diff --git a/src/agents/openai-responses.reasoning-replay.test.ts b/src/agents/openai-responses.reasoning-replay.test.ts
index 68cb352d02d..b5ccc50e4b4 100644
--- a/src/agents/openai-responses.reasoning-replay.test.ts
+++ b/src/agents/openai-responses.reasoning-replay.test.ts
@@ -30,6 +30,43 @@ function extractInputTypes(input: unknown[]) {
     .filter((t): t is string => typeof t === "string");
 }
 
+const ZERO_USAGE = {
+  input: 0,
+  output: 0,
+  cacheRead: 0,
+  cacheWrite: 0,
+  totalTokens: 0,
+  cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+} as const;
+
+function buildReasoningPart(id = "rs_test") {
+  return {
+    type: "thinking" as const,
+    thinking: "internal",
+    thinkingSignature: JSON.stringify({
+      type: "reasoning",
+      id,
+      summary: [],
+    }),
+  };
+}
+
+function buildAssistantMessage(params: {
+  stopReason: AssistantMessage["stopReason"];
+  content: AssistantMessage["content"];
+}): AssistantMessage {
+  return {
+    role: "assistant",
+    api: "openai-responses",
+    provider: "openai",
+    model: "gpt-5.2",
+    usage: ZERO_USAGE,
+    stopReason: params.stopReason,
+    timestamp: Date.now(),
+    content: params.content,
+  };
+}
+
 async function runAbortedOpenAIResponsesStream(params: {
   messages: Array<
     AssistantMessage | ToolResultMessage | { role: "user"; content: string; timestamp: number }
@@ -70,31 +107,10 @@ async function runAbortedOpenAIResponsesStream(params: {
 
 describe("openai-responses reasoning replay", () => {
   it("replays reasoning for tool-call-only turns (OpenAI requires it)", async () => {
-    const assistantToolOnly: AssistantMessage = {
-      role: "assistant",
-      api: "openai-responses",
-      provider: "openai",
-      model: "gpt-5.2",
-      usage: {
-        input: 0,
-        output: 0,
-        cacheRead: 0,
-        cacheWrite: 0,
-        totalTokens: 0,
-        cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
-      },
+    const assistantToolOnly = buildAssistantMessage({
       stopReason: "toolUse",
-      timestamp: Date.now(),
       content: [
-        {
-          type: "thinking",
-          thinking: "internal",
-          thinkingSignature: JSON.stringify({
-            type: "reasoning",
-            id: "rs_test",
-            summary: [],
-          }),
-        },
+        buildReasoningPart(),
         {
           type: "toolCall",
           id: "call_123|fc_123",
@@ -102,7 +118,7 @@ describe("openai-responses reasoning replay", () => {
           arguments: {},
         },
       ],
-    };
+    });
 
     const toolResult: ToolResultMessage = {
       role: "toolResult",
@@ -152,34 +168,10 @@ describe("openai-responses reasoning replay", () => {
   });
 
   it("still replays reasoning when paired with an assistant message", async () => {
-    const assistantWithText: AssistantMessage = {
-      role: "assistant",
-      api: "openai-responses",
-      provider: "openai",
-      model: "gpt-5.2",
-      usage: {
-        input: 0,
-        output: 0,
-        cacheRead: 0,
-        cacheWrite: 0,
-        totalTokens: 0,
-        cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
-      },
+    const assistantWithText = buildAssistantMessage({
       stopReason: "stop",
-      timestamp: Date.now(),
-      content: [
-        {
-          type: "thinking",
-          thinking: "internal",
-          thinkingSignature: JSON.stringify({
-            type: "reasoning",
-            id: "rs_test",
-            summary: [],
-          }),
-        },
-        { type: "text", text: "hello", textSignature: "msg_test" },
-      ],
-    };
+      content: [buildReasoningPart(), { type: "text", text: "hello", textSignature: "msg_test" }],
+    });
 
     const { types } = await runAbortedOpenAIResponsesStream({
       messages: [