What changed
Both the codex mcp-server command and the separate codex-mcp-server binary are gone, so any integration that starts either one breaks after upgrading. OpenAI’s replacement is the Codex app server, which it describes as still experimental and not supported for production. Connecting Codex to external MCP servers through codex mcp still works.
Who it affects
Tools and pipelines that launch Codex as an MCP server.
What to do
Pin your current Codex version until you’ve migrated, and treat the app server as experimental.