HttpRequest

interface HttpRequest {
  signal?: AbortSignal;
  baseEndpoint?: string;
  body?:
    | Blob
    | ArrayBuffer
    | FormData
    | URLSearchParams
    | ReadableStream<Uint8Array>
    | object
    | string
    | number
    | boolean
    | null;
  bodyContentType?: string | null;
  downloadProgress?: HttpProgressFn;
  endpoint: string;
  headers?: Headers;
  method: string;
  operation?: string;
  queryParams?: URLSearchParams;
  queryString?: string;
  readonly responseType?: HttpResponseType;
  readonly errorResponseType?: HttpResponseType;
  uploadProgress?: HttpProgressFn;
  withCredentials?: boolean;
  xsrf?: {
    cookieName: string;
    headerName: string;
    tokenProvider?: (context: {
      request: HttpRequest;
    }) => string | null | undefined;
  };
}

body is already the wire value. For JSON that is a JSON text string; sign HMAC or digests against that string (or other final bytes), not the original struct input.

• bodyContentType holds the inferred type of the builder's body. null suppresses that header. FormData owns its multipart boundary. HTTP inference follows a direct write to body and is not copied by object spread; an explicit bodyContentType assignment is copied. A replacement body is detected again, so declare its type with a content-type header. For the unchanged body, null suppresses library inference when there is no explicit header, but native Fetch may add its own string type.
• HTTP never writes inferred Content-Type into headers; interceptors see only declared headers. An explicit content-type header always wins over bodyContentType and detection, whether set by the builder, client defaults, an interceptor, or a raw fetchHandler request. body: undefined has no library-inferred Content-Type. Signers should read headers.get('content-type') ?? request.bodyContentType; do not configure internal fields.
• endpoint is the path with path parameters filled in; baseEndpoint is the client endpoint.
• Interceptors see queryParams as new URLSearchParams(queryString). A builder that returns URLSearchParams passes that instance through.
• operation is a static, low-cardinality endpoint identity for telemetry and diagnostics.
• downloadProgress and uploadProgress are the onDownloadProgress and onUploadProgress hooks of HttpExecuteOptions.
• responseType and errorResponseType are readonly: they are derived from the endpoint's output and error struct kinds and must not be changed. Each is set only when its struct is declared. An interceptor that short-circuits with makeResponse reads them to match the transport.