compat-checklisted

Analyze the API surface of this project (read name from CLAUDE.md or package.json) for backwards compatibility. Extracts the current contract surface (CLI flags, template placeholders, command names, argument flags, agent names, config keys), compares against a stored baseline, classifies each change by severity, and generates a migration guide when breaking changes are found. **Input:** `$ARGUMENTS` — optional flags: - `--diff` — compare current surface to most recent snapshot (default when snapshots exist) - `--snapshot` — capture current surface and save without diffing (default on first run) - `--since <date>` — diff against snapshot from this date (ISO format: YYYY-MM-DD) - `--propose <change-dir>` — diff proposed changes in `openspec/changes/<change-dir>/` against current surface - `--dry-run` — run all phases but skip saving the snapshot --- ## Phase 0: Argument Parsing Parse `$ARGUMENTS` to set runtime variables. **Variables to set:** - `MODE` — string, one of `"snapshot"`, `"diff"`, `"propose"`. Default: `"diff"` if `.claude/compat-snapshots/` contains any `.json` files; `"snapshot"` otherwise. - `COMPARE_DATE` — string (ISO date) or empty string. Default: `""` (use most recent snapshot). - `PROPOSE_DIR` — string or empty string. Default: `""`. - `DRY_RUN` — boolean. Default: `false`. **Parsing rules:** 1. Scan `$ARGUMENTS` for `--snapshot`. If found, set `MODE=snapshot`. 2. Scan for `--diff`. If found, set `MODE=diff`. 3. Scan for `--since <date>`. If found,