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mcp: allow Content-Type parameters in streamable transport - #878
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maciej-kisiel merged 2 commits intoApr 3, 2026
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Use `mime.ParseMediaType` to parse the `Content-Type` header instead of exact string matching. Previously, the server required an exact match on `application/json`. This allows the server to accept `application/json` with parameters (e.g. `charset=utf-8`), even though they are not required [1], following the robustness principle. Per RFC 8259 (section 8.1) [2], `application/json` is always UTF-8, so such parameters are technically redundant. However, parsing the media type makes the server more tolerant of client behavior, improving compatibility without compromising security. [1] https://datatracker.ietf.org/doc/html/rfc4627.html#section-6 [2] https://datatracker.ietf.org/doc/html/rfc8259.html#section-8.1
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This was referenced Jul 21, 2026
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Use
mime.ParseMediaTypeto parse theContent-Typeheader instead of exact string matching. Previously, the server required an exact match onapplication/json.This allows the server to accept
application/jsonwith parameters (e.g.charset=utf-8), even though they are not required, following the robustness principle.Per RFC 8259 (section 8.1),
application/jsonis always UTF-8, so such parameters are technically redundant. However, parsing the media type makes the server more tolerant of client behaviour, improving compatibility without compromising security.