fix(mcp): Nest MCP spans under HTTP transactions #5292
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Semver Impact of This PR🟢 Patch (bug fixes) 📋 Changelog PreviewThis is how your changes will appear in the changelog. New Features ✨Span Streaming
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Bug Fixes 🐛Google Genai
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Internal Changes 🔧Fastmcp
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sentrivana
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Jan 14, 2026
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See comments, but other than that LGTM!
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Codecov Results 📊✅ 13 passed | Total: 13 | Pass Rate: 100% | Execution Time: 7.35s All tests are passing successfully. ❌ Patch coverage is 1.82%. Project has 13629 uncovered lines. Files with missing lines (180)
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Description
Patch
StreamableHTTPServerTransport.handle_request()to store isolation and current scopes on the Starlette request object'sscopeattribute.Run MCP handlers in the context of the stored scopes, if these are available.
Modify
use_isolation_scope()anduse_scope()context managers to acceptNone. The MCP protocol allows for transport layers that are not HTTP-based, so the scopes may not be available.The Python MCP SDK uses an in-memory queue of requests. The HTTP propagation context is not active in the MCP decorators we patch, since they run after requests are retrieved from the queue.
Issues
Closes #5272
Closes PY-2022
Closes TET-1688
Reminders
tox -e linters.feat:,fix:,ref:,meta:)