diff --git a/src/agents/openai-ws-connection.ts b/src/agents/openai-ws-connection.ts
index 56cc4fb6964..a6e923ae1d5 100644
--- a/src/agents/openai-ws-connection.ts
+++ b/src/agents/openai-ws-connection.ts
@@ -39,9 +39,11 @@ export interface ResponseObject {
 }
 
 export interface UsageInfo {
-  input_tokens: number;
-  output_tokens: number;
-  total_tokens: number;
+  input_tokens?: number;
+  output_tokens?: number;
+  total_tokens?: number;
+  prompt_tokens?: number;
+  completion_tokens?: number;
 }
 
 export type OpenAIResponsesAssistantPhase = "commentary" | "final_answer";
diff --git a/src/agents/openai-ws-message-conversion.ts b/src/agents/openai-ws-message-conversion.ts
index 62f22aff26b..1c9e96dca58 100644
--- a/src/agents/openai-ws-message-conversion.ts
+++ b/src/agents/openai-ws-message-conversion.ts
@@ -548,7 +548,7 @@ export function buildAssistantMessageFromResponse(
     usage: buildUsageWithNoCost({
       input: normalizedUsage?.input ?? 0,
       output: normalizedUsage?.output ?? 0,
-      totalTokens: normalizedUsage?.total ?? response.usage?.total_tokens ?? 0,
+      totalTokens: normalizedUsage?.total ?? 0,
     }),
   });
 
diff --git a/src/agents/openai-ws-stream.test.ts b/src/agents/openai-ws-stream.test.ts
index eee7688bcff..d7bfa096293 100644
--- a/src/agents/openai-ws-stream.test.ts
+++ b/src/agents/openai-ws-stream.test.ts
@@ -862,7 +862,7 @@ describe("buildAssistantMessageFromResponse", () => {
 
   it("maps prompt_tokens and completion_tokens usage aliases", () => {
     const response = makeResponseObject("resp_5b", "Hello");
-    (response as unknown as { usage?: Record<string, number> }).usage = {
+    response.usage = {
       prompt_tokens: 44,
       completion_tokens: 11,
       total_tokens: 55,