Writing Plans Agent Skill

writing-plans

Turn an approved spec into an executable plan. Routed to by /feature (after spec approval) and /sprint.

Pre-flight

Read these, or STOP and surface the gap — never plan against an unapproved or missing spec:

• ${CLAUDE_PROJECT_DIR}/.codearbiter/specs/<slug>.md — the approved brainstorming spec. The single source of acceptance criteria. Absent or unapproved → STOP and route back to /feature.
• ${CLAUDE_PROJECT_DIR}/.codearbiter/CONTEXT.md — the stage: frontmatter (the maturity value) and project context.
• ${CLAUDE_PROJECT_DIR}/.codearbiter/tech-stack.md — file layout, build/test/lint invocations. A verification step cites a real command from here, never a guess.
• ${CLAUDE_PROJECT_DIR}/.codearbiter/coding-standards.md — structure and naming, so a task names the right path.

If --farm was requested: check that FARM_API_KEY is set in the environment (or .env at ${CLAUDE_PLUGIN_ROOT}/tools/.env). If absent, BLOCK immediately — cite ${CLAUDE_PLUGIN_ROOT}/includes/farm.md for setup instructions. Do not proceed; the farm dispatcher cannot run without an API key. Model selection happens later (at dispatch time in subagent-driven-development), so no model research is needed here.

Phase 1 — Criterion extraction · gate: BLOCK

Lift every acceptance criterion from the spec verbatim and assign each a stable ID (AC-01,

AC-02, …). This list is the coverage ledger for the whole plan — Phase 4 checks the task set

against it.

A criterion the spec leaves ambiguous is a [CONFIRM-NN] against

${CLAUDE_PROJECT_DIR}/.codearbiter/open-questions.md — surface it, do not invent the intent.

Gate: every acceptance criterion in the spec captured as a numbered AC-NN. A partial ledger does

not pass.

Phase 2 — Task decomposition · gate: BLOCK

Break the work into the smallest honest units. Each task is ~2–5 minutes of work and carries:

• id — T-01, T-02, … stable.
• path(s) — the exact file(s) the task touches, resolved against coding-standards.md. "Some files" is not a path.
• verification — one concrete command or observable that proves the task done (e.g., <test cmd> -k test_token_expiry passes, endpoint returns 401 on missing header). It cites a real tech-stack.md invocation or a directly observable behavior — never "looks right".
• maps-to — the tdd obligation this verification corresponds to. The verification *maps to* a tdd obligation; it does NOT replace tdd's own gates. tdd Phase 1 still derives and Phase 4 still verifies obligations against passing tests.
• covers — the AC-NN(s) this task advances.

Split anything that won't fit ~5 minutes or touches unrelated paths. Reject the trap of one

monolithic "implement the feature" task — that defeats the plan.

Gate: every task has at least one path AND a verification AND a maps-to. A task missing any of the

three blocks the plan.

Phase 3 — Order & MVP slice · gate: BLOCK

Order tasks so each runs only after what it depends on. Flag every dependency explicitly

(T-07 depends on T-03). A cycle is a decomposition error — return to Phase 2 and split.

Group the ordered tasks so the MVP slice is identifiable: the minimal contiguous task set that

satisfies the spec's core acceptance criteria and is shippable on its own. Everything past the slice

is incremental.

Gate: a complete dependency order with no cycle, and an explicitly marked MVP slice.

Phase 4 — Coverage proof & write · gate: BLOCK

Cross the ledger against the task set, both directions:

• Every AC-NN is covered by at least one task's covers. An uncovered criterion blocks — author the missing task.
• Every task advances at least one AC-NN. A task that covers nothing is scope creep — cut it or surface it.

Then write the plan to ${CLAUDE_PROJECT_DIR}/.codearbiter/plans/<slug>.md — <slug> matching the

spec — with the AC-NN ledger, the ordered task table (id · path(s) · verification · maps-to ·

covers · depends-on · status, initialized PENDING), the marked MVP slice, and any out-of-scope

item tagged inline [NEEDS-TRIAGE].

The status column is the pipeline's resume ledger: subagent-driven-development flips a task to

ACCEPTED the moment it accepts it, so an interrupted run (crash, compaction, closed session) is

re-entered by /feature at the first non-ACCEPTED task instead of restarted from brainstorming.

Gate: bijective coverage proven — no criterion without a task, no task without a criterion — and the

plan written to disk. This clears the path to execution: executing-plans (checkpointed, via

/feature) or subagent-driven-development (autonomous, via /sprint) — each routes every task

through tdd. The plan never hands off to tdd directly.

Phase 4-farm extension (only when --farm was requested)

When --farm was requested, after the bijective coverage gate passes and the .md plan is written,

produce the farm artifact (plan.json) — one MVP slice at a time — per

${CLAUDE_PLUGIN_ROOT}/skills/writing-plans/references/farm-plan.md. Load that leaf and follow it;

it owns the per-task failing-test + schema-valid plan.json procedure.

Gate: all failing tests written and confirmed failing; plan.json written and schema-valid. Both

artifacts exist before handing off to subagent-driven-development.

Hard rules

• MUST NOT plan against an absent or unapproved spec — STOP and route back to /feature.
• MUST NOT emit a task without an exact path AND a concrete verification step.
• MUST NOT let a task's verification stand in for a tdd gate — it maps to a tdd obligation, it does not replace one.
• MUST NOT write the plan while any acceptance criterion is uncovered or any task covers nothing.
• MUST NOT guess a verification command — cite tech-stack.md or STOP.
• MUST NOT resolve an ambiguous criterion by guessing — raise a [CONFIRM-NN].
• MUST NOT emit plan.json in --farm mode without writing and confirming each failing test first.
• MUST NOT set meta.model or meta.apiBaseUrl in plan.json — these belong to the dispatch step.
• MUST NOT proceed with --farm if FARM_API_KEY is absent — cite ${CLAUDE_PLUGIN_ROOT}/includes/farm.md and BLOCK.
• MUST, at exit, run the follow-up harvest (${CLAUDE_PLUGIN_ROOT}/includes/harvest.md) over any [NEEDS-TRIAGE] out-of-scope items — batch-confirm promoting them to open-tasks.md (work) or open-questions.md (decisions) so they don't die in the plan file.