fastmcp

v3.4.4 Feature

This release adds 1 notable feature for engineering teams evaluating rollout.

Published 18d AI Coding Tools

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✓ No known CVEs patched

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✓ No known CVEs patched in this version

Topics

agents fastmcp llms mcp mcp-clients mcp-servers

+3 more

mcp-tools model-context-protocol python

Affected surfaces

auth breaking_upgrade

Summary

AI summary

Updates Fixes 🐞, Enhancements ✨, and Docs 📚 across a mixed release.

Changes in this release

Type	Severity	Summary	CVE
Feature	Low	Adds Hugging Face OAuth provider support with docs and examples. Adds Hugging Face OAuth provider support with docs and examples. Source: llm_adapter@2026-07-16 Confidence: high	—
Bugfix	Medium	Relaxes host origin guard defaults to restore HTTP compatibility. Relaxes host origin guard defaults to restore HTTP compatibility. Source: llm_adapter@2026-07-16 Confidence: low	—
Bugfix	Medium	Restores HTTP host guard compatibility for existing deployments. Restores HTTP host guard compatibility for existing deployments. Source: granite4.1:30b@2026-07-16-audit Confidence: low	—
Other	Low	Introduces Hugging Face Auth Integration contributed by @evalstate. Introduces Hugging Face Auth Integration contributed by @evalstate. Source: granite4.1:30b@2026-07-16-audit Confidence: low	—

Full changelog

FastMCP 3.4.4 restores HTTP deployment compatibility after the 3.4.3 Host/Origin guard changed default behavior for existing ASGI, serverless, and reverse-proxy deployments. The guard implementation remains available for deployments that opt in with explicit trusted hosts and origins, while 3.x returns to accepting traffic that worked before the patch. This release also adds Hugging Face OAuth provider support, with docs and examples for public and private apps, PKCE, Dynamic Client Registration, and CIMD.

What's Changed

Enhancements ✨

Hugging Face Auth Integration by @evalstate in https://github.com/PrefectHQ/fastmcp/pull/4385

Fixes 🐞

Relax host origin guard defaults by @jlowin in https://github.com/PrefectHQ/fastmcp/pull/4439
Restore HTTP host guard compatibility by @jlowin in https://github.com/PrefectHQ/fastmcp/pull/4472

Docs 📚

Docs: add v3.4.4 changelog entries by @jlowin in https://github.com/PrefectHQ/fastmcp/pull/4473

New Contributors

@evalstate made their first contribution in https://github.com/PrefectHQ/fastmcp/pull/4385

Full Changelog: https://github.com/PrefectHQ/fastmcp/compare/v3.4.3...v3.4.4

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About fastmcp

The fast, Pythonic way to build MCP servers and clients.

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Related context

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Earlier breaking changes

v3.4.0 Proxy initialize now forwards upstream initialization, failing loudly on errors.