Codex supports remote MCP servers. Core can be registered as a remote MCP server and authenticated through Codex's OAuth flow.
Core MCP server URL:
https://core.gradien.ai/mcp
Recommended Setup
Run the guided installer:
npx -y @gradien/core-agent-setup install --base-url https://core.gradien.ai --yes --harness codex
The installer creates a short-lived Core signup/login session and registers Core with Codex.
Manual Setup
If you prefer to run the Codex commands yourself:
codex mcp add core --url https://core.gradien.ai/mcp
codex mcp login core
After browser login, a URL like http://127.0.0.1:<port>/callback/... is normal. That is the one-time local callback where Codex receives the OAuth code. The MCP server itself remains remote at https://core.gradien.ai/mcp.
Important Codex Notes
- Do not add
--oauth-resourcefor Core. Codex discovers the OAuth resource from Core protected-resource metadata, and adding it manually can duplicate theresourceparameter. - Do not narrow OAuth to
--scopes profile,email. Core may require the server-advertised scopes to select the correct workspace. - Do not extract or copy tokens from Codex auth/cache files. Codex owns those OAuth credentials.
- Older Codex builds have had fragile OAuth behavior. If Codex reports an experimental OAuth flag requirement or fails while parsing metadata, update Codex and retry.
Verify
Check the saved MCP entry:
codex mcp get core
codex mcp list
Current Codex CLI versions may not expose a direct tools/list command. After setup and login, restart Codex or open a fresh Codex session so the Core tools can load.
If a fresh session still reports AuthRequired, run:
codex mcp logout core
codex mcp login core
Then restart Codex again. If native OAuth still fails on a current Codex version, use the Core local bridge fallback only after a safe scoped Core credential is available.