> ## Documentation Index
> Fetch the complete documentation index at: https://vlyai-1c28d863.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# OpenAI Codex

> OpenAI's coding model. The fastest agent in vly for small, surgical changes — one-line fixes, single-function rewrites, tight refactors.

OpenAI Codex is the speed pick. When the change is small and well-defined — a typo, a one-line bug fix, a single function rewrite — Codex completes it noticeably faster than Claude Code or Gemini CLI.

## Strengths

<CardGroup cols={2}>
  <Card title="Surgical edits" icon="scissors">
    Small, targeted changes to a single file or function. Codex's outputs are tight, with minimal collateral.
  </Card>

  <Card title="Speed" icon="zap">
    Typically 1.5–2× faster than Claude Code on small changes. Compounds over many small iterations.
  </Card>

  <Card title="Low credit cost" icon="coins">
    Smaller, cheaper model — small changes cost fewer [credits](/features/billing/credits).
  </Card>

  <Card title="Style consistency" icon="paintbrush">
    Matches the surrounding code's style without drifting.
  </Card>
</CardGroup>

## When to pick Codex

<Tabs>
  <Tab title="One-line fixes">
    "Fix the typo on the homepage hero." Codex.
  </Tab>

  <Tab title="Single-function rewrites">
    "Refactor `formatDate` to use `Intl.DateTimeFormat` instead of manual concatenation." Codex.
  </Tab>

  <Tab title="Style tweaks">
    "Make the avatar 2px larger and add a subtle shadow." Codex.
  </Tab>

  <Tab title="Tight bug fixes">
    "When the user clicks delete, the confirmation modal shows up but doesn't close on confirm. Fix it." Codex.
  </Tab>
</Tabs>

## When not to pick Codex

For multi-file features, large refactors, or anything that requires reasoning about the whole project, [Claude Code](/features/agents/claude-code) is better. For multi-file design or schema work, [Gemini CLI](/features/agents/gemini-cli) often shines.

## Usage

Codex is available as a per-prompt agent override:

1. Submit your prompt as usual.
2. Below the input, change the agent dropdown to **OpenAI Codex**.
3. Submit.

Or set it as the workspace default in [agent preferences](/features/agents/agent-preferences).

## Tips

<Tip>
  **Codex shines on hot iteration loops.** Quick visual tweaks, repeated style adjustments, fast bug fixes — keep Codex selected and fly through 20 small prompts in 10 minutes.
</Tip>

<Tip>
  **For very small changes, consider [Code mode](/building/code-mode).** Sometimes editing the file directly is faster than even the fastest agent.
</Tip>

## Related

<CardGroup cols={3}>
  <Card title="Claude Code" icon="brain" href="/features/agents/claude-code">
    The default. For larger changes.
  </Card>

  <Card title="Gemini CLI" icon="sparkles" href="/features/agents/gemini-cli">
    For multi-file design work.
  </Card>

  <Card title="Choosing an agent" icon="git-branch" href="/features/agents/choosing-an-agent">
    The full decision tree.
  </Card>
</CardGroup>


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