$ca-review — diff review

Read-only review of a change. Routes to dispatching-parallel-agents (routines/dispatching-parallel-agents/SKILL.md): dispatches the reviewer fleet by path matrix, dedupes, then funnels through finding-triage → verdict-aggregator to a single in-memory verdict. No code is modified.

The change under review does not have to be yours. $ca-review #123 reviews an inbound pull request through the same fleet, the same matrix, and the same triage. That is the point of issue #80: a tool that only reviews the diff you just wrote is a linter for authors, not a gate for a team, and reviewing code you did NOT write is where a governance gate earns its keep.

It is an ARGUMENT, not a second command. The scope resolver already took one, the fleet is scope-agnostic, and every phase downstream operates on a diff regardless of where it came from — so a $ca-review-pr would be a whole public surface (catalog, three host projections, README counts, sidebar) whose only distinguishing feature is where the diff was fetched from.

Flow

1. Resolve scope from $ARGUMENTS:

   • empty → the current working diff (unchanged default).
   • a path → that path (unchanged).
   • #<number>, a bare number, or a GitHub PR URL → an INBOUND PR. Fetch its diff with gh pr diff <number> and review that. If gh is missing or unauthenticated, STOP and say so — do NOT silently fall back to the working diff, which would report a verdict on the wrong change under the PR's name.

   For a PR target, resolve the diff ONCE and review that text. Do not re-fetch per reviewer: the fleet runs in parallel, and a PR updated mid-review would otherwise have different reviewers reading different code and a triage that reconciles findings from two versions.

2. Build the unit list by path matrix; each matched reviewer is one read-only unit:

   Reviewer	Dispatched when scope touches
   security-reviewer	auth, middleware, secrets, deploy/CI, any security-sensitive path
   auth-crypto-reviewer	authn, crypto, key handling, secrets
   dependency-reviewer	package.json, lockfiles, base images, dependency manifests
   migration-reviewer	DB migration file add/modify
   coverage-auditor	any source change (test coverage vs. obligations)
   architecture-drift-reviewer	code that may diverge from accepted ADRs in .codearbiter/decisions/

3. Route to dispatching-parallel-agents with that unit list (read-only batch — no collision check). It dedupes overlapping findings, then funnels through finding-triage (severity + inline [NEEDS-TRIAGE] on out-of-scope items) → verdict-aggregator (single read-only verdict).

4. Surface the aggregated verdict: findings by severity, file:line, remediation, and the applicable control from <project-root>/.codearbiter/security-controls.md for security findings.

5. For a PR target, posting the verdict is a separate, confirmed step. Report locally first; post only on explicit instruction, with gh pr review <number> --comment --body-file <file>. A review comment on someone else's PR is outward-facing and effectively public the moment it lands — it notifies subscribers and cannot be un-sent. Never --request-changes or --approve from here: those carry merge authority, and this command produces a finding list, not a maintainer's decision.

Severity

• CRITICAL — exploitable vuln, secret exposure, banned primitive, data-integrity breach.
• HIGH — significant compliance gap or unsafe pattern.
• MEDIUM — standards deviation or coverage gap.
• LOW — informational or style.

Hard gate

Read-only — MUST NOT modify a file, and MUST NOT check out, merge, or otherwise move the repository to the PR's branch: reviewing an inbound PR means reading its DIFF, not adopting its code, and a checkout would run its content through hooks that trust the working tree. BLOCK on any CRITICAL or HIGH finding on your OWN change: it must be resolved before $ca-pr. On an inbound PR there is nothing local to block — the verdict is the deliverable. MUST NOT consume raw reviewer output — only the finding-triage → verdict-aggregator verdict. MUST NOT resolve a [CONFIRM-NN] surfaced during review by guessing.

When NOT to use

• Opening a PR (reviews dispatch automatically) → $ca-pr.
• A periodic full-codebase sweep → $ca-checkpoint.
• A pre-implementation threat model → $ca-threat-model.
• A question about the code → $ca-btw.