v4.0.0b4: Calm Befour the Storm

FastMCP 4 beta 4 improves modern multi-server clients and adds Prefect Horizon account commands. It also tightens proxy and CIMD security boundaries and fixes Unicode search and MCP inspect output.

What's Changed

Enhancements ✨

• Add Prefect Horizon account commands by @parkedwards in #4786
• Cap anthropic dependency to <1 by @craigie-ant in #4864

Security 🔒

• Scope Marvin App token to each job's declared permissions by @zzstoatzz in #4834
• Exclude Cookie from forwarded HTTP headers by @zzstoatzz in #4843
• Bump cryptography to 50.0.0 in the testing_demo example by @zzstoatzz in #4844
• Bound CIMD cache growth by @jlowin in #4852

Fixes 🐞

• Fix instructions in MCP inspect output by @zzstoatzz in #4873
• fix: support Unicode tokens in BM25 search by @zzstoatzz in #4889
• fix: support modern protocol in multi-server clients by @zzstoatzz in #4893

Docs 📚

• docs: fix idempotent tool hint wording by @Theater-ahyeon in #4875
• docs: prepare FastMCP 4 beta 4 by @zzstoatzz in #4914

Other Changes 🦾

• chore(deps): Update j178/prek-action action to v3 by @prefect-renovate[bot] in #4808
• chore(deps): Update dependency node to v24 by @prefect-renovate[bot] in #4807
• chore(deps): Update astral-sh/setup-uv action to v9 by @prefect-renovate[bot] in #4806
• Fix proxy forwarding of MCP transport headers by @jakekaplan in #4853
• Add FastMCP security report review skill by @zzstoatzz in #4859

New Contributors

• @prefect-renovate[bot] made their first contribution in #4808
• @craigie-ant made their first contribution in #4864
• @Theater-ahyeon made their first contribution in #4875

Full Changelog: v4.0.0b3...v4.0.0b4