FastMCP Files

Generated CLIs now preserve remote transports, empty arrays, and parameters whose names collide with their own helpers; mounted servers honor session visibility and mounted_components_raise_on_load_error, a stale client context no longer closes a newer session, and OAuth provider wrappers accept identity assertions. Tasks accept a redis-py credential provider that returns current credentials for each new connection (streaming providers such as redis-entraid's are rejected until Docket can refresh them safely), Redis 8.1.0 is excluded, and custom KeyringStore users must now install py-key-value-aio[keyring] explicitly. Thanks to our 16 contributors, including 9 first-time contributors.

What's Changed

Enhancements ✨

• Add server authoring guidance through the docs site by @zzstoatzz in https://github.com/PrefectHQ/fastmcp/pull/5703
• Support rotating Redis credentials for tasks by @zzstoatzz and @nazarii-plebanskyi-rf in https://github.com/PrefectHQ/fastmcp/pull/5970
• fix(client): forward max_sse_event_size through StreamableHttpTransport by @PrathmeshPawar2110 in https://github.com/PrefectHQ/fastmcp/pull/6016
• Add a downstream smoke for Redis credential providers by @zzstoatzz in https://github.com/PrefectHQ/fastmcp/pull/6044

Security 🔒

• Bump certifi to 2026.10.19 by @jakekaplan in https://github.com/PrefectHQ/fastmcp/pull/5989
• Let configured proxy headers replace forwarded ones regardless of case by @leopranzl in https://github.com/PrefectHQ/fastmcp/pull/5972

Fixes 🐞

• Fix maintained skill discovery on the docs site by @zzstoatzz in https://github.com/PrefectHQ/fastmcp/pull/5954
• Publish regular skill files for Mintlify discovery by @zzstoatzz in https://github.com/PrefectHQ/fastmcp/pull/5956
• Serialize HTTP and SSE transports in generate-cli by @asasemahmed in https://github.com/PrefectHQ/fastmcp/pull/5891
• fix(cli): preserve empty arrays in generated commands by @dailyun in https://github.com/PrefectHQ/fastmcp/pull/5961
• Fix session visibility lookups through mounted servers by @HootRock and @leopranzl in https://github.com/PrefectHQ/fastmcp/pull/5966
• Fix generated CLI JSON parameter name collisions by @Vittuu in https://github.com/PrefectHQ/fastmcp/pull/5959
• Escape server text in the fastmcp call elicitation prompt by @asasemahmed in https://github.com/PrefectHQ/fastmcp/pull/5909
• Map common audio extensions when Audio is given a path by @asasemahmed in https://github.com/PrefectHQ/fastmcp/pull/5919
• Drop clamped log records the logger is not enabled for by @asasemahmed in https://github.com/PrefectHQ/fastmcp/pull/5915
• Omit the output schema when an OpenAPI success response has no body by @asasemahmed in https://github.com/PrefectHQ/fastmcp/pull/5913
• Create the MCP config file on install when it is missing or empty by @asasemahmed in https://github.com/PrefectHQ/fastmcp/pull/5887
• Preserve credential providers when cloning task extensions by @zzstoatzz and @nazarii-plebanskyi-rf in https://github.com/PrefectHQ/fastmcp/pull/5984
• Exclude Redis 8.1.0 to preserve task reconnection by @zzstoatzz and @nazarii-plebanskyi-rf in https://github.com/PrefectHQ/fastmcp/pull/5985
• Remove unused keyring dependency by @zzstoatzz and @tom42-otera in https://github.com/PrefectHQ/fastmcp/pull/5987
• Fix static checks broken by ty 0.0.89 and pydantic 2.14 by @zzstoatzz in https://github.com/PrefectHQ/fastmcp/pull/6001
• Run dev inspector servers over stdio and stop mapping the deployment port to the proxy by @asasemahmed in https://github.com/PrefectHQ/fastmcp/pull/6029
• fix(json-schema): apply a Draft-4 boolean exclusive bound to its sibling by @kbkb628 in https://github.com/PrefectHQ/fastmcp/pull/5234
• Strip a URL scheme from a Clerk domain by @asasemahmed in https://github.com/PrefectHQ/fastmcp/pull/5921
• Fix generate-cli commands for tools with a json parameter by @andreivince in https://github.com/PrefectHQ/fastmcp/pull/6032
• Honor mounted_components_raise_on_load_error in AggregateProvider by @asasemahmed in https://github.com/PrefectHQ/fastmcp/pull/6026
• Reject streaming credential providers in TasksExtension by @zzstoatzz in https://github.com/PrefectHQ/fastmcp/pull/6043
• fix(client): keep stale contexts from closing newer sessions by @mikamikasuki in https://github.com/PrefectHQ/fastmcp/pull/6018
• fix(auth): expose identity assertions on OAuth provider wrappers by @computeaholic and @jonaseck2 in https://github.com/PrefectHQ/fastmcp/pull/6006
• Measure blocking duration with perf_counter in transform_fn generator test by @Lokeshrao69 in https://github.com/PrefectHQ/fastmcp/pull/6014

Docs 📚

• Clarify request state across mounted servers by @HootRock and @leopranzl in https://github.com/PrefectHQ/fastmcp/pull/5967
• Pass mcp_path through the remote OAuth custom routes example by @asasemahmed in https://github.com/PrefectHQ/fastmcp/pull/5925

New Contributors

• @dailyun made their first contribution in https://github.com/PrefectHQ/fastmcp/pull/5961
• @Vittuu made their first contribution in https://github.com/PrefectHQ/fastmcp/pull/5959
• @leopranzl made their first contribution in https://github.com/PrefectHQ/fastmcp/pull/5966
• @nazarii-plebanskyi-rf made their first contribution in https://github.com/PrefectHQ/fastmcp/pull/5970
• @tom42-otera made their first contribution in https://github.com/PrefectHQ/fastmcp/pull/5987
• @computeaholic made their first contribution in https://github.com/PrefectHQ/fastmcp/pull/6006
• @jonaseck2 made their first contribution in https://github.com/PrefectHQ/fastmcp/pull/6006
• @PrathmeshPawar2110 made their first contribution in https://github.com/PrefectHQ/fastmcp/pull/6016
• @Lokeshrao69 made their first contribution in https://github.com/PrefectHQ/fastmcp/pull/6014

Full Changelog: https://github.com/PrefectHQ/fastmcp/compare/v4.1.3...v4.1.4