With Codex – Claude and Codex Collaboration

This skill enables collaboration between Claude Code and OpenAI Codex CLI for second opinions, validation, and collaborative problem-solving.

CRITICAL REQUIREMENT

Claude Code MUST be running inside a tmux session for this skill to work.

If not in tmux, inform the user: “このスキルを使用するには、tmuxセッション内でClaude Codeを起動する必要があります。以下のコマンドを実行してください:

tmux new-session -s claude
claude

“

Environment Requirements

• WSL (Ubuntu) with tmux installed
• OpenAI Codex CLI installed and authenticated in WSL
• Claude Code running inside a tmux session
• Skill scripts at: ~/.claude/skills/with-codex/scripts/

Standard Workflow (MUST FOLLOW)

When this skill is triggered, ALWAYS execute these steps in order:

Step 1: Setup – Split pane and start Codex

~/.claude/skills/with-codex/scripts/codex-manager.sh setup

This splits the current tmux pane:

• Left pane: Claude Code (current)
• Right pane: Codex CLI (newly created, with dark background)

Step 2: Claude performs its own analysis first

Analyze the user’s request independently before querying Codex.

Step 3: Send the same prompt to Codex

~/.claude/skills/with-codex/scripts/codex-manager.sh send "YOUR_PROMPT_HERE"

Replace YOUR_PROMPT_HERE with the actual question/task from the user.

Step 4: Wait for Codex response

~/.claude/skills/with-codex/scripts/codex-manager.sh wait 60

Wait up to 60 seconds for Codex to complete its response.

Step 5: Capture Codex output

~/.claude/skills/with-codex/scripts/codex-manager.sh capture 200

Capture the last 200 lines of Codex’s output.

Step 6: Present combined results

Present results in this format:

## Claude's Analysis
[Your independent analysis]

## Codex's Analysis
[Captured response from Codex]

## Synthesis
- **Agreement**: [Points where both AIs agree]
- **Differences**: [Alternative perspectives from Codex]
- **Recommendation**: [Best combined approach]

Step 7: Cleanup (when conversation ends or user requests)

~/.claude/skills/with-codex/scripts/codex-manager.sh cleanup

Available Commands

Error Handling

If setup fails with “Not running inside tmux”:

• Inform user they need to start Claude Code inside tmux
• Provide the commands: tmux new-session -s claude then claude

Alternative: Non-Interactive Mode

Only use when tmux is unavailable or user explicitly requests:

codex exec "your prompt" 2>/dev/null

Best Practices

1. ALWAYS use tmux interactive mode by default
2. Let user see both AIs working side-by-side
3. Wait adequate time (30-60s) for complex Codex queries
4. Present both perspectives without bias
5. Acknowledge both AIs can be wrong – user makes final decision