principle-code-review

name

principle-code-review

description

Code review heuristics — five-axis review lens (correctness, security, design integrity, test coverage, comment quality); confidence-based filtering (no finding without a concrete failure scenario); review comment tone (observation over accusation); nitpick filtering; what counts as a real finding vs linter noise. Auto-load when writing or framing a review comment, deciding whether a PR finding is worth surfacing, reviewing a diff for correctness, or filtering review nitpicks.

Code Review

Principles for high-signal code review. For tool-specific mechanics (diff-size routing, suggestion-block format, GitHub workflow), see the reviewer agent.

Five-Axis Review Lens

Every review covers five axes:

• Correctness — off-by-ones, null paths, concurrency races, lost errors, unhandled edge cases, paired-guard predicate gaps (a check enforced by one sibling but missing in its pair).
• Security — injection, auth/authz gaps, secrets in code, unsafe deserialization, SSRF, missing input validation at trust boundaries.
• Design integrity — SOLID violations, leaky abstractions, tight coupling, circular deps, domain logic bleeding into infrastructure. For complexity / duplication / length, prefer Quality-stage output over subjective comments — see workflow-development.
• Tests — missing coverage on new branches, brittle tests, tests that mirror implementation rather than behavior.
• Comment quality — unnecessary comments (WHAT-not-WHY, restates-the-code, commented-out code, over-explained / decision-essay), doc-comments over the per-language cap, and stale comments (unchanged text, now wrong because the diff changed the code it describes — not merely code near it); hygiene-tier, in-diff + lines for the four categories, plus a stale comment's own context line when its described code changed, suggested-fix drop-simplify-or-rephrase, never an auto-rewrite. Caps live in principle-clean-code.

What's Not a Finding

Do not surface these:

• Formatting, import order, quote style — owned by the linter, not the reviewer.
• Stylistic preferences with no behavioral impact.
• Speculative "could be" comments without a concrete failure mode.

These erode review signal. If your only comment is a style preference, stay silent.

Confidence-Based Filtering

Before surfacing a finding, apply this filter:

1. Name the failure scenario. What breaks, under what inputs, in what deployment context? If you cannot articulate it, the finding is speculative — drop it.
2. One strong comment over five weak ones. Ten medium-confidence findings force the author to triage; two high-confidence findings close the loop.
3. Missing tests are a finding, not an afterthought. Untested new branches are incomplete work.

Confidence floor by severity:

Severity	Minimum confidence	Action if below floor
Critical	0.9	Must name an exploit or data-loss path
High	0.75	Must name a realistic failure scenario
Medium	0.5	Can surface; mark as "likely"
Low / Nit	Any	Drop unless the fix is a one-liner

Tone

Review the code, not the author.

• Observation language: "This path returns nil without checking the error" — not "You forgot to check the error."
• Acknowledge good work briefly. Silence is not approval; a short note reduces defensive reading.
• Frame as options for Medium/Low. "One option: …" not "You should …".
• Reserve mandates for Critical/High. Direct language is appropriate when the stakes are real.

Red Flags

Pattern	What it signals
Finding with no named failure scenario	Speculation — refine or drop
Five+ findings, none above Medium	Signal-to-noise failure — prioritize
Only linter-owned comments (style, formatting)	Scope creep — let the linter own these
Zero positive observations in a long review	Adversarial culture risk
Nitpick marked Critical	Severity inflation — recalibrate

When Code Review Hurts

• Throwaway prototypes — review cost exceeds value if you're about to discard the code.
• Hotfix rollbacks — reverting to a known-good state introduces no new logic to review.
• Trivially covered one-liners — if the tests already encode the contract, a comment adds ceremony without safety.