Forward clipboard copies to the terminal in Herdr sessions (#52557)

## Why

Herdr sessions can gain attached clients after Codex starts. Successful native clipboard copying should still forward the text to the attached terminal, even without inherited SSH variables.

## What changed

Detect Herdr sessions with `HERDR_ENV=1` and enable terminal forwarding for `/copy` and `Ctrl+O` even when native copying succeeds. Use OSC 52 directly when outside tmux, while preserving the native copy result.

## Testing

Add a routing test verifying that a Herdr session copies natively before sending OSC 52 and retains the successful native clipboard lease.

GitOrigin-RevId: c43c08ca037ff51e902267dc8636889493f5c30c

codex-rs/tui/src/clipboard_copy.rs

@@ -1,12 +1,12 @@
 //! Clipboard copy backend for the TUI's `/copy` command and `Ctrl+O` hotkey.
 //!
 //! Local copying uses the native clipboard, with WSL PowerShell as a fallback.
-//! In tmux, also forward to the attached terminal so clients attached after Codex
-//! started receive the copy. Over SSH without tmux, send OSC 52 directly.
+//! In tmux and Herdr, also forward to the attached terminal so clients attached after Codex
+//! started receive the copy. Over SSH without a multiplexer, send OSC 52 directly.
 //!
 //! Terminal writes have no delivery acknowledgement: a successful send must not
 //! suppress native copying. Both the host and attached client's clipboards may
-//! change. Outside tmux and SSH, use OSC 52 only if native copying fails.
+//! change. Outside tmux, Herdr, and SSH, use OSC 52 only if native copying fails.
 //!
 //! On Linux, X11 and some Wayland compositors require the process that wrote the
 //! clipboard to keep its handle open. `ClipboardLease` wraps the `arboard::Clipboard`
@@ -83,8 +83,8 @@ impl CopyStatus {
 
 /// Copy text to the system clipboard.
 ///
-/// Try native copying, then independently attempt terminal forwarding in tmux or
-/// SSH. A terminal send is best effort and does not confirm clipboard delivery.
+/// Try native copying, then independently attempt terminal forwarding in tmux,
+/// Herdr, or SSH. A terminal send is best effort and does not confirm clipboard delivery.
 /// Terminal forwarding may replace native HTML with plain text.
 ///
 /// Native or WSL success returns `Copied`, even if terminal forwarding fails.
@@ -114,6 +114,7 @@ fn copy_to_clipboard(
         text,
         format,
         CopyEnvironment {
+            herdr_session: std::env::var("HERDR_ENV").is_ok_and(|value| value == "1"),
             ssh_session: is_ssh_session(),
             wsl_session: is_wsl_session(),
             tmux_session: is_tmux_session(),
@@ -159,6 +160,7 @@ impl ClipboardLease {
 /// without touching real clipboards or terminal I/O.
 #[derive(Clone, Copy)]
 struct CopyEnvironment {
+    herdr_session: bool,
     ssh_session: bool,
     wsl_session: bool,
     tmux_session: bool,
@@ -214,9 +216,11 @@ fn copy_to_clipboard_with(
     });
     // Copy natively first: an X11 SelectionClear from a terminal write can otherwise
     // race with arboard reusing its ownership window and clear the new native data.
-    // Persistent tmux sessions may gain remote clients after Codex starts, so still
+    // Persistent multiplexer sessions may gain remote clients after Codex starts, so still
     // forward even when no SSH variables were inherited or native copying succeeded.
-    let terminal_result = (environment.tmux_session || environment.ssh_session).then(terminal_copy);
+    let terminal_result =
+        (environment.tmux_session || environment.herdr_session || environment.ssh_session)
+            .then(terminal_copy);
     match native_result {
         Ok(lease) => Ok(CopyOutcome::Copied(lease)),
         Err(native_error) => terminal_result
@@ -391,6 +395,7 @@ mod tests {
 
     fn remote_environment() -> CopyEnvironment {
         CopyEnvironment {
+            herdr_session: false,
             ssh_session: true,
             wsl_session: true,
             tmux_session: false,
@@ -406,6 +411,7 @@ mod tests {
 
     fn local_environment() -> CopyEnvironment {
         CopyEnvironment {
+            herdr_session: false,
             ssh_session: false,
             wsl_session: false,
             tmux_session: false,

codex-rs/tui/src/clipboard_copy/routing_tests.rs

@@ -17,6 +17,7 @@ fn local_tmux_preserves_native_html_when_terminal_silently_rejects_copy() {
         "**hello**",
         CopyFormat::Markdown,
         CopyEnvironment {
+            herdr_session: false,
             ssh_session: false,
             tmux_session: true,
             wsl_session: false,
@@ -48,6 +49,7 @@ fn copy_uses_osc52_when_tmux_fails_even_if_native_copy_succeeds() {
         "hello",
         CopyFormat::PlainText,
         CopyEnvironment {
+            herdr_session: false,
             ssh_session: false,
             tmux_session: true,
             wsl_session: false,
@@ -73,12 +75,42 @@ fn copy_uses_osc52_when_tmux_fails_even_if_native_copy_succeeds() {
 
 fn local_tmux_environment() -> CopyEnvironment {
     CopyEnvironment {
+        herdr_session: false,
         tmux_session: true,
         ssh_session: false,
         wsl_session: false,
     }
 }
 
+#[test]
+fn herdr_forwards_to_osc52_even_when_native_copy_succeeds() {
+    let calls = RefCell::new(Vec::new());
+    let result = copy_to_clipboard_with(
+        "hello",
+        CopyFormat::PlainText,
+        CopyEnvironment {
+            herdr_session: true,
+            ssh_session: false,
+            tmux_session: false,
+            wsl_session: false,
+        },
+        |_| panic!("Herdr should use OSC 52 directly"),
+        |_| {
+            calls.borrow_mut().push("osc52");
+            Ok(())
+        },
+        |text, html| {
+            assert_eq!((text, html), ("hello", None));
+            calls.borrow_mut().push("native");
+            Ok(Some(ClipboardLease::test()))
+        },
+        |_| panic!("native copy succeeded"),
+    );
+
+    assert!(matches!(result, Ok(CopyOutcome::Copied(Some(_)))));
+    assert_eq!(calls.into_inner(), vec!["native", "osc52"]);
+}
+
 #[test]
 fn oversized_tmux_copy_preserves_native_copy() {
     for (size, expected_calls) in [