Fix: add back fastreturn support (#16440)

packages/cli/src/ui/contexts/KeypressContext.tsx

@@ -19,6 +19,7 @@ import { ESC } from '../utils/input.js';
 import { parseMouseEvent } from '../utils/mouse.js';
 import { FOCUS_IN, FOCUS_OUT } from '../hooks/useFocus.js';
 import { appEvents, AppEvent } from '../../utils/events.js';
+import { terminalCapabilityManager } from '../utils/terminalCapabilityManager.js';
 
 export const BACKSLASH_ENTER_TIMEOUT = 5;
 export const ESC_TIMEOUT = 50;
@@ -143,6 +144,30 @@ function nonKeyboardEventFilter(
   };
 }
 
+/**
+ * Converts return keys pressed quickly after other keys into plain
+ * insertable return characters.
+ *
+ * This is to accommodate older terminals that paste text without bracketing.
+ */
+function bufferFastReturn(keypressHandler: KeypressHandler): KeypressHandler {
+  let lastKeyTime = 0;
+  return (key: Key) => {
+    const now = Date.now();
+    if (key.name === 'return' && now - lastKeyTime <= FAST_RETURN_TIMEOUT) {
+      keypressHandler({
+        ...key,
+        name: '',
+        sequence: '\r',
+        insertable: true,
+      });
+    } else {
+      keypressHandler(key);
+    }
+    lastKeyTime = now;
+  };
+}
+
 /**
  * Buffers "/" keys to see if they are followed return.
  * Will flush the buffer if no data is received for DRAG_COMPLETION_TIMEOUT_MS
@@ -641,6 +666,9 @@ export function KeypressProvider({
     process.stdin.setEncoding('utf8'); // Make data events emit strings
 
     let processor = nonKeyboardEventFilter(broadcast);
+    if (!terminalCapabilityManager.isKittyProtocolEnabled()) {
+      processor = bufferFastReturn(processor);
+    }
     processor = bufferBackslashEnter(processor);
     processor = bufferPaste(processor);
     let dataListener = createDataListener(processor);