Plan-then-execute implementation against SPEC.md. Native single-thread loop, no sub-agents. On test or build failure, auto-invokes the backprop skill before retrying — a failed verification always considers whether a new §V invariant would prevent recurrence. Triggers when the user asks to build, im

build — implement spec Single thread native plan→execute. You are main Claude. No swarm. LOAD 1. Read SPEC.md . If missing → tell user to invoke the spec skill first. Stop. 2. Read FORMAT.md once if not loaded. 3. Read §R if present — external facts the build must honor, ⊥ re derive or contradict. 4. Parse invocation args: §T.n → that task only next → lowest numbered row with status . or ~ all or empty → every . row in §T order High blast radius (shared module, auth, data, money, public §I)? Run /review first. Trivial & reversible? Skip planning ceremony, just do step EXECUTE. PLAN Native plan mode — you delegate to it, you do not reinvent task breakdown. For chosen task(s): 1. Cite every §V invariant that applies. Plan must respect all. 2. Cite every §I interface touched. Plan must preserve shape. 3. List files to create / edit. 4. Verification contract — name the EXACT test(s) / acceptance criteria that prove each §V touched. Which test, not "add tests". "Do TDD" alone backfires; the spec says what to check . Each §V touched → a named test that fails first. 5. Name verification command (test, build, lint) — this is the external oracle. Green = done; ⊥ "looks done". Show plan. Wait for user OK unless auto mode. EXECUTE Per task in order: 1. Flip §T.n status cell . → ~ . Just write to SPEC.md. 2. Edit code per plan. 3. Run verification command. 4. Pass → flip ~ → x . Next task. 5. Fail → invoke backprop skill. Do NOT retry blindly. FAIL → BACKPROP On test/build failure: 1. Read failure output. 2. Ask: is failure (a) my code bug, (b) spec wrong, or (c) unspecified edge case? 3. If (a) → fix code, re run. No spec change. 4. If (b) or (c) → invoke spec skill with bug: <cause first, let it update §V and §B, then resume build against updated spec. Rule: never silently fix root cause without considering backprop. §B is the memory that stops recurrence. WRITE POLICY Only flip §T status. No other SPEC.md edits from build. Other spec edits → invoke spec skill. Commit after each §T completes. Message: T<n : <goal line + §V cites. VERIFICATION Task x only if: Verification command (the oracle) exits 0. Every §V touched has its named test from the verification contract, and it passes. No §V invariant regressed (run full test suite at end). NON GOALS No sub agents. No parallel workers. Main thread only. No progress dashboards. cat SPEC.md grep §T is the dashboard. No speculative work beyond chosen task scope.