Complete input destination implementation audit

README.md

@@ -68,12 +68,14 @@ The [architecture goals](docs/policy/architecture.md#success-criteria) explain
 these priorities and how genuine new needs can justify extending the shared
 model. The [deferred scope](docs/roadmap/deferred.md) records deliberate exclusions.
 
-The [configuration contract](docs/config.md) describes implemented behavior. The
+The [configuration contract](docs/config.md) describes implemented behavior,
-[consumer adoption guide](docs/consumers/README.md) provides maintained simple
+including [input destinations](docs/config.md#input-destinations). The
-native-filesystem, layered, and sibling-inheritance examples alongside the migration shapes.
+[consumer adoption guide](docs/consumers/README.md) provides maintained simple,
-See the [development guide](docs/development.md) for repository orientation and the
+layered, and mounted-collection examples alongside the migration shapes. The
-[release procedure](docs/release.md) for maintainer-only candidate and publication
+accepted placement decision is recorded in [ADR 0011](docs/adr/0011-input-destinations.md).
-steps.
+See the [development guide](docs/development.md) for repository orientation and
+the [release procedure](docs/release.md) for maintainer-only candidate and
+publication steps.
 
 ConfigKit code is licensed under the [LGPL v3.0 or later](COPYRIGHT).
 

docs/consumers/README.md

@@ -111,6 +111,11 @@ lifetime and precedence rules.
 
 ## Input destinations and mounted collections
 
+Main and underlay inputs use the same destination field; imported application
+contributions inherit the declaring input's destination. A destination is an
+application mapping path, independent of filesystem context. The configuration
+contract owns the complete behavior and validation rules.
+
 The small [`Example_inputDestination`](../../examples/consumers/destinations_test.go)
 mounts one mapping source beneath literal collection/prompt keys and loads a
 second input without a destination to show that root placement remains the

docs/development.md

@@ -39,6 +39,7 @@ public behavior.
 | Task | Read |
 | --- | --- |
 | Repository orientation or component responsibility | [Component overview](internal/overview.md) |
+| Input destinations | [Configuration contract](config.md#input-destinations), [ADR 0011](adr/0011-input-destinations.md), and the destination tests below |
 | Documentation changes | The owning document |
 | Licensing, dependencies, attribution, or release-document changes | [Project grant](../COPYRIGHT) and [attribution](oss/attribution.md); release changes also follow the release procedure |
 | Architecture decisions or future work | [Deferred scope](roadmap/deferred.md) and relevant ADRs listed below |
@@ -55,6 +56,7 @@ Accepted decisions:
 - [Explicit overrides and safe explanation](adr/0005-explicit-overrides-and-safe-explanation.md)
 - [Keep the public facade root-owned](adr/0006-public-facade.md)
 - [Compare frozen effective configuration snapshots](adr/0010-effective-configuration-diff.md)
+- [Place inputs at literal application mapping paths](adr/0011-input-destinations.md)
 
 For cross-cutting changes, follow every applicable row. Completed implementation
 and remediation plans are preserved in Git history at `cb5b435`; use current
@@ -164,6 +166,7 @@ code changes. Use the component overview to find the corresponding implementatio
 | Composition, selected overlays, CLI precedence | [Composition](../internal/engine/compose_test.go), [overlay](../internal/engine/overlay_test.go), [selected overlays](../internal/engine/selected_overlay_test.go), [overrides](../internal/engine/override_test.go) | `go test ./internal/engine -run 'Compose\|Overlay\|Override'` |
 | Sibling inheritance, provenance, history, sensitivity | [Expansion](../internal/engine/inheritance_test.go), [destination scopes](../internal/engine/inheritance_walk_test.go), [origins](../internal/engine/inheritance_origin_test.go), [history](../internal/engine/inheritance_history_test.go), [secrets](../internal/engine/inheritance_secret_test.go), [public loading](../facade_inheritance_test.go) | `go test ./internal/engine -run 'Inheritance\|Inherited'` and `go test . -run '^TestFacadeInheritance\|^TestFacadeInheritedSecrets'` |
 | Layered loading and source equivalence | [Grouped lifecycle](../internal/engine/load_request_test.go), [layered facade](../facade_layered_test.go), [equivalence](../facade_equivalence_test.go) | `go test ./internal/engine -run '^TestGrouped'`, `go test . -run '^TestFacadeLayered'`, and `go test . -run '^TestEquivalentSourceForms'` |
+| Input destinations, mounted sources, and source ownership | [Destination engine tests](../internal/engine/destination_test.go), [tier and import tests](../internal/engine/destination_tiers_test.go), [integration and provenance tests](../internal/engine/destination_integration_test.go), [public facade tests](../facade_destination_test.go), and [consumer examples](../examples/consumers/destinations_test.go) | `go test ./internal/engine -run 'Destination|Mounted'`, `go test . -run 'Destination|FacadeMounted'`, and `go test ./examples/consumers -run 'CollectionBundle|CollectionPeer'` |
 | Schema, defaults, projection, cloning | [Schema](../internal/engine/schema_test.go), [decoding](../internal/engine/decode_test.go), [projection](../internal/engine/projection_test.go) | `go test ./internal/engine -run 'Schema\|Decode\|Projection\|Clone\|Inline\|CompareDocument'` |
 | Lifecycle, resolution, validation, callback ownership | [Loading](../internal/engine/load_test.go), [resolution](../internal/engine/resolution_test.go), [validation](../internal/engine/validation_test.go), [ownership](../internal/engine/callback_ownership_test.go), [independence](../internal/engine/independence_test.go) | `go test ./internal/engine -run 'Load\|Resolution\|Validation\|Validator\|Hook\|Callback\|Parallel'` |
 | Paths, metadata, provenance | [Paths](../internal/engine/path_test.go), [metadata](../internal/engine/metadata_test.go), [provenance](../internal/engine/provenance_test.go) | `go test ./internal/engine -run 'Path\|Metadata\|Provenance\|Queries'` |

docs/internal/overview.md

@@ -8,8 +8,10 @@ private state; public signatures and fields do not expose engine types.
 Implemented component owners:
 
 - `internal/engine` owns host and native-filesystem source acquisition,
-  grouped strict composition, recursive precedence assembly, and destination-local
+  grouped strict composition, recursive precedence assembly, per-input mapping
-  sibling inheritance before typed decoding. It also owns schema
+  placement within that assembly, and destination-local sibling inheritance
+  before typed decoding. It retains source placement alongside physical source
+  identity and owns schema
   inspection, lifecycle coordination, callback auditing,
   provenance/history, passive source-context retention, secret resolution and
   bootstrap, safe inspection rendering, and effective-value comparison over
@@ -41,11 +43,13 @@ these constraints and rejects exported aliases, fields, or signatures involving
 internal types.
 
 The [configuration contract](../config.md) owns implemented YAML and lifecycle
-semantics, including [effective configuration diffs](../config.md#effective-configuration-diffs).
+semantics, including [input destinations](../config.md#input-destinations) and
+[effective configuration diffs](../config.md#effective-configuration-diffs).
 The [consumer adoption guide](../consumers/README.md) owns application guidance.
 The [architecture policy](../policy/architecture.md) owns contributor
 boundaries; [ADR 0006](../adr/0006-public-facade.md) records the facade decision
 and [ADR 0010](../adr/0010-effective-configuration-diff.md) records the diff
+decision; [ADR 0011](../adr/0011-input-destinations.md) records the placement
 decision. See the [development guide](../development.md) for validation commands
 and [release procedure](../release.md) for source-candidate gates. [ADR
 0009](../adr/0009-sibling-inheritance.md) records why inheritance is a built-in

docs/policy/architecture.md

@@ -99,6 +99,13 @@ types, field meanings, defaults, normalization, semantic validation, and schema
 version policy. Applications also own main-file search conventions, CLI wiring,
 remote acquisition, runtime initialization, and resource checks.
 
+The engine applies each input's mapping destination within the existing source
+assembly and retains that placement with source identity and inspection records;
+the root facade owns the public fields and conversions. The
+[configuration contract](../config.md#input-destinations) defines the observable
+placement behavior, and [ADR 0011](../adr/0011-input-destinations.md) records the
+accepted decision.
+
 Library code must not depend on consuming applications or initialize their
 runtime resources. It must not perform implicit network access, discover
 application-specific paths, or change process-global state during ordinary `Load`.

docs/roadmap/implementation.md

@@ -1,8 +1,7 @@
 # Implement configuration input destinations
 
-Status: planned. Execute Stage 1 through Stage 12 in order, one focused stage
+Status: complete. Stages 1–12 are implemented and audited. The
-per Luna implementation prompt. The [feature roadmap](input-destinations.md)
+[feature roadmap](input-destinations.md) owns the approved behavior and rationale; the
-owns the approved behavior and rationale; the
 [consumer request](promptkit-feature-request.md#public-acceptance-scenarios)
 supplies the public acceptance scenarios. This document owns execution and
 completion evidence. Planning baseline: `6353598`.
@@ -504,7 +503,7 @@ structural pass.
 
 ## Stage 12 — Reconcile documentation and audit the complete implementation
 
-Status: planned. Scope: final integration audit and evidence, not release work.
+Status: complete. Scope: final integration audit and evidence, not release work.
 
 1. Update README navigation, consumer guidance, the component overview, and
    development reading/test maps. Add ADR 0011 to navigation. Update architecture
@@ -529,6 +528,24 @@ Status: planned. Scope: final integration audit and evidence, not release work.
    and owning contracts agree. Retain completed planning evidence until separately
    authorized release preparation.
 
+Audit evidence for the approved decisions and request acceptance surface:
+
+| Behavior reviewed | Evidence and what it proves |
+| --- | --- |
+| Root-owned `Input.Destination` and `SourceInfo.Destination`; detached conversions and publication | `TestSourceInfoDestinationConversionsAndCopies`, `TestFacadeFailedLoadExposesDetachedSourceDestination`, and `TestFacadeMountedMainAndUnderlayInspectionResourcesAndDiff` verify root/engine conversion, error records, and returned record detachment. `TestPublicFacadeBoundary` and `TestDependencyImportBoundary` verify no engine types cross the facade. |
+| Literal mapping keys, parsed numeric keys, reserved structural tokens, and invalid-path preflight | `TestNormalizeDestinationUsesLiteralMappingKeys`, `TestNormalizeDestinationRejectsIndicesAndReservedKeys`, and `TestLayeredLoadPreflightsDestinationsBeforeReadingSources` cover mapping-only normalization and rejection before reader consumption; `TestFacadeDestinationRootEmptyMappingNoSourceAndInvalidPaths` verifies the public error boundary. |
+| Placement of acquired bodies, empty mappings versus absence, imports, all source kinds, physical identity, and authored coordinates | `TestFacadeInputDestinationsAcrossSourceKinds` covers host/native/bytes/reader/mapping sources; `TestFacadeSameFragmentMountsAtSeparateCollectionDestinations` proves independent public collections can retain the same local key. `TestLayeredImportOnlyInputMaterializesDestination`, `TestLayeredHostImportsInheritInputDestinationTransitively`, `TestLayeredNativeFilesystemImportsInheritInputDestination`, and `TestLayeredDestinationsDoNotChangeRepeatedSourceIdentity` cover inherited import placement and unchanged identity. `TestPlaceDocumentWrapsEmptyMappingAndPreservesSourceCoordinates`, `TestPlaceDocumentPreservesAuthoredEntryCoordinates`, and `TestLayeredDestinationDiagnosticsUseEffectivePathsAndAuthoredLocations` distinguish fallback wrapper locations from authored coordinates. |
+| Strict composition, explicit-wrapper equivalence, precedence, empty values, and domain `version` overrides | `TestLayeredDestinationStrictCompositionBoundaries`, `TestLayeredDestinationMatchesExplicitlyWrappedInput`, `TestEmptyMountedMappingRetainsLowerChildren`, and `TestLayeredDestinationOverlayRetainsOrdinaryValueSemantics` prove existing group and overlay semantics are retained; the latter includes ordinary field-only updates rather than whole-record replacement. |
+| Main-owned version checks and imported, underlay, inheritance, overlay, CLI, and ancestor protection | `TestLayeredDestinationChecksVersionOnceOnComposedMain`, `TestLayeredDestinationVersionClaimsUsePlacedApplicationPaths`, `TestLayeredImportedVersionClaimsUseEffectiveDestination`, and `TestLayeredMountedVersionProtectionCoversInheritanceAndUpperTiers` cover effective paths, one main check, protected-path claims/ancestors, and nonclaiming mapping ancestors. `TestLoadVersionDestinationTypesKeepOrdinaryDecoding` preserves exact configured-path conversion and ordinary nested decoding. |
+| Final-shape sibling inheritance, no cross-collection lookup, one lifecycle, and failure without a usable partial result | `TestLayeredDestinationInheritanceUsesFinalSiblingScopes`, `TestLayeredDestinationInheritanceDoesNotSearchOtherCollections`, `TestLayeredDestinationLifecycleAndSensitiveInspectionUseFinalShape`, and `TestLayeredDestinationDecodeFailureReturnsNoResultOrLaterCallbacks` exercise these behaviors. Reused inheritance, lifecycle, and callback tests cover generic behavior that destination placement does not alter. |
+| Effective paths, presence, provenance/history, safe rendering, sensitivity, bilateral diff, and source-relative resources | `TestLayeredDestinationsRetainOriginsHistoryAndDetachedRecords`, `TestLayeredDestinationLifecycleAndSensitiveInspectionUseFinalShape`, `TestLayeredDestinationDiffUsesBilateralSensitivity`, `TestLayeredImportedInheritedValuesRetainResourceContexts`, and `TestFacadeMountedMainAndUnderlayInspectionResourcesAndDiff` connect mounted values to inspection. The imported-inheritance test specifically proves the inherited value keeps the declaring source's passive resource context. |
+| Shared depth/node limits and unchanged root/absence accounting | `TestPlaceDocumentRootAndBounds`, `TestDestinationPlacementCountsAgainstSharedNodeBudget`, `TestMultipleMountedInputsSharePlacementCharges`, `TestImportedEmptyBodiesChargeEachDestinationWrapper`, `TestSelectedOverlayAndCLIUsePlacementNodeCharges`, and `TestNoSourceAndRootPlacementAddNoWrapperCharges` cover per-document and aggregate limits without adding a new limit class. |
+| Maintained consumer usage and strict peer behavior | `Example_inputDestination`, `TestCollectionBundleAssemblesMountedPeersAndResources`, and `TestCollectionPeerPromptConflictsRemainStrict` verify the simple and representative collection examples against actual values, resources, source records, and conflict behavior. |
+
+The wider baseline-to-candidate review covered all 38 changed files (`6353598..2d8df22`): production changes are limited to the root facade fields/conversions, private input/import assembly and accounting, source record ownership, and the inheritance version-claim correction described above. The contract and tests do not impose identifier grammar, namespace uniqueness, main-only placement, source-read ordering, new budgets, nested version conversion, or expanded secret policy. The implementation wraps only acquired application bodies after processing source-root directives; placement does not change physical source identity, authored node locations, filesystem resolution, or later-tier semantics. Stage evidence above reuses existing general composition, resource, inheritance, version, lifecycle, sensitivity, and boundary tests where those behaviors are unchanged; mounted-specific cases are named separately.
+
+Completion record: audited source candidate `2d8df22dd1cb9fde8e60853da3e2260731acf2bb`. On `go1.26.8 linux/amd64`, `./scripts/check.sh` passed, including formatting, whitespace, documentation links, tests, vet, and build. `GOTOOLCHAIN=local GOPROXY=off go test -race ./...` also passed with dependency downloads disabled. No remaining implementation limitations were found; release preparation, CI, benchmark campaigns, and downstream upgrades remain separately scoped.
+
 Done: one complete layered load supports input destinations with coherent values,
 diagnostics, inspection, limits, and source ownership across the approved surface.
 

docs/roadmap/input-destinations.md

@@ -1,10 +1,10 @@
 # Configuration Input Destinations Roadmap
 
-Status: design decisions approved; implementation has not started. This roadmap
+Status: implemented. This roadmap records the approved behavior and rationale
-responds to the [PromptKit feature request](promptkit-feature-request.md) and owns
+for the [PromptKit feature request](promptkit-feature-request.md). The
-the target state and selected design decisions. The
+[implementation plan](implementation.md) records the completed sequence and
-[implementation plan](implementation.md) owns sequencing, implementation details,
+audit evidence; the [configuration contract](../config.md#input-destinations)
-and completion evidence.
+owns current behavior.
 
 ## Targeted end state
 
@@ -88,9 +88,9 @@ namespace ownership enforcement, dependency solving, live reload, filename-based
 identity, arbitrary transformations, or new merge strategies. PromptKit owns its
 collection inventory, qualified IDs, and execution semantics.
 
-## Current baseline
+## Implementation baseline (v0.7.1)
 
-The request reviewed v0.7.1. The current worktree has these relevant boundaries:
+The request reviewed v0.7.1. At that baseline, the relevant boundaries were:
 
 - [Input](../../layered.go) holds a source, import opt-in, and filesystem context,
   but no destination. Root types delegate to the engine through the existing

facade_destination_test.go

@@ -153,6 +153,36 @@ func TestFacadeImportedSourcesRetainInputDestination(t *testing.T) {
 	}
 }
 
+func TestFacadeSameFragmentMountsAtSeparateCollectionDestinations(t *testing.T) {
+	weatherDestination := configkit.Keys("collections", "weather", "prompts")
+	homeDestination := configkit.Keys("collections", "homewatch", "prompts")
+	result, err := configkit.LoadLayered(
+		configkit.Input{Source: configkit.NoSource()},
+		configkit.LayeredOptions[map[string]any]{Underlays: []configkit.Underlay{{Inputs: []configkit.Input{
+			{Source: configkit.Bytes("weather", []byte("summarize.alerts: {title: weather}\n")), Destination: weatherDestination},
+			{Source: configkit.Bytes("homewatch", []byte("summarize.alerts: {title: home}\n")), Destination: homeDestination},
+		}}}},
+	)
+	if err != nil {
+		t.Fatalf("LoadLayered: %v", err)
+	}
+	for _, test := range []struct {
+		path []string
+		want string
+	}{
+		{path: []string{"collections", "weather", "prompts", "summarize.alerts", "title"}, want: "weather"},
+		{path: []string{"collections", "homewatch", "prompts", "summarize.alerts", "title"}, want: "home"},
+	} {
+		if got := facadeDestinationValue(t, result.Config, test.path...); got != test.want {
+			t.Errorf("value at %v = %#v, want %q", test.path, got, test.want)
+		}
+	}
+	sources := result.Sources()
+	if len(sources) != 2 || sources[0].Destination.String() != weatherDestination.String() || sources[1].Destination.String() != homeDestination.String() {
+		t.Fatalf("independent collection source placements = %#v", sources)
+	}
+}
+
 type destinationCountingReader struct{ reads int }
 
 func (reader *destinationCountingReader) Read([]byte) (int, error) {

internal/engine/destination_tiers_test.go

@@ -131,6 +131,25 @@ func TestLayeredDestinationMatchesExplicitlyWrappedInput(t *testing.T) {
 	}
 }
 
+func TestEmptyMountedMappingRetainsLowerChildren(t *testing.T) {
+	t.Parallel()
+
+	destination := Keys("collections", "weather")
+	loaded, err := LoadLayered(
+		Input{Source: Bytes("empty-main", []byte("{}\n")), Destination: destination},
+		testSecretBinding(),
+		LayeredOptions[map[string]any]{Underlays: []Underlay{{Inputs: []Input{{
+			Source: Bytes("lower", []byte("prompt: {title: retained}\n")), Destination: destination,
+		}}}}},
+	)
+	if err != nil {
+		t.Fatalf("LoadLayered: %v", err)
+	}
+	if got := layeredMapValue(t, testLoaded(loaded).Config, "collections", "weather", "prompt", "title"); got != "retained" {
+		t.Fatalf("lower child beneath empty mounted mapping = %#v, want retained", got)
+	}
+}
+
 func TestLayeredDestinationOverlayRetainsOrdinaryValueSemantics(t *testing.T) {
 	t.Parallel()