diff --git a/PROJECT_STATE.md b/PROJECT_STATE.md
index b86f8dd..25f4554 100644
--- a/PROJECT_STATE.md
+++ b/PROJECT_STATE.md
@@ -7,11 +7,11 @@ ChatGPT MCP Server
 ## Status
 
 Planning complete.
-Phase 0 complete. Phase 1 complete. Phase 2 in progress.
+Phase 0 complete. Phase 1 complete. Phase 2 complete.
 
 ## Current Phase
 
-Phase 2 - OpenAI Integration
+Phase 3 — Not yet defined
 
 ## Completed Tasks
 
@@ -23,11 +23,8 @@ Phase 2 - OpenAI Integration
 - Task 1.4 — Safe logging helper (`src/utils/logging.js`) ✅
 - Task 2.1 — OpenAI client wrapper (`src/openai/client.js`) ✅
 - Task 2.2 — Response builder (`src/openai/responses.js`) ✅
+- Task 2.3 — Error handling and edge cases for OpenAI integration (tests) ✅
 
 ## Next Phase
 
-Phase 2 - OpenAI Integration
-
-## Next Pending Task
-
-Task 2.3 — Error handling and edge cases for OpenAI integration
+Phase 3 — Not yet defined
diff --git a/TASKS.md b/TASKS.md
index 07aab0e..ed3aea2 100644
--- a/TASKS.md
+++ b/TASKS.md
@@ -127,4 +127,8 @@ Requirements:
 - Mock OpenAI SDK network timeout errors separately from rate-limit errors.
 - Verify that no API keys or secrets are ever leaked in error messages across all tested paths.
 
-Status: ⏳ Pending
+Status: ✅ Complete
+
+---
+
+Phase 2 complete. Phase 3 not yet defined.
diff --git a/test/openai/responses.test.js b/test/openai/responses.test.js
index d42747d..3c9c248 100644
--- a/test/openai/responses.test.js
+++ b/test/openai/responses.test.js
@@ -30,6 +30,18 @@ function makeNetworkError() {
   return err;
 }
 
+function makeServerError() {
+  const err = new Error("Service unavailable");
+  err.status = 503;
+  return err;
+}
+
+function makeTimeoutError() {
+  const err = new Error("timeout");
+  err.code = "ETIMEDOUT";
+  return err;
+}
+
 // --- Import ---
 
 const { sendOpenAIResponse } = await import("../../src/openai/responses.js");
@@ -167,4 +179,38 @@ describe("sendOpenAIResponse", () => {
       sendOpenAIResponse(mockClient, { input: ["x"], model: "m", maxOutputTokens: -5 })
     ).rejects.toHaveProperty("kind", "ValidationError");
   });
+
+  it("throws ValidationError when maxOutputTokens is zero", async () => {
+    await expect(
+      sendOpenAIResponse(mockClient, { input: ["x"], model: "m", maxOutputTokens: 0 })
+    ).rejects.toHaveProperty("kind", "ValidationError");
+  });
+
+  it("throws ValidationError when maxOutputTokens is a non-positive float", async () => {
+    await expect(
+      sendOpenAIResponse(mockClient, { input: ["x"], model: "m", maxOutputTokens: 0.5 })
+    ).rejects.toHaveProperty("kind", "ValidationError");
+  });
+
+  it("throws ValidationError when maxOutputTokens is NaN", async () => {
+    await expect(
+      sendOpenAIResponse(mockClient, { input: ["x"], model: "m", maxOutputTokens: NaN })
+    ).rejects.toHaveProperty("kind", "ValidationError");
+  });
+
+  // ===== Error mapping edge cases (2) =====
+
+  it("maps status 503 to OpenAIRequestError", async () => {
+    mockCreate.mockRejectedValueOnce(makeServerError());
+    await expect(
+      sendOpenAIResponse(mockClient, { input: ["x"], model: "m" })
+    ).rejects.toHaveProperty("kind", "OpenAIRequestError");
+  });
+
+  it("maps timeout error (code ETIMEDOUT) to OpenAIRequestError", async () => {
+    mockCreate.mockRejectedValueOnce(makeTimeoutError());
+    await expect(
+      sendOpenAIResponse(mockClient, { input: ["x"], model: "m" })
+    ).rejects.toHaveProperty("kind", "OpenAIRequestError");
+  });
 });