ensures AWS always uses anthropic-version 2023-06-01 parser

src/proxy/middleware/request/sign-aws-request.ts

@@ -36,6 +36,9 @@ export const signAwsRequest: RequestPreprocessor = async (req) => {
 
   const credential = getCredentialParts(req);
   const host = AMZ_HOST.replace("%REGION%", credential.region);
+  // AWS only uses 2023-06-01 and does not actually check this header, but we
+  // set it so that the stream adapter always selects the correct transformer.
+  req.headers["anthropic-version"] = "2023-06-01";
 
   // Uses the AWS SDK to sign a request, then modifies our HPM proxy request
   // with the headers generated by the SDK.