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Systematically diagnose and fix bugs using structured debugging techniques. Use when investigating errors, unexpected behavior, failing tests, or production issues.
Codex 또는 Claude로 설치 이 Prompt를 복사해 Codex, Claude 또는 다른 어시스턴트에 붙여 넣으면 Skill 페이지를 검토하고 설치를 진행할 수 있습니다.
SOC 직업 분류 기준
| name | debugging |
| description | Systematically diagnose and fix bugs using structured debugging techniques. Use when investigating errors, unexpected behavior, failing tests, or production issues. |
| allowed-tools | ["Read","Grep","Glob","Bash"] |
| tags | ["debugging","errors","troubleshooting","logs","stack-trace","bugs","diagnostics"] |
| platforms | ["Claude","ChatGPT","Gemini"] |
| author | locusai |
Before fixing anything, confirm you can reproduce it:
# Run the failing command/test
npm test -- --grep "failing test name"
pytest -xvs test_file.py::test_name
# Check error logs
tail -100 logs/error.log
docker compose logs app --tail 100
Key questions:
TypeError: Cannot read properties of undefined (reading 'map')
at UserList (src/components/UserList.tsx:15:23)
at renderWithHooks (node_modules/react-dom/...)
Parse the stack trace:
TypeError — wrong type, likely null/undefinedCannot read properties of undefined — something is undefinedreading 'map' — trying to call .map() on undefinedUserList.tsx:15 — exact file and lineIf you don't know where the bug is, bisect:
# Git bisect to find the breaking commit
git bisect start
git bisect bad # Current commit is broken
git bisect good abc123 # This commit was working
# Git will checkout middle commits — test each one
git bisect run npm test
# Search for where the variable is set
grep -rn "userData\s*=" --include="*.ts" src/
# Check database state
psql -c "SELECT * FROM users WHERE id = 123"
# Check API response
curl -s http://localhost:3000/api/users/123 | jq .
// Temporary debug logging — REMOVE before committing
console.log('[DEBUG] userData:', JSON.stringify(userData, null, 2));
console.log('[DEBUG] typeof userData:', typeof userData);
console.log('[DEBUG] userData keys:', Object.keys(userData ?? {}));
import logging
logger = logging.getLogger(__name__)
logger.debug(f"user_data: {user_data!r}")
logger.debug(f"type: {type(user_data)}, len: {len(user_data) if user_data else 'N/A'}")
// Bug: data might not be loaded yet
const names = users.map(u => u.name);
// Fix: guard against undefined
const names = (users ?? []).map(u => u.name);
// Bug: not awaiting async operation
const data = fetchData(); // Returns Promise, not data
console.log(data.length); // undefined
// Fix: await the promise
const data = await fetchData();
// Bug: useEffect captures stale count
useEffect(() => {
const interval = setInterval(() => {
setCount(count + 1); // count is always 0
}, 1000);
return () => clearInterval(interval);
}, []);
// Fix: use functional update
setCount(prev => prev + 1);
// Bug: skips last element
for (let i = 0; i < arr.length - 1; i++) { ... }
// Fix: include last element
for (let i = 0; i < arr.length; i++) { ... }
// Bug: two requests, wrong order
fetchUser(1).then(setUser); // slow
fetchUser(2).then(setUser); // fast — finishes first, then gets overwritten
// Fix: cancel stale requests
const controller = new AbortController();
fetchUser(id, { signal: controller.signal }).then(setUser);
return () => controller.abort();
# Run the specific failing test
npm test -- --grep "the test that was failing"
# Run the full suite to check for regressions
npm test
# If applicable, test the specific scenario manually
curl -X POST http://localhost:3000/api/users -d '{"name": "test"}'
Design and implement RESTful APIs with proper routing, validation, error handling, and documentation. Use when building new API endpoints, designing API architecture, or improving existing APIs.
Create and optimize CI/CD pipelines with GitHub Actions, automated testing, deployment, and release workflows. Use when setting up continuous integration, deployment automation, or improving build pipelines.
Gather comprehensive project context before starting implementation. Use at the beginning of complex tasks to understand codebase structure, dependencies, patterns, and conventions before writing code.
Write well-structured conventional commit messages. Use when committing code changes to ensure consistent, parseable commit history that enables automated changelogs and semantic versioning.
Design database schemas, write efficient SQL queries, create migrations, and optimize database performance. Use when working with databases, writing queries, or designing data models.
Manage project dependencies — update packages, audit vulnerabilities, resolve conflicts, and keep dependencies healthy. Use when updating packages, fixing vulnerability alerts, or resolving dependency issues.