codex

# Codex: High-Reasoning AI Assistant for Claude Code

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## DEFAULT MODEL: Task-Based Model Selection with Read-Only Default

**Codex uses task-based model selection. Sandbox is `read-only` by default - only use `workspace-write` when user explicitly requests file editing.**

| Task Type | Model | Sandbox (default) | Sandbox (explicit edit) |
|-----------|-------|-------------------|------------------------|
| Code-related tasks | `gpt-5.2-codex` | read-only | workspace-write |
| General tasks | `gpt-5.2` | read-only | workspace-write |

- **Code-related tasks**: Use `gpt-5.2-codex` - optimized for agentic coding (56.4% SWE-Bench Pro)
- **General tasks**: Use `gpt-5.2` - high-reasoning general model
- **Sandbox default**: Always `read-only` unless user explicitly requests editing
- **Explicit editing**: Only when user says "edit", "modify", "write changes", etc., use `workspace-write`
- Always use `-c model_reasoning_effort=xhigh` for maximum capability

```bash
# Code task (read-only default)
codex exec -m gpt-5.2-codex -s read-only \
  -c model_reasoning_effort=xhigh \
  "analyze this function implementation"

# General task (read-only default)
codex exec -m gpt-5.2 -s read-only \
  -c model_reasoning_effort=xhigh \
  "explain this architecture"

# Code task with explicit edit request
codex exec -m gpt-5.2-codex -s workspace-write \
  -c model_reasoning_effort=xhigh \
  "edit this file to add the feature"

# General task with explicit edit request
codex exec -m gpt-5.2 -s workspace-write \
  -c model_reasoning_effort=xhigh \
  "modify the documentation file"
```

### Model Fallback Chain

If the primary model is unavailable, fallback gracefully:
1. **Code tasks**: `gpt-5.2-codex` → `gpt-5.2` → `gpt-5.1-codex-max`
2. **General tasks**: `gpt-5.2` → `gpt-5.1` → `gpt-5.1-codex-max`
3. **Reasoning effort**: `xhigh` → `high` → `medium`

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## CRITICAL: Always Use `codex exec`

**MUST USE**: `codex exec` for ALL Codex CLI invocations in Claude Code.

**NEVER USE**: `