fix(tui): preserve Codex wheel locations

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

@@ -108,11 +108,10 @@ 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;
-    /// - Codex does not negotiate mouse reports in current releases. Once its
-    ///   input layer is up (bracketed paste — the readiness signal the pane
-    ///   reads from the emulator) 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;
+    /// - Codex accepts location-aware crossterm mouse events but does not
+    ///   negotiate mouse reports in current releases. Once its input layer is
+    ///   up, the notch is sent in SGR form so Codex receives the pane-relative
+    ///   pointer location;
     /// - another harness enables alternate scrolling without mouse reporting,
     ///   so the notch becomes cursor-key input as xterm's alternate-scroll mode
     ///   specifies;
@@ -144,15 +143,23 @@ impl LocalSessions {
                 return;
             }
         }
-        // Codex gets cursor keys only once its input layer is up: a codex that
-        // is still painting (or a shell standing in for one) has nothing to
-        // consume them, and sending them would only garble its first paint.
+        // Codex handles crossterm mouse events but currently does not emit the
+        // DECSET sequence that would make `mouse_protocol` select the branch
+        // above. Bracketed paste is its input-readiness signal: before then a
+        // report could only garble the first paint. SGR is deliberate because
+        // it carries coordinates; the old arrow-key fallback moved composer
+        // history and discarded where the wheel event happened.
         let codex = self
             .sessions
             .row(session_id)
             .is_some_and(|row| row.provider == medulla::protocol::HarnessProvider::Codex)
             && self.sessions.bracketed_paste(session_id) == Some(true);
-        if codex || self.sessions.alternate_scroll(session_id) == Some(true) {
+        if codex {
+            let bytes = mouse::sgr_wheel(col, row, up);
+            let _ = self.sessions.write(session_id, &bytes);
+            return;
+        }
+        if 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/mouse.rs

@@ -144,6 +144,21 @@ fn sgr(button: u8, col: u16, row: u16, press: bool) -> Vec<u8> {
     .into_bytes()
 }
 
+/// Encode a location-aware SGR wheel report without relying on negotiated mode.
+///
+/// Codex accepts crossterm mouse events but does not currently ask its terminal
+/// to enable mouse reporting. The provider-specific fallback uses this after
+/// its input layer is known to be ready, preserving the pointer coordinates
+/// that cursor-key emulation necessarily loses.
+pub(super) fn sgr_wheel(col: u16, row: u16, up: bool) -> Vec<u8> {
+    let button = if up {
+        BUTTON_WHEEL_UP
+    } else {
+        BUTTON_WHEEL_DOWN
+    };
+    sgr(button, col, row, true)
+}
+
 /// A normal (X10) report: `ESC [ M Cb Cx Cy`, every field a byte offset by 32.
 fn normal(button: u8, col: u16, row: u16) -> Vec<u8> {
     // Widened before the `+ 1`, not after. The clamp below bounds the *result*,
@@ -194,7 +209,7 @@ pub fn wheel(
     Some(match encoding {
         // A wheel notch has no release, so there is no matching `m` report to
         // send after it — it is always encoded as a press.
-        MouseProtocolEncoding::Sgr => sgr(button, col, row, true),
+        MouseProtocolEncoding::Sgr => sgr_wheel(col, row, up),
         // UTF-8 encoding (DECSET 1005) is a dead end almost nothing negotiates,
         // and its multi-byte coordinates decode ambiguously. Treating it as the
         // normal encoding is what xterm-compatible terminals do for the low

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

@@ -297,12 +297,13 @@ fn alternate_scroll_without_mouse_reporting_gets_arrow_scroll_events() {
 }
 
 #[test]
-fn codex_without_mouse_or_alternate_scroll_gets_arrow_scroll_events() {
+fn codex_without_negotiated_mouse_mode_gets_location_aware_wheel_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.
+    // Current Codex releases enable bracketed paste and handle crossterm mouse
+    // events, but do not ask their terminal to enable mouse reporting. Preserve
+    // the pointer location by sending the SGR event Codex can already decode;
+    // cursor-key fallback would operate prompt history and discard (3,4).
     let id = sessions
         .open(sh(
             "printf '\\033[?2004hready'; sleep 0.3; cat -v; sleep 30",
@@ -320,9 +321,14 @@ fn codex_without_mouse_or_alternate_scroll_gets_arrow_scroll_events() {
 
     harnesses.scroll(&id, 3, 4, true, 3);
 
-    wait_for("Codex to receive translated wheel input", || {
-        text(&harnesses, &id).contains("^[[A^[[A^[[A")
+    wait_for("Codex to receive a location-aware wheel event", || {
+        text(&harnesses, &id).contains("[<64;4;5M")
     });
+    let out = text(&harnesses, &id);
+    assert!(
+        !out.contains("^[[A"),
+        "wheel must not navigate history: {out}"
+    );
     sessions.close(&id);
 }