fix(core): handle stateless MCP wrapper transport correlation

[logaretm]

This PR handles stateless MCP wrappers by using the connected transport instance as the stable MCP correlation key across wrapper layers.

I verified the issue and the fix by adding a regression test for stateless wrapper transports where the request path runs on the inner transport and the response path runs on the wrapper.

Closes #20290

[linear-code]

JS-2164 wrapMcpServerWithSentry: tool-call spans missing with stateless StreamableHTTPServerTransport

[Copilot]

Pull request overview

This PR fixes MCP server transport span correlation when using stateless wrapper transports (e.g. StreamableHTTPServerTransport with sessionIdGenerator: undefined) by using the connected transport instance as the correlation key across wrapper layers, and adds a regression test to cover this scenario.

Changes:

• Use the transport passed to connect() (instead of handler this) as the key for span/session correlation in transport wrappers.
• Add a regression test ensuring tool-call spans are properly completed for stateless wrapper transports.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
packages/core/src/integrations/mcp-server/transport.ts	Switch correlation/session operations to use the connected transport instance for wrapper-layer stability.
packages/core/test/lib/integrations/mcp-server/transportInstrumentation.test.ts	Add regression test reproducing stateless wrapper onmessage/send split and asserting span completion.

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