Stabilize unknown session delete E2E assertions

Assert the SDK-level delete failure prefix instead of the runtime-specific detail text so the tests pass against runtimes with different unknown-session wording.

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

Author: stephentoub

dotnet/test/E2E/ClientSessionManagementE2ETests.cs

@@ -35,10 +35,11 @@ public async Task Should_Delete_Session_By_Id()
     public async Task Should_Report_Error_When_Deleting_Unknown_Session_Id()
     {
         await Client.StartAsync();
+        const string UnknownSessionId = "00000000-0000-0000-0000-000000000000";
 
         await AssertFailureAsync(
-            () => Client.DeleteSessionAsync("00000000-0000-0000-0000-000000000000"),
-            "Session file not found");
+            () => Client.DeleteSessionAsync(UnknownSessionId),
+            $"Failed to delete session {UnknownSessionId}");
     }
 
     [Fact]

go/internal/e2e/client_api_e2e_test.go

@@ -50,12 +50,14 @@ func TestClientApiE2E(t *testing.T) {
 	})
 
 	t.Run("should report error when deleting unknown session id", func(t *testing.T) {
-		err := client.DeleteSession(t.Context(), "00000000-0000-0000-0000-000000000000")
+		sessionID := "00000000-0000-0000-0000-000000000000"
+		err := client.DeleteSession(t.Context(), sessionID)
 		if err == nil {
 			t.Fatal("Expected DeleteSession to fail for unknown id")
 		}
-		if !strings.Contains(strings.ToLower(err.Error()), "session file not found") {
-			t.Errorf("Expected error mentioning 'Session file not found', got %v", err)
+		expectedMessage := "failed to delete session " + sessionID
+		if !strings.Contains(strings.ToLower(err.Error()), expectedMessage) {
+			t.Errorf("Expected error mentioning %q, got %v", expectedMessage, err)
 		}
 	})
 

nodejs/test/e2e/client_api.e2e.test.ts

@@ -34,10 +34,11 @@ describe("Client session management", async () => {
 
     it("should report error when deleting unknown session id", async () => {
         await client.start();
+        const unknownSessionId = "00000000-0000-0000-0000-000000000000";
 
         await assertFailure(
-            () => client.deleteSession("00000000-0000-0000-0000-000000000000"),
-            "Session file not found"
+            () => client.deleteSession(unknownSessionId),
+            `Failed to delete session ${unknownSessionId}`
         );
     });
 

python/e2e/test_client_api_e2e.py

@@ -34,10 +34,11 @@ async def test_should_delete_session_by_id(self, ctx: E2ETestContext):
 
     async def test_should_report_error_when_deleting_unknown_session_id(self, ctx: E2ETestContext):
         await ctx.client.start()
+        unknown_session_id = "00000000-0000-0000-0000-000000000000"
 
         with pytest.raises(Exception) as exc_info:
-            await ctx.client.delete_session("00000000-0000-0000-0000-000000000000")
-        assert "session file not found" in str(exc_info.value).lower()
+            await ctx.client.delete_session(unknown_session_id)
+        assert f"failed to delete session {unknown_session_id}" in str(exc_info.value).lower()
 
     async def test_should_get_null_last_session_id_before_any_sessions_exist(
         self, ctx: E2ETestContext