feat(claude): merge client anthropic-beta flags and forward rate-limit headers

open-sse/utils/error.js

@@ -27,12 +27,13 @@ export function buildErrorBody(statusCode, message) {
  * @param {string} message - Error message
  * @returns {Response} HTTP Response object
  */
-export function errorResponse(statusCode, message) {
+export function errorResponse(statusCode, message, extraHeaders = null) {
   return new Response(JSON.stringify(buildErrorBody(statusCode, message)), {
     status: statusCode,
     headers: {
       "Content-Type": "application/json",
-      "Access-Control-Allow-Origin": "*"
+      "Access-Control-Allow-Origin": "*",
+      ...extraHeaders
     }
   });
 }
@@ -95,13 +96,13 @@ export async function parseUpstreamError(response, executor = null) {
  * @param {number} [resetsAtMs] - Optional precise cooldown expiry (ms epoch) for provider-specific quota errors
  * @returns {{ success: false, status: number, error: string, response: Response, resetsAtMs?: number }}
  */
-export function createErrorResult(statusCode, message, resetsAtMs) {
+export function createErrorResult(statusCode, message, resetsAtMs, extraHeaders = null) {
   return {
     success: false,
     status: statusCode,
     error: message,
     resetsAtMs,
-    response: errorResponse(statusCode, message)
+    response: errorResponse(statusCode, message, extraHeaders)
   };
 }
 
@@ -113,7 +114,7 @@ export function createErrorResult(statusCode, message, resetsAtMs) {
  * @param {string} retryAfterHuman - Human-readable retry info e.g. "reset after 30s"
  * @returns {Response}
  */
-export function unavailableResponse(statusCode, message, retryAfter, retryAfterHuman) {
+export function unavailableResponse(statusCode, message, retryAfter, retryAfterHuman, extraHeaders = null) {
   const retryAfterSec = Math.max(Math.ceil((new Date(retryAfter).getTime() - Date.now()) / 1000), 1);
   const msg = `${message} (${retryAfterHuman})`;
   return new Response(
@@ -121,8 +122,10 @@ export function unavailableResponse(statusCode, message, retryAfter, retryAfterH
     {
       status: statusCode,
       headers: {
+        ...extraHeaders,
         "Content-Type": "application/json",
-        "Retry-After": String(retryAfterSec)
+        // Intentionally mis-cased to prevent duplicate headers
+        "retry-after": String(retryAfterSec)
       }
     }
   );

open-sse/utils/upstreamHeaders.js

@@ -0,0 +1,12 @@
+const FORWARDED = new Set(["retry-after", "x-should-retry"]);
+const FORWARDED_PREFIX = "anthropic-ratelimit-";
+
+export function upstreamResponseHeaders(headers) {
+  const out = {};
+  if (typeof headers?.forEach !== "function") return out;
+  headers.forEach((value, name) => {
+    const key = name.toLowerCase();
+    if (FORWARDED.has(key) || key.startsWith(FORWARDED_PREFIX)) out[key] = value;
+  });
+  return out;
+}