RFC2616 says this: "It MUST be possible to combine the multiple header fields into one "field-name: field-value" pair, without changing the semantics of the me

RFC2616 says this: "It MUST be possible to combine the multiple header fields into one "field-name: field-value" pair, without changing the semantics of the message, by appending each subsequent field-value to the first, each separated by a comma." So, if the implementation folds the multiple headers into one with the various values as a comma separated list, it should all be compliant. I don't know rust well enough to tell if this one is compliant...it reads like it is not (looks like last header wins): https://github.com/deislabs/wagi/blob/main/src/http_util.rs#L22 https://github.com/deislabs/wagi/blob/main/src/http_util.rs#... Edit: It seems RFC7230 keeps most of that language, but makes one exception for Set-Cookie, but that's outbound in this context so it doesn't apply.