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http-custom-header-server-validation: no case sends an empty x-mcp-header value

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
75/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
typescript
Domain
testing

Research direction

Look at the http-custom-header-server-validation scenario in the conformance test suite. The issue is that it never sends an empty string for the annotated parameter, so a server incorrectly treating an empty header as missing passes. Add an accept case with body "" and an empty header to cover this edge case. Run the tests to verify the new case fails for a buggy server and passes after the fix.

Written by the indexing model from the issue text.

Description

The http-custom-header-server-validation scenario never sends an empty string for the annotated parameter, so a server that treats an empty Mcp-Param-* header as missing still passes. The client half is already covered: http-custom-headers sends empty_val: '' and expects the header to arrive present and empty.

The Go SDK server had exactly this bug (modelcontextprotocol/go-sdk#1288). I tried adding one more accept case to the existing scenario, with body "" and an empty header. go-sdk's current main fails it (10/11), and the fix in go-sdk#1289 passes 11/11. Happy to open the PR if you want this.

Dominant language
TypeScript
Stars
127
Forks
101
Avg merge
4d 7h
Merged PRs (30d)
6

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