codebase-review

A review of what the codebase is, where adversarial-review reviews what a diff changes. It hunts deepening opportunities — places where structure taxes every change that passes through — and ends only when the decider has dispositioned every surviving candidate. This skill is the portable protocol: an entry gate, a read-only review lane of lens-named finders, a skeptic pass that kills candidates before the report exists, and the disposition loop. Everything repo-specific — where reports land, the trigger threshold, where rejections are remembered, how the lane is run — lives in binding slots the team-workflow setup interview fills.

Read the team-workflow binding doc first. Full domain-modeling discipline (CONTEXT.md glossaries, ADR upkeep) is deliberately not part of this skill — it wants a skill of its own.

1. Triggers: an entry gate, never a calendar

The review runs when one of three gates opens, never on a schedule — a scheduled run reviews whatever the calendar happens to land on, and produces findings to match.

1. Pre-feature — a spec is about to land in an area; review that area first, in the spirit of "make the change easy, then make the easy change."
2. Lane-count threshold — N lanes have merged since the last review (N is a per-repo binding slot). Merged work is the pressure that degrades structure; the count measures the pressure.
3. Reported friction — a lane or the orchestrator reports the code fought them: a change that should have been local sprawled, a test that could only be written past an interface.

Scope follows the trigger. Pre-feature reviews the spec's blast radius. Lane-count and friction reviews cover the areas churned since the last review, weighted by git history — recently-changed code is where deepening pays, because it is where the next change lands. Gates are not exclusive — a spec can land just as the lane count crosses N; when more than one is open, the report names them all and the scope is the union of what the open gates set. A full sweep runs only once — a repo's first-ever review, whatever gates opened it; every later run is scoped by its triggers.

2. Execution: a read-only lane

The review runs as a delegated lane, claimed and tracked like any work item — how it is launched and tracked is the executor binding slot. Its contract is read-only: it changes no code and files no tickets; its deliverable is the report, and ticket filing belongs to the disposition loop (§5).

Before any finder runs, the lane reads the repo's rejection memory (binding slot): a candidate the decider rejected reopens on new evidence, never on repetition. A rerun that re-proposes a recorded rejection without new evidence has ignored the decider once and the memory twice.

Finder agents run as parallel subagents that never see each other's output — isolation is what makes two lenses landing on the same code a signal instead of an echo. Each holds one named lens from the menu, stated in the report. All five lenses run by default; a scoped run may drop a lens its scope cannot reach, naming the drop and the reason in the report:

• shallow modules / seams — interfaces nearly as complex as the implementations behind them; seams placed where nothing varies, or missing where something does.
• duplicated concepts — one concept implemented in several places, so one change must be made N times and is made N−1.
• dead code — code the deletion test clears for removal: delete it and no complexity reappears anywhere.
• boundaries-vs-reality — the declared module layout versus how change actually flows: imports that cross seams, layers honored in the diagram and bypassed in the code.
• test-pain — code that can only be tested past its interface, and the setup-heavy tests that prove it.

Finders and the skeptic speak the shared design vocabulary — depth, seams, locality, the deletion test — defined in references/design-vocabulary.md; every claim in the report is phrased in those terms, in the codebase's own domain names.

3. The skeptic

A finder's candidate is a hypothesis. Every candidate goes to a built-in skeptic whose brief is to kill it before the report exists — a separate agent in its own context, handed the candidate and its evidence and nothing of the finder's reasoning, so the kill attempt starts from the code rather than from the argument: re-read the code, find the second caller that makes the "duplicate" a real seam, the constraint that explains the "shallow" wrapper, the test that already covers the pain. Only candidates the skeptic fails to kill reach the report.

Survival is the only grade. A finder ranking its own findings — strong, worth exploring, speculative — is grading its own homework; the skeptic's failed kill is evidence, a badge is a mood.

4. The report

Plain markdown, posted on the tracker item the binding names. It carries:

• Every open gate, the scope they set, and any dropped lens with the reason its scope could not reach it.
• Deferred candidates from the previous run, at the top — deferral means carried forward, not quietly dropped.
• Each survivor: the claim, the evidence (files and lines), the skeptic's attempted kill and why it failed, the estimated cost, and the payoff in locality and leverage terms.
• Zero survivors is a verdict, stated as a success: "the codebase is fine" — the finders looked, the skeptic held the bar, and nothing survived. A review that must produce findings to feel finished manufactures them.

5. The disposition loop

The run is not finished at report time — an undispositioned report is a review that changed nothing. The orchestrator (or whoever ran the review) presents every survivor to the decider as a structured question card, grilling-style: the claim, the skeptic's verdict, cost and payoff, with the recommendation marked on an option — numbered-text fallback where no card tool exists. The decider dispositions each:

• Adopt — becomes a tracker ticket (to-tickets where bound) and rides normal lane flow.
• Reject — recorded in rejection memory with the load-bearing reason. The reason is the record's value: a future run needs to know why, so it can tell new evidence from repetition.
• Defer — carried at the top of the next run's report, where each is re-dispositioned or re-deferred, and named in session handoffs so it survives the context boundary.

The run's tracker item closes only when nothing is undispositioned.

6. Binding slots (the setup interview fills these per-repo)

• Report destination — the tracker item each run posts its report to and closes: a standing item, or the rule that creates one per run. It must be writable and closable — §4 posts to it and §5 closes it, so a read-only query cannot fill this slot.
• Lane-count threshold (N) — merged lanes since the last review that open gate 2.
• Rejection memory — where rejected candidates and their load-bearing reasons live.
• Executor mechanics — how the review lane is launched, claimed, and tracked (in repos running the orchestrate skill, its lane-launch machinery is the natural answer).

Done when (checkable)

• Every open gate is named in the report, and the scope matches — the union of what the open gates set (blast radius, churn-weighted, or first-ever full sweep).
• Rejection memory was read before any finder ran; nothing proposed re-litigates a recorded rejection without new evidence.
• Every finder's lens is stated; all five lenses ran, or every omitted lens is named in the report with the reason its scope could not reach it.
• Every candidate went through the skeptic — the report contains survivors only.
• Every survivor carries claim, file/line evidence, the attempted kill and why it failed, cost, and payoff; a zero-survivor run states the "codebase is fine" verdict.
• Deferred candidates from the previous run appear at the top, each re-dispositioned or re-deferred.
• Every survivor is dispositioned — adopted to a ticket, rejected into memory with its reason, or deferred — and the run's tracker item is closed.
• The lane changed no code and filed no tickets itself.

Attribution

This skill is adapted from Matt Pocock's improve-codebase-architecture (MIT). The core model is his: the hunt for deepening opportunities as the unit of review, weighting attention toward recently-changed code, per-candidate cards carrying files, problem, solution, and benefits, respecting recorded rejections so reviews don't re-suggest settled ground, and grounding every suggestion in the shared design vocabulary of his codebase-design (MIT), which the references doc adapts.

What this repo changes: event triggers replace on-demand invocation, the review runs as a read-only tracked lane, finders take named lenses in parallel, a skeptic pass replaces self-graded recommendation-strength badges, the report is plain markdown on a tracker item rather than an HTML artifact, zero survivors is an explicit success verdict, and the disposition loop — adopt / reject-into-memory / defer-and-carry, closing only when nothing is undispositioned — replaces the pick-one grilling loop.