Codex
Use Codex with One Horizon task context already included. Launch one task from Send to…, or queue runs with the One Horizon CLI Codex worker.
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:
- Open a task or initiative in One Horizon.
- Choose Send to… → Codex.
- One Horizon opens Codex with a structured prompt that includes task context.
Setup in One Horizon
- Open Settings → Preferences → Coding tools.
- Enable Codex.
- Open a task and use Send to… in the task details panel.
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 launcher mode-specific prompts like plan, build, or review.
Codex worker with the One Horizon CLI
The One Horizon CLI includes a Codex worker: a long-running command that connects queued agent sessions to Codex. The worker registers as your local Codex worker, sends heartbeats, polls sessions, claims one before execution, prepares a repo workspace, runs Codex, reports progress, and advances finished work when your workflow allows it.
Use it when you want Codex to handle a queue of well-scoped tasks, or when every run should follow the same repo prep, branch, check, and handoff steps.
The worker is experimental. Use it for small, well-bounded tasks and bug fixes, not large refactors or major redesigns. Review diffs, tests, and pull requests before you merge or ship.
Run one worker setup once before one worker watch or one worker start. Guided setup writes the local worker settings and starter workflow file the worker relies on; skipping it leaves automatic pickup without a saved configuration, and those commands report setup as incomplete.
Install the CLI, sign in, and pick a workspace as described on the CLI page. After one worker setup, run one worker doctor to check auth, workspace, workflow file, local worker registration, and the Codex command. Read Local workers for the worker execution model.
Codex and ChatGPT
Both are OpenAI products, but they are used differently in One Horizon:
- Codex: Send to… link from a task, or queued runs through the CLI Codex worker.
- 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…”
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.
- Install the Codex CLI if you do not already have it
- Run
codex mcp listin the terminal - Confirm you see
one_horizonpointing tohttps://mcp.onehorizon.ai/mcp - Run
codex mcp login one_horizon - If the server uses a different name on your machine, run
codex mcp login [name]instead - 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.