fix(tui): restore Codex harness scrolling

src/tui/src/ui/harness_pane/mod.rs

@@ -98,7 +98,10 @@ impl LocalSessions {
     ///   the notch is forwarded and *its* scrollback moves — which is the one
     ///   the operator means, because it holds the whole conversation rather than
     ///   the last screenful the emulator happened to retain;
-    /// - the harness enables alternate scrolling without mouse reporting (Codex),
+    /// - Codex does not negotiate mouse reports in current releases. Its TUI
+    ///   consumes cursor keys to move through the transcript, so a notch becomes
+    ///   cursor-key input even when it does not advertise alternate scrolling;
+    /// - another harness enables alternate scrolling without mouse reporting,
     ///   so the notch becomes cursor-key input as xterm's alternate-scroll mode
     ///   specifies;
     /// - otherwise our emulator's own retained lines move instead. Not as good,
@@ -118,7 +121,11 @@ impl LocalSessions {
                 return;
             }
         }
-        if self.sessions.alternate_scroll(session_id) == Some(true) {
+        let codex = self
+            .sessions
+            .row(session_id)
+            .is_some_and(|row| row.provider == medulla::protocol::HarnessProvider::Codex);
+        if codex || self.sessions.alternate_scroll(session_id) == Some(true) {
             let arrow = if up { b"\x1b[A" } else { b"\x1b[B" };
             let mut bytes = Vec::with_capacity(arrow.len() * rows);
             for _ in 0..rows {

src/tui/src/ui/harness_pane/tests/session.rs

@@ -29,13 +29,18 @@ use super::super::LocalSessions;
 /// `--session-id`, which `/bin/sh` would reject as an unknown option. Codex
 /// takes no preset id, so its argv is empty and the script is the whole command.
 pub(super) fn sh(script: &str) -> LaunchSpec {
+    sh_for(HarnessProvider::Codex, script)
+}
+
+/// A shell PTY carrying `provider` metadata for provider-specific input tests.
+fn sh_for(provider: HarnessProvider, script: &str) -> LaunchSpec {
     let mut env = HashMap::new();
     if let Ok(path) = std::env::var("PATH") {
         env.insert("PATH".to_string(), path);
     }
     env.insert("TERM".to_string(), "xterm-256color".to_string());
     LaunchSpec {
-        provider: HarnessProvider::Codex,
+        provider,
         preset: None,
         bin: "/bin/sh".to_string(),
         cwd: "/".to_string(),
@@ -291,6 +296,36 @@ fn alternate_scroll_without_mouse_reporting_gets_arrow_scroll_events() {
     sessions.close(&id);
 }
 
+#[test]
+fn codex_without_mouse_or_alternate_scroll_gets_arrow_scroll_events() {
+    let sessions = PtyManager::new();
+    let harnesses = harnesses(sessions.clone());
+    // Current Codex releases enable bracketed paste and enhanced keyboard input,
+    // but no longer advertise DECSET 1007. The provider still expects wheel
+    // scrolling to reach its transcript as cursor keys.
+    let id = sessions
+        .open(sh(
+            "printf '\\033[?2004hready'; sleep 0.3; cat -v; sleep 30",
+        ))
+        .unwrap();
+
+    wait_for("the Codex stand-in to become ready", || {
+        text(&harnesses, &id).contains("ready")
+    });
+    assert_eq!(sessions.alternate_scroll(&id), Some(false));
+    assert!(matches!(
+        sessions.mouse_protocol(&id),
+        Some((vt100::MouseProtocolMode::None, _))
+    ));
+
+    harnesses.scroll(&id, 3, 4, true, 3);
+
+    wait_for("Codex to receive translated wheel input", || {
+        text(&harnesses, &id).contains("^[[A^[[A^[[A")
+    });
+    sessions.close(&id);
+}
+
 #[test]
 fn alternate_screen_without_alternate_scroll_does_not_receive_arrows() {
     let sessions = PtyManager::new();
@@ -321,7 +356,8 @@ fn a_child_that_never_asked_for_the_mouse_gets_our_scrollback_instead() {
     let harnesses = harnesses(sessions.clone());
     // Enough lines to push history off a 30-row screen, and no mouse reporting.
     let id = sessions
-        .open(sh(
+        .open(sh_for(
+            HarnessProvider::Claude,
             "i=1; while [ $i -le 200 ]; do echo line-$i; i=$((i+1)); done; sleep 30",
         ))
         .unwrap();