Relay

The relay is a Cloudflare Worker backed by a Durable Object. It exposes the ChatGPT-facing Streamable HTTP MCP endpoint and accepts outbound WebSocket connections from local bridges.

Responsibilities

The relay:

• handles Cloudflare Access-authenticated ChatGPT-facing requests;
• accepts bridge WebSocket connections;
• stores safe connected-bridge metadata in Durable Object state;
• exposes mikoto_list_bridges;
• routes tool calls to a selected bridge;
• rejects duplicate connected bridge ids;
• returns bridge-selection, ambiguity, busy, timeout, and connection-lost errors;
• writes application diagnostics to stdout.

The relay does not discover local MCP servers and does not know Codex execution internals.

Durable Object State

The Durable Object owns connected bridge session state. It stores only safe metadata:

• bridge id;
• bridge OS;
• connection status;
• last heartbeat time;
• exposed tool snapshot;
• WebSocket/session data needed to restore hibernated connections.

It must not store secrets, local paths, environment variables, raw backend config, cookies, storage, tokens, raw HTML, or tool result payloads in bridge metadata.

Routing

Backend tools are exposed with backend-prefixed names such as codex.codex_chrome_read_start. Configured aliases may expose shorter names such as local_chrome_read_start.

Tool names do not include bridge names. A caller may omit bridge selection only when exactly one connected bridge exposes the requested tool. If multiple bridges expose the same tool, the caller must pass bridgeId to mikoto_call_tool.

Each bridge handles one tool call at a time. Concurrent calls to the same bridge receive a clear bridge_busy error. Tool calls have a fixed 5-minute wall-clock timeout.