From f866ca98f95fbd8cc092b1b805a5b5c66c48c021 Mon Sep 17 00:00:00 2001
From: Eric Rakestraw <eric@rakestraw.us>
Date: Wed, 7 Oct 2026 16:48:37 +0000
Subject: [PATCH] Retain validation report delivery errors in outcomes

---
 configkit_test.go           | 63 ++++++++++++++++++++++++++++++++++++-
 docs/roadmap/remediation.md |  3 ++
 validate.go                 |  8 +++--
 3 files changed, 71 insertions(+), 3 deletions(-)

diff --git a/configkit_test.go b/configkit_test.go
index 1b9acbb..73ef2e0 100644
--- a/configkit_test.go
+++ b/configkit_test.go
@@ -639,7 +639,7 @@ func TestConfigValidationYAMLWarningsAndShortWrites(t *testing.T) {
 	}
 
 	outcome = app.Execute(context.Background(), []string{"config", "validate"}, commandkit.Streams{Out: configKitPartialWriter{}, Err: io.Discard})
-	if outcome.Kind != commandkit.OutcomeOperational || !outcome.ReportIncomplete || !errors.Is(outcome.Cause, io.ErrShortWrite) {
+	if outcome.Kind != commandkit.OutcomeOperational || !outcome.ReportIncomplete || !errors.Is(outcome.Cause, io.ErrShortWrite) || !errors.Is(outcome.DeliveryError, io.ErrShortWrite) {
 		t.Fatalf("report short write outcome = %#v", outcome)
 	}
 	var delivered bytes.Buffer
@@ -657,3 +657,64 @@ func (configKitPartialWriter) Write(data []byte) (int, error) {
 	}
 	return len(data) - 1, nil
 }
+
+func TestValidationReportDeliveryErrorsAtEachWriteBoundary(t *testing.T) {
+	reportErr := errors.New("report failed")
+	diagnosticErr := errors.New("diagnostic failed")
+	app, _ := commandkit.New(commandkit.Identity{Name: "example"})
+	acquire := func(context.Context, commandkit.ConfigRequest, struct{}) (commandkit.Acquired[commandkit.ConfigView], error) {
+		return commandkit.Acquired[commandkit.ConfigView]{}, nil
+	}
+	if err := commandkit.RegisterConfig(app, commandkit.ConfigSuite[struct{}]{Scopes: []commandkit.ConfigScope[struct{}]{
+		{Name: "app", Operations: []commandkit.ConfigOperation{commandkit.ConfigValidate}, Acquire: acquire},
+		{Name: "promptkit", Operations: []commandkit.ConfigOperation{commandkit.ConfigValidate}, Acquire: acquire},
+	}}); err != nil {
+		t.Fatal(err)
+	}
+	for _, format := range []string{"text", "yaml"} {
+		writes := 2
+		if format == "yaml" {
+			writes = 3
+		}
+		for at := 1; at <= writes; at++ {
+			for _, brokenErr := range []bool{false, true} {
+				out := &validationBoundaryWriter{failAt: at, err: reportErr}
+				errStream := io.Writer(io.Discard)
+				if brokenErr {
+					errStream = failingWriter{diagnosticErr}
+				}
+				result := app.Execute(context.Background(), []string{"config", "validate", "--scope", "all", "--format", format}, commandkit.Streams{Out: out, Err: errStream})
+				if result.Kind != commandkit.OutcomeOperational || !result.ReportIncomplete || !errors.Is(result.Cause, reportErr) || !errors.Is(result.DeliveryError, reportErr) || (brokenErr && !errors.Is(result.DeliveryError, diagnosticErr)) {
+					t.Fatalf("format=%s at=%d brokenErr=%t result=%#v", format, at, brokenErr, result)
+				}
+				if at > 1 && out.written.Len() == 0 {
+					t.Fatal("lost completed prefix")
+				}
+			}
+		}
+	}
+	failedApp, _ := commandkit.New(commandkit.Identity{Name: "example"})
+	if err := commandkit.RegisterConfig(failedApp, commandkit.ConfigSuite[struct{}]{Scopes: []commandkit.ConfigScope[struct{}]{{Name: "app", Operations: []commandkit.ConfigOperation{commandkit.ConfigValidate}, Acquire: func(context.Context, commandkit.ConfigRequest, struct{}) (commandkit.Acquired[commandkit.ConfigView], error) {
+		return commandkit.Acquired[commandkit.ConfigView]{}, reportErr
+	}}}}); err != nil {
+		t.Fatal(err)
+	}
+	result := failedApp.Execute(context.Background(), []string{"config", "validate"}, commandkit.Streams{})
+	if !errors.Is(result.Cause, reportErr) || result.DeliveryError != nil {
+		t.Fatalf("acquisition failure=%#v", result)
+	}
+}
+
+type validationBoundaryWriter struct {
+	failAt, calls int
+	err           error
+	written       bytes.Buffer
+}
+
+func (w *validationBoundaryWriter) Write(p []byte) (int, error) {
+	w.calls++
+	if w.calls == w.failAt {
+		return 0, w.err
+	}
+	return w.written.Write(p)
+}
diff --git a/docs/roadmap/remediation.md b/docs/roadmap/remediation.md
index 72d0702..f681c27 100644
--- a/docs/roadmap/remediation.md
+++ b/docs/roadmap/remediation.md
@@ -57,6 +57,9 @@ architecture. The issues below affect behavior within the implemented structure.
 - R-04 complete: every help entry form finalizes report failures through the
   common diagnostic presentation path once.
 
+- R-05 complete: validation header/record write failures retain `DeliveryError`
+  separately from acquisition failures and combined diagnostic-stream failures.
+
 ## Findings and priority
 
 P1 means a supported invocation is blocked or its report content is corrupted.
diff --git a/validate.go b/validate.go
index d7ddc06..ba08773 100644
--- a/validate.go
+++ b/validate.go
@@ -68,11 +68,15 @@ func runConfigValidation[C any](invocation Invocation, suite ConfigSuite[C], inp
 		}
 		if input.Format == "yaml" && !writtenRecord {
 			if err := writeReport(invocation.Streams.Out, []byte("scopes:\n")); err != nil {
-				return validationFailure(err, diagnostics, true)
+				outcome := validationFailure(err, diagnostics, true)
+				outcome.DeliveryError = err
+				return outcome
 			}
 		}
 		if err := writeReport(invocation.Streams.Out, record); err != nil {
-			return validationFailure(err, diagnostics, true)
+			outcome := validationFailure(err, diagnostics, true)
+			outcome.DeliveryError = err
+			return outcome
 		}
 		writtenRecord = true
 	}