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OIDC discovery has no bounded default timeout

authRelated to authentication (Bearer, JWT, OAuth, WorkOS) for client or server.Related to authentication (Bearer, JWT, OAuth, WorkOS) for client or server.

bugSomething isn't working. Reports of errors, unexpected behavior, or broken functionality.Something isn't working. Reports of errors, unexpected behavior, or broken functionality.

Status: Open.

#4365 In PrefectHQ/fastmcp;

· fengjikui opened on Jun 24, 2026

Incoming W3C traceparent header not propagated to FastMCP's internal spans

enhancementImprovement to existing functionality. For issues and smaller PR improvements.Improvement to existing functionality. For issues and smaller PR improvements.

httpRelated to HTTP transport, networking, or web server functionality.Related to HTTP transport, networking, or web server functionality.

serverRelated to FastMCP server implementation or server-side functionality.Related to FastMCP server implementation or server-side functionality.

Status: Open.

#4358 In PrefectHQ/fastmcp;

· reachrazamair opened on Jun 24, 2026

Expose whether the connected client subscribed to tools-list-changed

enhancementImprovement to existing functionality. For issues and smaller PR improvements.Improvement to existing functionality. For issues and smaller PR improvements.

serverRelated to FastMCP server implementation or server-side functionality.Related to FastMCP server implementation or server-side functionality.

Status: Open.

#4356 In PrefectHQ/fastmcp;

· stickerdaniel opened on Jun 23, 2026

How to notify server when a client disconnects/fails?

bugSomething isn't working. Reports of errors, unexpected behavior, or broken functionality.Something isn't working. Reports of errors, unexpected behavior, or broken functionality.

serverRelated to FastMCP server implementation or server-side functionality.Related to FastMCP server implementation or server-side functionality.

Status: Open.

#4354 In PrefectHQ/fastmcp;

· davidbernat opened on Jun 22, 2026

OIDCProxy/Auth0Provider construction blocks on a discovery fetch with no timeout, failing server startup when the IdP is slow or down

authRelated to authentication (Bearer, JWT, OAuth, WorkOS) for client or server.Related to authentication (Bearer, JWT, OAuth, WorkOS) for client or server.

bugSomething isn't working. Reports of errors, unexpected behavior, or broken functionality.Something isn't working. Reports of errors, unexpected behavior, or broken functionality.

httpRelated to HTTP transport, networking, or web server functionality.Related to HTTP transport, networking, or web server functionality.

Status: Open.

#4353 In PrefectHQ/fastmcp;

· rjolaverria opened on Jun 22, 2026

Task tools receive Pydantic-model arguments as raw dicts

bugSomething isn't working. Reports of errors, unexpected behavior, or broken functionality.Something isn't working. Reports of errors, unexpected behavior, or broken functionality.

serverRelated to FastMCP server implementation or server-side functionality.Related to FastMCP server implementation or server-side functionality.

Status: Open.

#4349 In PrefectHQ/fastmcp;

· grant-zietsman opened on Jun 22, 2026

feat: add tool lifecycle hooks (setup/teardown) for resource cleanup on cancellation

enhancementImprovement to existing functionality. For issues and smaller PR improvements.Improvement to existing functionality. For issues and smaller PR improvements.

serverRelated to FastMCP server implementation or server-side functionality.Related to FastMCP server implementation or server-side functionality.

too-longExcessively verbose or unedited LLM output. Condense before triage.Excessively verbose or unedited LLM output. Condense before triage.

Status: Open.

#4340 In PrefectHQ/fastmcp;

· tcconnally opened on Jun 20, 2026

Invalid URL printed to log when using IPv6

bugSomething isn't working. Reports of errors, unexpected behavior, or broken functionality.Something isn't working. Reports of errors, unexpected behavior, or broken functionality.

httpRelated to HTTP transport, networking, or web server functionality.Related to HTTP transport, networking, or web server functionality.

serverRelated to FastMCP server implementation or server-side functionality.Related to FastMCP server implementation or server-side functionality.

Status: Open.

#4339 In PrefectHQ/fastmcp;

· Leseratte10 opened on Jun 20, 2026

python -m startup causes list_tools to return truncated results

bugSomething isn't working. Reports of errors, unexpected behavior, or broken functionality.Something isn't working. Reports of errors, unexpected behavior, or broken functionality.

needs more infoIssue lacks detail to reproduce or understand. Waiting for reporter to provide context.Issue lacks detail to reproduce or understand. Waiting for reporter to provide context.

serverRelated to FastMCP server implementation or server-side functionality.Related to FastMCP server implementation or server-side functionality.

Status: Open.

#4338 In PrefectHQ/fastmcp;

· yysdashe opened on Jun 19, 2026

ListToolsRequest validation error: "core/list" is not a valid method in mcp.types

bugSomething isn't working. Reports of errors, unexpected behavior, or broken functionality.Something isn't working. Reports of errors, unexpected behavior, or broken functionality.

high-priority

serverRelated to FastMCP server implementation or server-side functionality.Related to FastMCP server implementation or server-side functionality.

Status: Open.

#4337 In PrefectHQ/fastmcp;

· moumed opened on Jun 19, 2026

bug: CancelledError during tool execution silently discards partial result and leaks MCP server resources

bugSomething isn't working. Reports of errors, unexpected behavior, or broken functionality.Something isn't working. Reports of errors, unexpected behavior, or broken functionality.

serverRelated to FastMCP server implementation or server-side functionality.Related to FastMCP server implementation or server-side functionality.

Status: Open.

#4336 In PrefectHQ/fastmcp;

· tcconnally opened on Jun 19, 2026

Feature: Allow for custom MCP server responses when tool-level scope validation fails

authRelated to authentication (Bearer, JWT, OAuth, WorkOS) for client or server.Related to authentication (Bearer, JWT, OAuth, WorkOS) for client or server.

enhancementImprovement to existing functionality. For issues and smaller PR improvements.Improvement to existing functionality. For issues and smaller PR improvements.

Status: Open.

#4334 In PrefectHQ/fastmcp;

· gaokevin1 opened on Jun 19, 2026