Pre-Commit Code Verification
Automated verification pipeline before code lands. Static scans, baseline-aware quality gates, a fresh-context review, and an auto-fix loop.
Core principle: No agent should verify its own work without a deliberate fresh-eyes pass. Treat the diff as data, not as something you just wrote.
When to Use
- After implementing a feature or bug fix, before
git commitorgit push - When user says "commit", "push", "ship", "done", "verify", or "review before merge"
- After completing a task with 2+ file edits in a git repo
Skip for: documentation-only changes, pure config tweaks, or when user says "skip verification".
This skill vs github-code-review: This skill verifies YOUR changes before
committing. github-code-review reviews OTHER people's PRs on GitHub with
inline comments.
Step 1 — Get the diff
git diff --cached
If empty, try git diff then git diff HEAD~1 HEAD.
If git diff --cached is empty but git diff shows changes, tell the user to
git add <files> first. If still empty, run git status — nothing to verify.
If the diff exceeds 15,000 characters, split by file:
git diff --name-only
git diff HEAD -- specific_file.py
Step 2 — Static security scan
Scan added lines only. Any match is a security concern fed into Step 5.
# Hardcoded secrets
git diff --cached | grep "^+" | grep -iE "(api_key|secret|password|token|passwd)\s*=\s*['\"][^'\"]{6,}['\"]"
# Shell injection
git diff --cached | grep "^+" | grep -E "os\.system\(|subprocess.*shell=True"
# Dangerous eval/exec
git diff --cached | grep "^+" | grep -E "\beval\(|\bexec\("
# Unsafe deserialization
git diff --cached | grep "^+" | grep -E "pickle\.loads?\("
# SQL injection (string formatting in queries)
git diff --cached | grep "^+" | grep -E "execute\(f\"|\.format\(.*SELECT|\.format\(.*INSERT"
Step 3 — Baseline tests and linting
Detect the project language and run the appropriate tools. Capture the failure count BEFORE your changes as baseline_failures (stash changes, run, pop). Only NEW failures introduced by your changes block the commit.
Test frameworks (auto-detect by project files):
# Python (pytest)
python -m pytest --tb=no -q 2>&1 | tail -5
# Node (npm test)
npm test -- --passWithNoTests 2>&1 | tail -5
# Rust
cargo test 2>&1 | tail -5
# Go
go test ./... 2>&1 | tail -5
Linting and type checking (run only if installed):
# Python
which ruff && ruff check . 2>&1 | tail -10
which mypy && mypy . --ignore-missing-imports 2>&1 | tail -10
# Node
which npx && npx eslint . 2>&1 | tail -10
which npx && npx tsc --noEmit 2>&1 | tail -10
Baseline comparison: If baseline was clean and your changes introduce failures, that's a regression. If baseline already had failures, only count NEW ones.
Step 4 — Self-review checklist
Quick scan before the fresh-eyes review:
- No hardcoded secrets, API keys, or credentials
- Input validation on user-provided data
- SQL queries use parameterized statements
- File operations validate paths (no traversal)
- External calls have error handling (try/catch)
- No debug print/console.log left behind
- No commented-out code
- New code has tests (if test suite exists)
Step 5 — Fresh-eyes review
Poirot has no subagent delegation, so the "independent reviewer" is you with a deliberate context reset. Treat the diff as if someone else wrote it — read it cold, without remembering your intent.
Re-read the diff and evaluate against these categories. Fail-closed: if you can't fully trace a code path, mark it failed.
SECURITY (auto-FAIL): hardcoded secrets, backdoors, data exfiltration, shell injection, SQL injection, path traversal, eval()/exec() with user input, pickle.loads(), obfuscated commands.
LOGIC ERRORS (auto-FAIL): wrong conditional logic, missing error handling for I/O/network/DB, off-by-one errors, race conditions, code contradicts intent.
SUGGESTIONS (non-blocking): missing tests, style, performance, naming.
Return a verdict:
VERDICT: PASS | FAIL
Security issues: [list from static scan + review]
Logic errors: [list from review]
Regressions: [new test failures vs baseline]
New lint errors: [details]
Suggestions (non-blocking): [list]
All passed: Proceed to Step 7 (commit).
Any failures: Report what failed, then proceed to Step 6 (auto-fix).
Step 6 — Auto-fix loop
Maximum 2 fix-and-reverify cycles.
Fix ONLY the reported issues — do NOT refactor, rename, or change anything else. Do NOT add features.
After fixing, re-run Steps 1-5 (full verification cycle).
- Passed: proceed to Step 7
- Failed and attempts < 2: repeat Step 6
- Failed after 2 attempts: escalate to user with the remaining issues and
suggest
git stashorgit resetto undo
Step 7 — Commit
If verification passed:
git add -A && git commit -m "[verified] <description>"
The [verified] prefix indicates the fresh-eyes review passed.
Reference: Common Patterns to Flag
Python
# Bad: SQL injection
cursor.execute(f"SELECT * FROM users WHERE id = {user_id}")
# Good: parameterized
cursor.execute("SELECT * FROM users WHERE id = ?", (user_id,))
# Bad: shell injection
os.system(f"ls {user_input}")
# Good: safe subprocess
subprocess.run(["ls", user_input], check=True)
JavaScript
// Bad: XSS
element.innerHTML = userInput;
// Good: safe
element.textContent = userInput;
Pitfalls
- Empty diff — check
git status, tell user nothing to verify - Not a git repo — skip and tell user
- Large diff (>15k chars) — split by file, review each separately
- False positives — if review flags something intentional, note it before fixing
- No test framework found — skip regression check, verdict still runs
- Lint tools not installed — skip that check silently, don't fail
- Auto-fix introduces new issues — counts as a new failure, cycle continues