w: failed to hash prompt definition: %v", ErrPromptLoad, err)
-		}
-	}
 	return &resolvedPromptDefinition{definition: definition, hash: hash}, nil
 }
 
@@ -58,29 +39,14 @@ func (r *Runner) resolvePromptInspection(ctx context.Context, promptID string) (
 	if r == nil || r.promptDefs == nil {
 		return nil, fmt.Errorf("%w: prompt repository is not configured", ErrPromptLoad)
 	}
-	if indexed, ok := r.promptDefs.(promptInspectionRepository); ok {
-		inspection, err := indexed.GetPromptInspection(ctx, promptID)
-		if err != nil {
-			return nil, fmt.Errorf("%w: %w", ErrPromptLoad, err)
-		}
-		if inspection == nil {
-			return nil, fmt.Errorf("%w: prompt repository returned nil inspection", ErrPromptLoad)
-		}
-		return inspection, nil
-	}
-
-	selection, err := r.resolvePromptDefinition(ctx, promptID)
+	inspection, err := r.promptDefs.GetPromptInspection(ctx, promptID)
 	if err != nil {
-		return nil, err
+		return nil, promptLookupError(err)
 	}
-	definition := selection.definition
-	return &domain.PromptInspection{
-		PromptID:         definition.ID,
-		PromptHash:       selection.hash,
-		DefaultProfileID: definition.DefaultProfile,
-		Inputs:           append([]domain.PromptInput(nil), definition.Inputs...),
-		OutputContract:   definition.Validation,
-	}, nil
+	if inspection == nil {
+		return nil, fmt.Errorf("%w: prompt repository returned nil inspection", ErrPromptLoad)
+	}
+	return inspection, nil
 }
 
 // InspectPrompt resolves one explicit prompt without execution work.
@@ -90,7 +56,7 @@ func (r *Runner) InspectPrompt(ctx context.Context, promptID string) (*domain.Pr
 	}
 	select {
 	case <-ctx.Done():
-		return nil, fmt.Errorf("%w: %w", ErrPromptLoad, ctx.Err())
+		return nil, &OperationError{Category: ErrPromptLoad, Cause: ctx.Err()}
 	default:
 	}
 

internal/usecase/prompt_inspection_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"go.maximumdirect.net/promptkit/internal/domain"
+	"go.maximumdirect.net/promptkit/internal/prompt"
 	"go.maximumdirect.net/promptkit/internal/promptdef"
 )
 
@@ -23,20 +24,33 @@ type promptMetadataRepository struct {
 	lookupID      string
 }
 
-func (r *inspectionPromptRepository) GetPromptDefinition(
+func (r *inspectionPromptRepository) GetPromptSnapshot(
 	_ context.Context,
 	id string,
-) (*domain.PromptDefinition, error) {
+) (*domain.PromptDefinition, string, error) {
 	r.calls++
 	r.id = id
 	if r.err != nil {
-		return nil, r.err
+		return nil, "", r.err
 	}
-	return r.definition, nil
+	return r.definition, "captured-hash", nil
 }
 
-func (r *promptMetadataRepository) GetPromptDefinition(context.Context, string) (*domain.PromptDefinition, error) {
-	return nil, errors.New("full prompt definition should not be requested")
+func (r *inspectionPromptRepository) GetPromptInspection(ctx context.Context, id string) (*domain.PromptInspection, error) {
+	definition, hash, err := r.GetPromptSnapshot(ctx, id)
+	return fixturePromptInspection(definition, hash), err
+}
+
+func (*inspectionPromptRepository) GetRequirementSnapshot(string) (prompt.RequirementSnapshot, bool) {
+	return prompt.RequirementSnapshot{}, false
+}
+
+func (r *promptMetadataRepository) GetPromptSnapshot(context.Context, string) (*domain.PromptDefinition, string, error) {
+	return nil, "", errors.New("full prompt definition should not be requested")
+}
+
+func (*promptMetadataRepository) GetRequirementSnapshot(string) (prompt.RequirementSnapshot, bool) {
+	return prompt.RequirementSnapshot{}, false
 }
 
 func (r *promptMetadataRepository) GetPromptInspection(
@@ -71,15 +85,11 @@ func TestRunnerInspectPromptResolvesOneDefinitionWithoutExecutionCollaborators(t
 	if err != nil {
 		t.Fatalf("inspect prompt: %v", err)
 	}
-	wantHash, err := hashPromptDefinition(definition)
-	if err != nil {
-		t.Fatalf("hash prompt definition: %v", err)
-	}
 	if repository.calls != 1 || repository.id != " prompt-id " {
 		t.Fatalf("prompt lookup=(calls=%d id=%q), want one unchanged ID lookup", repository.calls, repository.id)
 	}
 	if inspection.PromptID != definition.ID ||
-		inspection.PromptHash != wantHash ||
+		inspection.PromptHash != "captured-hash" ||
 		inspection.DefaultProfileID != definition.DefaultProfile ||
 		!reflect.DeepEqual(inspection.Inputs, definition.Inputs) ||
 		inspection.OutputContract != definition.Validation {
@@ -96,7 +106,7 @@ func TestRunnerInspectPromptResolvesOneDefinitionWithoutExecutionCollaborators(t
 	}
 }
 
-func TestRunnerInspectPromptUsesOwnedMetadataWhenRepositorySupportsIt(t *testing.T) {
+func TestRunnerInspectPromptUsesOwnedCapturedMetadata(t *testing.T) {
 	repository := &promptMetadataRepository{inspection: domain.PromptInspection{
 		PromptID: "captured.prompt", PromptHash: "cached-prompt-hash",
 		DefaultProfileID: "partial-profile",
@@ -119,7 +129,7 @@ func TestRunnerInspectPromptUsesOwnedMetadataWhenRepositorySupportsIt(t *testing
 	}
 }
 
-func TestRunnerInspectPromptUsesCapturedHashWhenMetadataCapabilityIsAbsent(t *testing.T) {
+func TestRunnerInspectPromptUsesCapturedHashAndMetadata(t *testing.T) {
 	repository := &requirementInspectionPromptRepository{
 		definition: &domain.PromptDefinition{
 			ID: "captured.prompt", Inputs: []domain.PromptInput{{Name: "document"}},
@@ -128,7 +138,7 @@ func TestRunnerInspectPromptUsesCapturedHashWhenMetadataCapabilityIsAbsent(t *te
 	inspection, err := (&Runner{promptDefs: repository}).InspectPrompt(context.Background(), " requested-id ")
 	if err != nil || inspection.PromptID != "captured.prompt" ||
 		inspection.PromptHash != "captured-hash" || inspection.Inputs[0].Name != "document" {
-		t.Fatalf("captured-hash fallback inspection=(%+v, %v)", inspection, err)
+		t.Fatalf("captured inspection=(%+v, %v)", inspection, err)
 	}
 }
 

internal/usecase/repair_prefix.go

@@ -0,0 +1,48 @@
+package usecase
+
+import (
+	"encoding/json"
+	"strings"
+	"unicode/utf8"
+)
+
+// boundedDiagnosticJSON returns a JSON string prefix and whether it represents
+// the complete normalized input. It retains at most the useful prefix.
+func boundedDiagnosticJSON(value string, maxBytes int) ([]byte, bool) {
+	if maxBytes < 2 {
+		return nil, false
+	}
+	limit := maxBytes - 2
+	var prefix strings.Builder
+	used := 0
+	more := false
+	for i := 0; i < len(value); {
+		r, size := utf8.DecodeRuneInString(value[i:])
+		piece := value[i : i+size]
+		if r == utf8.RuneError && size == 1 {
+			piece = "\uFFFD"
+			i++
+			for i < len(value) {
+				r, size = utf8.DecodeRuneInString(value[i:])
+				if r != utf8.RuneError || size != 1 {
+					break
+				}
+				i++
+			}
+		} else {
+			i += size
+		}
+		if used+len(piece) > limit {
+			more = true
+			break
+		}
+		prefix.WriteString(piece)
+		used += len(piece)
+	}
+	normalized := prefix.String()
+	encoded, _ := json.Marshal(normalized)
+	if len(encoded) > maxBytes {
+		return truncateDiagnosticJSONValue(normalized, maxBytes), false
+	}
+	return encoded, !more
+}

internal/usecase/repair_prefix_test.go

@@ -0,0 +1,33 @@
+package usecase
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+	"unicode/utf8"
+)
+
+func TestBoundedDiagnosticJSON(t *testing.T) {
+	for _, input := range []string{"", "plain", "<&>\n\"", "雪☃", "a\xff\xfe\xffb", "\xff\xfe" + strings.Repeat("z", 100)} {
+		for budget := 0; budget <= 30; budget++ {
+			encoded, complete := boundedDiagnosticJSON(input, budget)
+			if budget < 2 {
+				if encoded != nil || complete {
+					t.Fatalf("budget %d: %q %v", budget, encoded, complete)
+				}
+				continue
+			}
+			if len(encoded) > budget || !utf8.Valid(encoded) {
+				t.Fatalf("budget %d: %q", budget, encoded)
+			}
+			var decoded string
+			if err := json.Unmarshal(encoded, &decoded); err != nil {
+				t.Fatal(err)
+			}
+			normalized := strings.ToValidUTF8(input, "\uFFFD")
+			if !strings.HasPrefix(normalized, decoded) || complete != (decoded == normalized) {
+				t.Fatalf("input %q budget %d: %q complete=%v normalized=%q", input, budget, decoded, complete, normalized)
+			}
+		}
+	}
+}

internal/usecase/repairer.go

@@ -117,27 +117,38 @@ func repairGuidance(mode domain.ValidationMode) (string, error) {
 }
 
 func formatRepairDiagnostics(errors []string) string {
-	diagnostics := make([]string, len(errors))
-	for index, diagnostic := range errors {
-		diagnostics[index] = strings.ToValidUTF8(diagnostic, "\uFFFD")
+	complete := []byte{'['}
+	fits := true
+	for _, diagnostic := range errors {
+		separator := 0
+		if len(complete) > 1 {
+			separator = 1
+		}
+		entry, whole := boundedDiagnosticJSON(diagnostic, maxRepairDiagnosticBytes-len(complete)-separator-1)
+		if !whole {
+			fits = false
+			break
+		}
+		if separator != 0 {
+			complete = append(complete, ',')
+		}
+		complete = append(complete, entry...)
 	}
-
-	complete, _ := json.Marshal(diagnostics)
-	if len(complete) <= maxRepairDiagnosticBytes {
-		return string(complete)
+	if fits {
+		return string(append(complete, ']'))
 	}
 
 	omission, _ := json.Marshal(omittedRepairDiagnostics)
 	encoded := make([]byte, 0, maxRepairDiagnosticBytes)
 	encoded = append(encoded, '[')
-	for _, diagnostic := range diagnostics {
-		entry, _ := json.Marshal(diagnostic)
+	for _, diagnostic := range errors {
 		separator := 0
 		if len(encoded) > 1 {
 			separator = 1
 		}
 		available := maxRepairDiagnosticBytes - len(encoded) - separator - 1 - len(omission) - 1
-		if len(entry) <= available {
+		entry, whole := boundedDiagnosticJSON(diagnostic, available)
+		if whole {
 			if separator != 0 {
 				encoded = append(encoded, ',')
 			}
@@ -151,7 +162,7 @@ func formatRepairDiagnostics(errors []string) string {
 		if separator != 0 {
 			encoded = append(encoded, ',')
 		}
-		encoded = append(encoded, truncateDiagnosticJSONValue(diagnostic, available)...)
+		encoded = append(encoded, entry...)
 		break
 	}
 	if len(encoded) > 1 {

internal/usecase/repairer_test.go

@@ -298,6 +298,23 @@ func TestFormatRepairDiagnosticsBoundsAndPreservesData(t *testing.T) {
 	}
 }
 
+func TestFormatRepairDiagnosticsEmptyAndEscapedOversize(t *testing.T) {
+	for _, values := range [][]string{nil, {}} {
+		if got := formatRepairDiagnostics(values); got != "[]" {
+			t.Fatalf("empty diagnostics = %q", got)
+		}
+	}
+	value := strings.Repeat("<&>\x00\xff\xfe", maxRepairDiagnosticBytes)
+	encoded := formatRepairDiagnostics([]string{value})
+	var got []string
+	if err := json.Unmarshal([]byte(encoded), &got); err != nil {
+		t.Fatal(err)
+	}
+	if len(encoded) > maxRepairDiagnosticBytes || len(got) != 2 || got[1] != omittedRepairDiagnostics || !strings.HasPrefix(strings.ToValidUTF8(value, "\uFFFD"), got[0]) {
+		t.Fatalf("oversize diagnostics length=%d, values=%d", len(encoded), len(got))
+	}
+}
+
 func manyRepairDiagnostics() []string {
 	diagnostics := make([]string, 1_000)
 	for index := range diagnostics {

internal/usecase/requirements_inspection.go

@@ -18,10 +18,6 @@ type RequirementInspectionRequest struct {
 	SessionID string
 }
 
-type requirementSnapshotRepository interface {
-	GetRequirementSnapshot(id string) (prompt.RequirementSnapshot, bool)
-}
-
 // InspectRequirements discovers prompt inputs and caller variables without
 // loading artifacts or performing execution preparation.
 func (r *Runner) InspectRequirements(
@@ -36,7 +32,7 @@ func (r *Runner) InspectRequirements(
 		return nil, fmt.Errorf("%w: session_id: %v", ErrInvalidRequest, err)
 	}
 	if err := ctx.Err(); err != nil {
-		return nil, fmt.Errorf("%w: %w", ErrPromptLoad, err)
+		return nil, &OperationError{Category: ErrPromptLoad, Cause: err}
 	}
 
 	selection, err := r.resolvePromptInspection(ctx, req.PromptID)
@@ -44,7 +40,7 @@ func (r *Runner) InspectRequirements(
 		return nil, err
 	}
 	if err := ctx.Err(); err != nil {
-		return nil, fmt.Errorf("%w: %w", ErrProfileLoad, err)
+		return nil, &OperationError{Category: ErrProfileLoad, Cause: err}
 	}
 	selectedProfileID := req.ProfileID
 	if strings.TrimSpace(selectedProfileID) == "" {
@@ -58,21 +54,17 @@ func (r *Runner) InspectRequirements(
 		return nil, err
 	}
 	if err := ctx.Err(); err != nil {
-		return nil, fmt.Errorf("%w: %w", ErrPromptLoad, err)
+		return nil, &OperationError{Category: ErrPromptLoad, Cause: err}
 	}
 
-	repository, ok := r.promptDefs.(requirementSnapshotRepository)
-	if !ok {
-		return nil, fmt.Errorf("%w: prompt repository does not provide captured requirement snapshots", ErrPromptLoad)
-	}
-	snapshot, ok := repository.GetRequirementSnapshot(selection.PromptID)
+	snapshot, ok := r.promptDefs.GetRequirementSnapshot(selection.PromptID)
 	if !ok {
 		return nil, fmt.Errorf("%w: captured requirement snapshot is unavailable", ErrPromptLoad)
 	}
 	definition := &domain.PromptDefinition{ID: selection.PromptID}
 	inspection, err := prompt.AnalyzeRequirements(ctx, definition, snapshot, req.Vars, directSessionID != "")
 	if err != nil {
-		return nil, fmt.Errorf("%w: %w", ErrPromptLoad, err)
+		return nil, &OperationError{Category: ErrPromptLoad, Cause: err}
 	}
 	inspection.ProfileID = profileIdentity
 	return &inspection, nil

internal/usecase/requirements_inspection_test.go

@@ -45,13 +45,6 @@ func (repository *inspectionProfileIdentityRepository) GetProfileIdentity(
 	return repository.identity, repository.identityErr
 }
 
-func (repository *requirementInspectionPromptRepository) GetPromptDefinition(
-	context.Context,
-	string,
-) (*domain.PromptDefinition, error) {
-	return repository.definition, repository.lookupErr
-}
-
 func (repository *requirementPromptMetadataRepository) GetPromptInspection(
 	_ context.Context,
 	id string,
@@ -71,6 +64,11 @@ func (repository *requirementInspectionPromptRepository) GetPromptSnapshot(
 	return repository.definition, "captured-hash", repository.lookupErr
 }
 
+func (repository *requirementInspectionPromptRepository) GetPromptInspection(ctx context.Context, id string) (*domain.PromptInspection, error) {
+	definition, hash, err := repository.GetPromptSnapshot(ctx, id)
+	return fixturePromptInspection(definition, hash), err
+}
+
 func (repository *requirementInspectionPromptRepository) GetRequirementSnapshot(
 	id string,
 ) (prompt.RequirementSnapshot, bool) {
@@ -163,7 +161,7 @@ func TestRunnerInspectRequirementsUsesPromptMetadataAndExactRequirementSnapshot(
 	}
 }
 
-func TestRunnerInspectRequirementsUsesProfileIdentityCapabilityOrFallback(t *testing.T) {
+func TestRunnerInspectRequirementsUsesProfileIdentity(t *testing.T) {
 	message, err := prompt.CompileTemplate("message", `{{.name}}`)
 	if err != nil {
 		t.Fatal(err)
@@ -177,7 +175,7 @@ func TestRunnerInspectRequirementsUsesProfileIdentityCapabilityOrFallback(t *tes
 	}
 	requestedID := "  literal-profile  "
 
-	t.Run("optional capability", func(t *testing.T) {
+	t.Run("identity lookup", func(t *testing.T) {
 		profiles := &inspectionProfileIdentityRepository{
 			inspectionProfileRepository: &inspectionProfileRepository{profile: &domain.ExecutionProfile{
 				ID: "repository-profile", ResolvedTarget: &domain.ExecutionTarget{},
@@ -196,21 +194,7 @@ func TestRunnerInspectRequirementsUsesProfileIdentityCapabilityOrFallback(t *tes
 		}
 	})
 
-	t.Run("full-profile fallback", func(t *testing.T) {
-		profiles := &inspectionProfileRepository{profile: &domain.ExecutionProfile{
-			ID: "repository-profile", ResolvedTarget: &domain.ExecutionTarget{},
-		}}
-		inspection, err := (&Runner{promptDefs: makePromptRepository(), profiles: profiles}).InspectRequirements(
-			context.Background(), RequirementInspectionRequest{
-				PromptID: "selected", ProfileID: requestedID, Vars: map[string]string{"name": "Ada"},
-			},
-		)
-		if err != nil || inspection.ProfileID != requestedID || profiles.calls != 1 || profiles.id != requestedID {
-			t.Fatalf("fallback inspection=(%+v, %v), full lookup=(%d,%q)", inspection, err, profiles.calls, profiles.id)
-		}
-	})
-
-	t.Run("capability failure", func(t *testing.T) {
+	t.Run("identity failure", func(t *testing.T) {
 		lookupErr := errors.New("profile identity lookup failed")
 		profiles := &inspectionProfileIdentityRepository{
 			inspectionProfileRepository: &inspectionProfileRepository{},
@@ -329,14 +313,6 @@ func TestRunnerInspectRequirementsClassifiesSelectionAndSnapshotFailures(t *test
 		}
 	})
 
-	t.Run("repository lacks snapshot capability", func(t *testing.T) {
-		_, err := (&Runner{promptDefs: &inspectionPromptRepository{definition: &domain.PromptDefinition{ID: "selected", DefaultProfile: "profile"}},
-			profiles: &inspectionProfileRepository{profile: &domain.ExecutionProfile{ID: "profile", ResolvedTarget: &domain.ExecutionTarget{}}},
-		}).InspectRequirements(context.Background(), RequirementInspectionRequest{PromptID: "selected"})
-		if !errors.Is(err, ErrPromptLoad) {
-			t.Fatalf("missing capability error=%v", err)
-		}
-	})
 	if _, err := (*Runner)(nil).InspectRequirements(context.Background(), RequirementInspectionRequest{PromptID: "selected"}); !errors.Is(err, ErrPromptLoad) {
 		t.Fatalf("nil runner error=%v", err)
 	}
@@ -348,11 +324,6 @@ func TestRunnerInspectRequirementsClassifiesSelectionAndSnapshotFailures(t *test
 	); !errors.Is(err, ErrProfileLoad) {
 		t.Fatalf("missing profile error=%v", err)
 	}
-	if _, err := (&Runner{promptDefs: &requirementInspectionPromptRepository{definition: &domain.PromptDefinition{ID: "selected", DefaultProfile: "profile"}},
-		profiles: &inspectionProfileRepository{profile: &domain.ExecutionProfile{ID: "profile"}},
-	}).InspectRequirements(context.Background(), RequirementInspectionRequest{PromptID: "selected"}); !errors.Is(err, ErrProfileLoad) {
-		t.Fatalf("unresolved profile error=%v", err)
-	}
 	if _, err := (&Runner{promptDefs: &requirementInspectionPromptRepository{lookupErr: promptdef.ErrPromptDefinitionNotFound}}).InspectRequirements(
 		context.Background(), RequirementInspectionRequest{PromptID: "missing"},
 	); !errors.Is(err, ErrPromptLoad) || !errors.Is(err, promptdef.ErrPromptDefinitionNotFound) {

internal/usecase/resolved_targets_test.go

@@ -58,6 +58,19 @@ func TestPreparationCompletesResolvedTargetThroughRequestOverrides(t *testing.T)
 	}
 }
 
+func TestResolvedTargetPreservesProviderMapSelection(t *testing.T) {
+	profile := &domain.ExecutionProfile{ResolvedTarget: &domain.ExecutionTarget{ExtraParams: map[string]any{"configured": true}}}
+	selected, _ := resolveExecutionTarget(profile, &domain.ExecutionTargetOverride{ExtraParams: map[string]any{}})
+	if selected.ExtraParams["configured"] != true {
+		t.Fatalf("empty override did not inherit provider settings: %#v", selected.ExtraParams)
+	}
+	profile.ResolvedTarget.ExtraParams = map[string]any{}
+	selected, _ = resolveExecutionTarget(profile, nil)
+	if selected.ExtraParams != nil {
+		t.Fatalf("empty provider settings changed projection: %#v", selected.ExtraParams)
+	}
+}
+
 func TestResolvedTargetCredentialAvailability(t *testing.T) {
 	profile := &domain.ExecutionProfile{ID: "direct", ResolvedTarget: &domain.ExecutionTarget{
 		Endpoint: "https://provider.example/v1", Model: "model", APIKeyRequired: true,

internal/usecase/runner.go

@@ -18,6 +18,7 @@ import (
 	"go.maximumdirect.net/promptkit/internal/capacity"
 	"go.maximumdirect.net/promptkit/internal/defaults"
 	"go.maximumdirect.net/promptkit/internal/domain"
+	"go.maximumdirect.net/promptkit/internal/generation"
 	"go.maximumdirect.net/promptkit/internal/jsonvalue"
 	"go.maximumdirect.net/promptkit/internal/llm"
 	"go.maximumdirect.net/promptkit/internal/observation"
@@ -42,17 +43,22 @@ var (
 
 // Runner executes the Promptkit core use case.
 type Runner struct {
+	identity                *runnerIdentity
 	promptDefs              promptdef.Repository
 	profiles                profile.Repository
 	artifacts               artifact.Reader
 	renderer                prompt.Renderer
 	llm                     llm.Client
-	validator               validate.Validator
+	validator               validate.ValidationPreparer
 	repairer                OutputRepairer
 	admitter                RunAdmitter
 	defaultTransientRetries uint64
 }
 
+// A non-zero-sized token gives each constructed runner a distinct identity
+// without retaining its collaborators in prepared handles.
+type runnerIdentity struct{ marker byte }
+
 // RunAdmitter reserves capacity for one resolved backend run.
 type RunAdmitter interface {
 	Admit(context.Context, string) (func(), error)
@@ -81,7 +87,7 @@ func NewRunner(
 	artifacts artifact.Reader,
 	renderer prompt.Renderer,
 	llmClient llm.Client,
-	validator validate.Validator,
+	validator validate.ValidationPreparer,
 	admitter RunAdmitter,
 ) *Runner {
 	return NewRunnerWithRepairer(
@@ -102,7 +108,7 @@ func NewRunnerWithRepairer(
 	artifacts artifact.Reader,
 	renderer prompt.Renderer,
 	llmClient llm.Client,
-	validator validate.Validator,
+	validator validate.ValidationPreparer,
 	repairer OutputRepairer,
 	admitter RunAdmitter,
 	defaultTransientRetries ...uint64,
@@ -112,6 +118,7 @@ func NewRunnerWithRepairer(
 		retries = defaultTransientRetries[0]
 	}
 	return &Runner{
+		identity:                &runnerIdentity{},
 		promptDefs:              promptDefs,
 		profiles:                profiles,
 		artifacts:               artifacts,
@@ -204,7 +211,7 @@ func (r *Runner) executePreparedRun(
 	outputArtifact := buildOutputArtifact(genResp.Content, prepared.OutputContract.Format)
 	validationResult, err := validateArtifact(ctx, &outputArtifact, 0)
 	if err != nil {
-		return nil, fmt.Errorf("%w: %w", ErrValidation, err)
+		return nil, &OperationError{Category: ErrValidation, Cause: err}
 	}
 
 	if r.shouldAttemptRepair(prepared.OutputContract, validationResult) {
@@ -238,7 +245,7 @@ func (r *Runner) executePreparedRun(
 
 			validationResult, err = validateArtifact(ctx, &outputArtifact, attemptsUsed)
 			if err != nil {
-				return nil, fmt.Errorf("%w: %w", ErrValidation, err)
+				return nil, &OperationError{Category: ErrValidation, Cause: err}
 			}
 		}
 	}
@@ -269,10 +276,10 @@ func (r *Runner) executePreparedRun(
 }
 
 func wrapGenerationError(err error) error {
-	if errors.Is(err, llm.ErrInvalidRequest) {
-		return fmt.Errorf("%w: %w", ErrInvalidRequest, err)
+	if _, ok := err.(*generation.PreparationError); ok {
+		return &OperationError{Category: ErrInvalidRequest, Cause: err}
 	}
-	return fmt.Errorf("%w: %w", ErrLLMGenerate, err)
+	return &OperationError{Category: ErrLLMGenerate, Cause: err}
 }
 
 func addTokenUsage(total, next domain.TokenUsage) domain.TokenUsage {
@@ -402,13 +409,9 @@ func (r *Runner) prepareValidation(
 	if r.validator == nil {
 		return noOpPreparedValidation{contract: contract}, nil
 	}
-	preparer, ok := r.validator.(validate.ValidationPreparer)
-	if !ok {
-		return nil, fmt.Errorf("%w: validator does not support prepared validation", ErrValidation)
-	}
-	plan, err := preparer.PrepareValidation(ctx, contract)
+	plan, err := r.validator.PrepareValidation(ctx, contract)
 	if err != nil {
-		return nil, fmt.Errorf("%w: %w", ErrValidation, err)
+		return nil, &OperationError{Category: ErrValidation, Cause: err}
 	}
 	if plan == nil {
 		return nil, fmt.Errorf("%w: validator returned nil prepared validation", ErrValidation)
@@ -432,11 +435,7 @@ func (r *Runner) structuredOutputFromValidationPlan(
 		}
 		return nil, fmt.Errorf("%w: prepared json_schema validation has no schema document", ErrValidation)
 	}
-	schemaDocument, err := jsonvalue.Copy(schemaDocument)
-	if err != nil {
-		return nil, fmt.Errorf("%w: invalid prepared json_schema schema document: %v", ErrValidation, err)
-	}
-	return structuredOutputSpec(def, schemaDocument), nil
+	return structuredOutputSpec(def, jsonvalue.CloneTrusted(schemaDocument)), nil
 }
 
 func (r *Runner) completePreparationWithStructuredOutput(
@@ -450,7 +449,7 @@ func (r *Runner) completePreparationWithStructuredOutput(
 	for name, ref := range req.Inputs {
 		art, readErr := r.artifacts.Read(ctx, ref)
 		if readErr != nil {
-			return nil, fmt.Errorf("%w: input %q: %w", ErrArtifactLoad, name, readErr)
+			return nil, &OperationError{Category: ErrArtifactLoad, Cause: fmt.Errorf("input %q: %w", name, readErr)}
 		}
 		if art.Name == "" {
 			art.Name = name
@@ -467,7 +466,7 @@ func (r *Runner) completePreparationWithStructuredOutput(
 	}
 	renderedPrompt, err := r.renderer.Render(ctx, definitionToRender, resolvedInputs, req.Vars)
 	if err != nil {
-		return nil, fmt.Errorf("%w: %w", ErrPromptRender, err)
+		return nil, &OperationError{Category: ErrPromptRender, Cause: err}
 	}
 	effectivePrompt := *renderedPrompt
 	if state.directSessionID != "" {
@@ -593,14 +592,16 @@ func mergeExecutionTargetOverride(base domain.ExecutionTarget, presence domain.E
 		out.APIKeyEnv = override.APIKeyEnv
 	}
 	if len(override.ExtraParams) > 0 {
-		out.ExtraParams = copyExtraParams(override.ExtraParams)
+		out.ExtraParams = override.ExtraParams
 	}
 	return out, presence
 }
 
 func resolveExecutionTarget(profileValue *domain.ExecutionProfile, override *domain.ExecutionTargetOverride) (domain.ExecutionTarget, domain.ExecutionTargetPresence) {
 	out := *profileValue.ResolvedTarget
-	out.ExtraParams = copyExtraParams(out.ExtraParams)
+	if len(out.ExtraParams) == 0 {
+		out.ExtraParams = nil
+	}
 	presence := profileValue.TargetPresence
 	if override != nil {
 		return mergeExecutionTargetOverride(out, presence, *override)
@@ -625,22 +626,8 @@ func validateAPIKey(apiKeyEnv string, apiKey string, apiKeyRequired bool) error
 	return nil
 }
 
-func copyExtraParams(src map[string]any) map[string]any {
-	if len(src) == 0 {
-		return nil
-	}
-	cp := make(map[string]any, len(src))
-	for k, v := range src {
-		cp[k] = v
-	}
-	return cp
-}
-
 func resolveOutputContract(def *domain.PromptDefinition, override *domain.OutputContract) (domain.OutputContract, error) {
 	contract := def.Validation
-	if contract.Format == "" {
-		contract.Format = def.OutputFormat
-	}
 	if override != nil {
 		contract = *override
 		if contract.Format == "" {
@@ -707,7 +694,3 @@ func buildOutputArtifact(content string, format domain.OutputFormat) domain.Arti
 		Hash:        hex.EncodeToString(hash[:]),
 	}
 }
-
-func hashPromptDefinition(def *domain.PromptDefinition) (string, error) {
-	return promptdef.HashDefinition(def)
-}

internal/usecase/runner_test.go

@@ -13,13 +13,17 @@ import (
 	"strings"
 	"sync"
 	"testing"
+	"text/template"
 	"time"
 
 	"go.maximumdirect.net/promptkit/internal/capacity"
 	"go.maximumdirect.net/promptkit/internal/defaults"
 	"go.maximumdirect.net/promptkit/internal/domain"
+	"go.maximumdirect.net/promptkit/internal/generation"
+	"go.maximumdirect.net/promptkit/internal/jsonvalue"
 	"go.maximumdirect.net/promptkit/internal/llm"
 	"go.maximumdirect.net/promptkit/internal/prompt"
+	"go.maximumdirect.net/promptkit/internal/promptdef"
 	"go.maximumdirect.net/promptkit/internal/validate"
 )
 
@@ -39,11 +43,61 @@ type staticPromptRepo struct {
 	def *domain.PromptDefinition
 }
 
-func (r staticPromptRepo) GetPromptDefinition(
+type capturedTemplateFixture struct {
+	id        string
+	templates prompt.CompiledTemplates
+}
+
+func (fixture capturedTemplateFixture) GetCompiledTemplates(id string) (prompt.CompiledTemplates, bool) {
+	return fixture.templates, id == fixture.id
+}
+
+func testCompiledRenderer(t *testing.T, definition *domain.PromptDefinition) prompt.Renderer {
+	t.Helper()
+	var templates prompt.CompiledTemplates
+	if definition.SessionID != "" {
+		var err error
+		templates.Session, err = prompt.CompileTemplate("session", definition.SessionID)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+	templates.Messages = make([]*template.Template, 0, len(definition.Templates))
+	for _, message := range definition.Templates {
+		compiled, err := prompt.CompileTemplate("message", message.Content)
+		if err != nil {
+			t.Fatal(err)
+		}
+		templates.Messages = append(templates.Messages, compiled)
+	}
+	return prompt.NewCompiledRenderer(capturedTemplateFixture{id: definition.ID, templates: templates})
+}
+
+func (r staticPromptRepo) GetPromptSnapshot(
 	context.Context,
 	string,
-) (*domain.PromptDefinition, error) {
-	return r.def, nil
+) (*domain.PromptDefinition, string, error) {
+	hash, err := promptdef.HashDefinition(r.def)
+	return r.def, hash, err
+}
+
+func (r staticPromptRepo) GetPromptInspection(ctx context.Context, id string) (*domain.PromptInspection, error) {
+	definition, hash, err := r.GetPromptSnapshot(ctx, id)
+	return fixturePromptInspection(definition, hash), err
+}
+
+func (staticPromptRepo) GetRequirementSnapshot(string) (prompt.RequirementSnapshot, bool) {
+	return prompt.RequirementSnapshot{}, false
+}
+
+func fixturePromptInspection(definition *domain.PromptDefinition, hash string) *domain.PromptInspection {
+	if definition == nil {
+		return nil
+	}
+	return &domain.PromptInspection{
+		PromptID: definition.ID, PromptHash: hash, DefaultProfileID: definition.DefaultProfile,
+		Inputs: append([]domain.PromptInput(nil), definition.Inputs...), OutputContract: definition.Validation,
+	}
 }
 
 type staticExecutionProfileRepo struct {
@@ -58,6 +112,10 @@ func (r staticExecutionProfileRepo) GetProfile(
 	return &value, nil
 }
 
+func (staticExecutionProfileRepo) GetProfileIdentity(_ context.Context, id string) (string, error) {
+	return id, nil
+}
+
 type staticArtifactReader struct{}
 
 func (staticArtifactReader) Read(
@@ -87,17 +145,40 @@ func (f *fakeExecutionProfileRepo) GetProfile(ctx context.Context, id string) (*
 	}
 	if p, ok := f.profiles[id]; ok {
 		cp := *p
+		if cp.ResolvedTarget != nil {
+			target := *cp.ResolvedTarget
+			target.ExtraParams = jsonvalue.CloneTrusted(target.ExtraParams).(map[string]any)
+			cp.ResolvedTarget = &target
+		}
 		return &cp, nil
 	}
 	return nil, errors.New("profile not found")
 }
 
-func (f *fakePromptRepo) GetPromptDefinition(ctx context.Context, id string) (*domain.PromptDefinition, error) {
+func (f *fakeExecutionProfileRepo) GetProfileIdentity(ctx context.Context, id string) (string, error) {
+	_, err := f.GetProfile(ctx, id)
+	return id, err
+}
+
+func (f *fakePromptRepo) GetPromptSnapshot(ctx context.Context, id string) (*domain.PromptDefinition, string, error) {
 	f.lastID = id
 	if f.err != nil {
-		return nil, f.err
+		return nil, "", f.err
 	}
-	return f.def, nil
+	if f.def == nil {
+		return nil, "", nil
+	}
+	hash, err := promptdef.HashDefinition(f.def)
+	return f.def, hash, err
+}
+
+func (f *fakePromptRepo) GetPromptInspection(ctx context.Context, id string) (*domain.PromptInspection, error) {
+	definition, hash, err := f.GetPromptSnapshot(ctx, id)
+	return fixturePromptInspection(definition, hash), err
+}
+
+func (*fakePromptRepo) GetRequirementSnapshot(string) (prompt.RequirementSnapshot, bool) {
+	return prompt.RequirementSnapshot{}, false
 }
 
 type fakeArtifactReader struct {
@@ -165,14 +246,6 @@ type fakeValidator struct {
 	validateCalls  int
 }
 
-func (f *fakeValidator) Validate(ctx context.Context, artifact *domain.Artifact, contract domain.OutputContract) (domain.ValidationResult, error) {
-	f.validateCalls++
-	if f.err != nil {
-		return domain.ValidationResult{}, f.err
-	}
-	return f.result, nil
-}
-
 func (f *fakeValidator) PrepareValidation(_ context.Context, contract domain.OutputContract) (validate.PreparedValidation, error) {
 	var schemaDocument any
 	if contract.ValidationMode == domain.ValidationJSONSchema {
@@ -186,17 +259,20 @@ func (f *fakeValidator) PrepareValidation(_ context.Context, contract domain.Out
 			schemaDocument = map[string]any{"type": "object"}
 		}
 	}
-	return &fakePreparedValidator{validator: f, contract: contract, schemaDocument: schemaDocument}, nil
+	return &fakePreparedValidator{validator: f, schemaDocument: schemaDocument}, nil
 }
 
 type fakePreparedValidator struct {
 	validator      *fakeValidator
-	contract       domain.OutputContract
 	schemaDocument any
 }
 
 func (p *fakePreparedValidator) Validate(ctx context.Context, artifact *domain.Artifact) (domain.ValidationResult, error) {
-	return p.validator.Validate(ctx, artifact, p.contract)
+	p.validator.validateCalls++
+	if p.validator.err != nil {
+		return domain.ValidationResult{}, p.validator.err
+	}
+	return p.validator.result, nil
 }
 
 func (p *fakePreparedValidator) SchemaDocument() any {
@@ -405,7 +481,7 @@ func TestRunnerDirectSessionResolution(t *testing.T) {
 			&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}},
 
 			defaultArtifactReader(),
-			prompt.NewGoRenderer(),
+			testCompiledRenderer(t, def),
 			&fakeLLM{forbid: true},
 			nil, nil)
 
@@ -452,7 +528,7 @@ func TestRunnerDirectSessionResolution(t *testing.T) {
 			&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}},
 
 			defaultArtifactReader(),
-			prompt.NewGoRenderer(),
+			testCompiledRenderer(t, def),
 			&fakeLLM{forbid: true},
 			nil, nil)
 
@@ -482,7 +558,7 @@ func TestRunnerDirectSessionResolution(t *testing.T) {
 			&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}},
 
 			defaultArtifactReader(),
-			prompt.NewGoRenderer(),
+			testCompiledRenderer(t, def),
 			&fakeLLM{forbid: true},
 			nil, nil)
 
@@ -842,7 +918,7 @@ func TestRunnerPrepareRequiredInputMissingFails(t *testing.T) {
 		&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}},
 
 		defaultArtifactReader(),
-		prompt.NewGoRenderer(),
+		testCompiledRenderer(t, def),
 		&fakeLLM{forbid: true},
 		nil, nil)
 
@@ -869,7 +945,7 @@ func TestRunnerPrepareUnknownTemplateInputReferenceFails(t *testing.T) {
 		&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}},
 
 		defaultArtifactReader(),
-		prompt.NewGoRenderer(),
+		testCompiledRenderer(t, def),
 		&fakeLLM{forbid: true},
 		nil, nil)
 
@@ -2074,7 +2150,7 @@ func TestRunnerRunCancellationPreservesGenerationCategory(t *testing.T) {
 	}
 }
 
-func TestRunnerRunLLMInvalidRequestMapsToUsecaseInvalidRequest(t *testing.T) {
+func TestRunnerRunInjectedInvalidRequestRemainsGenerationFailure(t *testing.T) {
 	runner := NewRunner(
 		&fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)},
 		&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}},
@@ -2089,11 +2165,8 @@ func TestRunnerRunLLMInvalidRequestMapsToUsecaseInvalidRequest(t *testing.T) {
 		ProfileID: "exec",
 		Inputs:    singleInputRef(),
 	})
-	if !errors.Is(err, ErrInvalidRequest) {
-		t.Fatalf("expected ErrInvalidRequest, got %v", err)
-	}
-	if errors.Is(err, ErrLLMGenerate) {
-		t.Fatalf("did not expect ErrLLMGenerate, got %v", err)
+	if !errors.Is(err, ErrLLMGenerate) || !errors.Is(err, llm.ErrInvalidRequest) {
+		t.Fatalf("expected generation error retaining cause, got %v", err)
 	}
 }
 
@@ -2401,7 +2474,7 @@ func TestRunnerSchedulesInitialAndRepairGenerationThroughOneBackendPool(t *testi
 	baseClient := &controlledRepairLLM{
 		events: make(chan controlledGeneration, 4),
 	}
-	scheduledClient := capacity.NewClient(manager, baseClient)
+	scheduledClient := generation.NewInjected(manager, baseClient)
 	admitter := &recordingRunAdmitter{next: manager}
 	runner := NewRunnerWithRepairer(
 		staticPromptRepo{def: promptDef(domain.FormatJSON, domain.ValidationJSON, 1)},
@@ -2507,7 +2580,6 @@ func promptDef(format domain.OutputFormat, mode domain.ValidationMode, attempts
 		DefaultProfile: "exec",
 		Inputs:         []domain.PromptInput{{Name: "transcript", Required: true}},
 		Templates:      []domain.PromptMessageTemplate{{Role: "user", Content: "x"}},
-		OutputFormat:   format,
 		Validation: domain.OutputContract{
 			ValidationMode: mode,
 			RepairAttempts: attempts,
@@ -2589,10 +2661,6 @@ func float64Ptr(v float64) *float64 {
 	return &v
 }
 
-func stringPtr(v string) *string {
-	return &v
-}
-
 func intPtr(v int) *int {
 	return &v
 }

internal/usecase/smoke_authentication.go

@@ -1,11 +1,8 @@
 package usecase
 
 import (
-	"bytes"
 	"context"
-	"encoding/json"
 	"fmt"
-	"io"
 	"net/http"
 
 	"go.maximumdirect.net/promptkit/internal/domain"
@@ -13,10 +10,12 @@ import (
 	"go.maximumdirect.net/promptkit/internal/llm"
 )
 
-type authenticationProbe struct {
-	client smokeHTTPGetter
+type smokeAuthenticationClient interface {
+	ProbeOpenRouterKey(context.Context, string, int, domain.ExecutionTarget) (llm.AuthenticationEvidence, error)
 }
 
+type authenticationProbe struct{ client smokeAuthenticationClient }
+
 type authenticationProbeOutcome struct {
 	supported           bool
 	applicable          *bool
@@ -26,16 +25,33 @@ type authenticationProbeOutcome struct {
 	failure             domain.ExecutionFailureKind
 }
 
-func (p authenticationProbe) run(
-	ctx context.Context,
-	backend domain.Backend,
-	target domain.SmokeTestTarget,
-) (authenticationProbeOutcome, error) {
+func (p authenticationProbe) run(ctx context.Context, backend domain.Backend, target domain.SmokeTestTarget) (authenticationProbeOutcome, error) {
 	outcome, err := p.support(backend)
 	if err != nil || !outcome.supported || (outcome.applicable != nil && !*outcome.applicable) {
 		return outcome, err
 	}
-	return p.runOpenRouterKey(ctx, target)
+	result, requestErr := p.client.ProbeOpenRouterKey(ctx, target.Endpoint, target.EffectiveSettings.TimeoutSeconds, target.EffectiveSettings)
+	outcome.evidence = result.HTTP
+	outcome.credentialsAccepted = result.Accepted
+	if result.Overflow {
+		outcome.reason = domain.SmokeTestReasonAuthenticationResponseLimitExceeded
+		outcome.failure = domain.ExecutionFailureOther
+	} else if result.Unrecognized {
+		outcome.reason = domain.SmokeTestReasonAuthenticationResponseUnrecognized
+		outcome.failure = domain.ExecutionFailureMalformedResponse
+	} else if requestErr != nil {
+		if !result.HTTP.DispatchInvoked {
+			return outcome, fmt.Errorf("execute authentication request: %w", requestErr)
+		}
+		outcome.failure = httpProbeFailure(ctx, requestErr)
+	} else if result.HTTP.ResponseReceived {
+		if result.HTTP.HTTPStatus != nil && *result.HTTP.HTTPStatus != http.StatusOK && *result.HTTP.HTTPStatus != http.StatusUnauthorized {
+			outcome.failure = generation.ClassifyFailure(llm.ErrUnexpectedStatus)
+		}
+	} else {
+		outcome.failure = httpProbeFailure(ctx, nil)
+	}
+	return outcome, nil
 }
 
 func (p authenticationProbe) support(backend domain.Backend) (authenticationProbeOutcome, error) {
@@ -48,11 +64,7 @@ func (p authenticationProbe) support(backend domain.Backend) (authenticationProb
 	}
 	switch *authentication.Kind {
 	case "none":
-		return authenticationProbeOutcome{
-			supported:  true,
-			applicable: boolPointer(false),
-			reason:     domain.SmokeTestReasonAuthenticationNotApplicable,
-		}, nil
+		return authenticationProbeOutcome{supported: true, applicable: boolPointer(false), reason: domain.SmokeTestReasonAuthenticationNotApplicable}, nil
 	case "openrouter_key":
 		if p.client == nil {
 			return authenticationProbeOutcome{reason: domain.SmokeTestReasonHTTPDiagnosticsUnavailable}, nil
@@ -62,129 +74,3 @@ func (p authenticationProbe) support(backend domain.Backend) (authenticationProb
 		return authenticationProbeOutcome{}, fmt.Errorf("%w: unsupported authentication probe kind %q", ErrInvalidRequest, *authentication.Kind)
 	}
 }
-
-func (p authenticationProbe) runOpenRouterKey(
-	ctx context.Context,
-	target domain.SmokeTestTarget,
-) (authenticationProbeOutcome, error) {
-	endpoint, err := endpointWithoutUserInfo(target.Endpoint)
-	if err != nil {
-		return authenticationProbeOutcome{}, fmt.Errorf("prepare authentication endpoint: %w", err)
-	}
-	response, evidence, requestErr := p.client.GetWithAuthenticationEvidence(
-		ctx,
-		endpoint,
-		target.EffectiveSettings.TimeoutSeconds,
-		target.EffectiveSettings,
-	)
-	if response != nil && response.Body != nil {
-		defer response.Body.Close()
-	}
-	outcome := authenticationProbeOutcome{
-		supported:  true,
-		applicable: boolPointer(true),
-		evidence:   evidence,
-	}
-	if evidence.ResponseReceived || response != nil {
-		status := evidence.HTTPStatus
-		if status == nil && response != nil {
-			status = &response.StatusCode
-		}
-		if status == nil {
-			outcome.failure = domain.ExecutionFailureMalformedResponse
-			outcome.reason = domain.SmokeTestReasonAuthenticationResponseUnrecognized
-			return outcome, nil
-		}
-		switch *status {
-		case http.StatusUnauthorized:
-			outcome.credentialsAccepted = boolPointer(false)
-		case http.StatusOK:
-			if response == nil || response.Body == nil {
-				outcome.reason = domain.SmokeTestReasonAuthenticationResponseUnrecognized
-				outcome.failure = domain.ExecutionFailureMalformedResponse
-				return outcome, nil
-			}
-			recognized, bodyErr := recognizedOpenRouterKeyResponse(response.Body)
-			if bodyErr != nil {
-				outcome.failure = httpProbeFailure(ctx, bodyErr)
-				return outcome, nil
-			}
-			if recognized {
-				outcome.credentialsAccepted = boolPointer(true)
-			} else {
-				outcome.reason = domain.SmokeTestReasonAuthenticationResponseUnrecognized
-				outcome.failure = domain.ExecutionFailureMalformedResponse
-			}
-		default:
-			outcome.failure = generation.ClassifyFailure(llm.ErrUnexpectedStatus)
-		}
-		return outcome, nil
-	}
-
-	if evidence.DispatchInvoked {
-		if requestErr != nil {
-			outcome.failure = httpProbeFailure(ctx, requestErr)
-		} else {
-			outcome.failure = httpProbeFailure(ctx, nil)
-		}
-		return outcome, nil
-	}
-	if requestErr != nil {
-		return outcome, fmt.Errorf("execute authentication request: %w", requestErr)
-	}
-	outcome.failure = generation.ClassifyFailure(llm.ErrTransport)
-	return outcome, nil
-}
-
-func recognizedOpenRouterKeyResponse(body io.Reader) (bool, error) {
-	contents, err := io.ReadAll(body)
-	if err != nil {
-		return false, err
-	}
-	var envelope map[string]json.RawMessage
-	if err := json.Unmarshal(contents, &envelope); err != nil || envelope == nil {
-		return false, nil
-	}
-
-	dataJSON, ok := envelope["data"]
-	if !ok || !isJSONObject(dataJSON) {
-		return false, nil
-	}
-	var data map[string]json.RawMessage
-	if err := json.Unmarshal(dataJSON, &data); err != nil || data == nil {
-		return false, nil
-	}
-	label, labelOK := data["label"]
-	freeTier, freeTierOK := data["is_free_tier"]
-	usage, usageOK := data["usage"]
-	if !labelOK || !isJSONString(label) || !freeTierOK || !isJSONBoolean(freeTier) || !usageOK {
-		return false, nil
-	}
-	var number any
-	usageDecoder := json.NewDecoder(bytes.NewReader(usage))
-	usageDecoder.UseNumber()
-	if usageDecoder.Decode(&number) != nil {
-		return false, nil
-	}
-	_, ok = number.(json.Number)
-	return ok, nil
-}
-
-func isJSONObject(value json.RawMessage) bool {
-	value = bytes.TrimSpace(value)
-	return len(value) > 0 && value[0] == '{'
-}
-
-func isJSONString(value json.RawMessage) bool {
-	value = bytes.TrimSpace(value)
-	if len(value) == 0 || value[0] != '"' {
-		return false
-	}
-	var parsed string
-	return json.Unmarshal(value, &parsed) == nil
-}
-
-func isJSONBoolean(value json.RawMessage) bool {
-	value = bytes.TrimSpace(value)
-	return bytes.Equal(value, []byte("true")) || bytes.Equal(value, []byte("false"))
-}

internal/usecase/smoke_authentication_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"io"
 	"net/http"
 	"strings"
 	"testing"
@@ -11,6 +12,58 @@ import (
 	"go.maximumdirect.net/promptkit/internal/domain"
 )
 
+type measuredAuthenticationBody struct {
+	reader io.Reader
+	read   int
+	closed bool
+}
+
+func (b *measuredAuthenticationBody) Read(p []byte) (int, error) {
+	n, err := b.reader.Read(p)
+	b.read += n
+	return n, err
+}
+func (b *measuredAuthenticationBody) Close() error { b.closed = true; return nil }
+
+func TestAuthenticationResponseRecognitionBound(t *testing.T) {
+	const maxAuthenticationResponseBytes = 1 << 20
+	valid := `{"data":{"label":"member","is_free_tier":false,"usage":0}}`
+	for _, test := range []struct {
+		name     string
+		size     int
+		declared int64
+		status   int
+		overflow bool
+	}{
+		{"exact limit", maxAuthenticationResponseBytes, -1, 200, false},
+		{"overflow unknown length", maxAuthenticationResponseBytes + 10, -1, 200, true},
+		{"overflow understated length", maxAuthenticationResponseBytes + 10, 1, 200, true},
+		{"unauthorized does not read", maxAuthenticationResponseBytes + 10, -1, 401, false},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			body := &measuredAuthenticationBody{reader: strings.NewReader(valid + strings.Repeat(" ", test.size-len(valid)))}
+			client := reachabilityClient(t, func(*http.Request) (*http.Response, error) {
+				return &http.Response{StatusCode: test.status, Header: make(http.Header), Body: body, ContentLength: test.declared}, nil
+			})
+			outcome, err := (authenticationProbe{client: client}).run(context.Background(), backendWithAuthenticationKind("openrouter_key"), domain.SmokeTestTarget{Endpoint: "https://example.invalid/key"})
+			if err != nil || !body.closed {
+				t.Fatalf("outcome = %+v, err = %v, closed = %v", outcome, err, body.closed)
+			}
+			if test.overflow {
+				if outcome.reason != domain.SmokeTestReasonAuthenticationResponseLimitExceeded || outcome.failure != domain.ExecutionFailureOther || outcome.credentialsAccepted != nil || body.read != maxAuthenticationResponseBytes+1 {
+					t.Fatalf("overflow = %+v, read = %d", outcome, body.read)
+				}
+			} else if test.status == 401 {
+				if body.read != 0 || outcome.credentialsAccepted == nil || *outcome.credentialsAccepted {
+					t.Fatalf("unauthorized = %+v, read = %d", outcome, body.read)
+				}
+			} else if outcome.credentialsAccepted == nil || !*outcome.credentialsAccepted {
+				t.Fatalf("exact limit = %+v", outcome)
+			}
+		})
+	}
+}
+
 func TestAuthenticationProbeApplicabilityAndHTTPAvailability(t *testing.T) {
 	client := reachabilityClient(t, func(*http.Request) (*http.Response, error) {
 		t.Fatal("authentication applicability unexpectedly dispatched")
@@ -159,21 +212,26 @@ func TestAuthenticationProbeInterpretsOpenRouterResponses(t *testing.T) {
 }
 
 func TestAuthenticationProbeRecognizesOnlyOneCompleteJSONObject(t *testing.T) {
-	for _, body := range []string{
-		`{"data":{"label":"member","is_free_tier":false,"usage":1}} {}`,
-		`{"data":[]}`,
-		`{"data":{"label":"member","is_free_tier":false,"usage":null}}`,
-		`{"data":{"label":"member","is_free_tier":0,"usage":1}}`,
-		`{"data":{"is_free_tier":false,"usage":1}}`,
-		`{"data":{"label":null,"is_free_tier":false,"usage":1}}`,
+	for _, tc := range []struct {
+		body     string
+		accepted bool
+	}{
+		{`{"data":{"label":"member","is_free_tier":false,"usage":1}} {}`, false},
+		{`{"data":[]}`, false},
+		{`{"data":{"label":"member","is_free_tier":false,"usage":null}}`, false},
+		{`{"data":{"label":"member","is_free_tier":0,"usage":1}}`, false},
+		{`{"data":{"is_free_tier":false,"usage":1}}`, false},
+		{`{"data":{"label":null,"is_free_tier":false,"usage":1}}`, false},
+		{`{"data":{"label":"","is_free_tier":false,"usage":1e2,"ignored":true},"ignored":true}`, true},
 	} {
-		if recognized, err := recognizedOpenRouterKeyResponse(strings.NewReader(body)); err != nil || recognized {
-			t.Errorf("recognized invalid account response %s", body)
+		client := reachabilityClient(t, func(*http.Request) (*http.Response, error) {
+			return &http.Response{StatusCode: http.StatusOK, Header: make(http.Header), Body: ioNopCloser(tc.body)}, nil
+		})
+		outcome, err := (authenticationProbe{client: client}).run(context.Background(), backendWithAuthenticationKind("openrouter_key"), domain.SmokeTestTarget{Endpoint: "https://example.invalid/key"})
+		if err != nil || (outcome.credentialsAccepted != nil && *outcome.credentialsAccepted) != tc.accepted {
+			t.Errorf("account response %s: outcome = %+v, error = %v", tc.body, outcome, err)
 		}
 	}
-	if recognized, err := recognizedOpenRouterKeyResponse(strings.NewReader(`{"data":{"label":"","is_free_tier":false,"usage":1e2,"ignored":true},"ignored":true}`)); err != nil || !recognized {
-		t.Fatal("valid minimal identifying response was rejected")
-	}
 }
 
 func TestAuthenticationProbeTreatsInterruptedResponseBodyAsTransportFailure(t *testing.T) {

internal/usecase/smoke_inference_case.go

@@ -25,7 +25,7 @@ type smokeInferenceCase struct {
 	kind             domain.SmokeTestKind
 	request          domain.GenerateRequest
 	expectedContent  string
-	jsonValidator    validate.Validator
+	jsonValidation   validate.PreparedValidation
 	schemaValidation validate.PreparedValidation
 }
 
@@ -52,11 +52,13 @@ func prepareSmokeInferenceCase(
 		}, nil
 	case domain.SmokeTestStructuredOutput:
 		validator := validate.NewFSValidator(smokeSchemaFS, ".")
-		preparer, ok := validator.(validate.ValidationPreparer)
-		if !ok {
-			return nil, fmt.Errorf("%w: private validator does not support prepared validation", ErrValidation)
+		jsonPlan, err := validator.PrepareValidation(ctx, domain.OutputContract{
+			Format: domain.FormatJSON, ValidationMode: domain.ValidationJSON,
+		})
+		if err != nil {
+			return nil, fmt.Errorf("%w: prepare private JSON validation: %w", ErrValidation, err)
 		}
-		plan, err := preparer.PrepareValidation(ctx, domain.OutputContract{
+		plan, err := validator.PrepareValidation(ctx, domain.OutputContract{
 			Format:         domain.FormatJSON,
 			ValidationMode: domain.ValidationJSONSchema,
 			SchemaPath:     smokeStructuredSchemaPath,
@@ -68,7 +70,7 @@ func prepareSmokeInferenceCase(
 		return &smokeInferenceCase{
 			kind:             kind,
 			expectedContent:  smokeStructuredExpectedContent,
-			jsonValidator:    validate.NewStandardValidator(""),
+			jsonValidation:   jsonPlan,
 			schemaValidation: plan,
 			request: newGenerationRequest(
 				domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: smokeStructuredPromptPrefix + smokeStructuredExpectedContent}}},
@@ -101,10 +103,7 @@ func (c *smokeInferenceCase) evaluate(ctx context.Context, response *domain.Gene
 		return facts, nil
 	case domain.SmokeTestStructuredOutput:
 		artifact := domain.Artifact{Body: []byte(response.Content)}
-		jsonResult, err := c.jsonValidator.Validate(ctx, &artifact, domain.OutputContract{
-			Format:         domain.FormatJSON,
-			ValidationMode: domain.ValidationJSON,
-		})
+		jsonResult, err := c.jsonValidation.Validate(ctx, &artifact)
 		if err != nil {
 			return facts, fmt.Errorf("%w: evaluate private smoke-test JSON: %w", ErrValidation, err)
 		}

internal/usecase/smoke_inference_case_test.go

@@ -2,6 +2,7 @@ package usecase
 
 import (
 	"context"
+	"errors"
 	"reflect"
 	"strings"
 	"testing"
@@ -102,6 +103,7 @@ func TestSmokeStructuredInferenceCaseUsesPrivatePreparedSchema(t *testing.T) {
 	}{
 		{name: "matches", content: caseValue.expectedContent, wantValidJSON: true, wantSchemaMatched: boolPointer(true)},
 		{name: "valid JSON misses schema", content: `{"status":"other"}`, wantValidJSON: true, wantSchemaMatched: boolPointer(false)},
+		{name: "scalar JSON misses schema", content: `42`, wantValidJSON: true, wantSchemaMatched: boolPointer(false)},
 		{name: "additional property misses schema", content: additionalPropertyContent, wantValidJSON: true, wantSchemaMatched: boolPointer(false)},
 		{name: "invalid JSON", content: `{invalid`, wantSchemaMatched: nil},
 		{name: "empty content", content: "", wantSchemaMatched: nil},
@@ -125,3 +127,19 @@ func TestSmokeStructuredInferenceCaseUsesPrivatePreparedSchema(t *testing.T) {
 		t.Fatalf("facts were populated without generated content: %+v", noResponseFacts)
 	}
 }
+
+func TestSmokeStructuredInferenceCaseHonorsCancellation(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	if _, err := prepareSmokeInferenceCase(ctx, domain.SmokeTestStructuredOutput, domain.SmokeTestTarget{}, 0); !errors.Is(err, context.Canceled) {
+		t.Fatalf("prepare error = %v, want cancellation", err)
+	}
+	caseValue, err := prepareSmokeInferenceCase(context.Background(), domain.SmokeTestStructuredOutput, domain.SmokeTestTarget{}, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	facts, err := caseValue.evaluate(ctx, &domain.GenerateResponse{Content: `{"status":"ok"}`})
+	if !errors.Is(err, context.Canceled) || facts.ValidJSON != nil || facts.SchemaMatched != nil {
+		t.Fatalf("evaluation facts = %+v, error = %v", facts, err)
+	}
+}

internal/usecase/smoke_reachability.go

@@ -14,7 +14,6 @@ import (
 
 type smokeHTTPGetter interface {
 	GetWithEvidence(context.Context, string, int) (*http.Response, llm.HTTPExecutionEvidence, error)
-	GetWithAuthenticationEvidence(context.Context, string, int, domain.ExecutionTarget) (*http.Response, llm.HTTPExecutionEvidence, error)
 }
 
 type reachabilityProbe struct {
@@ -22,12 +21,11 @@ type reachabilityProbe struct {
 }
 
 type reachabilityProbeOutcome struct {
-	supported       bool
-	reason          domain.SmokeTestReason
-	initialEndpoint string
-	reachable       *bool
-	evidence        llm.HTTPExecutionEvidence
-	failure         domain.ExecutionFailureKind
+	supported bool
+	reason    domain.SmokeTestReason
+	reachable *bool
+	evidence  llm.HTTPExecutionEvidence
+	failure   domain.ExecutionFailureKind
 }
 
 func (p reachabilityProbe) run(
@@ -45,7 +43,7 @@ func (p reachabilityProbe) run(
 	if err != nil {
 		return reachabilityProbeOutcome{}, fmt.Errorf("prepare reachability endpoint: %w", err)
 	}
-	result := reachabilityProbeOutcome{supported: true, initialEndpoint: endpoint}
+	result := reachabilityProbeOutcome{supported: true}
 	response, evidence, requestErr := p.client.GetWithEvidence(ctx, endpoint, timeoutSeconds)
 	if response != nil && response.Body != nil {
 		_ = response.Body.Close()

internal/usecase/smoke_reachability_test.go

@@ -62,7 +62,7 @@ func TestReachabilityProbeRemovesURLCredentials(t *testing.T) {
 	if observed == nil || observed.URL.User != nil || observed.Header.Get("Authorization") != "" {
 		t.Fatalf("probe request retained URL credentials: %+v", observed)
 	}
-	if result.initialEndpoint != "https://example.invalid/health?check=1" || result.evidence.CredentialsSupplied {
+	if result.evidence.Endpoint != "https://example.invalid/health?check=1" || result.evidence.CredentialsSupplied {
 		t.Fatalf("credential-free evidence = %+v", result)
 	}
 }
@@ -111,12 +111,9 @@ func TestReachabilityProbeIsUnsupportedWithoutHTTPClient(t *testing.T) {
 
 func reachabilityClient(t *testing.T, roundTrip func(*http.Request) (*http.Response, error)) *llm.OpenAICompatibleClient {
 	t.Helper()
-	client, err := llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{
+	client := llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{
 		HTTPClient: &http.Client{Transport: reachabilityProbeTransport(roundTrip)},
 	})
-	if err != nil {
-		t.Fatal(err)
-	}
 	return client
 }
 

internal/usecase/smoke_selection.go

@@ -3,10 +3,10 @@ package usecase
 import (
 	"context"
 	"fmt"
-	"net/url"
 
 	"go.maximumdirect.net/promptkit/internal/defaults"
 	"go.maximumdirect.net/promptkit/internal/domain"
+	"go.maximumdirect.net/promptkit/internal/llm"
 )
 
 const (
@@ -112,7 +112,9 @@ func (r *Runner) resolveSmokeTestTarget(ctx context.Context, req domain.SmokeTes
 		settings.BackendID = selection.backend.ID
 		settings.Endpoint = selection.backend.Endpoint
 		settings.APIKeyEnv = selection.backend.APIKeyEnv
-		settings.ExtraParams = copyExtraParams(selection.backend.ExtraParams)
+		if len(selection.backend.ExtraParams) > 0 {
+			settings.ExtraParams = selection.backend.ExtraParams
+		}
 		presence := domain.ExecutionTargetPresence{}
 		if req.Execution != nil {
 			settings, presence = mergeExecutionTargetOverride(settings, presence, *req.Execution)
@@ -144,7 +146,7 @@ func (r *Runner) resolveSmokeBackend(id string) (domain.Backend, error) {
 	}
 	backend, err := lookup.GetBackend(id)
 	if err != nil {
-		return domain.Backend{}, fmt.Errorf("%w: backend %q: %v", ErrProfileLoad, id, err)
+		return domain.Backend{}, &OperationError{Category: ErrProfileLoad, Cause: fmt.Errorf("backend %q: %w", id, err)}
 	}
 	return backend, nil
 }
@@ -176,7 +178,7 @@ func resolveSmokeTestEndpoint(kind domain.SmokeTestKind, baseEndpoint string, sm
 				return *authentication.Endpoint, nil
 			}
 			if authentication.Kind != nil && *authentication.Kind == "openrouter_key" {
-				return url.JoinPath(baseEndpoint, "key")
+				return llm.OpenRouterKeyEndpoint(baseEndpoint)
 			}
 		}
 	}

internal/usecase/smoke_selection_test.go

@@ -9,6 +9,7 @@ import (
 	"go.maximumdirect.net/promptkit/internal/configuration"
 	"go.maximumdirect.net/promptkit/internal/domain"
 	"go.maximumdirect.net/promptkit/internal/profile"
+	"go.maximumdirect.net/promptkit/internal/validate"
 )
 
 type selectionTestCollaborators struct {
@@ -41,9 +42,9 @@ func (c selectionTestLLM) Generate(context.Context, domain.GenerateRequest) (*do
 
 type selectionTestValidator struct{ state *selectionTestCollaborators }
 
-func (v selectionTestValidator) Validate(context.Context, *domain.Artifact, domain.OutputContract) (domain.ValidationResult, error) {
+func (v selectionTestValidator) PrepareValidation(context.Context, domain.OutputContract) (validate.PreparedValidation, error) {
 	v.state.validationCalls++
-	return domain.ValidationResult{}, errors.New("validation must not occur during target selection")
+	return nil, errors.New("validation must not occur during target selection")
 }
 
 type selectionTestRepositories struct {
@@ -57,6 +58,10 @@ func (r *selectionTestRepositories) GetProfile(ctx context.Context, id string) (
 	return r.profiles.GetProfile(ctx, id)
 }
 
+func (r *selectionTestRepositories) GetProfileIdentity(ctx context.Context, id string) (string, error) {
+	return r.profiles.GetProfileIdentity(ctx, id)
+}
+
 func (r *selectionTestRepositories) GetBackend(id string) (domain.Backend, error) {
 	return r.backends.GetBackend(id)
 }

internal/usecase/smoke_tester.go

@@ -17,6 +17,7 @@ import (
 type SmokeTester struct {
 	runner     *Runner
 	httpClient smokeHTTPGetter
+	authClient smokeAuthenticationClient
 	now        func() time.Time
 }
 
@@ -24,18 +25,22 @@ type SmokeTester struct {
 // leaves HTTP operations unsupported rather than falling back to another client.
 func NewSmokeTester(runner *Runner, httpClient *llm.OpenAICompatibleClient) *SmokeTester {
 	var getter smokeHTTPGetter
+	var authentication smokeAuthenticationClient
 	if httpClient != nil {
 		getter = httpClient
+		authentication = httpClient
 	}
-	return &SmokeTester{runner: runner, httpClient: getter, now: time.Now}
+	return &SmokeTester{runner: runner, httpClient: getter, authClient: authentication, now: time.Now}
 }
 
 func newSmokeTesterWithClock(runner *Runner, httpClient *llm.OpenAICompatibleClient, now func() time.Time) *SmokeTester {
 	var getter smokeHTTPGetter
+	var authentication smokeAuthenticationClient
 	if httpClient != nil {
 		getter = httpClient
+		authentication = httpClient
 	}
-	return &SmokeTester{runner: runner, httpClient: getter, now: now}
+	return &SmokeTester{runner: runner, httpClient: getter, authClient: authentication, now: now}
 }
 
 // Run selects and executes one diagnostic, retaining only factual results.
@@ -126,7 +131,7 @@ func (t *SmokeTester) Run(ctx context.Context, request domain.SmokeTestRequest)
 		return t.finishHTTP(ctx, report, finish)
 	case domain.SmokeTestAuthentication:
 		requestStartedAt := now().UTC()
-		outcome, err := (authenticationProbe{client: t.httpClient}).run(ctx, selection.backend, selection.target)
+		outcome, err := (authenticationProbe{client: t.authClient}).run(ctx, selection.backend, selection.target)
 		requestDuration := nonnegativeDuration(now().UTC().Sub(requestStartedAt))
 		if err != nil {
 			if contextErr := ctx.Err(); contextErr != nil {
@@ -210,6 +215,9 @@ func (t *SmokeTester) runInference(
 		report.Failure = generation.ClassifyFailure(contextErr)
 		return finish(contextErr)
 	}
+	if evidence.PreparationFailed && generationErr != nil {
+		return nil, &OperationError{Category: ErrInvalidRequest, Cause: generationErr}
+	}
 	if generationErr != nil {
 		report.Failure = generation.ClassifyFailure(generationErr)
 		report.Completed = true
@@ -346,7 +354,7 @@ func (t *SmokeTester) setSupport(report *domain.SmokeTestReport, selection *smok
 		report.Applicable = boolPointer(true)
 		return nil
 	case domain.SmokeTestAuthentication:
-		outcome, err := (authenticationProbe{client: t.httpClient}).support(selection.backend)
+		outcome, err := (authenticationProbe{client: t.authClient}).support(selection.backend)
 		if err != nil {
 			return err
 		}
@@ -430,12 +438,8 @@ func httpExecutionFacts(evidence llm.HTTPExecutionEvidence) domain.SmokeTestFact
 }
 
 func smokeReportTarget(target domain.SmokeTestTarget) (domain.SmokeTestTarget, error) {
-	cloned, err := domain.CloneSmokeTestReport(domain.SmokeTestReport{Target: target})
-	if err != nil {
-		return domain.SmokeTestTarget{}, fmt.Errorf("clone smoke-test target settings: %w", err)
-	}
-	target = cloned.Target
 	target.EffectiveSettings.APIKey = ""
+	var err error
 	target.Endpoint, err = endpointWithoutUserInfo(target.Endpoint)
 	if err != nil {
 		return domain.SmokeTestTarget{}, fmt.Errorf("%w: invalid resolved diagnostic endpoint", ErrInvalidRequest)

internal/usecase/smoke_tester_test.go

@@ -393,3 +393,22 @@ func (b cancelOnCloseSmokeBody) Close() error {
 	b.cancel()
 	return b.ReadCloser.Close()
 }
+
+func TestSmokeReportTargetRedactsCredentialsAndSanitizesEndpoints(t *testing.T) {
+	target := domain.SmokeTestTarget{
+		Endpoint: "https://user:password@example.invalid/key",
+		EffectiveSettings: domain.ExecutionTarget{
+			Endpoint:    "https://user:password@example.invalid/v1",
+			APIKey:      "secret",
+			ExtraParams: map[string]any{"nested": map[string]any{"value": "original"}},
+		},
+	}
+	got, err := smokeReportTarget(target)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.EffectiveSettings.ExtraParams["nested"].(map[string]any)["value"] != "original" ||
+		got.EffectiveSettings.APIKey != "" || got.Endpoint != "https://example.invalid/key" || got.EffectiveSettings.Endpoint != "https://example.invalid/v1" {
+		t.Fatalf("report target not redacted: %+v", got)
+	}
+}

internal/validate/cancellation_test.go

@@ -19,7 +19,7 @@ func TestValidationCancellationBeforeWorkDoesNotOpenSchemaSource(t *testing.T) {
 	source := &countingSchemaFS{FS: fstest.MapFS{
 		"schema.json": {Data: []byte(`{"type":"object"}`)},
 	}}
-	validator := NewFSValidator(source, ".").(ValidationPreparer)
+	validator := NewFSValidator(source, ".")
 	ctx, cancel := context.WithCancel(context.Background())
 	cancel()
 
@@ -35,17 +35,16 @@ func TestValidationCancellationBeforeWorkDoesNotOpenSchemaSource(t *testing.T) {
 	}
 }
 
-func TestValidationCancellationBetweenReferencedSchemaReadChunks(t *testing.T) {
+func TestValidationCancellationBetweenRootSchemaReadChunks(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	source := &controlledSchemaFS{
 		FS: fstest.MapFS{
-			"root.json":  {Data: []byte(`{"$ref":"child.json"}`)},
-			"child.json": {Data: []byte(`{"type":"string"}` + strings.Repeat(" ", schemaReadChunkSize*2))},
+			"root.json": {Data: []byte(`{"type":"string"}` + strings.Repeat(" ", schemaReadChunkSize*2))},
 		},
-		target: "child.json",
+		target: "root.json",
 		cancel: cancel,
 	}
-	validator := NewFSValidator(source, ".").(ValidationPreparer)
+	validator := NewFSValidator(source, ".")
 
 	plan, err := validator.PrepareValidation(ctx, domain.OutputContract{
 		ValidationMode: domain.ValidationJSONSchema,
@@ -57,8 +56,8 @@ func TestValidationCancellationBetweenReferencedSchemaReadChunks(t *testing.T) {
 	if reads := source.reads.Load(); reads != 1 {
 		t.Fatalf("controlled child reads = %d, want 1", reads)
 	}
-	if closes := source.closes.Load(); closes != 1 {
-		t.Fatalf("controlled child closes = %d, want 1", closes)
+	if closes := source.closes.Load(); closes != 2 {
+		t.Fatalf("controlled root closes = %d, want stat and read handles closed", closes)
 	}
 }
 
@@ -113,7 +112,7 @@ func TestCancellationDoesNotDetachBlockedSchemaRead(t *testing.T) {
 		started: started,
 		release: release,
 	}
-	validator := NewFSValidator(source, ".").(ValidationPreparer)
+	validator := NewFSValidator(source, ".")
 	type outcome struct {
 		plan PreparedValidation
 		err  error

internal/validate/schema_locations.go

@@ -0,0 +1,91 @@
+package validate
+
+import (
+	"context"
+	"fmt"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"github.com/santhosh-tekuri/jsonschema/v6"
+)
+
+// These schema-bearing positions mirror the inherited subschema tables in
+// jsonschema/v6 v6.0.2 draft.go. Annotation objects are deliberately excluded.
+func checkSchemaLocations(ctx context.Context, compiler *jsonschema.Compiler, resourceURL string, document any, pointer string, compiled *jsonschema.Schema) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+	object, ok := document.(map[string]any)
+	if !ok {
+		return nil
+	}
+	version := compiled.DraftVersion
+	mapKeys := []string{"definitions", "properties", "patternProperties", "dependencies"}
+	singleKeys := []string{"not", "additionalProperties", "items", "additionalItems"}
+	arrayKeys := []string{"allOf", "anyOf", "oneOf", "items"}
+	if version >= 6 {
+		singleKeys = append(singleKeys, "propertyNames", "contains")
+	}
+	if version >= 7 {
+		singleKeys = append(singleKeys, "if", "then", "else")
+	}
+	if version >= 2019 {
+		mapKeys = append(mapKeys, "$defs", "dependentSchemas")
+		singleKeys = append(singleKeys, "unevaluatedProperties", "unevaluatedItems", "contentSchema")
+	}
+	if version >= 2020 {
+		arrayKeys = append(arrayKeys, "prefixItems")
+	}
+	visit := func(value any, segments ...string) error {
+		switch value.(type) {
+		case map[string]any, bool:
+		default:
+			return nil
+		}
+		childPointer := pointer
+		for _, segment := range segments {
+			childPointer += "/" + strings.ReplaceAll(strings.ReplaceAll(segment, "~", "~0"), "/", "~1")
+		}
+		parsed, err := url.Parse(resourceURL)
+		if err != nil {
+			return err
+		}
+		parsed.Fragment = childPointer
+		child, err := compileJSONSchema(ctx, parsed.String(), compiler.Compile)
+		if err != nil {
+			return fmt.Errorf("compile declared schema %q: %w", childPointer, err)
+		}
+		return checkSchemaLocations(ctx, compiler, resourceURL, value, childPointer, child)
+	}
+	for _, key := range mapKeys {
+		entries, ok := object[key].(map[string]any)
+		if !ok {
+			continue
+		}
+		for name, value := range entries {
+			if err := visit(value, key, name); err != nil {
+				return err
+			}
+		}
+	}
+	for _, key := range singleKeys {
+		if value, ok := object[key]; ok {
+			if err := visit(value, key); err != nil {
+				return err
+			}
+		}
+	}
+	for _, key := range arrayKeys {
+		entries, ok := object[key].([]any)
+		if !ok {
+			continue
+		}
+		for i, value := range entries {
+			if err := visit(value, key, strconv.Itoa(i)); err != nil {
+				return err
+			}
+		}
+	}
+	return ctx.Err()
+}

internal/validate/schema_locations_test.go

@@ -0,0 +1,60 @@
+package validate
+
+import (
+	"context"
+	"strings"
+	"testing"
+)
+
+func TestSchemaLocationsCheckUnusedDeclarations(t *testing.T) {
+	for _, test := range []struct {
+		name, schema string
+		wantError    bool
+	}{
+		{"unused external", `{"$defs":{"unused":{"$ref":"other.json"}},"type":"string"}`, true},
+		{"annotation is data", `{"examples":[{"$ref":"other.json"}],"default":{"$ref":"other.json"},"type":"string"}`, false},
+		{"internal escaped key", `{"$defs":{"a/b~c":{"type":"string"}},"$ref":"#/$defs/a~1b~0c"}`, false},
+		{"URI escaped key", `{"$defs":{"a # %/雪":{"type":"string"}}}`, false},
+		{"internal anchor", `{"$defs":{"value":{"$anchor":"item","type":"string"}},"$ref":"#item"}`, false},
+		{"dynamic reference", `{"$dynamicAnchor":"node","type":"object","properties":{"child":{"$dynamicRef":"#node"}}}`, false},
+		{"recursive", `{"$id":"https://example.invalid/root","$defs":{"node":{"$anchor":"node","anyOf":[{"type":"null"},{"$ref":"#node"}]}},"$ref":"#/$defs/node"}`, false},
+		{"embedded old dialect annotation", `{"$defs":{"old":{"$id":"old","$schema":"http://json-schema.org/draft-07/schema#","$defs":{"unused":{"$ref":"other.json"}},"type":"string"}}}`, false},
+		{"embedded old dialect definition", `{"$defs":{"old":{"$id":"old","$schema":"http://json-schema.org/draft-07/schema#","definitions":{"unused":{"$ref":"other.json"}}}}}`, true},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			doc, err := decodeJSONValue(context.Background(), []byte(test.schema))
+			if err != nil {
+				t.Fatal(err)
+			}
+			_, err = compileSchemaDocument(context.Background(), "promptkit-schema:///root.json", doc)
+			if test.wantError && (err == nil || !strings.Contains(err.Error(), "external schema resource")) {
+				t.Fatalf("expected external resource error, got %v", err)
+			}
+			if !test.wantError && err != nil {
+				t.Fatal(err)
+			}
+		})
+	}
+}
+
+func TestSchemaLocationsPreserveRootValidation(t *testing.T) {
+	doc, err := decodeJSONValue(context.Background(), []byte(`{"$defs":{"number":{"type":"integer","minimum":2}},"$ref":"#/$defs/number"}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	schema, err := compileSchemaDocument(context.Background(), "promptkit-schema:///root.json", doc)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := schema.Validate(3); err != nil {
+		t.Fatalf("valid instance: %v", err)
+	}
+	if err := schema.Validate("not a number"); err == nil {
+		t.Fatal("invalid instance was accepted")
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	if _, err := compileSchemaDocument(ctx, "promptkit-schema:///root.json", doc); err != context.Canceled {
+		t.Fatalf("canceled compilation = %v", err)
+	}
+}

internal/validate/schema_portability_test.go

@@ -0,0 +1,46 @@
+package validate
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"testing/fstest"
+
+	"go.maximumdirect.net/promptkit/internal/domain"
+)
+
+func TestSchemaPreparationDoesNotDependOnSourceName(t *testing.T) {
+	for _, test := range []struct {
+		name, schema string
+		rejected     bool
+	}{
+		{"source name", `{"$defs":{"v":{"type":"integer"}},"$ref":"schema.json#/$defs/v"}`, true},
+		{"unused source name", `{"$defs":{"v":{"$ref":"schema.json"}}}`, true},
+		{"fragment", `{"$defs":{"v":{"type":"integer"}},"$ref":"#/$defs/v"}`, false},
+		{"explicit ID", `{"$id":"https://example.invalid/schema.json","$defs":{"v":{"type":"integer"}},"$ref":"schema.json#/$defs/v"}`, false},
+		{"embedded ID", `{"$defs":{"v":{"$id":"child","type":"integer"}},"$ref":"child"}`, false},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			dir := t.TempDir()
+			if err := os.WriteFile(filepath.Join(dir, "schema.json"), []byte(test.schema), 0600); err != nil {
+				t.Fatal(err)
+			}
+			fsys := fstest.MapFS{"schema.json": &fstest.MapFile{Data: []byte(test.schema)}}
+			for i, validator := range []ValidationPreparer{NewStandardValidator(dir), NewFSValidator(fsys, ".")} {
+				t.Run(fmt.Sprint(i), func(t *testing.T) {
+					_, err := validator.PrepareValidation(context.Background(), domain.OutputContract{Format: domain.FormatJSON, ValidationMode: domain.ValidationJSONSchema, SchemaPath: "schema.json"})
+					if test.rejected {
+						if err == nil || !strings.Contains(err.Error(), "source location") {
+							t.Fatalf("expected source-independent rejection, got %v", err)
+						}
+					} else if err != nil {
+						t.Fatal(err)
+					}
+				})
+			}
+		})
+	}
+}