commandkit/docs/roadmap/registration-alternatives.md

# Registration API alternatives

Status: design mockup for discussion; none of the alternatives is implemented or
selected by this document.

## Purpose and authority

Settle the public registration shape for the optional modules described in
[the module roadmap](modules.md), before finalizing its implementation plan.
[ADR 0001](../adr/0001-command-dispatch-and-inputs.md) selects explicit instance
registration, typed inputs, and standard-family ownership.
[ADR 0010](../adr/0010-optional-integration-modules.md) places optional handlers,
providers, and adapters in their owning modules and requires convenient family
registration through supported core contracts.

Design for the best, simplest, most coherent final API. CommandKit is an
unreleased prototype with no consumers; its signatures and private machinery
receive zero deference. Existing code supplies evidence of responsibilities and
can be reused where suitable. Accepted decisions remain authoritative.

The Go fragments below illustrate proposed consumer APIs. They are not runnable
examples, published contracts, or instructions to implement these names exactly.
Application loaders, domain command constructors, imports, and execution code
are omitted where unrelated to registration. No new inspection operations are
proposed here; deferred capabilities remain deferred.

## Common requirements

All alternatives must provide:

- A core-only consumer importing neither integration nor its upstream library.
- Integration-supplied standard commands and adapters; applications supply
  acquisition and domain context without constructing each standard handler.
- One `config` suite containing application, PromptKit, and other supported
  configuration scopes. Definition inspection remains independently selectable.
- Registration and help that leave acquisition callbacks uninvoked.
- Typed, presence-aware context flags and overrides, with invocation-local state.
- Registration errors for collisions and attempts to modify installed standard
  families. A failed registration operation must not partially install its inputs.
- No public Cobra types, root-private registry access, import-time installation,
  or ConfigKit/PromptKit dependencies in the core.

The ownership boundary is the complete installed group. There is no public
incremental operation for appending application commands underneath an installed
standard family, or replacing its handlers. Configuration composition happens
before installation through integration-owned scope declarations.

## Shared provider and scope mockup

The alternatives differ in how declarations reach the application registry.
They can use the same integration-owned provider declarations:

| Proposed declaration | Owner | Role |
| --- | --- | --- |
| `Scope[C]`, `Suite[C]`, `Selection` | `ckconfig` | Configuration capabilities, scope composition, and config/overlay inputs |
| `FromConfigKit[C, T]` | `ckconfig` | Adapt an application ConfigKit loader into a configuration scope |
| `ConfigScope[C]` | `ckprompt` | Adapt a PromptKit engine loader into a `ckconfig.Scope[C]` |
| `Suite[C]`, `FromEngine[C]` | `ckprompt` | Definition inspection providers and their engine adapter |
| Typed bindings, diagnostics, command declarations | `commandkit` | Shared command infrastructure, without upstream-library types |

These short names are proposed for consumer readability, rather than preserving
the prototype's root-package names. The two `Suite` types belong to distinct
integration packages and describe distinct resources. No universal suite,
provider, or integration interface is needed.

The illustrative adapter signatures are:

```go
// In ckconfig:
func FromConfigKit[C, T any](
    name, summary string,
    load func(context.Context, Selection, C) (*configkit.Result[T], error),
) Scope[C]

// In ckprompt:
func ConfigScope[C any](
    load func(context.Context, ckconfig.Selection, C) (*promptkit.Engine, error),
) ckconfig.Scope[C]

func FromEngine[C any](
    load func(context.Context, ckconfig.Selection, C) (*promptkit.Engine, error),
) Suite[C]
```

Using `ckconfig.Selection` for the PromptKit adapters describes their existing
configuration-selection inputs. It does not move that integration-specific type
back into the core. `ckprompt` already has the selected dependency on `ckconfig`.

These adapters construct declarations without acquiring providers or returning
errors. Option A validates the complete suite in `Register`; Option B validates
it in the complete-group factory; Option C validates it during core installation.
All validate before registry mutation. Invalid wiring, including a nil loader,
must remain detectable in the declaration rather than becoming an invocation-time
failure inside an otherwise non-nil wrapper. Invalid configuration returned by a
valid loader remains an invocation-time failure.

This consolidates declaration errors at a useful assembly boundary. It does not
require every future constructor to be infallible: constructors that perform
genuinely fallible work may still return errors. The existing adapter constructors
only reject nil loaders at construction, so they do not demonstrate that need.

Adapters supply appropriate supported operations. Provider declarations can also
describe supported subsets through typed callbacks, so callers need not enable
every available inspection operation. Advanced composition does not require
exposing individual standard command constructors.

Suites allow application context and explicitly bound selector flags where
needed. Configuration selectors may identify the scopes to which they apply;
definition selectors belong to their own suite. Share core binding primitives,
without forcing PromptKit definition providers to use a configuration-specific
selector wrapper. The exact selector constructors are a separate part of the
typed-input design, not a reason to add a registration framework.

### Consumer assumptions

The simple ConfigKit examples have no domain selectors, overrides, or application
state. Under the current generic sketch, their loader accepts an unused
`struct{}` context argument and their suite uses `struct{}` with no `NewContext`
callback. This makes the remaining type plumbing visible rather than hiding it
behind an `AppInput` type or helper. Whether to offer a context-free loader form
is evaluated below, with a focused convenience function recommended for Option A.
The generic sketches remain visible for comparison; they are not the recommended
shortest setup for that case.

In the composed examples, both loaders accept `*RunState` and all provider and
suite assembly is shown inline. The illustrative `newRunState` callback is
invoked by the selected handler, not during assembly. Application state can hold
an invocation-local cache shared by the selected configuration scopes. Separate
families do not acquire state together merely because both are registered.
Keeping the engine scope while omitting definition registration enables only
PromptKit configuration inspection; keeping definitions while omitting that
scope enables only definition inspection. Importing `ckprompt` enables neither.

`greet` and `sessionGroup` represent already constructed application-owned
commands, whose construction is identical across the alternatives. Their domain
implementation and the loaders' bodies are omitted; no integration assembly or
error handling is hidden in a `makeInspectionSuites` helper.

## Option A: integration convenience functions install complete groups

### Proposed public shape

```go
// Existing core concepts, evaluated for their final shape:
func New(identity Identity, commands ...Command) (*App, error)
func (app *App) Register(commands ...Command) error

// In the integration packages:
func Register[C any](app *commandkit.App, suite Suite[C]) error
```

Each integration's `Register` validates its declaration, assembles its complete
standard group privately, and installs that group through supported public core
registration. Applications do not receive individual standard handlers or need
to declare standard paths. The function name is qualified by its owning package:
`ckconfig.Register` or `ckprompt.Register`.

### Core-only consumer

```go
greet, err := makeGreetCommand() // Application-owned typed command.
if err != nil {
    return err
}
app, err := commandkit.New(identity, greet)
if err != nil {
    return err
}
// Execute using caller-owned context and streams.
```

Only `commandkit` is imported for command infrastructure. Help/version are
provided by construction; there is no inspection-provider setup.

### ConfigKit-only consumer

```go
app, err := commandkit.New(identity, greet)
if err != nil {
    return err
}
if err := ckconfig.Register(app, ckconfig.Suite[struct{}]{
    Scopes: []ckconfig.Scope[struct{}]{
        ckconfig.FromConfigKit("app", "Application settings.", loadAppConfig),
    },
}); err != nil {
    return err
}
```

This consumer imports `commandkit`, `ckconfig`, and the ConfigKit types used by
its loader, with no `ckprompt` or PromptKit dependency.

### Composed consumer

```go
app, err := commandkit.New(identity, sessionGroup)
if err != nil {
    return err
}
if err := ckconfig.Register(app, ckconfig.Suite[*RunState]{
    NewContext: newRunState,
    Scopes: []ckconfig.Scope[*RunState]{
        ckconfig.FromConfigKit("app", "Application settings.", loadAppConfig),
        ckprompt.ConfigScope(loadEngine),
    },
}); err != nil {
    return err
}
definitions := ckprompt.FromEngine(loadEngine)
definitions.NewContext = newRunState
if err := ckprompt.Register(app, definitions); err != nil {
    return err
}
```

The configuration suite installs `config` once with both scopes. Definition
registration independently installs the supplied `promptkit` operations.
`session restore` remains an application-owned command inside `sessionGroup`.

### Advantages

- Expresses the consumer task directly: install this integration's standard
  commands using these providers.
- Keeps standard assembly behind the integration facade and avoids exposing a
  family-builder API solely to support extraction.
- Works with ordinary core command/group concepts, without a new integration
  object, callback protocol, or application-wide options language.
- Provider validation and installation are coordinated within one call, without
  separate error checks for the declaration-only adapter constructors.
- Each module can evolve its provider declarations independently.

### Costs and limits

- Several integrations require several registration calls and error checks.
- Atomicity covers each call, not the entire application setup. If PromptKit
  registration fails after configuration succeeds, the app contains the earlier
  registration. The application can discard that unfinished app; no rollback
  framework is required for this assembly pattern.
- Standard group construction is not independently available to consumers.
  Tests exercise it through registration and the public application unless a
  concrete composition need later justifies another surface.

## Option B: integrations return complete command declarations

### Proposed public shape

Keep the same core construction and registration concepts, but expose integration
factories instead of installation functions:

```go
// In the integration packages:
func Command[C any](suite Suite[C]) (commandkit.Command, error)
```

`ckconfig.Command` returns the complete `config` group; `ckprompt.Command` returns
the supplied definition-inspection group. The returned core handle has private
implementation state. It does not expose child mutation or standard handlers.
Factory validation and group construction leave acquisition callbacks uninvoked.
Adapter declarations use the shared error-free constructors; suite wiring errors
are reported by `Command`, while registry collisions and placement errors are
reported by `New` or `Register`.

### Core-only consumer

The core-only sketch from Option A is unchanged. This design adds no required
integration dependency or configuration to core construction.

### ConfigKit-only consumer

```go
configCommand, err := ckconfig.Command(ckconfig.Suite[struct{}]{
    Scopes: []ckconfig.Scope[struct{}]{
        ckconfig.FromConfigKit("app", "Application settings.", loadAppConfig),
    },
})
if err != nil {
    return err
}
app, err := commandkit.New(identity, greet, configCommand)
if err != nil {
    return err
}
```

### Composed consumer

```go
configCommand, err := ckconfig.Command(ckconfig.Suite[*RunState]{
    NewContext: newRunState,
    Scopes: []ckconfig.Scope[*RunState]{
        ckconfig.FromConfigKit("app", "Application settings.", loadAppConfig),
        ckprompt.ConfigScope(loadEngine),
    },
})
if err != nil {
    return err
}
definitions := ckprompt.FromEngine(loadEngine)
definitions.NewContext = newRunState
promptCommand, err := ckprompt.Command(definitions)
if err != nil {
    return err
}
app, err := commandkit.New(identity,
    configCommand, promptCommand, sessionGroup,
)
if err != nil {
    return err
}
```

Alternatively, an existing app can receive the complete declarations in one
`app.Register(configCommand, promptCommand, sessionGroup)` call. Declaration
validation happens before registry mutation, so a collision rejects the whole
batch. No guarantee extends across separate registration calls.

### Advantages

- Uses one declaration model for both standard and domain commands.
- Supports batch registration without new core transaction machinery.
- Applications can assemble a collection of commands before constructing an app.
- Factories can be reused in larger application assembly code without receiving
  an app or modifying its registry.

### Costs and limits

- The common task requires constructing and holding additional command handles
  before installation, with separate factory and registry errors.
- The public factory makes standard-group composition part of the consumer API.
  Documentation must explain that these groups occupy their standard root
  namespaces; arbitrary nesting must not redefine standard command paths.
- Returning an ordinary command handle alone does not settle reservation rules.
  The registry must still recognize any selected standard-namespace restrictions
  rather than assume every valid command may be installed at any location.

## Option C: complete declarations validated during installation

### Proposed public shape

This variant of Option B defers suite validation and fallible group assembly to
core construction or registration:

```go
// In the integration packages:
func Command[C any](suite Suite[C]) commandkit.Command
```

A returned command is an uninstalled, potentially invalid declaration. `New` or
`Register` prepares and validates the complete batch before committing it. The
core needs a supported mechanism for integration-owned validation and assembly
without importing integration types or exposing backend machinery. The concrete
`DeferredGroup` proposal below makes that cost visible; the shorter consumer
syntax does not make that work disappear.

Preparation uses only declarations and metadata. It does not acquire providers
or call application context factories. Installation errors include both invalid
suite wiring and registry conflicts. For `New`, a failure yields no usable app;
for `Register`, it leaves the prior registry intact.

### Core-only consumer

The core-only sketch from Option A remains available. Option C does not require
changing every domain command constructor to defer its own validation.

### ConfigKit-only consumer

```go
app, err := commandkit.New(identity,
    greet,
    ckconfig.Command(ckconfig.Suite[struct{}]{
        Scopes: []ckconfig.Scope[struct{}]{
            ckconfig.FromConfigKit("app", "Application settings.", loadAppConfig),
        },
    }),
)
if err != nil {
    return err
}
```

### Composed consumer

```go
definitions := ckprompt.FromEngine(loadEngine)
definitions.NewContext = newRunState
app, err := commandkit.New(identity,
    ckconfig.Command(ckconfig.Suite[*RunState]{
        NewContext: newRunState,
        Scopes: []ckconfig.Scope[*RunState]{
            ckconfig.FromConfigKit("app", "Application settings.", loadAppConfig),
            ckprompt.ConfigScope(loadEngine),
        },
    }),
    ckprompt.Command(definitions),
    sessionGroup,
)
if err != nil {
    return err
}
```

An existing app can instead receive these declarations in one `Register` call.
No guarantee extends across separate calls.

### Advantages

- Retains Option B's collection and batch-composition capabilities.
- Removes intermediate command handles and complete-group factory error checks.
- Reports invalid wiring and installation conflicts at one installation boundary.

### Costs and limits

- A command handle no longer implies that its integration declaration has passed
  validation; consumers must install it to obtain that result.
- The core must support deferred integration validation and assembly while
  retaining batch atomicity and dependency independence.
- Standard-root placement and empty declarations still need explicit semantics,
  as in Option B.
- Declaration capture and reuse need care: deferring work must not accidentally
  let later suite mutations change installed commands or share invocation state.

## Ownership, collisions, and the core boundary

None of the alternatives needs to expose registry maps, an installed-config
boolean, individual handler constructors, or backend objects. Ordinary
registration can reject an occupied root path and commit a fully validated batch
without merging children. That protects installed-family ownership for all three designs.

The accepted ownership rule is clear for installed standard families: application
registration cannot replace them or add private operations underneath them.
[ADR 0001](../adr/0001-command-dispatch-and-inputs.md) also refers to reserved
standard families, while the [architecture policy](../policy/architecture.md)
explicitly describes an installed `promptkit` family. Neither provides a uniform,
explicit lifetime rule for every uninstalled optional family. That interpretation
must be decided deliberately rather than inferred from prototype flags.

**Recommendation:** help/version are reserved by core construction; an optional
standard family claims its complete root namespace when installed. Before that,
a domain group can occupy the name, but a subsequent integration installation
then fails with a collision. Neither registration order can replace a winner.
This avoids a core registry of every possible future integration namespace and
does not prohibit core-only applications from using an otherwise absent family
name. It preserves ownership throughout an installed family's lifetime.

**Alternative:** reserve the known standard names before integration installation.
This catches domain misuse earlier but constrains applications that never install
those integrations and requires the core to recognize the reserved names and an
installation distinction. If selected, a narrow standard-group constructor can
mark integration declarations; do not expose private registry state.

Before implementation, align the roadmap, policy, and ADR interpretation with
the selected lifetime rule. If it changes an accepted decision, record that
change through the ADR process; this mockup does not authorize weakening it.

Option A assembles and registers its group at the root internally. B and C expose
handles, so they additionally need enforceable root placement. For B, a proposed
`commandkit.RootGroup(name, summary, children...) (Command, error)` returns an
opaque group declaration that normal `New`/`Register` accepts at the root and
rejects as a child of another group. It adds one public core constructor for a
concrete placement need, without exposing its handlers or creating a second
`Family` type. C's deferred constructor carries the same root placement metadata.
Moving a returned standard declaration under `tools`, for example, is an assembly
error rather than silently producing `app tools config show`.

This public distinction represents placement, not proof of a caller's package
identity. Do not invent package-origin authentication. An explicit `Family` type
remains viable if a concrete responsibility eventually warrants a separate
model, but it is not needed merely to relocate packages.

## Validation and declaration ownership

The following timing distinguishes the proposals; none shifts declaration errors
to command execution:

| Boundary | Option A | Option B | Option C |
| --- | --- | --- | --- |
| Scope/provider adapter | Record declaration | Record declaration | Record declaration |
| Integration suite validation | Integration `Register` | Integration `Command` | Core `New`/`Register` through integration-owned preparation |
| Registry and placement checks | Core registration | Core `New`/`Register` | Core `New`/`Register` |
| Provider acquisition | Selected handler | Selected handler | Selected handler |

Recommended ownership behavior: successful installation captures the declaration
metadata it needs, so later edits to suite fields or declaration slices do not
change installed commands. Application callbacks and the runtime objects they
capture retain their documented application-owned lifecycle; this is not a
promise to deep-copy arbitrary application state. For B and C, the proposal below
makes capture happen when a declaration factory is called; installation does not
read mutable caller-owned declaration slices.

The empty-suite proposal below distinguishes a configuration suite with no
scopes from a definition suite with no capabilities. B and C use an explicit
no-op declaration for the latter; an invalid zero-value command remains an error.

## Comparison

| Consideration | Option A: `Register` | Option B: validated `Command` | Option C: deferred `Command` |
| --- | --- | --- | --- |
| Typical consumer task | Supply suite and install family | Supply suite, receive validated group, then install | Supply suite as a declaration to core installation |
| Integration exports for registration | One convenience function | One complete-group factory | One deferred-declaration factory |
| Suite errors reported at | Integration registration | Group construction | Core installation |
| Domain commands | Ordinary core declarations | Same | Same; infallible constructors not required |
| Atomicity | Each integration registration call | Each core registration batch | Each core registration batch, including preparation |
| Standard assembly visible to callers | Integration-owned | Complete group handle exposed | Deferred group handle exposed |
| Pre-assembly of mixed command collections | Separate domain declarations and family calls | Directly supported | Directly supported |
| Additional core mechanism | Ordinary groups/registration under the recommended reservation rule | Root-placement declaration and explicit no-op | Deferred preparation, root placement, and explicit no-op |
| Dependency isolation and lazy acquisition | Supported | Supported | Supported |

## Recommendation

Prefer **Option A: integration-owned `Register` functions with typed suites and
declaration-only adapters, plus the focused `RegisterApp` convenience below**.
Rank Option C second and Option B third.
The representative consumers benefit from installing standard behavior directly;
they do not demonstrate a need to collect standard command handles or roll back
all family registrations together. Per-call atomicity and discarding a failed
application setup are sufficient for these sketches.

Use ordinary group construction and registry collision handling wherever they
satisfy the selected ownership rules. Remove redundant prototype bookkeeping.
Adopt the proposed installed-family reservation rule only after its deliberate
policy/ADR reconciliation. With that rule, A needs no extra core family or
preparation abstraction. Add only capabilities serving a selected responsibility.

Do not ship both `Register` and `Command` merely to cover every possible assembly
style. Options B and C are credible alternatives if pre-assembly or batch
installation becomes a demonstrated consumer requirement. C reduces consumer
error-handling boilerplate but adds deferred preparation to the core contract;
B offers earlier validation with more explicit assembly steps. All preserve the
same module and capability boundaries.

Once this proposal is accepted, update the owning module roadmap with the chosen
public registration shape and reservation semantics. Its staged implementation
plan can then specify exact declarations and validation without asking the coding
agent to invent a family framework. Prototype-compatible names, intermediate
buildability, and mechanical file relocation are not selection criteria.

## Additional design work and proposed resolutions

These proposals address the requested follow-up areas. They are recommendations
for review, not new accepted contracts. Select their semantics before producing a
decision-complete implementation plan.

### 1. Registration choice and the full setup cost

Retain the ranking **A, C, B**. All three generic sketches include real adapter,
scope, and suite assembly. A's common case improves further with the focused
entry point below. C has the shortest mixed declaration expression but needs a
new public preparation contract, root-placement handling, and no-op representation.
B exposes early validation and batch composition at the cost of more intermediate
handles and error checks. None needs a transaction spanning separate calls.

### 2. A context-free application configuration entry point

**Recommendation for A:** add a single focused convenience function:

```go
// In ckconfig:
func RegisterApp[T any](
    app *commandkit.App,
    load func(context.Context, Selection) (*configkit.Result[T], error),
) error
```

Complete registration call site, assuming `greet` is already declared:

```go
app, err := commandkit.New(identity, greet)
if err != nil {
    return err
}
if err := ckconfig.RegisterApp(app, loadAppConfig); err != nil {
    return err
}
```

Here `loadAppConfig` accepts only `context.Context` and `ckconfig.Selection`.
`RegisterApp` adapts it internally, declares the standard `app` scope, and uses
the same validation and installation path as `Register`. A nil original loader
remains a declaration error. The default scope summary can be a plain application
configuration description; callers needing a different summary, additional
scopes, selectors, or state use `Register` with a typed suite.

This is an alternative entry point for a demonstrated common case, not an options
language or a second scope model. It does not install a suite to which more
scopes are appended later. An application needing composition selects the full
suite entry point from the start.

**Alternative:** keep only generic `Register`. A context-free loader can use the
following explicit wrapper and declaration, with no additional export:

```go
if err := ckconfig.Register(app, ckconfig.Suite[struct{}]{
    Scopes: []ckconfig.Scope[struct{}]{
        ckconfig.FromConfigKit("app", "Application settings.",
            func(ctx context.Context, selection ckconfig.Selection, _ struct{}) (*configkit.Result[AppConfig], error) {
                return loadAppConfig(ctx, selection)
            }),
    },
}); err != nil {
    return err
}
```

That is viable but makes simple consumers repeat plumbing unrelated to their
application. Prefer the one focused export; do not automatically add analogous
conveniences for every provider or family. If B or C is chosen, evaluate an
`AppCommand` factory for this same use case instead of adding A's registration
entry point to a factory-based design.

### 3. Empty suites and intentional no-op declarations

**Recommendation:** distinguish absence of resources from absence of an optional
family's operations, and validate supplied declarations before treating them as
empty.

| Declaration | Proposed result |
| --- | --- |
| Config suite with no scopes | Declaration error: there is no configuration resource to inspect |
| Named config scopes with no inspection operations | Install `config scopes`; report those scopes and their actual empty capability sets |
| Config scopes with some supplied operations | Install discovery and the operations supplied by at least one scope |
| Definition suite with no capabilities and otherwise valid wiring | Successful no-op; no `promptkit` namespace or help entry installed |
| Adapter constructed with a nil loader | Declaration error, even if its wrappers or selected capabilities would otherwise look empty |

Not calling a registration function remains the simplest way to omit a family.
The no-op case supports capability-driven assembly without requiring a special
conditional in every consuming application. It does not reserve an absent
namespace under the proposed installed-family rule.

For B and C only, add an explicit proposed `commandkit.NoCommand() Command`
representation. Core `New`/`Register` skips it. A zero-value `Command` remains
invalid. B returns the explicit no-op after validating an empty definition suite;
C's preparation returns it after validation. Invalid wiring is never swallowed
as a no-op. A needs neither a public no-op handle nor that extra export.

**Alternatives:** omit all empty suites successfully, or install configuration
discovery even with no scopes. Both avoid the configuration error, but may hide
missing resource wiring or expose a namespace with nothing to discover. Requiring
at least one definition capability is also viable, but adds conditional assembly
for an intentionally optional family. These are product choices, not necessities
inherited from the prototype.

### 4. Namespace reservation and placement

Prefer the installed-family lifetime rule described above. It protects complete
standard groups while keeping unused names available to core-only consumers.
Confirm or revise the relevant policy/ADR interpretation explicitly before
implementation. Pre-installation reservation remains a viable alternative; its
cost and required installation distinction are described above.

For B and C, enforce standard-root placement in the core declaration metadata,
not only in documentation. An ordinary wrapper group must reject a standard
root-only child during assembly/registration. A keeps standard handles private
and performs its complete root registration inside the integration function.

### 5. Declaration capture, installation, and reuse

**Recommendation:** A captures registration metadata when `Register` is called;
B and C capture it when their `Command` factory is called. Capture includes
scope names and descriptions, capability lists, selector applicability, bindings,
and callback references. Copy declaration collections and nested metadata
collections needed for these semantics, rather than retaining the caller's
mutable slices. Application callback closures and the state they reference stay
application-owned; this is not a deep-copy guarantee for arbitrary values.

After `declaration := ckconfig.Command(suite)`, changing `suite.Scopes` or a scope's
operation list does not change that declaration. C's deferred preparation reads
its captured declaration, not the later contents of `suite`. Invalid recorded
wiring also stays attached to that captured declaration.

B and C declarations may be installed in more than one application. Each registry
captures its own installed metadata and each invocation receives its own parsed
state. Callback references may remain shared, and consumer closures may share
state deliberately. This does not promise concurrent dispatch or make caller
state safe for concurrent use. A can likewise receive the same suite in separate
registration calls; each call captures the suite as it exists at that time.

**Alternative:** C could capture at installation. That permits editing a suite
through retained references until installation but makes a command handle's
meaning depend on subsequent mutations and installation timing. Factory-time
capture provides a clearer declaration model without freezing application state.

### 6. Declaration validation and Option C preparation

**Recommendation:** declaration-only adapters retain the original loader or a
private construction issue in their owning integration declarations. Validators
inspect that information before using generated wrappers. A non-nil wrapper must
not make an originally nil loader appear valid. No public invalid-loader flag,
root-private accessor, or provider invocation is needed.

For example, `ckprompt.FromEngine(nilLoader)` records invalid wiring; it is not
an empty suite. A deliberately absent capability is an absent callback in a
manually composed, otherwise valid suite, or an explicitly supported capability
selection. A zero definition suite expresses intentional absence. An upstream
configuration or named lookup error from a valid callback remains an invocation
result; it is not a registration error.

Errors identify the family and, where applicable, the scope, capability, or flag.
For example, `config scope "app": loader is nil` and
`promptkit: engine loader is nil` are illustrative diagnostic content, not exact
string contracts. Preserve wrapped error identity where a fallible declaration
operation supplies an error. Validate scope uniqueness, supported capability
wiring, selector declarations, and reserved-flag collisions from metadata.
Integrations validate their own provider and scope metadata; core command/binding
construction validates opaque binding handles and command/flag conflicts. Wrap
those errors with the integration context rather than inspecting private flag
fields or duplicating parser validation. This does not require a new public
registry inspection or binding bridge just for declaration validation.
Do not validate files, credentials, or application configuration during assembly.

If C is selected, its concrete proposed public preparation mechanism is:

```go
// In commandkit; needed only for Option C:
func DeferredGroup(
    name, summary string,
    prepare func() (Command, error),
) Command
```

This is a root-only deferred command declaration, not a startup hook. Its opaque
handle carries root identity and the preparation callback. Integration factories
capture the typed suite and supply their own metadata-only preparation function:

```go
func Command[C any](suite Suite[C]) commandkit.Command {
    captured := captureSuiteDeclaration(suite) // Integration-private metadata copy.
    return commandkit.DeferredGroup("config", "Inspect configuration.",
        func() (commandkit.Command, error) {
            // Validate captured wiring and assemble the complete standard group.
            // No acquisition callback or NewContext callback is invoked here.
            return prepareConfigGroup(captured)
        })
}
```

`captureSuiteDeclaration` and `prepareConfigGroup` identify integration-owned
responsibilities; they are not additional public exports. Capturing metadata can
record an invalid declaration without returning an error. Preparation reports
that error at installation.

Core `New`/`Register` prepares the entire supplied batch before mutation, checks
resolved declarations and placement against each other and the existing registry,
and commits only after success. A nil preparation callback or a prepared group's
root differing from its declared root is an assembly error. A deliberate no-op
is permitted; malformed declarations are not. Failure leaves the registry intact,
but cannot undo arbitrary effects inside a caller-supplied callback. Standard
integration preparation functions themselves are responsible for remaining
metadata-only. Registering the same declaration in another app may prepare it
again; no cross-application preparation cache or exactly-once promise is needed.

**Alternative for C:** store a captured wiring error and an already assembled
neutral group in a command declaration, reporting the error only at installation.
This can avoid a general preparation callback if all necessary assembly can be
completed without error-returning work. Its viability depends on the final core
constructors; it must not discard validation failures or expose an untyped payload.
C's callback form is the concrete mockup here, not a requirement to choose C.

### 7. Typed customization and absent context factories

**Recommendation:** an omitted `NewContext` supplies the zero value of `C` for
the selected invocation. For a struct, that is a fresh zero-valued struct; for
`*RunState`, it is nil. Do not silently allocate arbitrary pointer contexts or
reject every pointer-context declaration. A loader may intentionally accept nil.
Applications whose binding callbacks or loaders require allocated state supply
`NewContext`. A supplied factory returning nil has the same caller-owned meaning;
this is not a promise to inspect or repair arbitrary callback state.

The following realistic A sketch uses a value input with a shared cache pointer.
All integration assembly is visible. `strconv.Atoi`, the string parser, and core
bindings are illustrative public binding primitives; their final names do not
constrain the registration choice.

```go
type RunInput struct {
    Campaign commandkit.Supplied[string]
    Limit    commandkit.Supplied[int]
    Cache    *RunCache
}

campaignFlag := commandkit.ValueFlag[RunInput, string](
    commandkit.FlagMeta{Name: "campaign", Usage: "Select campaign inputs."},
    nil,
    func(raw string) (string, error) { return raw, nil },
    func(input *RunInput, value commandkit.Supplied[string]) {
        input.Campaign = value
    },
)
limitFlag := commandkit.ValueFlag[RunInput, int](
    commandkit.FlagMeta{Name: "limit", Usage: "Override the application's item limit."},
    nil, strconv.Atoi,
    func(input *RunInput, value commandkit.Supplied[int]) {
        input.Limit = value
    },
)
newInput := func() RunInput {
    return RunInput{Cache: newRunCache()}
}

app, err := commandkit.New(identity, sessionGroup)
if err != nil {
    return err
}
if err := ckconfig.Register(app, ckconfig.Suite[RunInput]{
    NewContext: newInput,
    Selectors: []ckconfig.Selector[RunInput]{
        {Binding: campaignFlag, Scopes: []string{"app", "promptkit"}},
        {Binding: limitFlag, Scopes: []string{"app"}},
    },
    Scopes: []ckconfig.Scope[RunInput]{
        ckconfig.FromConfigKit("app", "Application settings.", loadAppConfig),
        ckprompt.ConfigScope(loadEngine),
    },
}); err != nil {
    return err
}
definitions := ckprompt.FromEngine(loadEngine)
definitions.NewContext = newInput
definitions.Selectors = []commandkit.Flag[RunInput]{campaignFlag}
if err := ckprompt.Register(app, definitions); err != nil {
    return err
}
```

Configuration selectors carry configuration-scope applicability. Definition
selectors are plain typed flags for that family's input; they do not need a
list containing a fictitious configuration scope. Each loader in this sketch
receives `RunInput`; registration and help call neither loader nor `newInput`.

For `app config show --scope all --campaign spring --limit=0`, both scopes receive
the campaign selector, but only the `app` scope receives the limit override.
Its loader checks `input.Limit.Set` before applying `input.Limit.Value`; explicit
zero overrides an inherited limit, while omission leaves it unchanged. An explicit
`--campaign=` similarly remains supplied with an empty value. The bindings retain
presence rather than inferring it from nonzero values.

Scope filtering uses binding metadata so a selector not applicable to a scope
is not copied into that scope's input. It does not erase shared acquisition state
such as `Cache`, or require deep-copying application state. Selecting only a scope
to which a supplied selector does not apply does not add a new rejection rule:
the selector simply is not delivered to that scope. If a stricter unused-selector
policy is desired, decide it separately rather than inventing it in registration.

For `app promptkit show profile briefing --campaign spring`, definition inspection
receives the campaign input and fresh invocation state; it does not receive the
configuration-only limit flag or invoke the application configuration scope.

**Alternative:** require a context factory for every stateful suite. That makes
initialization explicit but adds boilerplate for value inputs that work correctly
with zero values. Prefer the zero-value default plus an explicit factory when
actual application state needs one.

## Decisions still requiring approval

The requested design work is now concrete, but these proposals remain unapproved:

1. Choose A with `RegisterApp`, C, or B.
2. Confirm empty configuration errors, discovery-only named scopes, and empty
   definition no-ops; B/C additionally need explicit no-op declarations.
3. Confirm installed-family namespace reservation and reconcile policy/ADR wording,
   or choose pre-installation reservation and its narrow core distinction.
4. Confirm declaration capture timing and reuse, and the proposed separation from
   caller-owned state and concurrent-dispatch guarantees.
5. Confirm the zero-value context default and the typed customization contracts.

If C is chosen, additionally select its preparation mechanism; if B is chosen,
select the root-placement constructor. Those extra exports are conditional and
are not additions to the recommended A API.