deep-code-review

Deep Code Review — 8-Angle Methodology

Extracted from Claude Code's bundled code-review skill. This is the most thorough code review methodology available.

Review for recall: catch every real bug a careful reviewer would catch in one sitting. Catching real bugs matters more than avoiding false positives.

Phase 0 — Gather the diff

Run git diff @{upstream}...HEAD (or git diff main...HEAD / git diff HEAD~1) to get the unified diff under review. If there are uncommitted changes, also run git diff HEAD and include working-tree changes.

Phase 1 — Find candidates (8 independent angles)

Each angle surfaces up to 6 candidate findings with file, line, summary, and 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. For every line ask: what input, state, timing, or platform makes this line wrong? Look for:

• Inverted/wrong conditions
• Off-by-one errors
• Null/undefined dereference
• Missing await
• Falsy-zero checks
• Wrong-variable copy-paste
• Error swallowed in catch
• Unescaped regex metacharacters

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 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?

Angle D — Reuse check

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.