fix: honor droid scrollback clear requests in panes (#4432)

Remove the droid-specific filter that discarded ED3 before PTY output
reached the terminal parser. Keeping stale scrollback beneath replayed
primary-screen frames duplicated the welcome header and old transcript.

Pass the original bytes to the parser and trackers. Add process-aware
regression coverage across PTY chunk boundaries and preserve ED2/ED3
screen-history separation and alternate-screen isolation.

Co-authored-by: ain3sh <ainesh.chatterjee@gmail.com>
Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>
Co-authored-by: JJ Liebig <jonathan.liebig@gmail.com>

3 files changed, 135 insertions, 174 deletions

diff --git a/src/pane/osc.rs b/src/pane/osc.rs
index a281af77..472fa7aa 100644
--- a/src/pane/osc.rs
+++ b/src/pane/osc.rs
@@ -1,4 +1,3 @@
-use std::borrow::Cow;
 use std::path::PathBuf;
 
 use tracing::info;
@@ -695,68 +694,6 @@ pub(super) fn current_transient_default_color_owner(shell_pid: u32) -> Option<u3
     (!foreground_job_is_shell(&job, shell_pid)).then_some(job.process_group_id)
 }
 
-fn foreground_job_uses_droid_scrollback_compat(job: &crate::platform::ForegroundJob) -> bool {
-    job.processes.iter().any(|process| {
-        process.name.eq_ignore_ascii_case("droid")
-            || process
-                .argv0
-                .as_deref()
-                .is_some_and(|argv0| argv0.eq_ignore_ascii_case("droid"))
-            || process.cmdline.as_deref().is_some_and(|cmdline| {
-                cmdline.eq_ignore_ascii_case("droid")
-                    || cmdline.starts_with("droid ")
-                    || cmdline.to_ascii_lowercase().contains("/droid")
-            })
-    })
-}
-
-pub(super) fn contains_scrollback_clear_sequence(bytes: &[u8]) -> bool {
-    bytes.windows(4).any(|window| window == b"\x1b[3J")
-        || bytes.windows(5).any(|window| window == b"\x1b[?3J")
-}
-
-fn strip_scrollback_clear_sequences<'a>(bytes: &'a [u8]) -> Cow<'a, [u8]> {
-    if !contains_scrollback_clear_sequence(bytes) {
-        return Cow::Borrowed(bytes);
-    }
-
-    let mut filtered = Vec::with_capacity(bytes.len());
-    let mut index = 0;
-    while index < bytes.len() {
-        let remaining = &bytes[index..];
-        if remaining.starts_with(b"\x1b[3J") {
-            index += 4;
-            continue;
-        }
-        if remaining.starts_with(b"\x1b[?3J") {
-            index += 5;
-            continue;
-        }
-        filtered.push(bytes[index]);
-        index += 1;
-    }
-
-    Cow::Owned(filtered)
-}
-
-pub(super) fn maybe_filter_primary_screen_scrollback_clear<'a>(
-    bytes: &'a [u8],
-    alternate_screen: bool,
-    foreground_job: Option<&crate::platform::ForegroundJob>,
-) -> Cow<'a, [u8]> {
-    // Droid redraws its primary-screen TUI with CSI 3 J, which erases pane
-    // scrollback inside herdr. Keep the hack scoped to Droid on the primary
-    // screen so normal terminal clear-history behavior still works elsewhere.
-    if alternate_screen
-        || !contains_scrollback_clear_sequence(bytes)
-        || !foreground_job.is_some_and(foreground_job_uses_droid_scrollback_compat)
-    {
-        return Cow::Borrowed(bytes);
-    }
-
-    strip_scrollback_clear_sequences(bytes)
-}
-
 #[cfg(target_os = "macos")]
 pub(super) fn should_restore_host_terminal_theme(
     owner_pgid: u32,
@@ -1351,81 +1288,6 @@ mod tests {
     }
 
     #[test]
-    fn droid_scrollback_compat_matches_process_name_and_cmdline() {
-        let name_only = crate::platform::ForegroundJob {
-            process_group_id: 42,
-            processes: vec![crate::platform::ForegroundProcess {
-                pid: 42,
-                name: "droid".to_string(),
-                argv0: None,
-                argv: Some(vec![
-                    "/opt/factory/droid".to_string(),
-                    "--resume".to_string(),
-                ]),
-                cmdline: Some("/opt/factory/droid --resume".to_string()),
-            }],
-        };
-        assert!(foreground_job_uses_droid_scrollback_compat(&name_only));
-
-        let cmdline_only = crate::platform::ForegroundJob {
-            process_group_id: 42,
-            processes: vec![crate::platform::ForegroundProcess {
-                pid: 42,
-                name: "bun".to_string(),
-                argv0: Some("bun".to_string()),
-                argv: Some(vec![
-                    "bun".to_string(),
-                    "/home/can/.local/bin/droid".to_string(),
-                    "--resume".to_string(),
-                ]),
-                cmdline: Some("/home/can/.local/bin/droid --resume".to_string()),
-            }],
-        };
-        assert!(foreground_job_uses_droid_scrollback_compat(&cmdline_only));
-
-        let shell = shell_job(7);
-        assert!(!foreground_job_uses_droid_scrollback_compat(&shell));
-    }
-
-    #[test]
-    fn strip_scrollback_clear_sequences_removes_ed3_only() {
-        let filtered = strip_scrollback_clear_sequences(b"a\x1b[3Jb\x1b[?3Jc\x1b[2Jd");
-        assert_eq!(filtered.as_ref(), b"abc\x1b[2Jd");
-    }
-
-    #[test]
-    fn primary_screen_droid_compat_ignores_scrollback_clear_only_for_droid() {
-        let droid_job = crate::platform::ForegroundJob {
-            process_group_id: 42,
-            processes: vec![crate::platform::ForegroundProcess {
-                pid: 42,
-                name: "droid".to_string(),
-                argv0: Some("droid".to_string()),
-                argv: Some(vec!["droid".to_string()]),
-                cmdline: Some("droid".to_string()),
-            }],
-        };
-
-        let filtered = maybe_filter_primary_screen_scrollback_clear(
-            b"\x1b[3J\x1b[2J",
-            false,
-            Some(&droid_job),
-        );
-        assert_eq!(filtered.as_ref(), b"\x1b[2J");
-
-        let shell = maybe_filter_primary_screen_scrollback_clear(
-            b"\x1b[3J\x1b[2J",
-            false,
-            Some(&shell_job(7)),
-        );
-        assert_eq!(shell.as_ref(), b"\x1b[3J\x1b[2J");
-
-        let alternate =
-            maybe_filter_primary_screen_scrollback_clear(b"\x1b[3J\x1b[2J", true, Some(&droid_job));
-        assert_eq!(alternate.as_ref(), b"\x1b[3J\x1b[2J");
-    }
-
-    #[test]
     fn host_theme_restore_waits_for_shell_and_non_alternate_screen() {
         assert!(!should_restore_host_terminal_theme(
             42,
diff --git a/src/pane/terminal.rs b/src/pane/terminal.rs
index c30ef415..c9d0b90a 100644
--- a/src/pane/terminal.rs
+++ b/src/pane/terminal.rs
@@ -1,4 +1,3 @@
-use std::borrow::Cow;
 use std::collections::hash_map::DefaultHasher;
 use std::hash::{Hash, Hasher};
 use std::sync::{Arc, Mutex};
@@ -33,8 +32,7 @@ use super::{
     },
     kitty_keyboard::KittyKeyboardTracker,
     osc::{
-        contains_scrollback_clear_sequence, current_transient_default_color_owner,
-        maybe_filter_primary_screen_scrollback_clear, parse_reported_cwd,
+        current_transient_default_color_owner, parse_reported_cwd,
         restore_host_terminal_theme_if_needed, write_host_terminal_theme_selective,
         AgentOscStateTracker, DefaultColorEvent, DefaultColorEventTracker, DefaultColorOscTracker,
         DefaultColorQuery, DefaultColorTrackedEvent, OscDebugTracker,
@@ -1381,43 +1379,18 @@ impl GhosttyPaneTerminal {
         }
         let terminal_title_changed = core.agent_osc_state.observe(bytes);
 
-        let alternate_screen = core
-            .terminal
-            .active_screen()
-            .map(|screen| screen == crate::ghostty::ActiveScreen::Alternate)
-            .unwrap_or(false);
-        let filtered_bytes = if shell_pid > 0 {
-            let foreground_job = (!alternate_screen && contains_scrollback_clear_sequence(bytes))
-                .then(|| crate::detect::foreground_job(shell_pid))
-                .flatten();
-            maybe_filter_primary_screen_scrollback_clear(
-                bytes,
-                alternate_screen,
-                foreground_job.as_ref(),
-            )
-        } else {
-            Cow::Borrowed(bytes)
-        };
-        if filtered_bytes.len() != bytes.len() {
-            debug!(
-                pane = pane_id.raw(),
-                shell_pid, "ignored scrollback clear sequence for droid compatibility"
-            );
-        }
-
-        core.kitty_keyboard.observe(filtered_bytes.as_ref());
+        core.kitty_keyboard.observe(bytes);
         let mut terminal_responses = Vec::new();
-        core.default_color_event_tracker
-            .observe(filtered_bytes.as_ref());
-        core.c1_xtgettcap_tracker.observe(filtered_bytes.as_ref());
+        core.default_color_event_tracker.observe(bytes);
+        core.c1_xtgettcap_tracker.observe(bytes);
         let c1_xtgettcap_responses = core.c1_xtgettcap_tracker.drain_pending();
-        core.decscusr_tracker.observe(filtered_bytes.as_ref());
+        core.decscusr_tracker.observe(bytes);
         let in_progress_default_color_event = core.default_color_event_tracker.in_progress_event();
         let default_color_events = core.default_color_event_tracker.drain_pending();
         let write_started = crate::render_prof::timer();
         self.write_pty_bytes_with_ordered_responses(
             &mut core,
-            filtered_bytes.as_ref(),
+            bytes,
             default_color_events,
             in_progress_default_color_event,
             c1_xtgettcap_responses,
@@ -1435,8 +1408,8 @@ impl GhosttyPaneTerminal {
         windows_recent_fallback::update_after_write(&mut core);
         crate::render_prof::duration_since("pty.ghostty_write", write_started);
 
-        let has_kitty_graphics_sequence = crate::kitty_graphics::is_enabled()
-            && contains_kitty_graphics_sequence(filtered_bytes.as_ref());
+        let has_kitty_graphics_sequence =
+            crate::kitty_graphics::is_enabled() && contains_kitty_graphics_sequence(bytes);
         if has_kitty_graphics_sequence {
             debug!(pane = pane_id.raw(), "processed kitty graphics sequence");
         }
diff --git a/src/pane/terminal/migration_tests.rs b/src/pane/terminal/migration_tests.rs
index 94d78a77..09e5df01 100644
--- a/src/pane/terminal/migration_tests.rs
+++ b/src/pane/terminal/migration_tests.rs
@@ -46,9 +46,13 @@ impl Harness {
     }
 
     fn write(&mut self, bytes: &[u8]) {
+        self.write_from_process(0, bytes);
+    }
+
+    fn write_from_process(&mut self, shell_pid: u32, bytes: &[u8]) {
         let result = self
             .pane
-            .process_pty_bytes(PaneId::from_raw(1), 0, bytes, &self.tx);
+            .process_pty_bytes(PaneId::from_raw(1), shell_pid, bytes, &self.tx);
         for reply in result.terminal_responses {
             self.effects.replies.extend_from_slice(&reply);
         }
@@ -111,6 +115,128 @@ impl Harness {
     }
 }
 
+#[cfg(target_os = "linux")]
+#[test]
+fn primary_screen_replay_honors_ed3_for_droid_at_chunk_boundaries() {
+    // A zero PID would bypass the former process-specific filter entirely.
+    // Use the real foreground-job lookup, with cleanup even on assertion failure.
+    struct ChildGuard(Box<dyn portable_pty::Child + Send + Sync>);
+    impl Drop for ChildGuard {
+        fn drop(&mut self) {
+            let _ = self.0.kill();
+            let _ = self.0.wait();
+        }
+    }
+    let pair = portable_pty::native_pty_system()
+        .openpty(portable_pty::PtySize {
+            rows: 24,
+            cols: 80,
+            pixel_width: 0,
+            pixel_height: 0,
+        })
+        .unwrap();
+    let mut command = portable_pty::CommandBuilder::new("bash");
+    command.args(["-c", "exec -a droid sleep 999"]);
+    let child = ChildGuard(pair.slave.spawn_command(command).unwrap());
+    let pid = child.0.process_id().unwrap();
+    let deadline = Instant::now() + Duration::from_secs(5);
+    loop {
+        let ready = crate::detect::foreground_job(pid).is_some_and(|job| {
+            job.processes
+                .iter()
+                .any(|process| process.cmdline.as_deref() == Some("droid 999"))
+        });
+        if ready {
+            break;
+        }
+        assert!(Instant::now() < deadline, "Droid foreground job not ready");
+        std::thread::sleep(Duration::from_millis(10));
+    }
+
+    for clear in ["\x1b[3J", "\x1b[?3J"] {
+        let prefix = format!("\x1b[?2026h\x1b[2J{clear}\x1b[H");
+        let frame = |label: &str| {
+            let mut bytes = format!("{prefix}welcome\r\n");
+            for row in 0..55 {
+                bytes.push_str(&format!("{label}-{row:02}\r\n"));
+            }
+            bytes.push_str("\x1b[?2026l");
+            bytes
+        };
+        let old = frame("old");
+        let new = frame("new");
+        // Whole writes catch the old filter; bytewise writes and every split
+        // within the erase prefix prove that PTY chunking cannot change ED3.
+        for chunk_size in [usize::MAX, 1, 7] {
+            for split in 0..=prefix.len() {
+                let mut harness = Harness::new(80, 24);
+                for bytes in old.as_bytes().chunks(chunk_size) {
+                    harness.write_from_process(pid, bytes);
+                }
+                assert!(harness
+                    .pane
+                    .recent_text_snapshot(256)
+                    .text
+                    .contains("old-00"));
+                harness.write_from_process(pid, &new.as_bytes()[..split]);
+                for bytes in new.as_bytes()[split..].chunks(chunk_size) {
+                    harness.write_from_process(pid, bytes);
+                }
+                let recent = harness.pane.recent_text_snapshot(256).text;
+                assert!(recent.contains("new-54"), "redraw must complete");
+                assert_eq!(
+                    recent.matches("welcome").count(),
+                    1,
+                    "{clear:?}, split {split}, chunk {chunk_size}: {recent}"
+                );
+                assert!(!recent.contains("old-"), "{recent}");
+                assert!(harness.pane.visible_text().contains("new-54"));
+                harness.pane.scroll_up(256);
+                let top = harness.pane.visible_text();
+                assert!(top.contains("welcome") && top.contains("new-00"), "{top}");
+                assert!(!top.contains("old-"), "{top}");
+            }
+        }
+    }
+}
+
+#[test]
+fn erase_display_preserves_screen_and_history_boundaries() {
+    for clear in [b"\x1b[3J".as_slice(), b"\x1b[?3J"] {
+        let mut harness = Harness::new(80, 24);
+        for row in 0..55 {
+            harness.write(format!("history-{row:02}\r\n").as_bytes());
+        }
+        assert!(harness
+            .pane
+            .recent_text_snapshot(256)
+            .text
+            .contains("history-00"));
+        let primary = harness.pane.recent_text_snapshot(256);
+        let visible = harness.pane.visible_text();
+
+        harness.write(b"\x1b[?1049h\x1b[2J\x1b[Halternate");
+        harness.write(clear);
+        assert!(harness.pane.visible_text().contains("alternate"));
+        harness.write(b"\x1b[?1049l");
+        assert_eq!(harness.pane.recent_text_snapshot(256), primary);
+        assert_eq!(harness.pane.visible_text(), visible);
+
+        // ED2 clears only the display, not prior shell output in scrollback.
+        harness.write(b"\x1b[2J\x1b[Hprompt");
+        assert_eq!(harness.pane.visible_text().trim(), "prompt");
+        assert!(harness
+            .pane
+            .recent_text_snapshot(256)
+            .text
+            .contains("history-00"));
+        harness.write(clear);
+        // ED3 clears history without erasing the current display.
+        assert_eq!(harness.pane.visible_text().trim(), "prompt");
+        assert_eq!(harness.pane.recent_text_snapshot(256).text.trim(), "prompt");
+    }
+}
+
 #[test]
 fn short_streams_are_invariant_at_every_byte_boundary() {
     let fixtures: &[&[u8]] = &[