/discover-acs

name: discover-acs
description: Use when a Ready feature needs its acceptance criteria discovered before specs are written. Triggers — "/engineer.discover-acs", "/engineer.acceptance-criteria", "discover ACs", "what must this feature do", "figure out acceptance criteria".

discover-acs

Discover a feature's acceptance criteria — Checkpoint 2. ACs are **decisions about what behaviors must work**, in **domain language**. They precede the Given/When/Then formalization that `atdd:atdd` produces.

Separating AC discovery (divergent decisions) from spec formalization (convergent encoding) is what protects domain language from leaking into implementation language.

When to use

On a feature with `autonomy_level` set and `status` of `ready` (greenfield) or `in-progress`/`done` (onboarded existing work). Produces `acs.md`.

**Two modes:**

• **Greenfield** — `status: ready`, no existing spec. Discover ACs from scratch via the four-pass interview.
• **Reverse-engineer** — onboarded feature (`in-progress`/`done`) that already has a spec (a Speckit `spec.md`, a design doc, shipped code). Extract candidate ACs from the existing material, then interview only for the gaps it leaves.

**Not for:** a parked feature (`discuss` to promote first); a feature that already has a complete `acs.md` (`feature-edit`); producing Given/When/Then specs (`atdd:atdd`); deciding whether to build the feature (`discuss`).

Workflow

**Step 0 — Entry gate.** Before starting, verify the prior checkpoint is complete: run `${CLAUDE_PLUGIN_ROOT}/scripts/dae_handoff.py <feature-dir> --through 1.5`. On a non-zero exit, **stop** and surface the gap to the human — do not proceed.

Verify branch hygiene: run `${CLAUDE_PLUGIN_ROOT}/scripts/dae_branch.py <feature-dir>`. On a non-zero exit, **stop** and surface the message to the human — switch branches and re-invoke. The check honors the `git.manual: true` manifest opt-out.

After the gate passes, show the **pipeline breadcrumb**: run `${CLAUDE_PLUGIN_ROOT}/scripts/dae_progress.py <feature-dir>` and present its output to the human — it shows where this checkpoint sits in the DAE pipeline. The breadcrumb is advisory: a non-zero exit or a missing `progress.md` never blocks the skill. Then create one TodoWrite todo per workflow step below. See `${CLAUDE_PLUGIN_ROOT}/references/progress-indicator.md`.

1. **Resolve + validate** — resolve the methodology root + manifest via `${CLAUDE_PLUGIN_ROOT}/scripts/dae_resolve.py` (see `references/resolving.md`); locate the feature. Reject if not found, if `status: parked` (→ `discuss` to promote first), or if `acs.md` already exists with content. Pick the mode: existing spec/code present → reverse-engineer; else → greenfield. 2. **Load** — `feature.md`, `CHARTER.md`, `manifest.yml`, prior `handoffs/`. Reverse-engineer mode: also load the existing spec / design doc / relevant code. **For code lookup in reverse-engineer mode** (surveying what exists, tracing what calls what), prefer LSP workspace-symbols / find-references when an LSP MCP capability is available; fall back to grep + Read otherwise. See `${CLAUDE_PLUGIN_ROOT}/references/code-lookup.md`. 3. **Discover the ACs:**

• **Greenfield** — interview in four passes, one question per turn, coverage prompts per pass.
• **Reverse-engineer** — extract candidate ACs from the existing material, organized by the four passes; then interview only for genuine gaps the material leaves undecided. Gap questions may be **batched** (e.g. one `AskUserQuestion` with up to 4) rather than one-per-turn — the existing material already carries the bulk.

The four passes:

• **Happy path** — the core journey, every behavior when all goes right
• **Edge cases** — empty / extreme / boundary / concurrency / partial state
• **Errors & security** — missing/malformed input, authorization, external failure, abuse
• **Cross-cutting** — audit, observability, idempotency, data lifecycle, performance

**3b. Domain coverage checklists (MANDATORY pass).** After the four interview passes, scan `feature.md`'s outcome and scope for surface signals and consult any matching checklist in `${CLAUDE_PLUGIN_ROOT}/references/ac-coverage/`:

| Signal phrase / keyword | Checklist file | |---|---| | public web page, site, marketing, HTML output | `web-seo.md` | | login, OAuth, auth, session, token, SSO | `auth-oauth.md` | | deploy, staging, production, infra, hosting, CI/CD | `deploy-model.md` | | UI component / page targeting humans | `accessibility.md` (when written) | | schema change, data backfill, migration, rename column | `data-migration.md` (when written) |

For each matched checklist: present its items as a single batched `AskUserQuestion` (multi-select) with the file's content as the option list. The human ticks "yes, this matters" / "no, out of scope" per item. Each ticked item becomes an AC candidate in Step 6/7. The checklists do **not** auto-create ACs without confirmation. image-titler shipped without a default `og:image` AC because nothing prompted the question — these checklists fix that class of gap.

4. **Enforce domain language** — when implementation leaks in ("returns 401", "the endpoint", table/class names), soft-warn and rephrase to the user-observable behavior; user confirms. Don't block — educate. 5. **Handle scope drift** — if a behavior surfaces outside `feature.md`'s outcome, offer three options: broaden `feature.md`, drop as out-of-scope, or park a separate `discuss`. User picks. 6. **Coverage check** — before writing, report ACs captured + which passes were covered; if a pass was skipped, prompt once. 7. **Write `acs.md`** — YAML frontmatter (`ac_count`, `high_priority_count`, `discovered`) + numbered `## AC-N: <name>` sections, each with `Priority`, `Type`, and a domain-language body. 8. **Review panel** — dispatch the standing adviser + advocate pair against `acs.md` per `${CLAUDE_PLUGIN_ROOT}/references/review-panel.md`. This is the cheapest place in