From 93a210b420af39d64329f3f3831e39e297cd8ac4 Mon Sep 17 00:00:00 2001
From: Codex <codex@palav.dev>
Date: Thu, 11 Jun 2026 16:11:56 -0400
Subject: [PATCH] Normalize application cursor arrows

---
 src/bin/dosh-client.rs | 78 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)

diff --git a/src/bin/dosh-client.rs b/src/bin/dosh-client.rs
index e7430c1..4eca73b 100644
--- a/src/bin/dosh-client.rs
+++ b/src/bin/dosh-client.rs
@@ -555,6 +555,7 @@ async fn run_terminal(
     let mut status_tick = tokio::time::interval(Duration::from_secs(1));
     let mut resize_tick = tokio::time::interval(Duration::from_millis(250));
     let mut last_size = size().unwrap_or((80, 24));
+    let mut input_normalizer = InputNormalizer::default();
     if let Some(frame) = first_frame {
         render_frame(&frame)?;
         if frame.closed {
@@ -591,6 +592,7 @@ async fn run_terminal(
                             break;
                         }
                         if cred.mode != "view-only" {
+                            let bytes = input_normalizer.normalize(&bytes);
                             let body = protocol::to_body(&Input { bytes })?;
                             let packet = protocol::encode_encrypted(
                                 PacketKind::Input,
@@ -673,6 +675,54 @@ async fn run_terminal(
     Ok(())
 }
 
+#[derive(Default)]
+struct InputNormalizer {
+    state: InputNormalizerState,
+}
+
+#[derive(Default)]
+enum InputNormalizerState {
+    #[default]
+    Ground,
+    Esc,
+    Ss3,
+}
+
+impl InputNormalizer {
+    fn normalize(&mut self, bytes: &[u8]) -> Vec<u8> {
+        let mut out = Vec::with_capacity(bytes.len());
+        for &byte in bytes {
+            match self.state {
+                InputNormalizerState::Ground => {
+                    out.push(byte);
+                    if byte == 0x1b {
+                        self.state = InputNormalizerState::Esc;
+                    }
+                }
+                InputNormalizerState::Esc => {
+                    if byte == b'O' {
+                        self.state = InputNormalizerState::Ss3;
+                    } else {
+                        out.push(byte);
+                        self.state = InputNormalizerState::Ground;
+                    }
+                }
+                InputNormalizerState::Ss3 => {
+                    if matches!(byte, b'A'..=b'D') {
+                        out.push(b'[');
+                        out.push(byte);
+                    } else {
+                        out.push(b'O');
+                        out.push(byte);
+                    }
+                    self.state = InputNormalizerState::Ground;
+                }
+            }
+        }
+        out
+    }
+}
+
 async fn send_resize(
     socket: &UdpSocket,
     addr: SocketAddr,
@@ -813,3 +863,31 @@ const TERMINAL_CLEANUP: &[u8] = concat!(
     "\x1b[?1049l"
 )
 .as_bytes();
+
+#[cfg(test)]
+mod tests {
+    use super::InputNormalizer;
+
+    #[test]
+    fn normalizes_ss3_cursor_keys_to_csi() {
+        let mut normalizer = InputNormalizer::default();
+        assert_eq!(normalizer.normalize(b"\x1bOA"), b"\x1b[A");
+        assert_eq!(normalizer.normalize(b"\x1bOB"), b"\x1b[B");
+        assert_eq!(normalizer.normalize(b"\x1bOC"), b"\x1b[C");
+        assert_eq!(normalizer.normalize(b"\x1bOD"), b"\x1b[D");
+    }
+
+    #[test]
+    fn preserves_split_ss3_cursor_state_between_reads() {
+        let mut normalizer = InputNormalizer::default();
+        assert_eq!(normalizer.normalize(b"\x1b"), b"\x1b");
+        assert_eq!(normalizer.normalize(b"O"), b"");
+        assert_eq!(normalizer.normalize(b"B"), b"[B");
+    }
+
+    #[test]
+    fn leaves_non_cursor_ss3_sequences_raw() {
+        let mut normalizer = InputNormalizer::default();
+        assert_eq!(normalizer.normalize(b"\x1bOP"), b"\x1bOP");
+    }
+}