diff --git a/src/run.ts b/src/run.ts
index d7263dd..7725f02 100644
--- a/src/run.ts
+++ b/src/run.ts
@@ -28,6 +28,28 @@ type RunOptions = {
   onCommand?: (cmd: Command) => void
 }
 
+function killTree(pid: number): void {
+  // Find any processes that escaped the process group (e.g. via setsid).
+  // This assumes pid === pgid, which holds because the child is spawned
+  // with detached: true (making it a process group leader).
+  try {
+    const result = Bun.spawnSync(["ps", "-eo", "pid,pgid"])
+    const output = result.stdout.toString()
+    const pgid = String(pid)
+    for (const line of output.split("\n")) {
+      const parts = line.trim().split(/\s+/)
+      if (parts[1] === pgid) {
+        const p = parseInt(parts[0]!, 10)
+        if (!isNaN(p) && p !== pid && p > 1) {
+          try { process.kill(p, "SIGKILL") } catch {}
+        }
+      }
+    }
+  } catch {}
+  // Kill the process group
+  try { process.kill(-pid, "SIGKILL") } catch {}
+}
+
 const SENTINEL_PREFIX = "__SHOUT_SENTINEL_"
 const VERBOSE_MARKER = "__SHOUT_CMD_"
 
@@ -235,7 +257,7 @@ export async function runFile(
     }
   } finally {
     if (proc.pid) {
-      try { process.kill(-proc.pid, "SIGKILL") } catch {}
+      killTree(proc.pid)
     }
   }
 }