[lesnik512]

Closes #330.

The fastmcp extra is now fastmcp>=4.0,<5, up from >=3.0 with no upper bound. Until now, pytest ran 4.x after uv lock --upgrade and floors ran 3.0, so nothing tested the newest 3.x. And the access log behaved differently depending on which major resolved. I took the issue's floor option over a pinned 3.x CI leg: lite-bootstrap 2.0 now supports one fastmcp major and documents one behaviour. fastmcp 4.0.0 was released on 2026-08-31.

• pyproject.toml: the fastmcp comment gives the new reason for the floor and for <5. 4.0 still has Provider and add_provider(), so ADR 0001 is unaffected. The typing-extensions>=4.15 line stays because fastmcp 4.0 pulls py-key-value-aio 0.4.4, which still requires it. The fastmcp-metrics comment now says 4.0 instead of 3.0.
• docs/integrations/fastmcp.md documents the 4.x access log. It records every message a client sends, including notifications, the server/discover request of a modern connection, and requests that fail before reaching a handler. The middleware needed no change.

Tests

test_fastmcp_access_log_records_notifications connects a Client in mode="legacy" with the access log on. It asserts that initialize, notifications/initialized and tools/list are each logged with their type. It passes on 4.x. I couldn't run it against 3.x for a red phase, because the new floor makes 3.x unresolvable. Per the upgrade guide, notifications never reached on_message on 3.x.

The full suite passes, 589 tests at 100% coverage (just test-ci). just lint (including ty) and just docs-build pass too.

I ran the floors job's steps locally for the fastmcp target on 3.11, 3.12, 3.13 and 3.14. CI excludes 3.15 for this target. All four resolve fastmcp 4.0.0 and pass scripts/floor_smoke.py. No other target installs fastmcp.

Breaking changes

• If you're pinned to fastmcp 3.x, you can't install 2.0. fastmcp 4 also raises its own floors to pydantic 2.12 and Starlette 1.0.1. See the upgrade guide.
• With the access log on, it now has records for notifications and pre-handler failures.
• 2.0 can't install alongside fastmcp 5 until the bound is lifted.