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Codex

Use Codex as a coding companion with your One Horizon task context already included. This integration is optimized for task (& initiative) handoff from One Horizon into Codex while you implement work.

Codex launch uses the deep link codex://new?prompt=... from One Horizon.

How this integration works

Unlike the ChatGPT integration, Codex here is a launch flow from One Horizon:

  1. You open a task or initiative in One Horizon
  2. You choose Send to app → Codex
  3. One Horizon opens Codex with a structured prompt that includes your task context
Send tasks and initiatives from One Horizon to Codex

Setup in One Horizon

  1. Open Settings → Preferences → Coding tools
  2. Enable Codex
  3. Open any task and use Send to app in the task details panel
Enable Codex in your One Horizon account preferences

What gets sent to Codex

One Horizon builds a structured prompt from the task, including:

  • Task ID, title, and description
  • Parent initiative context (when available)
  • Goal, product, and skill labels (when available)

Depending on the task type, One Horizon can also send mode-specific prompts like plan, build, or review.

Auto-generated prompt passed to Codex

Codex and ChatGPT

Both are OpenAI products, but they are used differently in One Horizon:

  • Codex: direct task handoff via deep link from the task panel
  • ChatGPT: MCP connector setup in ChatGPT Developer Mode for broader tool calling

If you want MCP connector setup in ChatGPT, see ChatGPT.

Troubleshooting

Codex does not open

  • Make sure Codex is installed on your machine
  • Ensure your system can handle the codex:// URL scheme
  • Try again after reopening your browser or One Horizon

Prompt does not appear as expected

One Horizon also copies prompt content to your clipboard as fallback. Paste manually in Codex if needed.

Codex is not shown in “Send to app”

Enable Codex in Settings → Preferences → Coding tools first.

One Horizon MCP is enabled, but Codex still cannot find One Horizon

You do not need the Codex CLI for normal Codex Desktop use. Use it here only as a reset step when the One Horizon MCP entry looks enabled in Codex, but Codex still cannot find One Horizon.

  1. Install the Codex CLI if you do not already have it
  2. Run codex mcp list in the terminal
  3. Confirm you see one_horizon pointing to https://mcp.onehorizon.ai/mcp
  4. Run codex mcp login one_horizon
  5. If the server uses a different name on your machine, run codex mcp login [name] instead
  6. Restart the Codex CLI or open a new thread in Codex Desktop

Codex can hold on to stale MCP state, so restarting the CLI or opening a fresh thread in Desktop is often what makes One Horizon show up properly again.

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  • How this integration works
  • Setup in One Horizon
  • What gets sent to Codex
  • Codex and ChatGPT
  • Troubleshooting
  • Back to top