fix: report cancelled device-code sign-in as auth error instead of invalid params

src/CodexAcpClient.ts

@@ -293,7 +293,10 @@ export class CodexAcpClient {
 
         if (!acp.CreateElicitationResponse.isAccept(first.response)) {
             await this.codexClient.accountLoginCancel({loginId: loginResponse.loginId});
-            return false;
+            throw RequestError.requestCancelled(
+                {methodId: "chat-gpt-device-code", action: first.response.action},
+                "ChatGPT device code sign-in was cancelled",
+            );
         }
 
         const result = await loginCompletedPromise;

src/CodexAcpServer.ts

@@ -1226,7 +1226,7 @@ export class CodexAcpServer {
         const isAuthenticated = await this.runWithProcessCheck(() => this.codexAcpClient.authenticate(_params, elicitationRequester));
         if (!isAuthenticated) {
             logger.log("Authenticate request failed");
-            throw RequestError.invalidParams();
+            throw RequestError.authRequired({methodId: _params.methodId}, "Sign-in did not complete");
         }
         await this.refreshAuthState(this.getAuthProviderForAuthenticateRequest(_params));
         logger.log("Authenticate request completed");

src/__tests__/CodexACPAgent/CodexAcpClient.test.ts

@@ -274,7 +274,7 @@ describe('ACP server test', { timeout: 40_000 }, () => {
         });
     });
 
-    it('should cancel ChatGPT device code login when URL elicitation is declined', async () => {
+    it.each(["decline", "cancel"] as const)('should cancel ChatGPT device code login when URL elicitation is answered with %s', async (action) => {
         const { deviceFixture, codexAppServerClient } = createDeviceCodeFixture();
         const codexAcpAgent = deviceFixture.getCodexAcpAgent();
         await codexAcpAgent.initialize({
@@ -283,16 +283,39 @@ describe('ACP server test', { timeout: 40_000 }, () => {
         });
         const cancelSpy = vi.spyOn(codexAppServerClient, "accountLoginCancel")
             .mockResolvedValue({ status: "canceled" });
-        deviceFixture.setElicitationResponse({ action: "decline" });
+        deviceFixture.setElicitationResponse({ action });
 
         await expect(codexAcpAgent.authenticate({ methodId: "chat-gpt-device-code" }, 42))
-            .rejects.toThrow();
+            .rejects.toMatchObject({
+                code: -32800,
+                message: "Request cancelled: ChatGPT device code sign-in was cancelled",
+                data: { methodId: "chat-gpt-device-code", action },
+            });
         expect(cancelSpy).toHaveBeenCalledWith({ loginId: "login-1" });
         expect(deviceFixture.getAcpConnectionEvents([])
             .some(event => event.method === "completeElicitation"))
             .toBe(false);
     });
 
+    it('should report an incomplete sign-in when ChatGPT device code login fails', async () => {
+        const { deviceFixture, completeLogin, loginCompletedSubscribed } = createDeviceCodeFixture();
+        const codexAcpAgent = deviceFixture.getCodexAcpAgent();
+        await codexAcpAgent.initialize({
+            protocolVersion: 1,
+            clientCapabilities: { elicitation: { url: {} } },
+        });
+        deviceFixture.setElicitationResponse({ action: "accept" });
+
+        const authPromise = codexAcpAgent.authenticate({ methodId: "chat-gpt-device-code" }, 42);
+        await vi.waitFor(() => expect(loginCompletedSubscribed()).toBe(true));
+        completeLogin(false);
+        await expect(authPromise).rejects.toMatchObject({
+            code: -32000,
+            message: "Authentication required: Sign-in did not complete",
+            data: { methodId: "chat-gpt-device-code" },
+        });
+    });
+
     it('should complete URL elicitation when login finishes before the elicitation response', async () => {
         const { deviceFixture, completeLogin, loginCompletedSubscribed } = createDeviceCodeFixture();
         const codexAcpAgent = deviceFixture.getCodexAcpAgent();