node: serve MCP stateless - #540
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MCP 2026-07-28 removed sessions, and the SDK serves it over HTTP only in stateless mode. A stateful handler also refused legacy-version clients that already send the per-request _meta protocol version tag, with -32022 for a version it lists as supported. Nothing on the node used sessions: no server-initiated notifications, no server-to-client requests, and the per-agent server is chosen per request.
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This pull request configures the MCP server handlers to run in stateless mode, removing sessions and serving over HTTP only. It updates the associated tests and documentation to reflect this change, including asserting that GET requests on /mcp return a 405 Method Not Allowed status. A review comment recommends updating the newly added integration test to use http.NewRequestWithContext with a timeout context to prevent potential test hangs, in accordance with the repository style guide.
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I wonder if this can help us to simplify the code #387, I need to read more about MCP,.but seems this protocol does a lot of breaking changes |
The stateless MCP handler has no standalone SSE stream, so GET /mcp is 405 Method Not Allowed instead of the 400 the stateful handler returned. The unit test in internal/node was updated; this integration test still expected 400 and failed in CI.
The bridge holds no per-caller state: one id space, no broadcast side. A sessionless server does not mint or echo Mcp-Session-Id, and the node's own /mcp handler no longer does. Nothing reads the constant value it sent.
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MCP 2026-07-28 removed sessions, and the Go SDK serves that revision over HTTP only in stateless mode. Keeping the node's handler stateful had a second cost: the SDK refuses a legacy-version request that also carries the new per-request
_metaprotocol version tag, answering-32022for a version it lists as supported. Newer agent CLIs send that tag on old-protocol sessions, so they could not use the node at all.Nothing on the node used sessions: it sends no server-initiated notifications, makes no server-to-client requests, and the per-agent server is chosen per request, which stateless mode preserves.
GET /mcpnow answers405, which the spec reserves for servers without a standalone stream.internal/node/mcp.go: both handlers getStreamableHTTPOptions{Stateless: true}.initializewith header2025-11-25plus the_metatag is served and gets noMcp-Session-Id; it fails with-32022on the stateful handler.mcp_test.go:GET /mcpexpects405.node-api.md: the/mcprow says sessionless.Verified with an agent CLI that sends the tag, against a node built from this branch.