Finishing Implementation Elenchus

Finishing implementation (verify → fix loop)

The post-execution stage of the Elenchus pipeline (elenchus-build → brainstorming → elenchus-plan → execution → THIS). After a frontend feature is built, this runs a bounded verify→fix loop: report-only verifier subagents drive the running app with Playwright MCP and report what passed / failed / needs a human / is missing; the chairman (this thread) implements the fixes one by one; repeat.

Separation of concerns is the whole design:

• Verifier subagents (finishing-verifier, a no-Write sandbox) only verify → report. They drive the browser and return a fixed schema. They never touch code.
• The chairman reads the reports, reconciles them against the checklist, and implements the fixes. Verification and repair never live in the same agent.

Built with the writing-skills skill. It is not an anonymized council — verifiers aren't debating a premise, they're observing a browser. (The two-verifier default gives cross-checking, not Socratic dissent.)

The loop

running app + spec/plan
  │
  ▼
[Precondition gate] confirm the app is running + its URL. NEVER start the dev server.
  │   If the port isn't open, ask the user to confirm the URL; require it before pass 1.
  ▼
[Derive checklist] one testable item per named feature (route/page/interaction +
  │   expected observable outcome). This is what every verifier checks.
  ▼
[Config gate — ONCE] propose {iterations (default 3), verifier structure (default two
  │   cross-checked: Sonnet + highest tier)}; user confirms/edits; then run unattended.
  ▼
[Fix-pass ×N] ── verify (dispatch configured verifiers, SEQUENTIALLY) ──► each drives the
  │              browser through the WHOLE checklist, returns PASSED/FAILED/NEEDS-HUMAN/
  │              MISSING + evidence ──► chairman MERGES (flag disagreements) + RECONCILES
  │              every item ──► chairman IMPLEMENTS fixes one by one (FAILED + MISSING)
  ▼
[Final confirm pass] one more verification, NO fixes — captures post-fix reality
  ▼
[Report] docs/elenchus/<slug>-finishing.md: per-item results across passes, the fixes the
        chairman made, verifier disagreements, and what remains NEEDS-HUMAN.

Precondition gate (before anything)

• The user runs the dev server; you never start it. (Project convention.) Ask the user to confirm the URL. If the port isn't open, say so and ask for the right URL — do not launch a server, do not guess.
• A quick Bash reachability check (e.g. curl -sI <url>) is fine to confirm it's up. If it isn't reachable, stop and get a working URL first — a run against a dead URL produces only NEEDS-HUMAN.
• Confirm the Playwright MCP is actually connected BEFORE dispatching — run claude mcp list and check playwright shows ✔ Connected, not ⏸ Pending approval. A verifier dispatched while the server is pending gets no browser_* tools and can only return NEEDS-HUMAN (wasting the dispatch). If it's pending/missing, have the user approve it and install the browser (see Install) and restart — then dispatch.

Derive the acceptance checklist

From the spec + plan, write one testable item per named feature: the route/page or interaction, and the expected observable outcome in the browser. This is the contract every verifier checks and the chairman reconciles against — so nothing is silently skipped.

Configuration gate (once, then unattended)

Propose the run config and let the user edit it, once, after the checklist:

• Iterations: N fix-passes (default 3) plus one free final no-fix confirm pass (a run does N+1 verifications).
• Verifier structure: default two independent, cross-checked verifiers per pass — Sonnet and the highest tier (model: fable; model: opus fallback) — each drives the full checklist; the chairman merges. The user may change the count, the tiers, or drop to one. State the per-pass seat-call cost.

After the user confirms, run the loop to completion without further gates.

Each fix-pass

1. Verify — dispatch the configured verifiers, ONE AT A TIME (sequential). The Playwright MCP drives a single browser session per server — running verifiers in parallel makes them fight over tabs/navigation and produces false results. So dispatch verifier A, wait, then verifier B. Each is subagent_type: finishing-verifier, pinned to its tier (model: sonnet / model: fable), and its prompt carries the app URL + the full checklist. The agent enforces the hard rules (observe the browser, NEEDS-HUMAN when it can't, report-only, the schema). Have each verifier start from a fresh browser_navigate (and browser_close between seats) so state doesn't bleed.
2. Merge + reconcile. Combine the verifiers' reports. Every checklist item must appear — a dropped item is itself a reported gap, not an omission. Where the two verifiers disagree on an item (one PASSED, one FAILED), flag it and treat it as not-yet-passing; never silently pick one.
3. Fix (chairman only). For each FAILED and MISSING item, formulate and implement the fix one by one — real edits, following the codebase's patterns. NEEDS-HUMAN items are surfaced to the user, never faked or auto-passed. Keep changes minimal and scoped to the failing item.

Loop to the next pass to confirm the fixes and catch regressions, up to N.

Final confirm pass + report

• After the last fix-pass, run one more verification with no fixing to capture the true post-fix state.
• Gitignore docs/elenchus/ first (append the line, create .gitignore if absent), then write the run report to docs/elenchus/<slug>-finishing.md: each checklist item's result across passes, the fixes the chairman implemented, any verifier disagreements, and everything still NEEDS-HUMAN. Surface failures plainly — no silent skips.
• No approval verdict. The skill reports what works, what it fixed, and what a human must still check. It does not declare the feature "done" — that's the user's call.

Dispatch notes

• Verifier agent = finishing-verifier (Read/Grep/Glob + Context7 + Playwright browser tools, no Write/Edit, no recursion — report-only by construction). It reaches the Playwright MCP the same session-scoped way seats reach Context7 (wired in the repo-root .mcp.json).
• Named-agent fallback + restart. A freshly-installed finishing-verifier.md isn't dispatchable until Claude Code restarts (agents register at session start). If subagent_type: finishing-verifier errors "agent type not found," fall back to subagent_type: general-purpose with the finishing-verifier instructions inlined, and tell the user to restart so the sandbox (and its no-Write guarantee) applies next run.
• Graceful degradation. If the highest tier can't be reached, run the remaining verifier and say so in the report. Never silently collapse two verifiers onto one model.

Common mistakes (from baseline testing)

• Reading the source and issuing a PASS/FAIL as if browser-verified. The #1 baseline failure — agents confidently substitute code-reading for observation. Verifiers MUST drive the browser; when they can't, the answer is NEEDS-HUMAN, not an asserted verdict.
• Free-form findings instead of the fixed schema. Baseline runs used ad-hoc labels ("BROKEN", "NEEDS WORK") the chairman can't reconcile. Enforce PASSED/FAILED/NEEDS-HUMAN/ MISSING per item.
• Burying "couldn't verify" in a footnote instead of marking each affected item NEEDS-HUMAN.
• Running the two verifiers in parallel — they contend over the one browser session and produce false results. Sequential only.
• Letting a verifier fix code, or letting the chairman skip fixing and just hand back a report. Verifiers report; the chairman fixes. Both halves are required.
• Starting the dev server yourself. The user runs it; you ask for the URL.
• Silently dropping a checklist item the verifier didn't mention — reconcile every item.

Rationalization table (excuse → reality)

Red flags — stop if you catch yourself

• About to mark an item PASSED/FAILED without having driven the browser for it.
• About to dispatch two verifiers in parallel against one app.
• About to let a verifier edit code, or to end without the chairman fixing FAILED/MISSING.
• About to start the dev server instead of asking for the URL.
• About to declare the feature "done" — that's the user's call; you report + fix + surface.

Install / sync

• Skill: skills/finishing-implementation-elenchus/ (archive) → sync to ~/.claude/skills/finishing-implementation-elenchus/ (runtime).
• Agent: agents/finishing-verifier.md (canonical) → mirror to .claude/agents/; restart before the first dispatch or use the named-agent fallback.
• Playwright MCP: wired in the repo-root .mcp.json (npx @playwright/mcp@latest), the same project-scope pattern as Context7. Ships no secrets. To reuse an existing logged-in session, add --storage-state <path> to its args.
• First-run MCP prerequisites (one-time). A project-scoped MCP server is pending approval until the user approves it — verify with claude mcp list. Approve the playwright server (via the /mcp command or by restarting claude and accepting the project-server prompt), and install the browser binary once with npx playwright install chromium. MCP servers connect at session start, so restart after approving. Until playwright shows ✔ Connected, verifier seats have no browser tools and every item comes back NEEDS-HUMAN.