feat: add Community FastMCP v3 support via middleware #22
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Use FastMCP v3's official Middleware system instead of monkey-patching for cleaner, more maintainable integration. Maintains full backwards compatibility with v2. - Add MCPCatMiddleware for v3 with on_initialize, on_call_tool, on_list_tools - Add version detection (is_community_fastmcp_v3, is_community_fastmcp_v2) - Extract MCP client info and actor identity from middleware context - Support context parameter injection, get_more_tools, tool registry - Update tests to be version-agnostic with get_lowlevel_server helper
kashishhora
approved these changes
Jan 29, 2026
| [project.optional-dependencies] | ||
| community = [ | ||
| "fastmcp>=2.7.0,!=2.9.*", | ||
| "fastmcp==3.0.0b1", |
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shouldn't pin version here, right?
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| _version = getattr(fastmcp, "__version__", "0.0.0") | ||
| # v3 starts at 3.0.0b1 | ||
| IS_FASTMCP_V3 = _version.startswith("3.") or _version.startswith("3") |
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The first check makes the second redundant? Also this would match 30 and above I guess but less of an issue.
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Summary
fastmcp>=3.0.0b1) using v3's official Middleware system instead of monkey-patching, while maintaining full backwards compatibility with v2MCPCatMiddlewarewithon_initialize,on_call_tool, andon_list_toolshooks that handle event tracking, context parameter injection, tool registry, client info extraction, and actor identificationis_community_fastmcp_v3,is_community_fastmcp_v2) and updatetrack()routing logic to select the appropriate integration pathTest plan
.venv/bin/python -m pytest tests/ -v(255 passed, 2 skipped).venv/bin/python -m pytest tests/community/ -v(63 passed)get_more_tools(report missing) feature works with v3