diff --git a/src/agents/openai-ws-message-conversion.ts b/src/agents/openai-ws-message-conversion.ts
index 9f3e8f2a0b3..30ce8997b20 100644
--- a/src/agents/openai-ws-message-conversion.ts
+++ b/src/agents/openai-ws-message-conversion.ts
@@ -292,7 +292,9 @@ export function planTurnInput(params: {
 }): PlannedTurnInput {
   if (params.previousResponseId && params.lastContextLength > 0) {
     const newMessages = params.context.messages.slice(params.lastContextLength);
-    const toolResults = newMessages.filter((message) => (message as AnyMessage).role === "toolResult");
+    const toolResults = newMessages.filter(
+      (message) => (message as AnyMessage).role === "toolResult",
+    );
     if (toolResults.length > 0) {
       return {
         mode: "incremental_tool_results",
diff --git a/src/agents/openai-ws-stream.test.ts b/src/agents/openai-ws-stream.test.ts
index 09218eaa97f..79092da284b 100644
--- a/src/agents/openai-ws-stream.test.ts
+++ b/src/agents/openai-ws-stream.test.ts
@@ -18,6 +18,7 @@ import {
   convertTools,
   createOpenAIWebSocketStreamFn,
   hasWsSession,
+  planTurnInput,
   releaseWsSession,
 } from "./openai-ws-stream.js";
 
@@ -901,6 +902,120 @@ describe("buildAssistantMessageFromResponse", () => {
 
 // ─────────────────────────────────────────────────────────────────────────────
 
+describe("planTurnInput", () => {
+  const replayModel = { input: ["text"] };
+
+  it("uses incremental tool result replay when a previous response id and new tool results exist", () => {
+    const context = {
+      systemPrompt: "You are helpful.",
+      messages: [
+        userMsg("Run ls"),
+        assistantMsg([], [{ id: "call_1|fc_1", name: "exec", args: { cmd: "ls" } }]),
+        toolResultMsg("call_1|fc_1", "file.txt"),
+      ] as Parameters<typeof convertMessagesToInputItems>[0],
+      tools: [],
+    };
+
+    const turnInput = planTurnInput({
+      context,
+      model: replayModel,
+      previousResponseId: "resp_prev",
+      lastContextLength: 2,
+    });
+
+    expect(turnInput.mode).toBe("incremental_tool_results");
+    expect(turnInput.previousResponseId).toBe("resp_prev");
+    expect(turnInput.inputItems).toEqual([
+      {
+        type: "function_call_output",
+        call_id: "call_1",
+        output: "file.txt",
+      },
+    ]);
+  });
+
+  it("restarts with full context when follow-up turns have no new tool results", () => {
+    const turn1Response = {
+      id: "resp_turn1_reasoning",
+      object: "response",
+      created_at: Date.now(),
+      status: "completed",
+      model: "gpt-5.2",
+      output: [
+        {
+          type: "reasoning",
+          id: "rs_turn1",
+          content: "Thinking before tool call",
+        },
+        {
+          type: "function_call",
+          id: "fc_turn1",
+          call_id: "call_turn1",
+          name: "exec",
+          arguments: '{"cmd":"ls"}',
+        },
+      ],
+      usage: { input_tokens: 12, output_tokens: 8, total_tokens: 20 },
+    } as ResponseObject;
+
+    const context = {
+      systemPrompt: "You are helpful.",
+      messages: [
+        userMsg("Run ls"),
+        buildAssistantMessageFromResponse(turn1Response, {
+          api: "openai-responses",
+          provider: "openai",
+          id: "gpt-5.2",
+        }),
+      ] as Parameters<typeof convertMessagesToInputItems>[0],
+      tools: [],
+    };
+
+    const turnInput = planTurnInput({
+      context,
+      model: replayModel,
+      previousResponseId: "resp_turn1_reasoning",
+      lastContextLength: context.messages.length,
+    });
+
+    expect(turnInput.mode).toBe("full_context_restart");
+    expect(turnInput.previousResponseId).toBeUndefined();
+    expect(turnInput.inputItems.map((item) => item.type)).toEqual([
+      "message",
+      "reasoning",
+      "function_call",
+    ]);
+    expect(turnInput.inputItems[1]).toMatchObject({ type: "reasoning", id: "rs_turn1" });
+    expect(turnInput.inputItems[2]).toMatchObject({
+      type: "function_call",
+      call_id: "call_turn1",
+      id: "fc_turn1",
+    });
+  });
+
+  it("uses full context on the initial turn", () => {
+    const context = {
+      systemPrompt: "You are helpful.",
+      messages: [userMsg("Hello!")] as Parameters<typeof convertMessagesToInputItems>[0],
+      tools: [],
+    };
+
+    const turnInput = planTurnInput({
+      context,
+      model: replayModel,
+      previousResponseId: null,
+      lastContextLength: 0,
+    });
+
+    expect(turnInput).toMatchObject({
+      mode: "full_context_initial",
+      inputItems: [{ type: "message", role: "user", content: "Hello!" }],
+    });
+  });
+});
+
+// ─────────────────────────────────────────────────────────────────────────────
+
 describe("createOpenAIWebSocketStreamFn", () => {
   const modelStub = {
     api: "openai-responses",