diff --git a/src/agent.rs b/src/agent.rs
index 9ed48f7..9431d81 100644
--- a/src/agent.rs
+++ b/src/agent.rs
@@ -1152,7 +1152,7 @@ pub fn spawn(job: Job, bot_id: u64, tx: Sender<(u64, StreamEvent)>, cancel: Arc<
                 // any picture, shown and kept.
                 let finish = |history: &mut Vec<Message>, output: &str, status: ToolStatus, image: Option<String>| {
                     // A click that changed nothing on the screen is trouble too, though it "worked".
-                    if matches!(status, ToolStatus::Failed | ToolStatus::Denied) || !repeat_note.is_empty() || output.contains("畫面和上一步完全一樣") {
+                    if matches!(status, ToolStatus::Failed | ToolStatus::Denied) || !repeat_note.is_empty() || output.contains(crate::computer::NOOP_TAG) {
                         trouble.set(true);
                     }
                     job.note(crate::oplog::Record::ToolFinished { op: job.op.clone(), call_id: call.id.clone(), status: format!("{status:?}").to_lowercase() });
diff --git a/src/cloudbox.rs b/src/cloudbox.rs
index 5820617..d490457 100644
--- a/src/cloudbox.rs
+++ b/src/cloudbox.rs
@@ -2085,7 +2085,7 @@ fn box_look(script: Option<&str>, after: Option<String>, pointer: bool) -> Resul
         same
     };
     if unchanged {
-        text.push_str("\n⚠️ 畫面和上一步完全一樣：這一步沒有點到東西。不要再做同一步；換一個編號、換一個方法（網頁用 browser_* 工具，或直接開網址），或用 hand_over_computer 請使用者幫忙。");
+        text.push_str(crate::computer::NOOP_NOTE);
     }
     if lines.is_empty() {
         text.push_str("\n畫面上沒有可以照編號點的東西：只好照圖上的位置點 x、y。");
diff --git a/src/computer.rs b/src/computer.rs
index de3435d..c511067 100644
--- a/src/computer.rs
+++ b/src/computer.rs
@@ -220,6 +220,12 @@ pub fn is_pointer_step(name: &str) -> bool {
     matches!(name, "computer_use_click" | "computer_use_scroll" | "computer_use_drag")
 }
 
+/// The screen-did-not-change note. The sentence is for the model; the tag at the end is for
+/// the harness (agent.rs): control flow matches the TAG, never the words (a wording change
+/// used to silently turn off the whole "same click did nothing" guard).
+pub const NOOP_TAG: &str = "[[noop]]";
+pub const NOOP_NOTE: &str = "\n⚠️ 畫面和上一步完全一樣：這一步沒有點到東西。不要再做同一步；換一個編號、換一個方法（網頁用 browser_* 工具，或直接開網址），或用 hand_over_computer 請使用者幫忙。[[noop]]";
+
 /// What the bot is told after computer_use_show (the picture itself goes into the chat).
 pub const SHOWN_NOTE: &str = "已把這台電腦現在的畫面（使用者看到的樣子，沒有編號）放進聊天，使用者看得到這張圖；你也看得到，可以用一兩句話說明畫面上有什麼";
 
@@ -1147,7 +1153,7 @@ fn look(after: Option<String>, pointer: bool) -> Result<(String, Option<String>)
         same
     };
     if unchanged {
-        text.push_str("\n⚠️ 畫面和上一步完全一樣：這一步沒有點到東西。不要再做同一步；換一個編號、換一個方法（網頁用 browser_* 工具，或直接開網址），或用 hand_over_computer 請使用者幫忙。");
+        text.push_str(crate::computer::NOOP_NOTE);
     }
     if hidden > 0 {
         text.push_str(&format!("\n（「{app}」有 {hidden} 個按鈕被別的視窗擋住或不在這個桌面，沒有編號：先 computer_use_open_app 把它叫到前面。）"));
@@ -1772,6 +1778,12 @@ mod mac {
 mod tests {
     use super::*;
 
+    #[test]
+    fn the_noop_note_carries_its_tag() {
+        // The harness matches NOOP_TAG; the sentence may be reworded, the tag may not drift.
+        assert!(NOOP_NOTE.contains(NOOP_TAG));
+    }
+
     /// Keys wait when the app in front isn't the one of the latest look (no real key is pressed
     /// here: the check refuses before anything is sent, or there is no front app at all).
     #[test]