diff --git a/apps/myelin/src/orchestration/app.rs b/apps/myelin/src/orchestration/app.rs
index 7f5827f..d5da374 100644
--- a/apps/myelin/src/orchestration/app.rs
+++ b/apps/myelin/src/orchestration/app.rs
@@ -2375,7 +2375,8 @@ fn spawn_stop_listener(
     }
 
     #[cfg(target_os = "linux")]
-    swactor_process::spawn_os_stop_signal_wait(sender, actor);
+    swactor_process::spawn_os_stop_signal_wait(sender, actor)
+        .map_err(|error| format!("install orchestrator stop signal handler: {error}"))?;
     Ok(())
 }
 
diff --git a/crates/process/src/operations.rs b/crates/process/src/operations.rs
index 040db23..65a9fe7 100644
--- a/crates/process/src/operations.rs
+++ b/crates/process/src/operations.rs
@@ -147,19 +147,22 @@ fn spawn_stop_channel_wait_thread(
 }
 
 /// Wait for SIGINT/SIGTERM and notify an actor once.
+///
+/// Signal handlers are installed before this function returns. A caller may
+/// therefore publish readiness immediately after a successful return without
+/// racing the operating system's default signal action.
 #[cfg(target_os = "linux")]
-pub fn spawn_os_stop_signal_wait(sender: ExternalSender, actor: ActorAddress) {
+pub fn spawn_os_stop_signal_wait(sender: ExternalSender, actor: ActorAddress) -> io::Result<()> {
+    let mut signals = signal_hook::iterator::Signals::new([
+        signal_hook::consts::signal::SIGINT,
+        signal_hook::consts::signal::SIGTERM,
+    ])?;
     thread::spawn(move || {
-        let Ok(mut signals) = signal_hook::iterator::Signals::new([
-            signal_hook::consts::signal::SIGINT,
-            signal_hook::consts::signal::SIGTERM,
-        ]) else {
-            return;
-        };
         if signals.forever().next().is_some() {
             let _ = sender.send_to(actor, ProcessStopSignal);
         }
     });
+    Ok(())
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
diff --git a/xtask/src/demo/mod.rs b/xtask/src/demo/mod.rs
index 3bb5bda..6788392 100644
--- a/xtask/src/demo/mod.rs
+++ b/xtask/src/demo/mod.rs
@@ -503,7 +503,8 @@ fn run_supervisor(args: &[String]) -> Result<(), String> {
         })
         .map_err(|error| format!("spawn supervisor stop actor: {error}"))?;
     #[cfg(target_os = "linux")]
-    swactor_process::spawn_os_stop_signal_wait(runtime.create_sender(), stop_actor);
+    swactor_process::spawn_os_stop_signal_wait(runtime.create_sender(), stop_actor)
+        .map_err(|error| format!("install supervisor stop signal handler: {error}"))?;
     println!("demo: dashboard on http://localhost:{port}");
     println!("  /view/fleet        — per-node cards (pid, lifecycle)");
     println!("  /view/demo-control — Fleet Control: stages, feeds, kill / provision / edge");
diff --git a/xtask/src/demo/node.rs b/xtask/src/demo/node.rs
index b7e0a2f..2734c50 100644
--- a/xtask/src/demo/node.rs
+++ b/xtask/src/demo/node.rs
@@ -256,7 +256,8 @@ pub fn run_node_role(supervisor_addr_json: &str, attempt: u64) -> Result<(), Str
         })
         .map_err(|error| format!("spawn node stop actor: {error}"))?;
     #[cfg(target_os = "linux")]
-    swactor_process::spawn_os_stop_signal_wait(runtime.create_sender(), stop_actor);
+    swactor_process::spawn_os_stop_signal_wait(runtime.create_sender(), stop_actor)
+        .map_err(|error| format!("install node stop signal handler: {error}"))?;
 
     // The actor owns lifecycle; the entrypoint waits only for its terminal signal.
     completion.wait();