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| 1 | +--- |
| 2 | +'@objectstack/mcp': patch |
| 3 | +'@objectstack/runtime': patch |
| 4 | +--- |
| 5 | + |
| 6 | +fix(mcp,runtime)!: the stateless `/api/v1/mcp` surface answers `GET` and `DELETE` with `405` and `Allow: POST`, so an MCP client stops re-opening a GET stream that ends at once |
| 7 | + |
| 8 | +Clause-②: yes (narrowing) |
| 9 | +Metadata-protocol: none |
| 10 | + |
| 11 | +<!-- adr-0087: not-required (no-migration-prescription) A transport verb answer on the MCP HTTP surface: no key of any metadata schema is removed, renamed or re-shaped, no export, type or error code is removed or renamed, and the 405 body is the MCP SDK transport's own. There is nothing for `objectstack migrate meta` to rewrite and no tombstone. --> |
| 12 | + |
| 13 | +**BREAKING** accept-set narrowing at the MCP HTTP transport (`MCPServerRuntime.handleHttpRequest`, `@objectstack/mcp`), and on the standalone server's `/api/v1/mcp` route (`createDispatcherPlugin`, `@objectstack/runtime`). |
| 14 | + |
| 15 | +- **Before.** The transport is stateless (no session id) and closes its per-request server when the request ends. A `GET` still reached the SDK's stream handler, which answered `200 text/event-stream` and then lost the stream when the server closed. An MCP client reads a GET stream that ends as a dropped connection and opens another one: claude-code re-opened it 2–3 times a second for as long as a session stayed connected. A `DELETE` answered `200` and ended nothing, because no session exists. Every other verb answered `405` with `Allow: GET, POST, DELETE`. |
| 16 | +- **Now.** Every verb but `POST` that reaches the transport (`OPTIONS` with CORS off; with CORS on the CORS middleware's `204` answers first on both doors) answers `405` with `Allow: POST` and the JSON-RPC body `{"jsonrpc":"2.0","error":{"code":-32000,"message":"Method not allowed."},"id":null}`, before a server is built. This is the Streamable HTTP transport's answer for a server that offers no GET stream and does not end sessions. The MCP SDK client treats a `405` on GET as "no stream offered" and does not retry it. |
| 17 | +- **The standalone server.** `createDispatcherPlugin` mounts `/api/v1/mcp` for `GET`, `POST` and `DELETE`, and now also declares it a path whose domain decides every verb (the declaration `/mcp/skill` and `/keys` already carry). Before, a `PUT`, a `PATCH` or an `OPTIONS` with CORS off matched no route there and the HTTP adapter answered it itself: `405` with `Allow: DELETE, GET, HEAD, POST` and a `METHOD_NOT_ALLOWED` envelope, to an anonymous caller too. Now those verbs reach the dispatcher like the mounted ones: an anonymous caller gets `401`, a signed-in one the transport's `405` with `Allow: POST`. A `createHonoApp` host already handed every verb to the dispatcher, so both doors now answer every verb alike. |
| 18 | +- **Unchanged.** `POST` (JSON-RPC: `initialize`, `tools/list`, `tools/call`, …) answers exactly as before. An anonymous caller is refused `401` before any verb answer, on every verb and on both doors. |
| 19 | +- **Who sees it.** A client that opens the GET stream on `/api/v1/mcp` now gets `405` instead of a `200` stream that ends at once. Nothing was ever sent on that stream. On the standalone server, an anonymous `PUT`, `PATCH` or `OPTIONS` (CORS off; with CORS on the CORS middleware's `204` answers `OPTIONS` first on both doors) on `/api/v1/mcp` now gets `401` instead of `405`. |
| 20 | + |
| 21 | +**The remedy.** None needed for an MCP client: it stops opening the stream. A probe or health check that read `GET /api/v1/mcp` as `200` should send a `POST initialize` instead. |
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