[Server] Enforce x-mcp-header where a request uses it (SEP-2243) - #453
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chr-hertel merged 2 commits intoAug 18, 2026
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August 18, 2026 19:10
Only top-level properties were inspected, so an annotation on a nested property was silently unenforced - the header could say anything. The walk now follows a chain of properties keys to any depth and reads the argument at that exact path. Integer values compare numerically, so a client writing 42.0 for a body value of 42 is no longer rejected.
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Pull request overview
This PR updates the server-side StandardHeaderValidator to correctly enforce x-mcp-header annotations beyond top-level tool input properties, ensuring nested Mcp-Param-* headers are validated against the exact body argument path. It also relaxes numeric comparison so integer header/body values can agree even when serialized differently (e.g., 42 vs 42.0).
Changes:
- Recursively discover
x-mcp-headerannotations through nestedpropertieschains and validate headers against the corresponding nested argument path. - Add numeric-aware comparison for mirrored params to avoid rejecting equivalent integer values with different decimal renderings.
- Extend unit tests to cover nested mirroring discovery, unreachable annotations, nested argument validation, and numeric comparison behavior.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
src/Server/Stateless/StandardHeaderValidator.php |
Recursively extracts mirrored properties and validates Mcp-Param-* values against nested arguments; adds numeric comparison behavior. |
tests/Unit/Server/Stateless/StandardHeaderValidatorTest.php |
Adds coverage for nested x-mcp-header discovery and nested/header numeric validation. |
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is_numeric() and loose == both treat a string like "042" as equal to "42", so a string argument could pass header validation against a header that doesn't match it exactly. Gate the numeric comparison on the argument's actual type and a decimal-only header instead.
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Stacked on #452. The request-side half of
x-mcp-header; the definition-side half merged as #441.StandardHeaderValidatorinspected only top-level properties, so an annotation on a nested property was silently unenforced — theMcp-Param-*header could say anything. The walk now follows a chain ofpropertieskeys to any depth and reads the argument at that exact path.Integer values compare numerically, so a client writing
42.0for a body value of42is no longer rejected.Part of SEP-2243.
Cross-fork PRs can only target
main, so this diff also carries its ancestors until they merge. Only the last commit(s) belong to this PR — GitHub's "Commits" tab separates them.