feat(proxy): update endpoint resolution order for 'anyrouter' platform

src/server/routes/proxy/upstreamEndpoint.test.ts

@@ -185,7 +185,17 @@ describe('resolveUpstreamEndpointCandidates', () => {
       'claude-opus-4-6',
       'openai',
     );
-    expect(openaiOrder).toEqual(['messages', 'chat']);
+    expect(openaiOrder).toEqual(['messages', 'chat', 'responses']);
+
+    const claudeOrder = await resolveUpstreamEndpointCandidates(
+      {
+        ...baseContext,
+        site: { ...baseContext.site, platform: 'anyrouter' },
+      },
+      'claude-opus-4-6',
+      'claude',
+    );
+    expect(claudeOrder).toEqual(['messages', 'chat', 'responses']);
 
     const responsesOrder = await resolveUpstreamEndpointCandidates(
       {

src/server/routes/proxy/upstreamEndpoint.ts

@@ -931,9 +931,10 @@ export async function resolveUpstreamEndpointCandidates(
   );
   if (sitePlatform === 'anyrouter') {
     // anyrouter deployments are effectively anthropic-protocol first.
-    return downstreamFormat === 'responses'
-      ? ['responses', 'messages', 'chat']
-      : ['messages', 'chat'];
+    if (downstreamFormat === 'responses') {
+      return ['responses', 'messages', 'chat'];
+    }
+    return ['messages', 'chat', 'responses'];
   }
 
   const preferred = preferredEndpointOrder(