From 36dcb891b02c887f8635d42fc8ccc115a590253a Mon Sep 17 00:00:00 2001
From: Charles Packer <packercharles@gmail.com>
Date: Sun, 4 Jan 2026 19:19:34 -0800
Subject: [PATCH] fix: patch release event leaks (#463)

Co-authored-by: Letta <noreply@letta.com>
---
 src/cli/components/PasteAwareTextInput.tsx | 33 ++++------------------
 src/cli/utils/kittyProtocolDetector.ts     | 11 +++++---
 2 files changed, 13 insertions(+), 31 deletions(-)

diff --git a/src/cli/components/PasteAwareTextInput.tsx b/src/cli/components/PasteAwareTextInput.tsx
index ceed5a3..7b2cf17 100644
--- a/src/cli/components/PasteAwareTextInput.tsx
+++ b/src/cli/components/PasteAwareTextInput.tsx
@@ -461,42 +461,21 @@ export function PasteAwareTextInput({
       // in use-input.js, which parses it as return + shift/ctrl/meta flags.
       // The useInput handler at line 186 then handles the newline insertion.
 
-      // Kitty keyboard protocol: Arrow keys
-      // Format: ESC[1;modifier:event_typeX where X is A/B/C/D for up/down/right/left
-      // Event types: 1=press, 2=repeat, 3=release
-      // Handle press AND repeat events, ignore release
-      {
-        // Match ESC[1;N:1X or ESC[1;N:2X (press or repeat)
-        // biome-ignore lint/suspicious/noControlCharactersInRegex: ESC sequence matching
-        const arrowMatch = sequence.match(/^\x1b\[1;\d+:[12]([ABCD])$/);
-        if (arrowMatch) {
-          // Emit standard arrow key sequence
-          internal_eventEmitter.emit("input", `\x1b[${arrowMatch[1]}`);
-          return;
-        }
-        // Ignore arrow key release events only
-        // biome-ignore lint/suspicious/noControlCharactersInRegex: ESC sequence matching
-        if (/^\x1b\[1;\d+:3[ABCD]$/.test(sequence)) {
-          return;
-        }
-      }
+      // Note: Arrow keys with modifiers are now handled natively by parseKeypress
+      // since we use kitty protocol flag 1 only (no event types).
+      // With flag 1, arrows come as ESC[1;modifierD which parseKeypress recognizes.
+      // Previously we handled ESC[1;modifier:eventD format (with flag 7) here.
 
       // fn+Delete (forward delete): ESC[3~ - standard ANSI escape sequence
-      // Also handle kitty extended format: ESC[3;modifier:event_type~
-      // Event types: 1=press, 2=repeat, 3=release
+      // With kitty flag 1, modifiers come as ESC[3;modifier~ (no event type).
       // Use caretOffsetRef which is updated synchronously via onCursorOffsetChange
       // biome-ignore lint/suspicious/noControlCharactersInRegex: ESC sequence matching
-      if (sequence === "\x1b[3~" || /^\x1b\[3;\d+:[12]~$/.test(sequence)) {
+      if (sequence === "\x1b[3~" || /^\x1b\[3;\d+~$/.test(sequence)) {
         // Set timestamp so ink-text-input skips its delete handling
         globalThis.__lettaForwardDeleteTimestamp = Date.now();
         forwardDeleteAtCursor(caretOffsetRef.current);
         return;
       }
-      // Ignore forward delete release events
-      // biome-ignore lint/suspicious/noControlCharactersInRegex: ESC sequence matching
-      if (/^\x1b\[3;\d+:3~$/.test(sequence)) {
-        return;
-      }
 
       // Option+Delete sequences (check first as they're exact matches)
       // - iTerm2/some terminals: ESC + DEL (\x1b\x7f)
diff --git a/src/cli/utils/kittyProtocolDetector.ts b/src/cli/utils/kittyProtocolDetector.ts
index c82e05b..23530fd 100644
--- a/src/cli/utils/kittyProtocolDetector.ts
+++ b/src/cli/utils/kittyProtocolDetector.ts
@@ -137,10 +137,13 @@ export function isKittyProtocolEnabled(): boolean {
 
 function enableKittyKeyboardProtocol() {
   try {
-    // Enable keyboard progressive enhancement flags.
-    // Use 7 (=1|2|4): DISAMBIGUATE_ESCAPE_CODES | REPORT_EVENT_TYPES | REPORT_ALTERNATE_KEYS
-    // This matches what crossterm-based TUIs (e.g., codex) request.
-    fs.writeSync(process.stdout.fd, "\x1b[>7u");
+    // Enable keyboard progressive enhancement with flag 1 (DISAMBIGUATE_ESCAPE_CODES) only.
+    // Previously used flag 7 (1|2|4) but flag 2 (REPORT_EVENT_TYPES) causes release events
+    // that leak into input when typing fast in iTerm2/Kitty/etc.
+    // Flag 4 (REPORT_ALTERNATE_KEYS) provides data we don't use.
+    // Gemini CLI uses flag 1 only - this is the proven approach.
+    // See: .notes/csi-u-release-events-fix.md for full analysis.
+    fs.writeSync(process.stdout.fd, "\x1b[>1u");
     kittyEnabled = true;
   } catch {
     // Ignore errors