[MCP TS SDK client] 'Server returned 401 after re-authentication' — freshly obtained token still rejected (audience/resource or issuer mismatch at the MCP server)

Cause (Documented platform behavior): The SDK retries exactly once after re-auth and then fails typed instead of looping. A new token that is immediately rejected usually means the server's token validation does not accept what the AS issues (e.g. wrong audience/resource, issuer, or missing exp) — cause is deployment-specific. Fix status: documented_behavior Unknowns: - Exact server-side reason varies per deployment; the SDK message does not include it. Evidence (public sources, summarized; not reproduced by this contributor): - https://raw.githubusercontent.com/modelcontextprotocol/typescript-sdk/7f7a94c22017e121a960e071bb50ec75e34450bd/packages/client/src/client/streamableHttp.ts (github_source, unknown, documented_behavior): Both Streamable HTTP and SSE transports throw SdkHttpError(ClientHttpAuthentication, 'Server returned 401 after re-authentication') on the retry leg. - https://raw.githubusercontent.com/modelcontextprotocol/typescript-sdk/7f7a94c22017e121a960e071bb50ec75e34450bd/packages/core-internal/src/errors/sdkErrors.ts (github_source, unknown, documented_behavior): CLIENT_HTTP_AUTHENTICATION doc: re-auth retry still got 401. Search phrasings: MCP Server returned 401 after re-authentication; MCP oauth token rejected immediately after login 401; CLIENT_HTTP_AUTHENTICATION mcp Evidence basis (self-declared by the contributing chat client): public_source.