diff --git a/src/computer.rs b/src/computer.rs
index dddc149..33ef2d3 100644
--- a/src/computer.rs
+++ b/src/computer.rs
@@ -430,6 +430,20 @@ pub fn ask_permission(pane: &str) {
     let _ = spawn_reaped(&mut std::process::Command::new("open").arg(format!("x-apple.systempreferences:com.apple.preference.security?{pane}")));
 }
 
+const NO_ACCESSIBILITY: &str = "macOS 還沒讓 AnyBot 使用「輔助使用」，所以讀不到、也按不了這台電腦上的 App。這台電腦上已經跳出詢問並打開「系統設定 → 隱私權與安全性 → 輔助使用」：請使用者把 AnyBot 打開（只要一次），再叫我試一次。";
+
+/// agent-desktop's PERM_DENIED (no 輔助使用), as words the bot can pass on — and the person asked.
+fn plain_permission_words(t: String) -> String {
+    if !t.contains("PERM_DENIED") {
+        return t;
+    }
+    ask_permission("Privacy_Accessibility");
+    match t.split_once("，但讀不到它的畫面") {
+        Some((opened, _)) => format!("{opened}，但讀不到它的畫面：{NO_ACCESSIBILITY}"),
+        None => NO_ACCESSIBILITY.to_string(),
+    }
+}
+
 /// The app a shown name stands for (「計算機」 → Calculator), from the apps' display names.
 #[cfg(target_os = "macos")]
 fn app_named(name: &str) -> Option<String> {
@@ -503,8 +517,16 @@ fn run_inner(name: &str, v: &Value) -> Result<(String, Option<String>), String>
             return Err("使用者正在自己操作這台電腦（已取得控制權）。請等他交還控制權後再操作。".into());
         }
     }
+    // Reading and using apps by their controls needs 輔助使用: without it macOS answers
+    // PERM_DENIED and nobody was asked. Ask (prompt + the Settings pane, now and then) and say it
+    // plainly; opening an app still opens it.
+    let by_controls = name == "computer_use_read_app" || run_text_mode_name(name, v).is_some();
+    if cfg!(target_os = "macos") && by_controls && name != "computer_use_open_app" && !crate::axread::trusted(false) {
+        ask_permission("Privacy_Accessibility");
+        return Err(NO_ACCESSIBILITY.into());
+    }
     if let Some(r) = run_text_mode(name, v) {
-        return r;
+        return r.map(|(t, img)| (plain_permission_words(t), img)).map_err(plain_permission_words);
     }
     if !cfg!(any(target_os = "macos", target_os = "linux")) {
         return Err("操作畫面只支援 macOS 和 Linux".into());