`high effort → 3+5 angles × 6 candidates → 1-vote verify (recall-biased) → ≤10 findings`

You are reviewing for **recall** at high effort: catch every real bug a careful
reviewer would catch in one sitting. At this level, catching real bugs matters
more than avoiding false positives. Err on the side of surfacing.

## Phase 0 — Gather the diff

Run `git diff @{upstream}...HEAD` (or `git diff main...HEAD` / `git diff HEAD~1`
if there's no upstream) to get the unified diff under review. If there are
uncommitted changes, or the range diff is empty, also run `git diff HEAD` and
include the working-tree changes in scope — the review often runs before the
commit. If a PR number, branch name, or file path was passed as an argument,
review that target instead. Treat this diff as the review scope.

## Phase 1 — Find candidates (3 correctness angles + 3 cleanup angles + 1 altitude angle + 1 conventions angle, up to 6 each)

Run **8 independent finder angles** via the Agent tool. Each
surfaces **up to 6 candidate findings** with `file`, `line`, a one-line
`summary`, and a concrete `failure_scenario`.

### Angle A — line-by-line diff scan

Read every hunk in the diff, line by line. Then Read the enclosing function for
each hunk — bugs in unchanged lines of a touched function are in scope (the PR
re-exposes or fails to fix them). For every line ask: what input, state, timing,
or platform makes this line wrong? Look for inverted/wrong conditions,
off-by-one, null/undefined deref, missing `await`, falsy-zero checks,
wrong-variable copy-paste, error swallowed in catch, unescaped regex metachars.

### Angle B — removed-behavior auditor

For every line the diff DELETES or replaces, name the invariant or behavior it
enforced, then search the new code for where that invariant is re-established.
If you can't find it, that's a candidate: a removed guard, a dropped error
path, a narrowed validation, a deleted test that was covering a real case.

### Angle C — cross-file tracer

For each function the diff changes, find its callers (Grep for the symbol) and
check whether the change breaks any call site: a new precondition, a changed
return shape, a new exception, a timing/ordering dependency. Also check callees:
does a parallel change in the same PR make a call unsafe?

### Reuse

The angles above hunt for bugs; this one and the next two hunt for cleanup in
the changed code. Flag new code that re-implements something the codebase
already has — Grep shared/utility modules and files adjacent to the change,
and name the existing helper to call instead.

### Simplification

Flag unnecessary complexity the diff adds: redundant or derivable state,
copy-paste with slight variation, deep nesting, dead code left behind. Name
the simpler form that does the same job.

### Efficiency

Flag wasted work the diff introduces: redundant computation or repeated I/O,
independent operations run sequentially, blocking work added to startup or
hot paths. Also flag long-lived objects built from closures or captured
environments — they keep the entire enclosing scope alive for the object's
lifetime (a memory leak when that scope holds large values); prefer a
class/struct that copies only the fields it needs. Name the cheaper
alternative.

### Altitude

Check that each change is implemented at the right depth, not as a fragile
bandaid. Special cases layered on shared infrastructure are a sign the fix
isn't deep enough — prefer generalizing the underlying mechanism over adding
special cases.

### Conventions (CLAUDE.md)

Find the CLAUDE.md files that govern the changed code: the user-level
~/.claude/CLAUDE.md, the repo-root CLAUDE.md, plus any CLAUDE.md or
CLAUDE.local.md in a directory that is an ancestor of a changed file (a
directory's CLAUDE.md only applies to files at or below it). Read each one
that exists, then check the diff for clear violations of the rules they state.

Only flag a violation when you can quote the exact rule and the exact line
that breaks it — no style preferences, no vague "spirit of the doc"
inferences. In the finding, name the CLAUDE.md path and quote the rule so the
report can cite it. If no CLAUDE.md applies, return nothing for this angle.

Cleanup, altitude, and conventions candidates use the same
`file`/`line`/`summary` shape; in `failure_scenario`, state the concrete
cost (what is duplicated, wasted, harder to maintain, or which CLAUDE.md rule
is broken) instead of a crash. Correctness bugs always outrank cleanup,
altitude, and conventions findings when the output cap forces a cut.

Pass every candidate with a nameable failure scenario through — finders that
silently drop half-believed candidates bypass the verify step and are the
dominant cause of misses.

## Phase 2 — Verify (1-vote, recall-biased)

Dedup near-duplicates (same defect, same location, same reason → keep one). For
each remaining candidate, run **one verifier** via the Agent tool:
give it the diff, the relevant file(s), and the candidate; it returns exactly
one of **CONFIRMED / PLAUSIBLE / REFUTED**.

**PLAUSIBLE by default** — do not refute a candidate for being "speculative" or
"depends on runtime state" when the state is realistic: concurrency races,
nil/undefined on a rare-but-reachable path (error handler, cold cache, missing
optional field), falsy-zero treated as missing, off-by-one on a boundary the
code does not exclude, retry storms / partial failures, regex/allowlist that
lost an anchor. These are PLAUSIBLE.

**REFUTED** only when constructible from the code: factually wrong (quote the
actual line); provably impossible (type/constant/invariant — show it); already
handled in this diff (cite the guard); or pure style with no observable effect.

Keep **CONFIRMED and PLAUSIBLE**. Drop REFUTED.

## Output

Return findings as a JSON array of at most 10 objects:

```json
[
  {
    "file": "path/to/file.ext",
    "line": 123,
    "summary": "one-sentence statement of the bug",
    "failure_scenario": "concrete inputs/state → wrong output/crash"
  }
]
```

Ranked most-severe first. If more than 10 survive, keep the 10 most
severe. If nothing survives verification, return `[]`.
