Debug Error

Guided workflow for diagnosing errors/failures and producing a durable fix.

Usage

/debug

Use this after pasting an error message, log output, or describing a failure.

What It Does

1. Understand the Failure

• Extracts error type, message, codes, stack trace, reproduction steps
• Captures expected vs actual behavior and environment/context
• Pinpoints failing module/function and triggering inputs
• Notes execution context: service/container, working directory, env vars
• Confirms environment is properly configured

2. Trace Root Cause

• Walks call stack upward until finding first invalid state/data
• Inspects inputs at each layer (params, config, environment, cwd)
• Adds temporary instrumentation if unclear (prints context to stderr)
• For test failures: narrows with pytest --collect-only, -k, etc.
• Classifies issue (data, state, logic, integration, configuration)
• Checks surrounding code and recent changes for regressions
• Records original trigger and fixes at the source (not symptom)

Temporary instrumentation (Python):

import sys, traceback

def debug_context(note, **kwargs):
    print(f"DEBUG {note}: {kwargs}", file=sys.stderr)
    print(''.join(traceback.format_stack(limit=15)), file=sys.stderr)

3. Validate Root Cause

• Explains how root cause produces observed failure
• Scans for other paths that could hit same issue
• Proves via minimal reproduction or targeted test

4. Plan the Fix

• Addresses underlying bug, not symptom
• Outlines candidate fixes, notes trade-offs
• Provides step-by-step resolution plan
• Suggests targeted tests or monitoring to prevent recurrence
• Adds defense-in-depth: validates inputs at boundaries, fails fast

5. Apply Project Standards

• Respects/updates existing AIDEV-* notes
• Follows logging levels (warning for expected, error with exc_info=True for unexpected)
• Keeps FastAPI code async-first
• Scopes changes to the fix

Notes

• Always trace to root cause before fixing
• Add temporary instrumentation if needed, remove after
• Validate the fix resolves the issue
• Consider adding tests to prevent recurrence