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stdio_server busy-loops at 100% CPU on Windows after the host suspends and resumes

v1Affects the v1.x maintenance lineAffects the v1.x maintenance line

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3411 In modelcontextprotocol/python-sdk;

· pangi opened on Aug 28, 2026

test_safe_join_rejects_symlink_escape fails on Windows without elevation or Developer Mode

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3408 In modelcontextprotocol/python-sdk;

· iam-kira opened on Aug 28, 2026

Tool input schemas carry a pydantic-derived title on every property

v1Affects the v1.x maintenance lineAffects the v1.x maintenance line

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3391 In modelcontextprotocol/python-sdk;

· wromansky opened on Aug 25, 2026

[v2] Expose request cancellation on MCPServer tool Context

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3389 In modelcontextprotocol/python-sdk;

· morluto opened on Aug 25, 2026

A tool returning a non-finite float puts invalid JSON in the text content block

v1Affects the v1.x maintenance lineAffects the v1.x maintenance line

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3385 In modelcontextprotocol/python-sdk;

· jayhemnani9910 opened on Aug 25, 2026

ClientSessionGroup raises KeyError when a server exposes no tools, resources or prompts

v1Affects the v1.x maintenance lineAffects the v1.x maintenance line

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3384 In modelcontextprotocol/python-sdk;

· jayhemnani9910 opened on Aug 25, 2026

OAuthClientProvider auth lock is permanently poisoned when httpx closes async_auth_flow from a different task (RuntimeError: The current task is not holding this lock)

v1Affects the v1.x maintenance lineAffects the v1.x maintenance line

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3382 In modelcontextprotocol/python-sdk;

· flanker-stack opened on Aug 25, 2026

pyjwt[crypto] as an unconditional dependency blocks installation on platforms without a cryptography wheel (e.g. Windows on ARM)

v1Affects the v1.x maintenance lineAffects the v1.x maintenance line

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3373 In modelcontextprotocol/python-sdk;

· jtauschl opened on Aug 24, 2026

Client SSRF / protocol confusion: streamable HTTP transport follows server 3xx into internal+loopback services (follow_redirects=True, no host validation; #2106 closed but fix #2180 never merged)

v1Affects the v1.x maintenance lineAffects the v1.x maintenance line

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3358 In modelcontextprotocol/python-sdk;

· trickyfalcon opened on Aug 21, 2026

[v2] Allow MCPServer to disable subscriptions/listen

spec-2026-07-28Concerns the SDK's implementation of the 2026-07-28 MCP spec revisionConcerns the SDK's implementation of the 2026-07-28 MCP spec revision

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3357 In modelcontextprotocol/python-sdk;

· owlofjaylan opened on Aug 21, 2026

bug(client/streamable_http): prevent infinite SSE reconnect loops with bounded exponential backoff

v1Affects the v1.x maintenance lineAffects the v1.x maintenance line

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3356 In modelcontextprotocol/python-sdk;

· AAH20 opened on Aug 21, 2026

Server.call_tool()'s input-validation error result discards jsonschema.ValidationError's structured fields, leaving only free-text prose

v1Affects the v1.x maintenance lineAffects the v1.x maintenance line

v2Affects the v2 line (2.x on main)Affects the v2 line (2.x on main)

Status: Open.

#3351 In modelcontextprotocol/python-sdk;

· allableaidev opened on Aug 21, 2026