🤖 Disable SSH ControlMaster for timed commands

When ControlMaster multiplexing is enabled, killing the SSH client
doesn't kill the remote command - it continues running under the master
connection. Disable multiplexing for commands with timeout to ensure
killing the SSH process reliably terminates the remote command.

This is simpler than wrapping remote commands with timeout utilities.

Author: ammar-agent

src/runtime/SSHRuntime.ts

@@ -90,21 +90,10 @@ export class SSHRuntime implements Runtime {
     parts.push(command);
 
     // Join all parts with && to ensure each step succeeds before continuing
-    let fullCommand = parts.join(" && ");
-
-    // Wrap command with timeout if specified
-    // This ensures the remote command is killed even if the SSH connection persists
-    // (e.g., due to ControlMaster multiplexing)
-    if (options.timeout !== undefined) {
-      // Use timeout command with KILL signal after timeout expires
-      // The timeout value is slightly longer than our local timeout to ensure
-      // the local timeout fires first in normal cases
-      const remoteTimeout = Math.ceil(options.timeout) + 1;
-      fullCommand = `timeout --signal=KILL ${remoteTimeout} bash -c ${shescape.quote(fullCommand)}`;
-    }
+    const fullCommand = parts.join(" && ");
 
     // Wrap in bash -c with shescape for safe shell execution
-    const remoteCommand = options.timeout ? fullCommand : `bash -c ${shescape.quote(fullCommand)}`;
+    const remoteCommand = `bash -c ${shescape.quote(fullCommand)}`;
 
     // Build SSH args
     const sshArgs: string[] = ["-T"];
@@ -128,9 +117,19 @@ export class SSHRuntime implements Runtime {
     // ControlMaster=auto: Create master connection if none exists, otherwise reuse
     // ControlPath: Unix socket path for multiplexing
     // ControlPersist=60: Keep master connection alive for 60s after last session
-    sshArgs.push("-o", "ControlMaster=auto");
-    sshArgs.push("-o", `ControlPath=${this.controlPath}`);
-    sshArgs.push("-o", "ControlPersist=60");
+    // 
+    // IMPORTANT: Disable multiplexing when timeout is set, because:
+    // - Killing an SSH client with multiplexing doesn't kill the remote command
+    // - The remote command continues running under the master connection
+    // - Without multiplexing, killing SSH reliably terminates the remote command
+    if (options.timeout === undefined) {
+      sshArgs.push("-o", "ControlMaster=auto");
+      sshArgs.push("-o", `ControlPath=${this.controlPath}`);
+      sshArgs.push("-o", "ControlPersist=60");
+    } else {
+      // Explicitly disable multiplexing for timed commands
+      sshArgs.push("-o", "ControlMaster=no");
+    }
 
     // Set comprehensive timeout options to ensure SSH respects the timeout
     // ConnectTimeout: Maximum time to wait for connection establishment (DNS, TCP handshake, SSH auth)