tdd

name	tdd
description	Multi-agent TDD orchestrator. Runs RED → GREEN → REFACTOR for one FR via three forked subagents (test-writer / implementer / refactorer) with a strict tdd-result hand-off contract, bounded retries, and a deterministic halt path. Replaces the previous single-context /tdd.
argument-hint	<FR-id>

TDD Orchestrator (Multi-Agent)

Execute the TDD cycle for $ARGUMENTS (an FR ID — STE-NNN, ULID, or specs/frs/<id>.md path) by orchestrating three forked-subagent stages. Each stage runs in an isolated context paired via Claude Code's context: fork + agent: mechanism, so the test-writer cannot see the implementer's plan, the implementer cannot see other ACs' implementations, and the refactorer cannot see per-AC reasoning.

The orchestrator itself runs in the main context (no context: fork on this skill) so it can drive the loop, parse hand-off blocks, and halt on bounded-retry exhaustion.

Architecture

Stage	Child skill	Subagent	Cycle granularity
RED	tdd-write-test	tdd-test-writer	once per FR, batched across all ACs
GREEN	tdd-implement	tdd-implementer	once per AC — N forks for N ACs
REFACTOR	tdd-refactor	tdd-refactorer	exactly once at end after all GREEN

Children carry context: fork + user-invocable: false + an agent: field naming the subagent. The orchestrator invokes them via the Skill tool with the rendered prompt body.

Inputs

• $ARGUMENTS resolves to a single FR.
• The FR's ACs come from specs/frs/<id>.md § Acceptance Criteria.
• The project test command comes from CLAUDE.md (Key Commands / Gating rule).

Procedure

1. Resolve the FR + collect ACs

Read specs/frs/<id>.md. Extract the AC list (every AC-<prefix>.<N> line under ## Acceptance Criteria). This is the batched input for the test-writer and the per-AC dispatch list for the implementer.

2. Stage RED — invoke tdd-write-test once with the batched AC list

Pass the test-writer:

• The FR file path.
• The full AC list (batched — every AC, in order).
• The project test command (the failing-test command target).

The child fork runs in isolation with tools: Read, Grep, Glob, Write, Edit, Bash (allowlist; no Agent, no Web tools). It writes failing tests for every AC, runs them once to confirm RED, and ends with a single tdd-result fenced block.

3. Stage GREEN — invoke tdd-implement once per AC

For each AC in order:

• Pass the implementer only that AC's text + the failing-test command target.
• The child fork runs in isolation, writes the minimum code to turn the failing test GREEN, re-runs the command, and ends with a single tdd-result fenced block.

The orchestrator dispatches N forks for N ACs — each implementer invocation sees one AC, never the full list. This per-AC isolation is the load-bearing property: it stops the implementer from optimizing across ACs in ways the test-writer didn't anticipate.

4. Stage REFACTOR — invoke tdd-refactor exactly once at end of FR

After every AC is GREEN, run the refactorer once with the full list of source files modified across the per-AC implementer runs. The refactorer cleans up cross-AC duplication while keeping every test GREEN — empty refactor is a valid outcome (files: []).

The single-once-at-end batching is by design. Per-AC isolation matters most for the test-writer-cannot-see-implementation guarantee; refactor isolation matters less because by then all tests are GREEN and the refactorer's correctness gate is "tests still pass." A single global pass costs less and sees cross-AC duplication that per-AC refactor wouldn't catch.

Hand-off contract — the tdd-result fenced block

Every child ends its turn with exactly one fenced ```tdd-result block, parsed deterministically by parseTddResultBlock(...) from adapters/_shared/src/tdd_result.ts. Locate via extractTddResultBlock(stdout) against the child's full output.

Required fields per role:

role: test-writer | implementer | refactorer
status: ok | failed
files:
  - path/to/file.ts
command: bun test path/to/file.test.ts
output_excerpt: |
  first 40 lines of test runner output
notes: optional one-liner

• role must equal the role being invoked (test-writer / implementer / refactorer).
• files may be empty ([]) for the refactorer when no refactor was needed.
• output_excerpt is the first 40 lines of test runner output — must show RED for test-writer, GREEN for implementer + refactorer.
• notes is optional; everything else is required.

Failure modes (5 modes)

The orchestrator distinguishes:

• (A) false-RED — test-writer's tdd-result says status: ok, but re-running its command does not produce a failure (the tests don't actually fail).
• (B) implementer can't reach GREEN — implementer's tdd-result says status: failed, or status: ok but re-running the command shows RED.
• (C) refactorer breaks GREEN — refactorer's tdd-result says status: failed, or status: ok but re-running the command shows RED.
• (D) format violation — extractTddResultBlock or parseTddResultBlock rejects the child's output (no fenced block, multiple fences, missing role, missing required field, wrong role for the invocation, invalid status).
• (E) maxTurns exhaustion — child stopped after maxTurns: 8 without producing a parseable block. Counts as a failed attempt under whichever of (A) / (B) / (C) applies to the calling role.

Retry budget — bounded

Backed by recordTddFailure(...) from adapters/_shared/src/tdd_retry_state.ts:

• Modes A / B / C / E (semantic): max 2 attempts per role per AC. After the second failure, halt.
• Mode D (format): single targeted retry — re-prompt with "re-emit your last message with a valid tdd-result block." After the second format failure, halt.

Format and semantic budgets are independent — a format violation does not consume the semantic-failure budget.

Retry prompt — isolation rule (load-bearing)

When retrying a child after a semantic failure, the orchestrator's retry prompt injects only raw failing-test output — no orchestrator-side analysis, no "the test fails because X — fix Y." Anything more leaks information that defeats the test-writer-cannot-see-implementation guarantee. The retry prompt template is:

The previous attempt did not satisfy the success criterion. Below is the
raw output of running the failing-test command. Re-emit your work as a
single `tdd-result` fenced block at the end of your turn.

<raw stdout/stderr from the test runner — no analysis>

For a mode-D format violation, the retry prompt is even narrower: "re-emit your last message with a valid tdd-result fenced block at the end of your turn." No semantic re-prompt.

Halt path

When the bounded budget is exhausted, the orchestrator:

1. Calls formatHaltReport(...) from adapters/_shared/src/tdd_halt_report.ts with { mode, role, ac, retryCount, lastBlock?, rawOutput? }.
2. Emits the rendered report (failure mode + retry count + last tdd-result block, or raw output if no block was emitted).
3. Exits non-zero — the halt is a real failure surfacing, not a routine pause.

Pacing

The halt path does pause for the operator. This is intentional — the bounded-retry cap means halt only fires after a real failure. Routine TDD cycles (no retries needed) run end-to-end without operator interaction. /implement Phase 3 invokes this orchestrator inline.

Rules

• Do NOT bypass the hand-off contract — tdd-result is the only return channel.
• Do NOT inject orchestrator-side analysis into retry prompts.
• Do NOT skip the per-AC implementer dispatch (one fork per AC; no batching).
• Do NOT run the refactorer per-AC — once at end of FR after all ACs are GREEN.
• Do NOT silently swallow format violations — surface mode D, retry once, halt.
• Do NOT modify or delete tests during the implementer/refactorer stage — if a test is wrong, the child emits status: failed and the operator decides.

Red flags

• "I'll write the implementation alongside the tests for speed" → no — write tests in the test-writer fork only.
• "I'll skip the format-violation retry, just re-spawn the child" → no — single targeted retry, halt after that.
• "I'll feed the child my analysis of why its last attempt failed" → no — retry prompt injects only raw failing-test output.