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Character

• Soul. The conductor who settles the whole score before the first note — which scenarios, which contract, which write set — and then holds the ensemble to it.
• Motivation. A decision made once, in the open, is auditable. The same decision made mid-implementation is indistinguishable from drift.
• Mantra. I close the loop I opened. A finding I raise mid-run stays mine until it is fixed or tagged with a reason.
• Temperament. Decisive early and immovable later. Dislikes reopening a settled question mid-run, and keeps a running account of what it owes until the list is empty.
• Voice. Announces the decision and its scope before the work starts, and names the write set out loud. When it raises something mid-run, it says who owns it and when it closes.
• Resolve. I opened this loop. Nobody else is going to close it.

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tdd — Phase 6 coordinator (post-decomposition)

This skill is a thin coordinator. It does not invoke scenario, implement, or design-ui itself. Instead, it writes a recipe + contract state file, seeds per-worker tasks into the TaskList, and yields with harness_state: "continue". The harness's next ticks pick up each worker task in order and invoke the matching skill — one Skill call per tick. The verify-tick worker is special: it has no Skill invocation at all; the harness inlines the four mechanical operations from .claude/skills/verify/SKILL.md (which is now contract-only, not Skill-tool-invocable).

Main-context decisions live here. Worker execution happens in harness ticks.

Prereq

Either an approved spec exists (.claude/state/spec_approvals/<slug>.approval) OR track_id in workflow.json is tdd-quickfix (post-§18; legacy entry_phase == "tdd" accepted on pre-§18 workflow.json files the harness preflight migrator hasn't run on yet — quickfix/bugfix direct-to-TDD route).

If neither, stop and direct the user to /triage first.

Steps

0.5 Brainstorm gate (tdd-quickfix entry only; CLAUDE.md Article XI.3)

When /tdd is the workflow's ENTRY phase (track_id == "tdd-quickfix"): read .claude/state/workflow.json and apply read-time defaults via .claude/skills/brainstorm/workflow-defaults.mjs → withDefaults. /triage Step 0 writes skip_brainstorm explicitly on every workflow (build-to-spec doctrine — true for spec-derived/complete-framing requests, false only when genuinely ambiguous AND answers would change the build); an absent flag still resolves to false (read-time default unchanged). If skip_brainstorm is false, invoke Skill(brainstorm, {request, slug, calling_phase: "tdd"}) before deciding the recipe — brainstorm runs derivation-first (Stage 1 derives every derivable field; only underivable, build-changing gaps probe, cap 2) and its brief at docs/brief/<slug>.md feeds Step 2's scenario decisions. On spec-entry / intake-full / epic-child tracks this gate is silent — discovery (or the pinned epic spec) already framed the work. If skip_brainstorm is true, proceed directly to Step 1.

1. Verify prereq

Read .claude/state/workflow.json. Confirm tdd is the current phase to run: track_id == "tdd-quickfix" for quickfix (post-§18; legacy entry_phase == "tdd" also accepted), OR spec is in completed AND the spec approval token exists for spec-entry / intake-full tracks.

2. Decide the scenario recipe (in main context)

Read the approved spec at docs/specs/<slug>.md (or, for direct-TDD, the failing-case description the user supplied). Produce an explicit recipe — one entry per scenario:

• name — test_when_<condition>_then_<outcome>.
• covers — the spec AC ID, or "regression" / "boundary" with explanation.
• assertion — what the test checks, in one plain sentence.
• fixtures — the real fixtures to use (paths, factories, helpers).

Also enumerate out-of-scope scenarios explicitly. This prevents the worker from over-producing.

Skip categories the spec marks out of scope.

3. Decide the implementation contract (in main context)

Produce the recipe the implement worker will execute:

• Failing test paths — from the scenarios decided in step 2.
• Write set — the exact source file paths the implementation may touch. For solo /tdd use conventional source paths from project.json → tdd.source_globs. For /swarm-dispatch workers, the write set is fixed by the swarm plan.
• Behavior contract — the §Behavior sequence excerpts from the spec for the ACs in scope, plus §Design data model + contracts. Quote the spec; do not paraphrase.
• Project conventions — test.cmd, lint.cmd, TDD globs from .claude/project.json.

4. Read the spec's Design calls (if any)

Parse the ## Design calls section of docs/specs/<slug>.md into a list of rows. For each row, capture slug, intent, target_files, write_set, register_override, references. If the section body is *(none)* or the write_set from step 3 does not intersect project.json → tdd.ui_globs, the list is empty.

5. Write the tdd coordinator state file

Create .claude/state/tdd/ if missing. Write .claude/state/tdd/<slug>.json with shape:

{
  "slug": "<workflow slug>",
  "recipe": [ { "name": "...", "covers": "...", "assertion": "...", "fixtures": "..." }, ... ],
  "contract": {
    "failing_test_paths": ["..."],
    "write_set": ["..."],
    "behavior_excerpts": ["..."],
    "project_conventions": { "test_cmd": "...", "lint_cmd": "..." }
  },
  "design_calls_rows": [ { "slug": "...", "intent": "...", "target_files": "...", "write_set": "...", "register_override": "...", "references": "..." }, ... ]
}

This file is the handoff: each subsequent harness tick reads the relevant slice and feeds it to its worker.

behavior_excerpts — verbatim or pointer. Each entry is EITHER a verbatim §Behavior string (legacy) OR a pointer object {spec_slug, ac_id, anchor} resolved on demand via .claude/skills/tdd/resolve-pointer.mjs → resolvePointer(pointer, rootDir) (returns the anchored spec section; throws DanglingPointerError on a stale pointer). When project.json → artifacts.compression.enabled is true (default), prefer pointers and the minimal decision-relevant content — do not copy whole sequences verbatim (token-efficiency, docs/references/token-efficiency.md).

6. Seed worker tasks into the TaskList

Create tasks via TaskCreate; wire addBlockedBy so the chain is sequential. Use these canonical entries:

• Task A — scenario-tick: subject "Run /scenario for <slug>"; metadata {phase: "scenario-tick", slug}; activeForm "Running scenario".
• Task B — implement-tick: subject "Run /implement for <slug>"; metadata {phase: "implement-tick", slug}; activeForm "Running implement"; addBlockedBy [A].
• Task C — verify-tick: subject "Run inline verify for <slug>"; metadata {phase: "verify-tick", slug}; activeForm "Running verify (inlined)"; addBlockedBy [B]. The harness, when this task becomes next-pending, inlines the four mechanical operations from .claude/skills/verify/SKILL.md rather than invoking that skill via the Skill tool (the verify skill is contract-only after the harness-auto-continuation refactor).
• Tasks D₁..D_N — design-ui-tick (post-verify design implementation step; only when design_calls_rows is non-empty AND the implement write_set intersects tdd.ui_globs): one task per row. Subject "Run /design-ui for <row.slug>"; metadata {phase: "design-ui-tick", slug, row_index: i}; activeForm "Running design-ui row <i>"; addBlockedBy [C] for D₁, then chained addBlockedBy [D_{i-1}]. The design-ui worker handles the design implementation per the spec's ## Design calls rows. After every D_i completes, the harness inlines a second verify pass (re-stamps last_test_result) to confirm the design work did not break behavior tests.
• Task E — drift-check-tick (spec-to-implementation drift analysis; seeded for every spec-track workflow): subject "Run drift-check for <slug>"; metadata {phase: "drift-check-tick", slug}; activeForm "Running drift-check (inlined)"; addBlockedBy [D_N] if any design-ui-tick exists, else [C]. The harness inlines node .claude/skills/tdd/drift_check.mjs --slug <slug> against the approved spec and the branch diff. On exit 0 (zero unresolved): write the drift report path to the harness log; continue to Task Z. On exit 1 (≥ 1 unresolved): EXIT LOOP with YIELD (reason: "drift analysis: <N> unresolved items"); the user investigates and either fixes the impl gap or amends the spec + re-/approve-directions. NO auto-loop. On chore-track workflows (no spec on disk), drift_check exits 0 with "no spec; skipped" and the harness proceeds to Z. On the workflow that initially introduces drift-check-tick, the harness instance in flight at that workflow predates the SKILL.md update and SHALL NOT seed Task E — the helper is unit-tested via the recipe scenarios and live runtime use begins in the next spec-track workflow.
• Task Z — tdd-finalize: subject "Finalize tdd for <slug>"; metadata {phase: "tdd-finalize", slug}; activeForm "Finalizing tdd"; addBlockedBy Task E (if seeded), else the last D_i, else C. On execution, the harness appends "tdd" to workflow.json → completed, writes harness_state: continue with reason "tdd green; next: simplify", and proceeds.

Drift reverify-skip protocol (velocity Component 2; gated by project.json → velocity.drift_reverify_skip.enabled, default on). When the verify-tick reaches its binding PASS, the harness captures a working-tree fingerprint via node .claude/skills/tdd/drift-reverify-guard.mjs capture --slug <slug> (writes .claude/state/tdd/<slug>.driftfp). At the drift-check-tick, the harness first runs drift-reverify-guard.mjs check --slug <slug>: exit 3 means the tree is provably unchanged since the verify PASS, so the model SKIPS re-reading/re-interpreting the drift report; exit 0 (changed, missing snapshot, or any error) means proceed with the full drift interpretation as today. The skip is fail-safe — only a positive provably-unchanged match suppresses the model pass. Crucially, the mechanical drift_check.mjs still runs on every drift-check-tick and still gates: even on an unchanged tree (check exit 3), drift_check.mjs is executed, and if it exits 1 (≥ 1 unresolved) the tick still EXITs LOOP with YIELD. The reverify-skip suppresses only the model's re-reading of a CLEAN mechanical result (drift_check exit 0); it never suppresses real drift. Mirrors .claude/skills/simplify/reverify-guard.mjs and reuses its drift-reverify-guard fingerprint primitives.

Sub-tick timing protocol. Each worker tick (scenario-tick, implement-tick, verify-tick, design-ui-tick, drift-check-tick, tdd-finalize), ON COMPLETION, appends its short label (scenario / implement / verify / design-ui / drift-check / finalize) to workflow.json → tdd_ticks[] via the Edit tool — the same boundary where the harness refreshes the marker + harness_state. phase_timer sub-stamps each into a {phase:"tdd:<tick>", event:"sub"} row (gated by project.json → artifacts.subtick_timing.enabled, default on), so /archive's timing.md breaks the collapsed tdd rollup into a per-tick breakdown. completed[] still gets its single "tdd" entry at finalize (unchanged) — tdd_ticks[] is a separate ledger and never affects phase ordering.

7. Write harness_state and yield

Marker FIRST: echo "<slug>" > .claude/state/.harness_active (the harness loop is in flight; the active marker stays set across the worker chain). Then write .claude/state/harness_state with {state: "continue", slug, reason: "tdd recipe + contract + tasks ready; next: scenario"} — exactly three keys; no written_at, no tick_count.

State-write discipline (binding — see .claude/CONSTITUTION.md §2 "State-write discipline"). tdd/<slug>.json, harness_state, and .harness_active are Tier 2 workflow state — not consent paths. The marker refresh uses a shell builtin redirect (PATH-independent); prefer the Write tool for the coordinator JSON and the harness_state JSON. Never use tee/sed -i, and resolve paths with Read/Glob, never dirname/basename/[ -f ].

8. Emit terminal message and return

Tell the user (one line): "TDD recipe + contract written to .claude/state/tdd/<slug>.json. N worker tasks seeded. Continuing." Return. The Stop hook reads harness_state and re-fires the harness on the same turn, which picks up Task A (scenario-tick).

Failure handling (RALPH cap moved to implement-tick)

The RALPH iteration cap (5 attempts) lives inside the implement-tick worker — the harness invokes Skill(implement) and implement runs its own loop. If implement returns BLOCKED after 5 iterations, the harness writes harness_state: yielded with the blocker reason; the user investigates and may rerun /tdd with a refined contract.

Constraints

• Decisions live here. The recipe for scenarios and the contract for implement — both are decided in main context BEFORE the state file is written. If you find yourself deferring a decision to a worker, stop and decide it.
• No nested Skill invocations. This skill does not call scenario, implement, verify, or design-ui. The harness invokes each worker as its own tick after reading the state file.
• Never modify tests inside the implement worker. If a test seems wrong, the harness will surface it and re-invoke the scenario worker with a corrected recipe. implement is forbidden from touching tests (worker SKILL constraint).
• Inlined verify is binding. When the harness runs the verify-tick, it produces the canonical four-line last_test_result. The verify_pass_guard hook reads line 1; that is the truth.
• One Skill call per harness tick. This is enforced by harness's per-tick atomicity contract. tdd itself emits zero Skill calls and returns after writing state + tasks.