# 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, definition-registered distinct-ID sequence
  composition within strict tiers, and immediate-parent-relative import
  placement within that assembly. Higher-priority sequences replace lower
  sequences as whole values. The engine also owns destination-local sibling
  inheritance before typed decoding, plus shared source-version checking with
  sanitized declaration evidence.
  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 placement, registration, replacement, and history behavior; the
[consumer guide](../consumers/README.md#identified-prompt-sequences) shows the
maintained example.
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.