FeatherSpec 1.2.0 — Versioned & Updatable

Added

• Versioning: the template carries a FeatherSpecVersion: stamp in AGENTS.md's managed
  settings block; releases are annotated git tags surfaced as GitHub Releases, recorded here
  and in the version ledger.
• /sdd-featherspec-update: check the installed template version (check mode works even
  on customized, unstamped projects via feature probes) and update safely — fetches the
  recorded base and the target release as real trees, classifies every file by canonical-hash
  three-way comparison, previews everything before writing, migrates around preserved
  customizations, surfaces conflicts instead of choosing sides, keeps a rollback point,
  validates the result mechanically, and moves the version stamp only after success.
  Resumable at any point; re-running after success is a free health check.
• Version ledger: an append-only appendix in the update command's body recording
  per-release semantic migration knowledge back to 0.1.0 — renames, key migrations, slot
  edits, data notes, semantic flips, and version probes for unstamped projects.

Changed

• AGENTS.md: the managed settings block gains the version stamp and is now managed by
  /sdd-setup and /sdd-featherspec-update; the DocLanguage comment is condensed to one
  line to keep the constitution under its line target; .sdd-update/ joins the volatile,
  gitignored working locations.

Upgrading an existing project

Copy two files from this release into your repo — that is the whole install:

• .claude/commands/sdd-featherspec-update.md
• .github/prompts/sdd-featherspec-update.prompt.md (skip if you removed the Copilot half; restart VS Code afterwards if you kept it)

Then run /sdd-featherspec-update. It detects your current version (stamped or not, however customized), previews everything before writing, preserves every customization, and stamps your project 1.2.0. /sdd-featherspec-update check alone answers "which version am I on?". Details: Updating & Versioning.