fix(client): handle 404 by clearing session ID per MCP spec#1805
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lanxevo3 wants to merge 3 commits intomodelcontextprotocol:mainfrom
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fix(client): handle 404 by clearing session ID per MCP spec#1805lanxevo3 wants to merge 3 commits intomodelcontextprotocol:mainfrom
lanxevo3 wants to merge 3 commits intomodelcontextprotocol:mainfrom
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OAuth 2.1 §3.2 requires token endpoint requests to use application/x-www-form-urlencoded regardless of grant type. Add an explicit header.set() call immediately before the fetch in executeTokenRequest() to prevent any addClientAuthentication implementation from accidentally overriding the Content-Type. Fixes modelcontextprotocol/inspector#1160
… spec Per MCP spec §Session Management (2025-03-26), when a client receives HTTP 404 in response to a request containing an Mcp-Session-Id, it MUST clear the session ID. Previously, both send() (POST) and _startOrAuthSse() (GET) would throw StreamableHTTPError without clearing _sessionId, permanently breaking the client with stale session IDs. This change: - Adds SdkErrorCode.ClientHttpNotFound - On 404, clears this._sessionId before throwing, so subsequent calls do not keep failing with the same stale session ID - Leaves full re-initialization to the caller (as InitializeRequest involves capability negotiation owned by the Client layer) Fixes modelcontextprotocol#1708.
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@modelcontextprotocol/client
@modelcontextprotocol/server
@modelcontextprotocol/express
@modelcontextprotocol/hono
@modelcontextprotocol/node
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Per MCP spec Section "Session Management" (2025-03-26), when a client receives HTTP 404 in response to a request containing an
Mcp-Session-Id, it MUST clear the session ID. Previously, bothsend()(POST) and_startOrAuthSse()(GET) threwStreamableHTTPErrorwithout clearing_sessionId, permanently breaking SDK-based clients with stale session IDs.Changes
packages/core/src/errors/sdkErrors.ts
ClientHttpNotFound = 'CLIENT_HTTP_NOT_FOUND'error codepackages/client/src/client/streamableHttp.ts
this._sessionId = undefinedbefore throwing, so subsequent calls don't keep retrying with the same dead session IDBefore
404 with
Mcp-Session-Id→ throw error with stale session ID still set → client permanently brokenAfter
404 with
Mcp-Session-Id→ clearthis._sessionId→ throw informative error → caller can re-initialize cleanlyFixes #1708.