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ClientSession never sends notifications/cancelled when call_tool is cancelled — server-side coroutines leak

Status: Open.

#2507 In modelcontextprotocol/python-sdk;

· sherman94062 opened on Apr 26, 2026

Was it a bad idea to stream the text generation process using Context.report_progress()?

questionFurther information is requestedFurther information is requested

Status: Open.

#2501 In modelcontextprotocol/python-sdk;

· lottopotato opened on Apr 24, 2026

Concurrent server-side requests are serialized end-to-end by BaseSession

Status: Open.

#2489 In modelcontextprotocol/python-sdk;

· demoray opened on Apr 21, 2026

Split the core from the server and client implementations

Status: Open.

#2486 In modelcontextprotocol/python-sdk;

· leiserfg opened on Apr 21, 2026

RequestResponder.cancel sends JSON-RPC response, violating cancellation spec

Status: Open.

#2480 In modelcontextprotocol/python-sdk;

· q-thomasdickson opened on Apr 20, 2026

Return 405 on GET when stateless_http=True

Status: Open.

#2474 In modelcontextprotocol/python-sdk;

· itomise opened on Apr 19, 2026

MCPServer unconditionally declares prompts, resources, tools capabilities on initialize

Status: Open.

#2473 In modelcontextprotocol/python-sdk;

· 0717376 opened on Apr 19, 2026

session_idle_timeout is not exposed via streamable_http_app() and can cancel active requests

bugSomething isn't workingSomething isn't working

fix proposedBot has a verified fix diff in the commentBot has a verified fix diff in the comment

P2Moderate issues affecting some users, edge cases, potentially valuable featureModerate issues affecting some users, edge cases, potentially valuable feature

ready for workEnough information for someone to start working onEnough information for someone to start working on

Status: Open.

#2455 In modelcontextprotocol/python-sdk;

· shaun0927 opened on Apr 16, 2026

stdio_client crashes on malformed UTF-8 from child stdout instead of surfacing parse error

bugSomething isn't workingSomething isn't working

fix proposedBot has a verified fix diff in the commentBot has a verified fix diff in the comment

P2Moderate issues affecting some users, edge cases, potentially valuable featureModerate issues affecting some users, edge cases, potentially valuable feature

ready for workEnough information for someone to start working onEnough information for someone to start working on

Status: Open.

#2454 In modelcontextprotocol/python-sdk;

· shaun0927 opened on Apr 16, 2026

feat: Add roots enforcement utility to FastMCP (get_roots, assert_within_roots, @within_roots_check)

enhancementRequest for a new feature that's not currently supportedRequest for a new feature that's not currently supported

needs decisionIssue is actionable, needs maintainer decision on whether to implementIssue is actionable, needs maintainer decision on whether to implement

P2Moderate issues affecting some users, edge cases, potentially valuable featureModerate issues affecting some users, edge cases, potentially valuable feature

Status: Open.

#2453 In modelcontextprotocol/python-sdk;

· NeelakandanNC opened on Apr 16, 2026

Windows: TextIOWrapper in stdio_server() emits CRLF instead of LF, corrupting newline-delimited JSON messages

bugSomething isn't workingSomething isn't working

fix proposedBot has a verified fix diff in the commentBot has a verified fix diff in the comment

P2Moderate issues affecting some users, edge cases, potentially valuable featureModerate issues affecting some users, edge cases, potentially valuable feature

ready for workEnough information for someone to start working onEnough information for someone to start working on

Status: Open.

#2433 In modelcontextprotocol/python-sdk;

· DonovanDeHart opened on Apr 13, 2026

Initialize call hangs forever if MCP server does not return a Content-Type: text/plain

bugSomething isn't workingSomething isn't working

fix proposedBot has a verified fix diff in the commentBot has a verified fix diff in the comment

P2Moderate issues affecting some users, edge cases, potentially valuable featureModerate issues affecting some users, edge cases, potentially valuable feature

ready for workEnough information for someone to start working onEnough information for someone to start working on

Status: Open.

#2432 In modelcontextprotocol/python-sdk;

· HenriChabert opened on Apr 13, 2026