whatsnew — on-demand generator

Emits a structured "what's new" fragment for a set of changes. The fragment is a gitignored handoff buffer; a per-project routing workflow turns it into whatever surface the project wants. The generator makes no assumption about the destination, and it never touches CHANGELOG.md — semantic-release owns that file at release time.

This skill is not a mandatory workflow phase. It is invoked on demand (and, when a project wires whatsnew.route_workflow, handed off to that routing workflow). Version is never stored in the fragment: the routing target reads the shipped version at publish time.

Steps

1. Build the entries (main context). Decide the keepachangelog entries for the change — one object per user-visible change, not per file. Write a JSON array to an entries file (for example under .claude/state/whatsnew/), each object shaped { "category": "<Added|Changed|Deprecated|Removed|Fixed|Security>", "title": "<short headline>", "body": "<one or two sentences>", "highlight": <bool, optional> }.
2. Run the generator. Invoke the entrypoint with --slug <slug> --entries-file <path> (optionally --project-root <root>). It validates the entries, writes the fragment to .claude/state/whatsnew/<slug>.json, and resolves the optional routing target.
3. Routing (optional). If project.json → whatsnew.route_workflow names a workflow, that workflow is the documented consumer of the fragment; it reads the fragment and writes its own committed output. If the knob is absent or null, the generator still succeeds and the fragment simply sits at the conventional path unconsumed.

Companion files

• whatsnew.mjs — the generator entrypoint. Reads the entries file, writes the fragment, reports the routing target.
• fragment-writer.mjs — validates entries and serializes the fragment { slug, generated_at, entries[{category, title, body, highlight?}] }. No version field.
• route-resolver.mjs — resolves project.json → whatsnew.route_workflow (string track id, or null by read-time default).
• classifier.mjs — defines the canonical keepachangelog category set that fragment-writer.mjs validates entries against.

Constraints

• Never writes CHANGELOG.md. That file is owned by semantic-release in CI. The generator only ever writes the gitignored fragment.
• No stored version. The version is read at publish time by the routing target, never written into the fragment.
• Transient fragment. .claude/state/whatsnew/<slug>.json is gitignored; a routing workflow that needs persistence commits its own rendered output, not the buffer.
• Routing is the project's concern. The generator is generic; it makes no assumption about where the fragment ends up. Projects with no routing target simply leave whatsnew.route_workflow unset.