Codex System — Planning, Design & Complex Implementation
Codex CLI handles planning, design, and complex code implementation.
Detailed rules: .claude/rules/codex-delegation.md
Two Roles of Codex
1. Planning & Design
- Architecture design, module composition
- Implementation plan creation (step breakdown, dependency ordering)
- Trade-off evaluation, technology selection
- Code review (quality and correctness analysis)
2. Complex Implementation
- Complex algorithms, optimization
- Debugging with unknown root causes
- Advanced refactoring
- Multi-step implementation tasks
When to Consult (MUST)
| Situation | Trigger Examples |
|---|
| Planning | "Create a plan" "Architecture" |
| Design decisions | "How to design?" |
| Complex implementation | "How to implement?" "How to build?" |
| Debugging | "Why doesn't this work?" "Error" "Debug" |
| Trade-off analysis | "Which is better?" "Compare" |
| Refactoring | "Refactor" "Simplify" |
| Code review | "Review" "Check" |
When NOT to Consult
- Simple file edits, typo fixes
- Tasks that simply follow explicit user instructions
- git commit, test execution, lint
- Codebase analysis → general-purpose subagent (Opus 1M context)
- External information retrieval → general-purpose subagent (Opus, WebSearch/WebFetch)
- Multimodal processing → Gemini CLI (PDF/video/audio/images)
How to Consult
Subagent Pattern (Recommended)
Task tool parameters:
- subagent_type: "general-purpose"
- run_in_background: true (optional)
- prompt: |
Consult Codex about: {topic}
codex exec --model gpt-5.4 --sandbox read-only --full-auto "
{question for Codex}
" 2>/dev/null
Return CONCISE summary (key recommendation + rationale).
Direct Call (responses up to ~50 lines)
codex exec --model gpt-5.4 --sandbox read-only --full-auto "Brief question" 2>/dev/null
Having Codex Implement Code
codex exec --model gpt-5.4 --sandbox workspace-write --full-auto "
Implement: {task description}
Requirements: {requirements}
Files: {file paths}
" 2>/dev/null
Sandbox Modes
| Mode | Use Case |
|---|
read-only | Design, review, debug analysis |
workspace-write | Implementation, fixes, refactoring |
Task Templates
Implementation Planning
codex exec --model gpt-5.4 --sandbox read-only --full-auto "
Create an implementation plan for: {feature}
Context: {relevant architecture/code}
Provide:
1. Step-by-step plan with dependencies
2. Files to create/modify
3. Key design decisions
4. Risks and mitigations
" 2>/dev/null
Design Review
codex exec --model gpt-5.4 --sandbox read-only --full-auto "
Review this design approach for: {feature}
Context: {relevant code or architecture}
Evaluate:
1. Is this approach sound?
2. Alternative approaches?
3. Potential issues?
4. Recommendations?
" 2>/dev/null
Debug Analysis
codex exec --model gpt-5.4 --sandbox read-only --full-auto "
Debug this issue:
Error: {error message}
Code: {relevant code}
Context: {what was happening}
Analyze root cause and suggest fixes.
" 2>/dev/null
Language Protocol
- Ask Codex in English
- Receive response in English
- Execute based on advice
- Report to user in the user's language
Why Codex?
- Deep reasoning: Complex analysis and problem-solving
- Planning expertise: Architecture and implementation strategies
- Code mastery: Complex algorithms, optimization, debugging
- Consistency: Same project context via
context-loader skill
