# Internal Component Overview

ConfigKit exposes one supported root `configkit` package. The root owns public
named types, declaration comments, constructors, and explicit conversion/wrapper
code. It delegates loading and frozen inspection to `internal/engine` through
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, per-input mapping
  and sequence-item placement, YAML collection declarations and operations for
  identified sequences, and application identity registrations for strict
  composition, inheritance, and final validation. It applies the selected
  collection operation at precedence boundaries and owns dependency-ready,
  destination-local inheritance before typed decoding. CLI assignment follows
  inheritance and decoding, before application resolution. The engine also owns
  shared source-version checking with sanitized declaration evidence.
  Explicit import discovery supports declared paths, directory searches, and
  globs; load-wide defaults and source-local empty-selection evidence cross the
  root facade without changing acquisition order. Import and inheritance
  resolution share dependency-ready scheduling within their composition scopes.
  It retains each source's effective 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
  frozen inspection snapshots. It never imports the root package.
- Root `Source`, `Filesystem`, `Input`, `Underlay`, `Path`, `Secret`, records,
  lifecycle callbacks, results, and bootstrap reports are root-defined wrappers
  or records. Callback wrappers pass only live engine context during a callback;
  `Result.Config` is detached and its private inspection remains frozen
  independently.
- Root conversion files explicitly cross the path, record, callback, secret, and
  error boundaries. There are no public aliases, anonymous engine embeddings, or
  public engine bridge methods.
- Root `Diff` and `Difference` provide the public comparison boundary and
  convert detached engine records to root-owned paths and snapshots; consumer
  examples own presentation of the safe changed regions.
- `internal/document` owns the parser-independent ordered tree and cloning.
  `internal/yaml` is the sole upstream YAML adapter and parser/dumper boundary.
- Engine mechanism tests own source, composition, inheritance, decoding,
  callback, provenance,
  source-context, secret, history, rendering, and bootstrap behavior. Root tests
  own public API compatibility, facade integration, documentation links, and
  dependency/public boundary checks. Consumer examples remain under
  `examples/consumers`.

Dependency direction is root to engine to document/YAML support. The root may
import only `internal/engine` among project internal production packages; engine
and its supporting packages do not import root. The root boundary test enforces
these constraints and rejects exported aliases, fields, or signatures involving
internal types.

The [configuration contract](../config.md) owns implemented YAML and lifecycle
semantics, including [input destinations](../config.md#input-destinations),
[shared source-version checks](../config.md#shared-source-version-checks), and
[effective configuration diffs](../config.md#effective-configuration-diffs).
The [strict composition contract](../config.md#strict-document-composition)
owns sequence declarations, identity, operations, ownership, and final
validation; [CLI overrides](../config.md#explicit-cli-overrides) own override
ordering. The [consumer guide](../consumers/README.md#identified-prompt-sequences)
links maintained workflow examples.
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
post-assembly structural operation. [ADR 0012](../adr/0012-relative-import-destinations.md)
records the relative-import extension; [ADR 0013](../adr/0013-shared-source-version-checks.md)
records the source-version decision.
[ADR 0014](../adr/0014-sequence-placement-and-composition.md) records explicit
sequence placement and composition. [ADR 0015](../adr/0015-shared-dependency-ready-ordering.md)
records the shared dependency-ready ordering decision; [ADR
0016](../adr/0016-independent-import-controls.md) records the independent
selection controls. [ADR 0017](../adr/0017-collection-sequence-policy.md) and
[ADR 0018](../adr/0018-cli-after-structural-resolution.md) record collection
operations and CLI ordering. The [import internals](imports.md) document candidate and
namespace identities, discovery and scheduling, and the bounded algorithms.