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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

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

McpError is not pickle-safe and fails to unpickle

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.

#2431 In modelcontextprotocol/python-sdk;

· rain87 opened on Apr 13, 2026

[v1.x] Server-side outputSchema validation blocks tool error reporting (isError: true)

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.

#2429 In modelcontextprotocol/python-sdk;

· kimsehwan96 opened on Apr 13, 2026

Specific ToolNotFoundError for easier handling than ToolError in multi-tenant environments

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

P3Nice to haves, rare edge casesNice to haves, rare edge cases

Status: Open.

#2422 In modelcontextprotocol/python-sdk;

· DevonFulcher opened on Apr 10, 2026

Bug: AssertionError: Request already responded to — cancellation race in v1.27.0

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.

#2416 In modelcontextprotocol/python-sdk;

· bbarwik opened on Apr 9, 2026

Introduce strategy/registry pattern for type handling in _create_output_model()

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

P3Nice to haves, rare edge casesNice to haves, rare edge cases

Status: Open.

#2408 In modelcontextprotocol/python-sdk;

· dgenio opened on Apr 9, 2026

StreamableHTTP client: _handle_reconnection resets attempt counter to 0, causing infinite retry loop

Status: Open.

#2393 In modelcontextprotocol/python-sdk;

· jeffplourde opened on Apr 5, 2026

Inline $ref in tool inputSchema for LLM consumption (parity with typescript-sdk)

Status: Open.

#2384 In modelcontextprotocol/python-sdk;

· felixweinberger opened on Apr 2, 2026