troubleshoot-bug

name	troubleshoot-bug
description	Systematically troubleshoot bugs by tracing data flow through code, comparing expected vs actual behavior. Use when investigating why stored data differs from expected values, or when a feature works in one code path but not another.
argument-hint	["ticket-id or bug description"]
allowed-tools	Read, Grep, Glob, Bash(psql:*), Bash(git:*)

Bug Troubleshooting Workflow

When troubleshooting a bug, follow this systematic approach:

1. Gather Evidence

Start by understanding what the user is seeing vs what they expect:

• Read the .env file to get PostgreSQL credentials
• Query the database directly using psql with credentials from .env
• Check the actual output (email sent, API response, UI display)
• Compare stored data vs what was sent/displayed
• Document the discrepancy clearly

Example:

# Read credentials from .env and query directly
PGPASSWORD='<from .env>' psql -h <POSTGRES_HOST> -p <POSTGRES_PORT> -U <POSTGRES_USER> -d <POSTGRES_DB> --set=sslmode=require -c "SELECT id, sender_email, sender_name FROM messages WHERE ticket_id = 123;"

2. Find Recent Changes

Check if this area was recently modified:

# Find recent commits that touched relevant files
git log --oneline -10 -- <file>

# Show what changed in a specific commit
git show <commit-hash> -p

Look for:

• New parameters added but not fully integrated
• Refactors that may have missed edge cases
• Features that work for immediate actions but not deferred ones (scheduled jobs, webhooks)

3. Trace the Data Flow

Follow the code path from input to output:

1. Entry point: Find where data enters (API route, form handler)
2. Processing: Follow through business logic, transformations
3. Storage: Check what gets saved to database
4. Output: Check what gets sent/displayed

For each step, verify the value is what you expect. The bug is where expected != actual.

4. Identify the Root Cause

Common patterns:

• New parameter not propagated: Added to one place but not all code paths
• Fallback masking the issue: Default value hides missing data
• Scheduled/async code diverged: Immediate path works, deferred path doesn't
• Type mismatch: JSON string vs array, null vs undefined

5. Check for Similar Issues

Once you find the bug, search for the same pattern elsewhere:

# Find similar code that might have the same issue
grep -r "similar_pattern" src/

Pay special attention to:

• Scheduled jobs / background workers
• Webhook handlers
• Batch processing code
• Any code that was copy-pasted from the buggy code

6. Fix and Verify

• Fix the root cause, not just the symptom
• If you find related issues, fix them too
• Ensure the fix works for all code paths (immediate AND deferred)

7. Document Findings

Summarize:

• What was the bug?
• Why did it happen?
• What was the fix?
• Were there related issues?