Retry idempotent session detach

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 69723dd2-e732-43c6-9f9a-a16c2de3a628

Author: jmoseley

nodejs/src/session.ts

@@ -1969,9 +1969,12 @@ export class CopilotSession {
         if (this.disconnected) {
             return;
         }
-        const response = (await this.connection.sendRequest("session.detach", {
-            sessionId: this.sessionId,
-        })) as { success: boolean; error?: string };
+        let response: { success: boolean; error?: string } = { success: false };
+        for (let attempt = 0; attempt < 2 && !response.success; attempt++) {
+            response = (await this.connection.sendRequest("session.detach", {
+                sessionId: this.sessionId,
+            })) as { success: boolean; error?: string };
+        }
         if (!response.success) {
             throw new Error(
                 `Failed to disconnect session ${this.sessionId}: ${response.error || "Unknown error"}`

nodejs/test/client.test.ts

@@ -2208,7 +2208,24 @@ describe("CopilotClient", () => {
             await expect(session.disconnect()).resolves.toBeUndefined();
             expect(
                 sendRequest.mock.calls.filter(([method]) => method === "session.detach")
-            ).toHaveLength(2);
+            ).toHaveLength(3);
+        });
+
+        it("retries an unsuccessful detach response before disconnecting", async () => {
+            const sendRequest = vi
+                .fn()
+                .mockResolvedValueOnce({ success: false, error: "cleanup raced" })
+                .mockResolvedValueOnce({ success: true });
+            const session = new CopilotSession(
+                "test-session",
+                { sendRequest } as any,
+                undefined,
+                undefined
+            );
+
+            await expect(session.disconnect()).resolves.toBeUndefined();
+            await expect(session.getEvents()).rejects.toThrow("has been disconnected");
+            expect(sendRequest).toHaveBeenCalledTimes(2);
         });
 
         it("detaches a session when asynchronously disposed", async () => {