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fastmcp releases

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

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18 shown

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v3.4.0 Breaking risk
Auth Breaking upgrade

fastmcp-remote + proxy failure handling + auth token lifespan

Open
No immediate action
v3.3.1 Bug fix

Component import decoupling

Open
Review required
v3.3.0 Mixed
Auth

fastmcp-slim + OAuth proxy hardening

Open
v3.2.4 Breaking risk
Breaking changes
  • Background tasks now scoped to authorization context instead of MCP session
Security fixes
  • FileUpload validates actual decoded base64 size instead of trusting client-reported size
  • Fixed HTTP header forwarding to unrelated remote servers
  • AuthKit auto-binds token audience to resource URL (RFC 8707)
Notable features
  • Keycloak OAuth provider for enterprise authentication
  • Parameter descriptions automatically extracted from docstrings
  • Added response_title and response_description to ctx.elicit()
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v2.14.7 Bug fix

## What's Changed ### Fixes 🐞 * fix(deps): cap fakeredis to <2.35.0 to prevent startup crash on 2.x

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v3.2.3 Bug fix

Fixes ImportError in tasks extra by pinning incompatible fakeredis version.

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v3.2.1 Breaking risk
Breaking changes
  • Google OAuth now uses sub (user ID) for client_id instead of aud
  • CSP removed from tool metadata (retained on resources)
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v3.2.0 Breaking risk
Breaking changes
  • App tool calls routed via ___-prefixed names
Security fixes
  • SSRF/path traversal prevention (GHSA-vv7q-7jx5-f767)
  • Dropped diskcache (CVE-2025-69872)
  • JWT algorithm restrictions and OAuth scope enforcement
Notable features
  • FastMCPApp provider for composable interactive applications
  • Built-in providers: FileUpload, Approval, Choice, FormInput, GenerativeUI
  • fastmcp dev apps browser preview with MCP inspector
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v3.1.0 New feature
Notable features
  • CodeMode transform: staged BM25 discovery, schema inspection, sandbox execution
  • SearchTools transform for client-side BM25 tool discovery
  • Prefab Apps integration for Python-native UI building
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v3.0.2 Bug fix
Security fixes
  • Prevents MCP transport auth headers from leaking to downstream OpenAPI APIs
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v3.0.1 Breaking risk
Notable features
  • verify_id_token option for OIDCProxy for providers issuing opaque access tokens
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v3.0.0 Breaking risk
Breaking changes
  • Component storage and execution refactored to provider abstraction
  • FileSystemProvider, OpenAPIProvider, ProxyProvider, SkillsProvider introduced
  • Component versioning model added
Security fixes
  • SSRF/path traversal prevention (GHSA-vv7q-7jx5-f767)
  • Dropped diskcache (CVE-2025-69872)
  • Bumped PyJWT >= 2.12.0 (CVE-2026-32597)
Notable features
  • Provider/transform architecture for extensible component discovery
  • FastMCP CLI: list, call, generate-cli, install commands
  • Component versioning with VersionFilter transform
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v2.14.5 Bug fix

Fixes a memory leak in the memory:// docket broker where cancelled tasks accumulated.

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v2.14.3 Bug fix

Fixes HTTP transport timeout bug defaulting to 5 seconds instead of respecting MCP's 30-second standard.

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Beta — feedback welcome: [email protected]