feat(cli): press Esc to interrupt a running turn

While a turn runs the main thread is blocked in the conversation loop,
so nothing reads the keyboard. Add an EscapeInterruptMonitor that, for
the duration of a turn on an interactive terminal, switches stdin to a
minimal non-canonical mode (echo/line-buffering off; ISIG and output
processing untouched, unlike full raw mode) and polls for a lone ESC
byte. Escape sequences such as arrow keys are recognized and swallowed.
On Esc it trips the TurnInterruptSignal: the in-flight request is
aborted and control returns to the REPL prompt with the session intact.

Permission prompts read whole lines from stdin mid-turn, so stdin
ownership is coordinated through a StdinPromptGate: while a prompt holds
a lease the listener restores canonical mode and stops consuming bytes.

Also:
- spinner shows '(esc to interrupt)' and the banner/help mention Esc
- WorkerStatus/WorkerEventKind gain an 'interrupted' lifecycle state
- non-terminal stdin and non-unix platforms skip the listener; Ctrl+C
  interruption still works there

Closes the Esc-to-interrupt feature request (#3196).

rust/Cargo.lock

@@ -2247,6 +2247,7 @@ dependencies = [
  "crossterm",
  "log",
  "mock-anthropic-service",
+ "nix",
  "plugins",
  "pulldown-cmark",
  "runtime",

rust/crates/runtime/src/worker_boot.rs

@@ -34,6 +34,9 @@ pub enum WorkerStatus {
     ToolPermissionRequired,
     ReadyForPrompt,
     Running,
+    /// The user stopped the turn mid-run (e.g. Esc or Ctrl+C); the worker
+    /// is back at the prompt with the session intact.
+    Interrupted,
     Finished,
     Failed,
 }
@@ -46,6 +49,7 @@ impl std::fmt::Display for WorkerStatus {
             Self::ToolPermissionRequired => write!(f, "tool_permission_required"),
             Self::ReadyForPrompt => write!(f, "ready_for_prompt"),
             Self::Running => write!(f, "running"),
+            Self::Interrupted => write!(f, "interrupted"),
             Self::Finished => write!(f, "finished"),
             Self::Failed => write!(f, "failed"),
         }
@@ -82,6 +86,7 @@ pub enum WorkerEventKind {
     PromptMisdelivery,
     PromptReplayArmed,
     Running,
+    Interrupted,
     Restarted,
     Finished,
     Failed,
@@ -1461,6 +1466,23 @@ mod tests {
     use std::fs;
     use std::process::Command;
 
+    #[test]
+    fn interrupted_status_serializes_and_displays_as_snake_case() {
+        assert_eq!(WorkerStatus::Interrupted.to_string(), "interrupted");
+        assert_eq!(
+            serde_json::to_string(&WorkerStatus::Interrupted).expect("should serialize"),
+            "\"interrupted\""
+        );
+        assert_eq!(
+            serde_json::from_str::<WorkerStatus>("\"interrupted\"").expect("should deserialize"),
+            WorkerStatus::Interrupted
+        );
+        assert_eq!(
+            serde_json::to_string(&WorkerEventKind::Interrupted).expect("should serialize"),
+            "\"interrupted\""
+        );
+    }
+
     #[test]
     fn allowlisted_trust_prompt_auto_resolves_then_reaches_ready_state() {
         let registry = WorkerRegistry::new();

rust/crates/rusty-claude-cli/Cargo.toml

@@ -24,6 +24,8 @@ tokio = { version = "1", features = ["rt-multi-thread", "signal", "time"] }
 tools = { path = "../tools" }
 log = "0.4"
 
+[target.'cfg(unix)'.dependencies]
+nix = { version = "0.29", features = ["term", "poll"] }
 
 [lints]
 workspace = true

rust/crates/rusty-claude-cli/src/interrupt.rs

@@ -0,0 +1,280 @@
+//! Esc-key interruption for running turns.
+//!
+//! While a turn runs, the main thread is blocked inside the conversation
+//! loop, so rustyline is not reading the keyboard. This module spawns a
+//! listener thread that switches stdin to a minimal non-canonical mode
+//! (line buffering and echo off; signal handling and output processing
+//! stay enabled, unlike full raw mode) and watches for a lone Escape
+//! byte. When one arrives it trips the shared [`TurnInterruptSignal`],
+//! which the conversation loop and the streaming API client poll to wind
+//! the turn down gracefully.
+//!
+//! Permission prompts read whole lines from stdin mid-turn, so stdin
+//! ownership is coordinated through [`StdinPromptGate`]: while a prompt
+//! holds a lease, the listener restores canonical mode and stops
+//! consuming bytes.
+
+use std::io::IsTerminal;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Arc, Mutex, PoisonError};
+use std::thread::JoinHandle;
+
+use runtime::TurnInterruptSignal;
+
+/// Terminal-mode bookkeeping guarded by the gate mutex. `saved` holds the
+/// canonical-mode termios while non-canonical mode is active.
+#[derive(Default)]
+struct TtyMode {
+    #[cfg(unix)]
+    saved: Option<nix::sys::termios::Termios>,
+}
+
+#[derive(Default)]
+struct GateState {
+    /// True while a permission prompt owns stdin.
+    busy: AtomicBool,
+    /// Tells the listener thread to exit at the end of the turn.
+    stop: AtomicBool,
+    /// Serializes stdin reads and terminal-mode flips.
+    mode: Mutex<TtyMode>,
+}
+
+/// Classification of one chunk of bytes read from the terminal.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum EscClassification {
+    /// A bare ESC byte: the user pressed the Escape key.
+    LoneEscape,
+    /// ESC followed by more bytes: the prefix of a terminal escape
+    /// sequence such as an arrow or function key.
+    EscapeSequence,
+    /// Anything else (regular type-ahead, control characters, ...).
+    Other,
+}
+
+#[cfg_attr(not(unix), allow(dead_code))]
+fn classify_escape_chunk(bytes: &[u8]) -> EscClassification {
+    match bytes {
+        [0x1b] => EscClassification::LoneEscape,
+        [0x1b, ..] => EscClassification::EscapeSequence,
+        _ => EscClassification::Other,
+    }
+}
+
+/// Hands exclusive stdin ownership to interactive prompts while the
+/// Esc listener is running.
+#[derive(Clone)]
+pub struct StdinPromptGate {
+    shared: Arc<GateState>,
+}
+
+impl StdinPromptGate {
+    /// Takes stdin away from the Esc listener for the lifetime of the
+    /// returned lease: the terminal returns to canonical mode so a
+    /// line-based prompt (e.g. the permission approval prompt) behaves
+    /// normally. Listening resumes when the lease is dropped.
+    pub fn lease(&self) -> StdinPromptLease<'_> {
+        self.shared.busy.store(true, Ordering::SeqCst);
+        // Wait for the listener's current poll cycle to release the
+        // terminal, then restore canonical mode for line input.
+        #[allow(unused_mut)]
+        let mut mode = self
+            .shared
+            .mode
+            .lock()
+            .unwrap_or_else(PoisonError::into_inner);
+        #[cfg(unix)]
+        tty::restore(&mut mode);
+        drop(mode);
+        StdinPromptLease {
+            shared: &self.shared,
+        }
+    }
+}
+
+/// RAII lease returned by [`StdinPromptGate::lease`].
+pub struct StdinPromptLease<'a> {
+    shared: &'a GateState,
+}
+
+impl Drop for StdinPromptLease<'_> {
+    fn drop(&mut self) {
+        self.shared.busy.store(false, Ordering::SeqCst);
+    }
+}
+
+/// Background listener that maps a lone Esc keypress to
+/// [`TurnInterruptSignal::interrupt`].
+pub struct EscapeInterruptMonitor {
+    shared: Arc<GateState>,
+    join_handle: Option<JoinHandle<()>>,
+}
+
+impl EscapeInterruptMonitor {
+    /// Spawns the listener for the duration of one turn. Returns `None`
+    /// when stdin is not an interactive terminal or the platform does not
+    /// support terminal-mode switching; Ctrl+C interruption still works
+    /// in those cases.
+    pub fn spawn(signal: TurnInterruptSignal) -> Option<(Self, StdinPromptGate)> {
+        if !std::io::stdin().is_terminal() {
+            return None;
+        }
+
+        #[cfg(not(unix))]
+        {
+            let _ = signal;
+            None
+        }
+
+        #[cfg(unix)]
+        {
+            let shared = Arc::new(GateState::default());
+            let thread_shared = Arc::clone(&shared);
+            let join_handle = std::thread::spawn(move || listener_loop(&thread_shared, &signal));
+            let gate = StdinPromptGate {
+                shared: Arc::clone(&shared),
+            };
+            Some((
+                Self {
+                    shared,
+                    join_handle: Some(join_handle),
+                },
+                gate,
+            ))
+        }
+    }
+
+    /// Stops the listener and restores the terminal before control
+    /// returns to the line editor.
+    pub fn stop(mut self) {
+        self.shared.stop.store(true, Ordering::SeqCst);
+        if let Some(join_handle) = self.join_handle.take() {
+            let _ = join_handle.join();
+        }
+    }
+}
+
+#[cfg(unix)]
+fn listener_loop(shared: &GateState, signal: &TurnInterruptSignal) {
+    let mut buffer = [0u8; 64];
+
+    while !shared.stop.load(Ordering::SeqCst) {
+        if shared.busy.load(Ordering::SeqCst) {
+            std::thread::sleep(std::time::Duration::from_millis(25));
+            continue;
+        }
+
+        let mut mode = shared.mode.lock().unwrap_or_else(PoisonError::into_inner);
+        if shared.busy.load(Ordering::SeqCst) || shared.stop.load(Ordering::SeqCst) {
+            continue;
+        }
+        if !tty::enable_noncanonical(&mut mode) {
+            // Terminal refused the mode switch; Esc support is
+            // unavailable for this turn but Ctrl+C still works.
+            return;
+        }
+        if !tty::wait_readable(100) {
+            continue;
+        }
+
+        let count = tty::read_pending(&mut buffer);
+        if classify_escape_chunk(&buffer[..count]) == EscClassification::LoneEscape {
+            // A slow terminal may split an escape sequence across reads;
+            // only treat ESC as the Esc key when nothing follows it.
+            if tty::wait_readable(50) {
+                let _ = tty::read_pending(&mut buffer);
+                continue;
+            }
+            signal.interrupt();
+        }
+        // Other bytes are intentionally swallowed: type-ahead is not
+        // preserved while a turn is running.
+    }
+
+    let mut mode = shared.mode.lock().unwrap_or_else(PoisonError::into_inner);
+    tty::restore(&mut mode);
+}
+
+#[cfg(unix)]
+mod tty {
+    use std::os::fd::{AsFd, AsRawFd};
+
+    use nix::poll::{poll, PollFd, PollFlags, PollTimeout};
+    use nix::sys::termios::{self, LocalFlags, SetArg, SpecialCharacterIndices};
+
+    use super::TtyMode;
+
+    /// Disables line buffering and echo while leaving signal generation
+    /// (ISIG) and output post-processing (OPOST) untouched, so Ctrl+C and
+    /// streamed output keep working. No-op when already active.
+    pub(super) fn enable_noncanonical(mode: &mut TtyMode) -> bool {
+        if mode.saved.is_some() {
+            return true;
+        }
+        let stdin = std::io::stdin();
+        let Ok(saved) = termios::tcgetattr(&stdin) else {
+            return false;
+        };
+        let mut noncanonical = saved.clone();
+        noncanonical.local_flags &= !(LocalFlags::ICANON | LocalFlags::ECHO);
+        noncanonical.control_chars[SpecialCharacterIndices::VMIN as usize] = 0;
+        noncanonical.control_chars[SpecialCharacterIndices::VTIME as usize] = 0;
+        if termios::tcsetattr(&stdin, SetArg::TCSANOW, &noncanonical).is_err() {
+            return false;
+        }
+        mode.saved = Some(saved);
+        true
+    }
+
+    pub(super) fn restore(mode: &mut TtyMode) {
+        if let Some(saved) = mode.saved.take() {
+            let _ = termios::tcsetattr(std::io::stdin(), SetArg::TCSANOW, &saved);
+        }
+    }
+
+    pub(super) fn wait_readable(timeout_ms: u16) -> bool {
+        let stdin = std::io::stdin();
+        let mut fds = [PollFd::new(stdin.as_fd(), PollFlags::POLLIN)];
+        matches!(poll(&mut fds, PollTimeout::from(timeout_ms)), Ok(ready) if ready > 0)
+            && fds[0]
+                .revents()
+                .is_some_and(|revents| revents.contains(PollFlags::POLLIN))
+    }
+
+    pub(super) fn read_pending(buffer: &mut [u8]) -> usize {
+        nix::unistd::read(std::io::stdin().as_raw_fd(), buffer).unwrap_or(0)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{classify_escape_chunk, EscClassification};
+
+    #[test]
+    fn lone_escape_byte_is_the_esc_key() {
+        assert_eq!(
+            classify_escape_chunk(&[0x1b]),
+            EscClassification::LoneEscape
+        );
+    }
+
+    #[test]
+    fn escape_followed_by_more_bytes_is_a_sequence() {
+        // Up arrow: ESC [ A
+        assert_eq!(
+            classify_escape_chunk(&[0x1b, 0x5b, 0x41]),
+            EscClassification::EscapeSequence
+        );
+        // Alt+f style: ESC f
+        assert_eq!(
+            classify_escape_chunk(&[0x1b, b'f']),
+            EscClassification::EscapeSequence
+        );
+    }
+
+    #[test]
+    fn regular_bytes_are_ignored() {
+        assert_eq!(classify_escape_chunk(b"hello"), EscClassification::Other);
+        assert_eq!(classify_escape_chunk(&[]), EscClassification::Other);
+        assert_eq!(classify_escape_chunk(&[0x03]), EscClassification::Other);
+    }
+}

rust/crates/rusty-claude-cli/src/main.rs

@@ -16,6 +16,7 @@
 )]
 mod init;
 mod input;
+mod interrupt;
 mod render;
 mod setup_wizard;
 
@@ -7717,7 +7718,7 @@ impl LiveCli {
   \x1b[2mDirectory\x1b[0m        {}\n\
   \x1b[2mSession\x1b[0m          {}\n\
   \x1b[2mAuto-save\x1b[0m        {}\n\n\
-  Type \x1b[1m/help\x1b[0m for commands · \x1b[1m/status\x1b[0m for live context · \x1b[2m/resume latest\x1b[0m jumps back to the newest session · \x1b[1m/diff\x1b[0m then \x1b[1m/commit\x1b[0m to ship · \x1b[2mTab\x1b[0m for workflow completions · \x1b[2mShift+Enter\x1b[0m for newline",
+  Type \x1b[1m/help\x1b[0m for commands · \x1b[1m/status\x1b[0m for live context · \x1b[2m/resume latest\x1b[0m jumps back to the newest session · \x1b[1m/diff\x1b[0m then \x1b[1m/commit\x1b[0m to ship · \x1b[2mTab\x1b[0m for workflow completions · \x1b[2mShift+Enter\x1b[0m for newline · \x1b[2mEsc\x1b[0m interrupts a running turn",
             self.model,
             self.permission_mode.as_str(),
             git_branch,
@@ -7742,7 +7743,10 @@ impl LiveCli {
     fn prepare_turn_runtime(
         &self,
         emit_output: bool,
-    ) -> Result<(BuiltRuntime, HookAbortMonitor), Box<dyn std::error::Error>> {
+    ) -> Result<
+        (BuiltRuntime, HookAbortMonitor, runtime::TurnInterruptSignal),
+        Box<dyn std::error::Error>,
+    > {
         let hook_abort_signal = runtime::HookAbortSignal::new();
         let turn_interrupt_signal = runtime::TurnInterruptSignal::new();
         let runtime = build_runtime(
@@ -7758,9 +7762,10 @@ impl LiveCli {
         )?
         .with_hook_abort_signal(hook_abort_signal.clone())
         .with_turn_interrupt_signal(turn_interrupt_signal.clone());
-        let hook_abort_monitor = HookAbortMonitor::spawn(hook_abort_signal, turn_interrupt_signal);
+        let hook_abort_monitor =
+            HookAbortMonitor::spawn(hook_abort_signal, turn_interrupt_signal.clone());
 
-        Ok((runtime, hook_abort_monitor))
+        Ok((runtime, hook_abort_monitor, turn_interrupt_signal))
     }
 
     fn replace_runtime(&mut self, runtime: BuiltRuntime) -> Result<(), Box<dyn std::error::Error>> {
@@ -7770,16 +7775,31 @@ impl LiveCli {
     }
 
     fn run_turn(&mut self, input: &str) -> Result<(), Box<dyn std::error::Error>> {
-        let (mut runtime, hook_abort_monitor) = self.prepare_turn_runtime(true)?;
+        let (mut runtime, hook_abort_monitor, turn_interrupt_signal) =
+            self.prepare_turn_runtime(true)?;
+        let mut permission_prompter = CliPermissionPrompter::new(self.permission_mode);
+        let mut escape_monitor = None;
+        if let Some((monitor, stdin_gate)) =
+            interrupt::EscapeInterruptMonitor::spawn(turn_interrupt_signal)
+        {
+            permission_prompter = permission_prompter.with_stdin_gate(stdin_gate);
+            escape_monitor = Some(monitor);
+        }
         let mut spinner = Spinner::new();
         let mut stdout = io::stdout();
         spinner.tick(
-            "🦀 Thinking...",
+            if escape_monitor.is_some() {
+                "🦀 Thinking... (esc to interrupt)"
+            } else {
+                "🦀 Thinking..."
+            },
             TerminalRenderer::new().color_theme(),
             &mut stdout,
         )?;
-        let mut permission_prompter = CliPermissionPrompter::new(self.permission_mode);
         let result = runtime.run_turn(input, Some(&mut permission_prompter));
+        if let Some(monitor) = escape_monitor {
+            monitor.stop();
+        }
         hook_abort_monitor.stop();
         match result {
             Ok(summary) => {
@@ -7920,7 +7940,7 @@ impl LiveCli {
                         *self.runtime.session_mut() = result.compacted_session.clone();
 
                         // Build a new runtime with the compacted session and retry
-                        let (mut new_runtime, hook_abort_monitor) =
+                        let (mut new_runtime, hook_abort_monitor, _turn_interrupt_signal) =
                             self.prepare_turn_runtime(true)?;
                         drop(hook_abort_monitor);
 
@@ -8010,7 +8030,8 @@ impl LiveCli {
     }
 
     fn run_prompt_compact(&mut self, input: &str) -> Result<(), Box<dyn std::error::Error>> {
-        let (mut runtime, hook_abort_monitor) = self.prepare_turn_runtime(false)?;
+        let (mut runtime, hook_abort_monitor, _turn_interrupt_signal) =
+            self.prepare_turn_runtime(false)?;
         let mut permission_prompter = CliPermissionPrompter::new(self.permission_mode);
         let result = runtime.run_turn(input, Some(&mut permission_prompter));
         hook_abort_monitor.stop();
@@ -8023,7 +8044,8 @@ impl LiveCli {
     }
 
     fn run_prompt_compact_json(&mut self, input: &str) -> Result<(), Box<dyn std::error::Error>> {
-        let (mut runtime, hook_abort_monitor) = self.prepare_turn_runtime(false)?;
+        let (mut runtime, hook_abort_monitor, _turn_interrupt_signal) =
+            self.prepare_turn_runtime(false)?;
         let mut permission_prompter = CliPermissionPrompter::new(self.permission_mode);
         let result = runtime.run_turn(input, Some(&mut permission_prompter));
         hook_abort_monitor.stop();
@@ -8048,7 +8070,8 @@ impl LiveCli {
     }
 
     fn run_prompt_json(&mut self, input: &str) -> Result<(), Box<dyn std::error::Error>> {
-        let (mut runtime, hook_abort_monitor) = self.prepare_turn_runtime(false)?;
+        let (mut runtime, hook_abort_monitor, _turn_interrupt_signal) =
+            self.prepare_turn_runtime(false)?;
         let mut permission_prompter = CliPermissionPrompter::new(self.permission_mode);
         let result = runtime.run_turn(input, Some(&mut permission_prompter));
         hook_abort_monitor.stop();
@@ -9520,6 +9543,7 @@ fn render_repl_help() -> String {
         "  Ctrl-R               Reverse-search prompt history".to_string(),
         "  Tab                  Complete commands, modes, and recent sessions".to_string(),
         "  Ctrl-C               Clear input (or exit on empty prompt)".to_string(),
+        "  Esc                  Interrupt the running turn".to_string(),
         "  Shift+Enter/Ctrl+J   Insert a newline".to_string(),
         "  Auto-save            .claw/sessions/<workspace-fingerprint>/<session-id>.jsonl"
             .to_string(),
@@ -12503,11 +12527,20 @@ impl runtime::HookProgressReporter for CliHookProgressReporter {
 
 struct CliPermissionPrompter {
     current_mode: PermissionMode,
+    stdin_gate: Option<interrupt::StdinPromptGate>,
 }
 
 impl CliPermissionPrompter {
     fn new(current_mode: PermissionMode) -> Self {
-        Self { current_mode }
+        Self {
+            current_mode,
+            stdin_gate: None,
+        }
+    }
+
+    fn with_stdin_gate(mut self, stdin_gate: interrupt::StdinPromptGate) -> Self {
+        self.stdin_gate = Some(stdin_gate);
+        self
     }
 }
 
@@ -12516,6 +12549,12 @@ impl runtime::PermissionPrompter for CliPermissionPrompter {
         &mut self,
         request: &runtime::PermissionRequest,
     ) -> runtime::PermissionPromptDecision {
+        // Take stdin back from the Esc listener (restoring canonical
+        // mode) for the duration of this line-based prompt.
+        let _stdin_lease = self
+            .stdin_gate
+            .as_ref()
+            .map(interrupt::StdinPromptGate::lease);
         println!();
         println!("Permission approval required");
         println!("  Tool             {}", request.tool_name);