Expose turn token usage in the SDK (#4700)

It's present on the event, add it to the final result as well.

sdk/typescript/tests/responsesProxy.ts

@@ -3,6 +3,22 @@ import http from "node:http";
 const DEFAULT_RESPONSE_ID = "resp_mock";
 const DEFAULT_MESSAGE_ID = "msg_mock";
 
+type ResponseCompletedUsage = {
+  input_tokens: number;
+  input_tokens_details: { cached_tokens: number } | null;
+  output_tokens: number;
+  output_tokens_details: { reasoning_tokens: number } | null;
+  total_tokens: number;
+};
+
+const DEFAULT_COMPLETED_USAGE: ResponseCompletedUsage = {
+  input_tokens: 42,
+  input_tokens_details: { cached_tokens: 12 },
+  output_tokens: 5,
+  output_tokens_details: null,
+  total_tokens: 47,
+};
+
 type SseEvent = {
   type: string;
   [key: string]: unknown;
@@ -157,17 +173,26 @@ export function assistantMessage(text: string, itemId: string = DEFAULT_MESSAGE_
   };
 }
 
-export function responseCompleted(responseId: string = DEFAULT_RESPONSE_ID): SseEvent {
+export function responseCompleted(
+  responseId: string = DEFAULT_RESPONSE_ID,
+  usage: ResponseCompletedUsage = DEFAULT_COMPLETED_USAGE,
+): SseEvent {
+  const inputDetails = usage.input_tokens_details
+    ? { ...usage.input_tokens_details }
+    : null;
+  const outputDetails = usage.output_tokens_details
+    ? { ...usage.output_tokens_details }
+    : null;
   return {
     type: "response.completed",
     response: {
       id: responseId,
       usage: {
-        input_tokens: 0,
-        input_tokens_details: null,
-        output_tokens: 0,
-        output_tokens_details: null,
-        total_tokens: 0,
+        input_tokens: usage.input_tokens,
+        input_tokens_details: inputDetails,
+        output_tokens: usage.output_tokens,
+        output_tokens_details: outputDetails,
+        total_tokens: usage.total_tokens,
       },
     },
   };

sdk/typescript/tests/run.test.ts

@@ -38,6 +38,11 @@ describe("Codex", () => {
         },
       ];
       expect(result.items).toEqual(expectedItems);
+      expect(result.usage).toEqual({
+        cached_input_tokens: 12,
+        input_tokens: 42,
+        output_tokens: 5,
+      });
       expect(thread.id).toEqual(expect.any(String));
     } finally {
       await close();

sdk/typescript/tests/runStreamed.test.ts

@@ -52,9 +52,9 @@ describe("Codex", () => {
         {
           type: "turn.completed",
           usage: {
-            cached_input_tokens: 0,
-            input_tokens: 0,
-            output_tokens: 0,
+            cached_input_tokens: 12,
+            input_tokens: 42,
+            output_tokens: 5,
           },
         },
       ]);