agent mcp: bound the in-agent socket round trip so a stalled harness cannot hang a turn

hive-agent-mcp/src/mcp/render.rs

@@ -343,19 +343,38 @@ pub(super) async fn matrix_unread_summary() -> Option<Vec<MatrixRoomUnread>> {
 pub(super) async fn dial_agent_socket(
     req: &hive_agent_sock::Request,
 ) -> Option<hive_agent_sock::Response> {
-    use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
-    use tokio::net::UnixStream;
     let socket = std::env::var_os("HIVE_AGENT_SOCKET").map(std::path::PathBuf::from)?;
     if !socket.exists() {
         return None;
     }
-    let mut stream = UnixStream::connect(&socket).await.ok()?;
-    let mut line = serde_json::to_string(req).ok()?;
-    line.push('\n');
-    stream.write_all(line.as_bytes()).await.ok()?;
-    let mut lines = BufReader::new(stream).lines();
-    let resp_line = lines.next_line().await.ok()??;
-    serde_json::from_str(&resp_line).ok()
+    dial_socket(&socket, req, AGENT_SOCKET_DEADLINE).await
+}
+
+/// Longest a tool call waits on the in-agent socket, connect through reply.
+/// Matches the server's own per-connection request-line deadline: a harness
+/// that accepts and then stalls must not hang the model's turn.
+const AGENT_SOCKET_DEADLINE: std::time::Duration = std::time::Duration::from_secs(30);
+
+/// One round trip on the socket at `socket`, abandoned (as `None`) after
+/// `deadline`.
+async fn dial_socket(
+    socket: &std::path::Path,
+    req: &hive_agent_sock::Request,
+    deadline: std::time::Duration,
+) -> Option<hive_agent_sock::Response> {
+    use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
+    use tokio::net::UnixStream;
+    tokio::time::timeout(deadline, async {
+        let mut stream = UnixStream::connect(socket).await.ok()?;
+        let mut line = serde_json::to_string(req).ok()?;
+        line.push('\n');
+        stream.write_all(line.as_bytes()).await.ok()?;
+        let mut lines = BufReader::new(stream).lines();
+        let resp_line = lines.next_line().await.ok()??;
+        serde_json::from_str(&resp_line).ok()
+    })
+    .await
+    .ok()?
 }
 
 /// Query the harness's in-agent socket for this agent's local todos
@@ -540,7 +559,36 @@ pub fn annotate_retries(mut s: String, retries: u32) -> String {
 
 #[cfg(test)]
 mod tests {
-    use super::{format_ack, format_recv};
+    use super::{dial_socket, format_ack, format_recv};
+
+    #[tokio::test]
+    async fn a_socket_that_accepts_and_never_answers_is_given_up_on() {
+        let path = std::env::temp_dir().join(format!(
+            "hive-agent-mcp-dial-test-{}-{}.sock",
+            std::process::id(),
+            std::time::SystemTime::now()
+                .duration_since(std::time::UNIX_EPOCH)
+                .unwrap()
+                .as_nanos()
+        ));
+        let listener = tokio::net::UnixListener::bind(&path).unwrap();
+        // Accept, then hold the connection open without ever replying.
+        let _stalled = tokio::spawn(async move {
+            let conn = listener.accept().await;
+            std::future::pending::<()>().await;
+            drop(conn);
+        });
+
+        let resp = dial_socket(
+            &path,
+            &hive_agent_sock::Request::ListReminders,
+            std::time::Duration::from_millis(100),
+        )
+        .await;
+        let _ = std::fs::remove_file(&path);
+
+        assert!(resp.is_none());
+    }
 
     fn msg(id: i64, from: &str, body: &str) -> hive_sh4re::inbox::DeliveredMessage {
         hive_sh4re::inbox::DeliveredMessage {