diff-review

Diff Review — precise, budget-capped, two lenses in one pass

Why this skill exists: two generic review agents (go-reviewer + code-simplifier) spent 197k + 136k tokens and 97 + 58 tool calls reviewing ONE staged diff (2026-07-27). The measured waste had four parts:

• a second derivation of the repo context that the caller already had;
• a second run of the test suites that the caller already ran;
• unbounded whole-tree consumer sweeps;
• two separate contexts that each loaded the same diff.

This skill keeps the review QUALITY disciplines (evidence-first, adversarial, file:line findings) and deletes the waste structurally.

Scope contract (RIGID)

The unit of review is the STAGED DIFF: git diff --cached. Nothing else is in scope unless a hunk drags it in.

The caller's prompt MUST declare, and you MUST trust without re-running:

• Already verified: which test suites/lints/gates ran and their results. Re-running any of them is budget theft — CI re-proves them anyway.
• Intent: what the change is supposed to do, in 1-3 sentences.
• Known constraints: pinned contracts, protected surfaces, prior review findings already applied.

If the caller declared nothing, spend ONE tool call asking the diff itself (git diff --cached --stat) and proceed — never block on missing context.

Budgets (RIGID)

• ≤ 20 tool calls total. Count them. At 20, stop and report with what you have.
• ≤ 15 file reads, and reads are TARGETED: Read with offset/limit around the hunk, never whole large files; the diff already shows the change.
• One hop of coupling, found by grep. For each changed/added exported symbol and each changed behavior (for example a return-shape change): ONE grep -rn for its call sites. Read only the call sites the grep surfaces. NEVER sweep docs/, .evolve/runs/, or knowledge-base/ unless a hunk edits them.
• Run nothing the caller declared green. You can run at most ONE cheap compile/probe (go build ./pkg, a 5-line script). Use it only to settle a finding that a read cannot settle, and only for a finding that you report.