diff --git a/internal/runtime/executor/codex_websockets_execute.go b/internal/runtime/executor/codex_websockets_execute.go
index f8c51ef0..fb1fb719 100644
--- a/internal/runtime/executor/codex_websockets_execute.go
+++ b/internal/runtime/executor/codex_websockets_execute.go
@@ -251,8 +251,8 @@ func (e *CodexWebsocketsExecutor) Execute(ctx context.Context, auth *cliproxyaut
 		}
 	}
 
-	if optimizeMultiAgentV2 {
-		sess.markMultiAgentV2Optimized(conn)
+	if optimizeMultiAgentV2 || multiAgentV2Conflict {
+		sess.setMultiAgentV2Optimized(conn, optimizeMultiAgentV2 && !multiAgentV2Conflict)
 	}
 
 	outputItemsByIndex := make(map[int64][]byte)
diff --git a/internal/runtime/executor/codex_websockets_session.go b/internal/runtime/executor/codex_websockets_session.go
index 9c721ca7..10219fc3 100644
--- a/internal/runtime/executor/codex_websockets_session.go
+++ b/internal/runtime/executor/codex_websockets_session.go
@@ -164,13 +164,17 @@ func (s *codexWebsocketSession) writeMessage(conn *websocket.Conn, msgType int,
 	return conn.WriteMessage(msgType, payload)
 }
 
-func (s *codexWebsocketSession) markMultiAgentV2Optimized(conn *websocket.Conn) {
+func (s *codexWebsocketSession) setMultiAgentV2Optimized(conn *websocket.Conn, optimized bool) {
 	if s == nil || conn == nil {
 		return
 	}
 	s.connMu.Lock()
 	if s.conn == conn {
-		s.multiAgentV2OptimizedConn = conn
+		if optimized {
+			s.multiAgentV2OptimizedConn = conn
+		} else {
+			s.multiAgentV2OptimizedConn = nil
+		}
 	}
 	s.connMu.Unlock()
 }
diff --git a/internal/runtime/executor/codex_websockets_spawn_agent_test.go b/internal/runtime/executor/codex_websockets_spawn_agent_test.go
index fc3771b6..6b3faacd 100644
--- a/internal/runtime/executor/codex_websockets_spawn_agent_test.go
+++ b/internal/runtime/executor/codex_websockets_spawn_agent_test.go
@@ -27,7 +27,7 @@ func TestCodexWebsocketsExecutorRestoresMultiAgentV2NamespaceAcrossIncrementalTu
 	} {
 		t.Run(tt.name, func(t *testing.T) {
 			upgrader := websocket.Upgrader{CheckOrigin: func(*http.Request) bool { return true }}
-			capturedPayload := make(chan []byte, 3)
+			capturedPayload := make(chan []byte, 6)
 			var connectionCount atomic.Int32
 			var requestCount atomic.Int32
 			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, request *http.Request) {
@@ -51,7 +51,7 @@ func TestCodexWebsocketsExecutorRestoresMultiAgentV2NamespaceAcrossIncrementalTu
 						t.Errorf("write websocket response: %v", errWrite)
 						return
 					}
-					if turn == 3 {
+					if turn == 6 {
 						return
 					}
 				}
@@ -126,6 +126,31 @@ func TestCodexWebsocketsExecutorRestoresMultiAgentV2NamespaceAcrossIncrementalTu
 				t.Fatalf("user-defined collaboration-optimize namespace was rewritten: %s", conflictingClientPayload)
 			}
 
+			fourthRequest := []byte(`{"model":"gpt-5.4","previous_response_id":"resp_3","input":[{"type":"function_call_output","call_id":"call_3","output":"done"}]}`)
+			fourthClientPayload := execute(fourthRequest)
+			fourthUpstreamPayload := <-capturedPayload
+			if strings.Contains(string(fourthUpstreamPayload), "collaboration") || strings.Contains(string(fourthUpstreamPayload), "spawn_agent") {
+				t.Fatalf("post-conflict incremental upstream request unexpectedly contains collaboration tools: %s", fourthUpstreamPayload)
+			}
+			if !strings.Contains(string(fourthClientPayload), `"namespace":"collaboration-optimize"`) {
+				t.Fatalf("user-defined namespace was rewritten on the post-conflict incremental turn: %s", fourthClientPayload)
+			}
+
+			fifthClientPayload := execute(codexSpawnAgentTestPayload())
+			fifthUpstreamPayload := <-capturedPayload
+			if namespace := gjson.GetBytes(fifthUpstreamPayload, "input.0.tools.0.name").String(); namespace != "collaboration-optimize" {
+				t.Fatalf("re-enabled upstream namespace = %q, want collaboration-optimize", namespace)
+			}
+			assertCodexSpawnAgentClientNamespace(t, fifthClientPayload)
+
+			sixthRequest := []byte(`{"model":"gpt-5.4","previous_response_id":"resp_5","input":[{"type":"function_call_output","call_id":"call_5","output":"done"}]}`)
+			sixthClientPayload := execute(sixthRequest)
+			sixthUpstreamPayload := <-capturedPayload
+			if strings.Contains(string(sixthUpstreamPayload), "collaboration") || strings.Contains(string(sixthUpstreamPayload), "spawn_agent") {
+				t.Fatalf("re-enabled incremental upstream request unexpectedly contains collaboration tools: %s", sixthUpstreamPayload)
+			}
+			assertCodexSpawnAgentClientNamespace(t, sixthClientPayload)
+
 			if got := connectionCount.Load(); got != 1 {
 				t.Fatalf("upstream websocket connections = %d, want 1", got)
 			}
diff --git a/internal/runtime/executor/codex_websockets_stream.go b/internal/runtime/executor/codex_websockets_stream.go
index 84ea8495..1cad7676 100644
--- a/internal/runtime/executor/codex_websockets_stream.go
+++ b/internal/runtime/executor/codex_websockets_stream.go
@@ -258,8 +258,8 @@ func (e *CodexWebsocketsExecutor) ExecuteStream(ctx context.Context, auth *clipr
 		}
 	}
 
-	if optimizeMultiAgentV2 {
-		sess.markMultiAgentV2Optimized(conn)
+	if optimizeMultiAgentV2 || multiAgentV2Conflict {
+		sess.setMultiAgentV2Optimized(conn, optimizeMultiAgentV2 && !multiAgentV2Conflict)
 	}
 
 	out := make(chan cliproxyexecutor.StreamChunk)