fix(acp): send SIGINT to blox acp proxy for graceful shutdown (#454)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: matt2e

Cargo.lock

@@ -397,9 +397,7 @@ pub fn start_session(
                 .map(|q| !q.is_empty())
                 .unwrap_or(false);
 
-            if has_queued {
-                log::info!("Skipping auto review for branch {branch_id}: queued sessions pending");
-            } else {
+            if !has_queued {
                 let store_for_auto = Arc::clone(&store_for_status);
                 let registry_for_auto = Arc::clone(&registry);
                 let app_handle_for_auto = app_handle.clone();

apps/staged/src-tauri/Cargo.lock

@@ -14,3 +14,4 @@ anyhow = "1"
 async-trait = "0.1"
 log = "0.4"
 blox-cli = { path = "../blox-cli" }
+nix = { version = "0.29", features = ["signal"] }

apps/staged/src-tauri/src/session_runner.rs

@@ -27,6 +27,9 @@ use tokio::sync::Mutex;
 use tokio_util::compat::{TokioAsyncReadCompatExt, TokioAsyncWriteCompatExt};
 use tokio_util::sync::CancellationToken;
 
+use nix::sys::signal::{self, Signal};
+use nix::unistd::Pid;
+
 use crate::types::blox_acp_command;
 
 // =============================================================================
@@ -283,6 +286,13 @@ impl AgentDriver for AcpDriver {
             // the actions executor does) and logging it to aid debugging.
             .stderr(Stdio::null())
             .kill_on_drop(true);
+        // Put remote proxies in their own process group so we can send SIGINT
+        // to the entire group (sq + its child processes) for graceful shutdown.
+        // Without this, only `sq` receives SIGINT and hangs waiting for its
+        // child (the blox acp proxy) which never got the signal.
+        if self.is_remote {
+            cmd.process_group(0);
+        }
         // For local shells extra_env is set on the clean environment; for
         // remote spawns it augments the inherited environment.
         for (k, v) in &self.extra_env {
@@ -397,6 +407,7 @@ impl AgentDriver for AcpDriver {
             _ = cancel_token.cancelled() => {
                 log::info!("Session {session_id} cancelled");
                 writer.finalize().await;
+                graceful_stop(&mut child, self.is_remote).await;
                 return Ok(());
             }
             result = run_acp_protocol(
@@ -406,12 +417,45 @@ impl AgentDriver for AcpDriver {
         };
 
         writer.finalize().await;
-        let _ = child.kill().await;
+        graceful_stop(&mut child, self.is_remote).await;
 
         protocol_result
     }
 }
 
+/// Gracefully stop the ACP child process.
+///
+/// For remote blox proxies, sends SIGINT so the Go process can run its
+/// deferred cleanup (calling `StopProcess` on the bloxlet, which marks the
+/// remote command as COMPLETE). Falls back to SIGKILL after a timeout.
+///
+/// For local processes, sends SIGKILL immediately.
+async fn graceful_stop(child: &mut tokio::process::Child, is_remote: bool) {
+    if is_remote {
+        let Some(pid) = child.id() else {
+            // Process already exited on its own — no cleanup needed.
+            return;
+        };
+        let Ok(pid) = i32::try_from(pid) else {
+            let _ = child.kill().await;
+            return;
+        };
+        // Send SIGINT to the process group (negative PID) so both `sq`
+        // and its child processes (the blox acp proxy) receive the signal.
+        // The process was spawned with process_group(0) so its PGID == PID.
+        if signal::kill(Pid::from_raw(-pid), Signal::SIGINT).is_ok() {
+            if let Ok(Ok(_status)) =
+                tokio::time::timeout(Duration::from_secs(5), child.wait()).await
+            {
+                return;
+            }
+        }
+        let _ = child.kill().await;
+        return;
+    }
+    let _ = child.kill().await;
+}
+
 #[derive(Debug, PartialEq, Eq)]
 enum RemoteLineOutcome {
     Emit(String),

crates/acp-client/Cargo.toml

@@ -16,21 +16,6 @@
 //!    full session orchestration, streaming, and database integration
 //! 2. **Simple one-shot interface** (`run_acp_prompt`) - For simple prompting
 //!    without session management
-//!
-//! # Example (Simple)
-//!
-//! ```rust,no_run
-//! use acp_client::{find_acp_agent, run_acp_prompt};
-//! use std::path::Path;
-//!
-//! #[tokio::main(flavor = "current_thread")]
-//! async fn main() -> anyhow::Result<()> {
-//!     let agent = find_acp_agent().ok_or_else(|| anyhow::anyhow!("No ACP agent found"))?;
-//!     let response = run_acp_prompt(&agent, Path::new("."), "Hello!").await?;
-//!     println!("Agent response: {}", response);
-//!     Ok(())
-//! }
-//! ```
 
 mod driver;
 mod simple;
@@ -43,6 +28,6 @@ pub use driver::{
 };
 pub use simple::run_acp_prompt;
 pub use types::{
-    discover_providers, find_acp_agent, find_acp_agent_by_id, find_command, AcpAgent,
-    AcpProviderInfo,
+    discover_providers, find_acp_agent, find_acp_agent_by_id, find_command, known_agent_commands,
+    AcpAgent, AcpProviderInfo,
 };

crates/acp-client/src/driver.rs

@@ -111,6 +111,11 @@ pub fn find_acp_agent_by_id(provider_id: &str) -> Option<AcpAgent> {
         })
 }
 
+/// Return the CLI command names of all known agents (for error messages).
+pub fn known_agent_commands() -> Vec<&'static str> {
+    KNOWN_AGENTS.iter().map(|a| a.command).collect()
+}
+
 /// Find the first available ACP agent.
 ///
 /// Tries each known agent in order and returns the first one found.

crates/acp-client/src/lib.rs

@@ -26,8 +26,12 @@ impl AcpAiProvider {
     /// An ACP provider, or an error if no ACP agent is available
     pub fn new(working_dir: PathBuf) -> Result<Self> {
         // Verify an agent is available
-        acp_client::find_acp_agent()
-            .ok_or_else(|| anyhow::anyhow!("No ACP agent found (tried goose, claude-agent-acp)"))?;
+        acp_client::find_acp_agent().ok_or_else(|| {
+            anyhow::anyhow!(
+                "No ACP agent found (tried {})",
+                acp_client::known_agent_commands().join(", ")
+            )
+        })?;
         Ok(Self { working_dir })
     }