# ConfigKit v0.5.0

This minor release adds source-backed layered configuration and built-in sibling
inheritance, so applications can load one complete configuration while retaining
presence, source context, and explainable derivation.

## Summary

- `LoadLayered` combines ordered underlay groups beneath the main input, selected
  overlay, and explicit CLI overrides. Inputs within a group still compose
  strictly; precedence tiers combine mappings recursively. The main input
  remains the owner of the optional schema-version check.
- `NewFilesystem(...).File(...)` accepts caller-owned `fs.FS` sources, and
  `Mapping(...)` snapshots supported built-in values as a labeled source.
  `Result.SourceContext` and `Resolution.SourceContext` expose passive resource
  contexts for values from file-backed sources.
- `extends` now resolves a mapping against one named sibling after source
  precedence and before typed decoding. Inherited values count as explicit
  input. Origins, history, explanations, and redacted rendering retain the
  source and the structural path by which a value reached its destination.
  Review corrections preserve immutable nested-history evidence and bounded
  expansion work.

See the [configuration contract](../config.md#layered-loading),
[inheritance rules](../config.md#sibling-inheritance), and
[consumer examples](../consumers/README.md) for current behavior.

## Compatibility and upgrade

This is an intentional pre-v1 incompatible minor release for configurations
that use `extends` as ordinary data. That key is now reserved wherever an input
mapping occurs; it is consumed before decoding. Rename any such YAML key and
corresponding Go field, then rebuild. No collection registration or opt-in flag
is available. Configurations without `extends` retain their existing meaning.

Applications adopting the new features may move source-backed defaults into
explicit `Underlay` groups, use `SourceContext` for relative resources, or
replace application-owned sibling merging with one `extends` relationship per
mapping. Adoption is optional. The maintained
[named-preset example](../consumers/README.md#named-sibling-inheritance)
shows inherited `false` and destination-local nested resolution.

Select the new module version:

```sh
go get gitea.maximumdirect.net/eric/ConfigKit@v0.5.0
```

The minimum Go line remains 1.25. Linux amd64 and arm64 remain the
release-validated targets; macOS remains best-effort. The YAML dependency is
unchanged at `go.yaml.in/yaml/v4 v4.0.0-rc.6`.

[COPYRIGHT](https://gitea.maximumdirect.net/eric/ConfigKit/src/tag/v0.5.0/COPYRIGHT) | [LICENSE](https://gitea.maximumdirect.net/eric/ConfigKit/src/tag/v0.5.0/LICENSE) | [ATTRIBUTION](https://gitea.maximumdirect.net/eric/ConfigKit/src/tag/v0.5.0/docs/oss/attribution.md)