diff --git a/packages/openai-adapters/src/apis/OpenAI.test.ts b/packages/openai-adapters/src/apis/OpenAI.test.ts
new file mode 100644
index 00000000000..70fd3fa7081
--- /dev/null
+++ b/packages/openai-adapters/src/apis/OpenAI.test.ts
@@ -0,0 +1,38 @@
+import { describe, expect, it } from "vitest";
+
+import { OpenAIApi } from "./OpenAI.js";
+
+describe("OpenAIApi timeout conversion", () => {
+  const baseConfig = {
+    provider: "openai" as const,
+    apiKey: "test-key",
+  };
+
+  it("converts requestOptions.timeout from seconds to milliseconds", () => {
+    const api = new OpenAIApi({
+      ...baseConfig,
+      requestOptions: { timeout: 300 },
+    });
+
+    expect(api.openai.timeout).toBe(300_000);
+  });
+
+  it("preserves an explicit zero timeout instead of falling back to the SDK default", () => {
+    const api = new OpenAIApi({
+      ...baseConfig,
+      requestOptions: { timeout: 0 },
+    });
+
+    // The schema permits `timeout: 0`, and the SDK resolves its own default
+    // with `?? DEFAULT_TIMEOUT`, so 0 must survive as 0 rather than becoming
+    // undefined and silently turning into the 10-minute default.
+    expect(api.openai.timeout).toBe(0);
+  });
+
+  it("leaves the SDK default in place when no timeout is configured", () => {
+    const api = new OpenAIApi(baseConfig);
+
+    // 10 minutes — the OpenAI SDK's DEFAULT_TIMEOUT.
+    expect(api.openai.timeout).toBe(600_000);
+  });
+});
diff --git a/packages/openai-adapters/src/apis/OpenAI.ts b/packages/openai-adapters/src/apis/OpenAI.ts
index d0f8d30ca3a..3f750110c3d 100644
--- a/packages/openai-adapters/src/apis/OpenAI.ts
+++ b/packages/openai-adapters/src/apis/OpenAI.ts
@@ -45,7 +45,14 @@ export class OpenAIApi implements BaseLlmApi {
       apiKey: config.apiKey ?? "",
       baseURL: this.apiBase,
       fetch: customFetch(config.requestOptions),
-      timeout: config?.requestOptions?.timeout || undefined,
+      // requestOptions.timeout is in seconds; the OpenAI SDK expects ms.
+      // Nullish rather than truthy: the schema permits `timeout: 0`, and both
+      // the SDK (`options.timeout ?? DEFAULT_TIMEOUT`) and our own
+      // getAgentOptions treat 0 as a real value, not as "unset".
+      timeout:
+        config?.requestOptions?.timeout != null
+          ? config.requestOptions.timeout * 1000
+          : undefined,
     });
   }
   modifyChatBody<T extends ChatCompletionCreateParams>(body: T): T {