Fix & Debugging

Fix & Debugging

You are helping a developer fix a bug or debug an issue. Follow a systematic approach: understand the problem, trace the root cause, design a minimal fix, then implement and verify.

Language/Framework Selection

Parse $ARGUMENTS to detect the optional --lang parameter:

• --lang=spring or --lang=java: Use Java/Spring Boot specialized agents
• --lang=typescript or --lang=ts: Use TypeScript specialized agents
• --lang=nestjs: Use NestJS specialized agents
• --lang=react: Use React frontend specialized agents
• --lang=aws: Use AWS specialized agents (architecture, CloudFormation, IaC)
• --lang=python or --lang=py: Use Python specialized agents
• --lang=general or no flag: Use general-purpose agents (default)

Agent Mapping by Language:

Current Context

The command will automatically gather context information when needed:

• Current git branch and status
• Recent commits and changes
• Available when the repository has history

Core Principles

• Understand before fixing: Never fix what you don't understand
• Find root cause: Symptoms can be deceiving - trace back to the real issue
• Minimal changes: Fix only what's broken, avoid scope creep
• Verify completely: Confirm the fix works and doesn't break other things
• Use TodoWrite: Track all progress throughout
• Structured user interaction: Use the AskUserQuestion tool in all phases where you need to ask structured questions to the user (Phase 1: Problem Capture, Phase 3: Root Cause Analysis, Phase 4: Fix Design, Phase 7: Verification). Always use AskUserQuestion for clarifications, confirmations, and decisions rather than plain text questions.
• No time estimates: DO NOT provide or request time estimates or implementation timelines at any phase

Phase 1: Problem Capture

Goal: Understand exactly what's wrong

Initial issue: $ARGUMENTS

Actions:

1. Create todo list with all phases
2. Gather problem details:
   • What is the exact error message or unexpected behavior?
   • When did this start happening?
   • Can you reproduce it consistently?
   • What are the reproduction steps?
   • Any recent changes that might be related?
3. Use the AskUserQuestion tool to gather all missing information in a clear, organized format:
   • Error messages, logs, or stack traces
   • Steps to reproduce
   • Expected vs actual behavior
   • Environment details (local, staging, production)
4. Wait for user answers before proceeding to evidence collection

Phase 2: Evidence Collection

Goal: Gather all relevant information about the failure

Actions:

1. Use the Task tool to launch 2-3 general-debugger subagents in parallel with different focuses:

   • Analyze stack traces and error messages
   • Trace execution paths related to the failure
   • Check recent git changes that might have introduced the bug

   Example Task tool usage:

Task(
  description: "Analyze error and trace execution path",
  prompt: "Analyze this error: [error description]. Trace the execution path from entry point to failure. Identify the exact failure point and potential causes.",
  subagent_type: "general-debugger"
)

Example agent prompts:

• "Analyze this stack trace: [trace]. Identify the root cause and exact failure point"
• "Trace the execution flow for [feature/function] and identify where it deviates from expected behavior"
• "Check recent git changes (last 5-10 commits) for changes that could have caused [issue]"
• "Analyze the data flow for [operation] and identify where data becomes corrupted/invalid"

2. Once agents return, read all identified critical files
3. Compile evidence summary with key findings

Phase 3: Root Cause Analysis

Goal: Identify the exact root cause of the issue

CRITICAL: Do not proceed to fixing until root cause is confirmed.

Actions:

1. Use the Task tool to launch 2 general-debugger subagents with analysis focus:

   • Deep dive into the most likely failure point
   • Verify hypothesis with code analysis

2. Synthesize findings into root cause statement:

   • What: Exact condition causing the failure
   • Where: File and line where the bug originates
   • Why: Underlying reason this happens
   • When: Conditions that trigger the bug

3. Use the AskUserQuestion tool to confirm root cause with user before proceeding

4. Wait for user confirmation before moving to Fix Design

Phase 4: Fix Design

Goal: Design the minimal, safest fix

DO NOT PROCEED WITHOUT ROOT CAUSE CONFIRMATION

Actions:

1. Use the Task tool to launch 2-3 general-software-architect subagents in parallel with different approaches:

   • Minimal surgical fix (smallest possible change)
   • Defensive fix (adds guards and validation)
   • Comprehensive fix (addresses similar issues elsewhere)

2. Review approaches considering:

   • Risk of regression
   • Side effects on other code
   • Test coverage implications

3. Present to user:

   • Brief summary of each approach
   • Trade-offs and risks
   • Your recommendation with reasoning

4. Use the AskUserQuestion tool to ask user which approach they prefer

5. Wait for user response before proceeding to implementation

Phase 5: Implementation

Goal: Implement the fix

DO NOT START WITHOUT USER APPROVAL

Actions:

1. Wait for explicit user approval
2. Re-read all affected files to ensure current state
3. Implement fix following chosen approach
4. Make minimal, focused changes
5. Add or update comments explaining the fix if non-obvious
6. Update todos as you progress

Phase 6: Build & Test

Goal: Ensure the code compiles and all tests pass

Actions:

1. Compile/Build the project:

   • Run the appropriate build command for the project
   • Maven: mvn compile or mvn package -DskipTests
   • Gradle: ./gradlew build -x test or ./gradlew compileJava
   • npm: npm run build
   • Other: Use project-specific build command

2. Fix any compilation errors before proceeding

3. Run tests:

   • Run unit tests for affected components first
   • Run full test suite if quick tests pass
   • Maven: mvn test or mvn verify
   • Gradle: ./gradlew test
   • npm: npm test

4. If tests fail:

   • Analyze failure: Is it related to our fix or pre-existing?
   • If related to fix: Return to Phase 5 and adjust
   • If pre-existing: Document and proceed (not our scope)

5. Confirm all green before proceeding to verification

Phase 7: Verification & Review

Goal: Confirm the fix is correct and doesn't introduce regressions

Actions:

1. Use the Task tool to launch 2 general-code-reviewer subagents:

   • Review fix for correctness and potential regressions
   • Check for similar issues that might need the same fix

2. Use the AskUserQuestion tool to confirm with user:

   • Does the fix resolve the original issue?
   • Any unexpected behavior observed?
   • Should we add tests to prevent regression?

3. Wait for user feedback before finalizing

4. If regression tests needed:

   • Propose test cases that would catch this bug
   • Use AskUserQuestion to ask if user wants to implement the tests
   • Implement tests if user approves
   • Run tests again to confirm new tests pass

Phase 8: Summary

Goal: Document what was fixed and learned

Actions:

1. Mark all todos complete
2. Summarize:
   • Problem: What was broken
   • Root Cause: Why it was broken
   • Fix: What was changed
   • Files Modified: List of changes
   • Tests Added: If any
   • Prevention: How to avoid similar issues

Usage Examples

# With error message (general agents)
/devkit.fix-debugging NullPointerException in UserService.getUserProfile()

# With bug description
/devkit.fix-debugging Users are seeing stale data after profile update

# Java/Spring Boot debugging
/devkit.fix-debugging --lang=spring Bean injection failing in OrderService

# TypeScript debugging
/devkit.fix-debugging --lang=typescript Type error in async handler

# NestJS debugging
/devkit.fix-debugging --lang=nestjs Dependency injection circular reference in AuthModule

# React debugging
/devkit.fix-debugging --lang=react Component not re-rendering after state update

# Python debugging
/devkit.fix-debugging --lang=python TypeError in async FastAPI endpoint handler

# Python debugging
/devkit.fix-debugging --lang=py Import circular dependency in Django models

# AWS infrastructure debugging
/devkit.fix-debugging --lang=aws CloudFormation stack creation failing with IAM error

# AWS architecture issues
/devkit.fix-debugging --lang=aws Lambda function timeout causing API Gateway 504 errors

# With test failure
/devkit.fix-debugging Test UserServiceTest.testGetProfile is failing intermittently

# With performance issue
/devkit.fix-debugging API response time increased from 50ms to 2s after last deploy

# With production issue
/devkit.fix-debugging Production errors: "Connection pool exhausted" every 2 hours

Integration with Sub-agents

This command leverages specialized sub-agents using the Task tool.

Execution Instructions

Agent Selection: Based on the --lang parameter, select the appropriate agents:

General Agents (default, or --lang=general)

• Debugger: developer-kit:general-debugger
• Software Architect: developer-kit:general-software-architect
• Code Reviewer: developer-kit:general-code-reviewer

Java/Spring Boot Agents (--lang=spring or --lang=java)

• Debugger: developer-kit:general-debugger
• Software Architect: developer-kit:java-software-architect-review
• Code Reviewer: developer-kit:spring-boot-code-review-expert

TypeScript Agents (--lang=typescript or --lang=ts)

• Debugger: developer-kit:general-debugger
• Software Architect: developer-kit:typescript-software-architect-review
• Code Reviewer: developer-kit:general-code-reviewer

NestJS Agents (--lang=nestjs)

• Debugger: developer-kit:general-debugger
• Software Architect: developer-kit:typescript-software-architect-review
• Code Reviewer: developer-kit:nestjs-code-review-expert

React Agents (--lang=react)

• Debugger: developer-kit:general-debugger
• Software Architect: developer-kit:react-software-architect-review
• Code Reviewer: developer-kit:general-code-reviewer

Python Agents (--lang=python or --lang=py)

• Debugger: developer-kit:general-debugger
• Software Architect: developer-kit:python-software-architect-expert
• Code Reviewer: developer-kit:python-code-review-expert
• Security Expert: developer-kit:python-security-expert

AWS Agents (--lang=aws)

• Debugger: developer-kit:aws-architecture-review-expert
• Software Architect: developer-kit:aws-solution-architect-expert
• Code Reviewer: developer-kit:aws-architecture-review-expert
• CloudFormation Expert: developer-kit:aws-cloudformation-devops-expert

Fallback: If specialized agents are not available, fall back to general-purpose agent.

1. general-debugger - Analyzes errors, traces execution, finds root cause
2. general-software-architect / java-software-architect-review / typescript-software-architect-review - Designs fix approaches with trade-offs
3. general-code-reviewer / spring-boot-code-review-expert / nestjs-code-review-expert - Reviews fix for quality and regressions

Usage Pattern

// General agents (default)
Task(
  description: "Brief task description",
  prompt: "Detailed prompt for the sub-agent",
  subagent_type: "developer-kit:general-debugger"
)

// Java/Spring Boot agents (when --lang=spring or --lang=java)
Task(
  description: "Brief task description",
  prompt: "Detailed prompt for the sub-agent",
  subagent_type: "developer-kit:java-software-architect-review"
)

// TypeScript agents (when --lang=typescript or --lang=ts)
Task(
  description: "Brief task description",
  prompt: "Detailed prompt for the sub-agent",
  subagent_type: "developer-kit:typescript-software-architect-review"
)

// NestJS agents (when --lang=nestjs)
Task(
  description: "Brief task description",
  prompt: "Detailed prompt for the sub-agent",
  subagent_type: "developer-kit:nestjs-code-review-expert"
)

// React agents (when --lang=react)
Task(
  description: "Brief task description",
  prompt: "Detailed prompt for the sub-agent",
  subagent_type: "developer-kit:react-frontend-development-expert"
)

// Python agents (when --lang=python or --lang=py)
Task(
  description: "Analyze Python error and trace execution",
  prompt: "Analyze this Python error and identify the root cause",
  subagent_type: "developer-kit:general-debugger"
)

Task(
  description: "Review Python architecture",
  prompt: "Review the Python architecture using Clean Architecture and DDD principles",
  subagent_type: "developer-kit:python-software-architect-expert"
)

Task(
  description: "Review Python code quality",
  prompt: "Review Python code for quality, Pythonic patterns, and best practices",
  subagent_type: "developer-kit:python-code-review-expert"
)

// AWS agents (when --lang=aws)
Task(
  description: "Debug AWS infrastructure issue",
  prompt: "Analyze CloudFormation template and AWS resources to identify the root cause",
  subagent_type: "developer-kit:aws-architecture-review-expert"
)

Task(
  description: "Fix CloudFormation template",
  prompt: "Review and fix the CloudFormation template issues",
  subagent_type: "developer-kit:aws-cloudformation-devops-expert"
)

Task(
  description: "Redesign AWS architecture",
  prompt: "Propose architectural fixes following AWS best practices",
  subagent_type: "developer-kit:aws-solution-architect-expert"
)

Important Notes

• Each sub-agent operates with its own context window
• Multiple sub-agents can be launched in parallel for different perspectives
• The main Claude maintains control and coordination of the overall process

Todo Management

Throughout the process, maintain a todo list like:

[ ] Phase 1: Problem Capture
[ ] Phase 2: Evidence Collection
[ ] Phase 3: Root Cause Analysis
[ ] Phase 4: Fix Design
[ ] Phase 5: Implementation
[ ] Phase 6: Build & Test
[ ] Phase 7: Verification & Review
[ ] Phase 8: Summary

Update the status as you progress through each phase.

Quick Debug Mode

For simple issues, you can skip some phases:

When to use quick mode:

• Error message clearly points to the issue
• Recent, obvious change caused the bug
• Simple typo or configuration error

Quick mode flow:

1. Phase 1: Problem Capture (simplified)
2. Phase 3: Root Cause Analysis (focused)
3. Phase 5: Implementation
4. Phase 6: Build & Test
5. Phase 8: Summary

Tell the user: "This appears to be a straightforward issue. Would you like to proceed with quick debug mode?"

Note: This command follows a systematic debugging approach to ensure bugs are fixed correctly the first time, with minimal risk of regression.