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Oceanum.io

ChatGPT

ChatGPT on the web connects to MCP servers over the network only, so the hosted endpoint is the only option there — it has no local-server route.

Current status

Section titled “Current status”

There is currently no supported, working way to connect ChatGPT on the web to the Datamesh MCP server. This was last checked on 14 October 2026 with ChatGPT on the web, on a Pro plan, using its custom MCP server setup; other plans weren’t tested.

That setup offers OAuth or no authentication, with no API-key or custom-header field, and neither option works with the hosted server today:

  • OAuth — hosted sign-in (the “sign in with Oceanum.io” flow) currently doesn’t work for ChatGPT.
  • No authentication — the hosted server requires a Datamesh token on every request, so ChatGPT’s requests are rejected (HTTP 401).

Without a token field, the X-DATAMESH-TOKEN header and bearer-token routes used by other clients aren’t available. To use the Datamesh from an assistant today, use Claude, OpenAI Codex or one of the IDEs, such as Cursor.

ChatGPT desktop app

Section titled “ChatGPT desktop app”

OpenAI’s Codex documentation says the ChatGPT desktop app shares its MCP configuration with the Codex CLI and IDE extension — see One config for the CLI and the desktop app on the Codex page. Configuring the Datamesh that way hasn’t been tested for the ChatGPT desktop app, so this page doesn’t document it as a working route.

Where to add the server

Section titled “Where to add the server”

Once hosted sign-in works for ChatGPT, custom MCP servers are added from Plugins: select +, then Add custom MCP server (see OpenAI’s connection guide), with the server URL https://mcp.oceanum.io/datamesh. OpenAI notes that “Account and workspace policies apply to adding and using custom MCP servers”, so check your plan and, in a workspace, your administrator’s settings.

Keep your token safe

Section titled “Keep your token safe”

Your Datamesh token grants access to all of your organisation’s permissioned datasources — including the ability to modify or delete them. Treat it as a secret, never paste it into a chat, and prefer the hosted read-only server for exploratory use.