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 commit or git 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 stash or git reset to 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