fix: set a stable terminal identity for panes

src/pane.rs

@@ -30,6 +30,17 @@ pub use self::{
 };
 
 const RELEASE_REACQUIRE_SUPPRESSION: std::time::Duration = std::time::Duration::from_secs(1);
+const PANE_TERM: &str = "xterm-256color";
+const PANE_COLORTERM: &str = "truecolor";
+
+fn apply_pane_terminal_env(cmd: &mut CommandBuilder) {
+    // Each pane is rendered by herdr's own terminal layer, not the outer terminal
+    // that launched the app. Advertising the inherited TERM leaks the host terminal
+    // identity into shells and across SSH, which breaks redraw and cursor movement
+    // when the remote side lacks matching terminfo entries.
+    cmd.env("TERM", PANE_TERM);
+    cmd.env("COLORTERM", PANE_COLORTERM);
+}
 
 #[derive(Debug, Clone, Copy)]
 struct PendingAgentRelease {
@@ -246,6 +257,7 @@ impl PaneRuntime {
         let mut cmd = CommandBuilder::new(&shell);
         cmd.cwd(cwd);
         cmd.env(crate::HERDR_ENV_VAR, crate::HERDR_ENV_VALUE);
+        apply_pane_terminal_env(&mut cmd);
         crate::integration::apply_pane_env(&mut cmd, pane_id);
         Self::spawn_command_builder(
             pane_id,
@@ -279,6 +291,7 @@ impl PaneRuntime {
         cmd.arg(command);
         cmd.cwd(cwd);
         cmd.env(crate::HERDR_ENV_VAR, crate::HERDR_ENV_VALUE);
+        apply_pane_terminal_env(&mut cmd);
         crate::integration::apply_pane_env(&mut cmd, pane_id);
         for (key, value) in extra_env {
             cmd.env(key, value);
@@ -859,6 +872,58 @@ impl PaneRuntime {
 mod tests {
     use super::*;
 
+    fn capture_shell_output(command: &str, extra_env: &[(&str, &str)]) -> String {
+        let pair = native_pty_system()
+            .openpty(PtySize {
+                rows: 24,
+                cols: 80,
+                pixel_width: 0,
+                pixel_height: 0,
+            })
+            .unwrap();
+        let output_path = std::env::temp_dir().join(format!(
+            "herdr-pane-term-test-{}-{}.txt",
+            std::process::id(),
+            std::time::SystemTime::now()
+                .duration_since(std::time::UNIX_EPOCH)
+                .unwrap()
+                .as_nanos()
+        ));
+        let mut cmd = CommandBuilder::new("/bin/sh");
+        cmd.arg("-c");
+        cmd.arg(format!("{command} > '{}'", output_path.display()));
+        cmd.cwd(std::env::current_dir().unwrap());
+        cmd.env("TERM", "xterm-ghostty");
+        cmd.env("COLORTERM", "falsecolor");
+        apply_pane_terminal_env(&mut cmd);
+        for (key, value) in extra_env {
+            cmd.env(key, value);
+        }
+
+        let mut child = pair.slave.spawn_command(cmd).unwrap();
+        let status = child.wait().unwrap();
+        assert!(status.success(), "shell command failed: {status:?}");
+
+        let output = std::fs::read_to_string(&output_path).unwrap();
+        let _ = std::fs::remove_file(output_path);
+        output
+    }
+
+    #[test]
+    fn pane_terminal_identity_overrides_outer_terminal_env() {
+        let output = capture_shell_output("printf '%s\\n%s\\n' \"$TERM\" \"$COLORTERM\"", &[]);
+        assert_eq!(output, "xterm-256color\ntruecolor\n");
+    }
+
+    #[test]
+    fn pane_terminal_identity_allows_explicit_override() {
+        let output = capture_shell_output(
+            "printf '%s\\n%s\\n' \"$TERM\" \"$COLORTERM\"",
+            &[("TERM", "vt100"), ("COLORTERM", "24bit")],
+        );
+        assert_eq!(output, "vt100\n24bit\n");
+    }
+
     #[tokio::test]
     async fn focus_events_are_forwarded_when_enabled() {
         let (tx, mut rx) = mpsc::channel(4);