fix responses (#5113)

Author: colegottdank

packages/cost/models/providers/helicone.ts

@@ -16,8 +16,9 @@ export class HeliconeProvider extends BaseProvider {
       return `${this.baseUrl}/anthropic/v1/messages`;
     }
 
-    // Use responses endpoint for pro and codex models
-    const isResponsesEndpoint = endpoint.providerModelId.includes("gpt-5-pro") ||
+    // Use responses endpoint for pro/codex models or when bodyMapping is RESPONSES
+    const isResponsesEndpoint = requestParams.bodyMapping === "RESPONSES" ||
+                                 endpoint.providerModelId.includes("gpt-5-pro") ||
                                  endpoint.providerModelId.includes("gpt-5-codex");
 
     const path = isResponsesEndpoint ? "/responses" : "/chat/completions";
@@ -56,25 +57,7 @@ export class HeliconeProvider extends BaseProvider {
       return JSON.stringify(anthropicBody);
     }
 
-    const isResponsesEndpoint = endpoint.providerModelId.includes("gpt-5-pro") ||
-                                 endpoint.providerModelId.includes("gpt-5-codex");
-
-    if (isResponsesEndpoint) {
-      // Convert messages to input format for /responses endpoint
-      const { messages, ...rest } = context.parsedBody;
-      let input = "";
-      if (Array.isArray(messages)) {
-        input = messages.map((m: any) => m.content).join("\n");
-      }
-
-      return JSON.stringify({
-        ...rest,
-        model: endpoint.providerModelId,
-        input,
-      });
-    }
-
-    // Standard chat completions format for OpenAI models
+    // Standard format - just pass through with correct model
     return JSON.stringify({
       ...context.parsedBody,
       model: endpoint.providerModelId,

worker/src/lib/ai-gateway/SimpleAIGateway.ts

@@ -159,10 +159,11 @@ export class SimpleAIGateway {
         });
         continue;
       }
+
       if (
         attempt.authType === "ptb" &&
-        this.requestWrapper.heliconeHeaders.gatewayConfig.bodyMapping !==
-          "NO_MAPPING"
+        this.requestWrapper.heliconeHeaders.gatewayConfig.bodyMapping ===
+          "OPENAI"
       ) {
         const validationResult = validateOpenAIChatPayload(finalBody);
         if (isErr(validationResult)) {