diff --git a/crates/codex-runtime/tests/runtime_binary.rs b/crates/codex-runtime/tests/runtime_binary.rs
index 1e3b73d..073855b 100644
--- a/crates/codex-runtime/tests/runtime_binary.rs
+++ b/crates/codex-runtime/tests/runtime_binary.rs
@@ -20,14 +20,20 @@ fn runner_socket(dir: &Path) -> PathBuf {
     dir.join("runner.sock")
 }
 
+/// The worker's socket, once it accepts. A worker binary never run before can take macOS a few
+/// seconds to start: it checks a new executable file on its first exec, and cargo places the
+/// binary anew for each test run.
 async fn wait_connect(socket: &Path) -> UnixStream {
-    for _ in 0..100 {
+    let deadline = tokio::time::Instant::now() + Duration::from_secs(10);
+    loop {
         if let Ok(stream) = UnixStream::connect(socket).await {
             return stream;
         }
+        if tokio::time::Instant::now() >= deadline {
+            panic!("worker socket not ready at {}", socket.display());
+        }
         tokio::time::sleep(Duration::from_millis(20)).await;
     }
-    panic!("worker socket not ready at {}", socket.display());
 }
 
 async fn spawn_worker(socket: &Path) -> tokio::process::Child {
diff --git a/crates/runner/src/launch.rs b/crates/runner/src/launch.rs
index d20b843..c5d9b56 100644
--- a/crates/runner/src/launch.rs
+++ b/crates/runner/src/launch.rs
@@ -688,10 +688,15 @@ mod tests {
     /// consumes the permit, then runs `behavior`, which writes transcript lines with `report`
     /// as the real helper does. It cannot present a grant, so it tests CodeSpace's side only.
     /// It runs under bash: the carriers' numbers can exceed 9, which dash, Linux's `sh`, cannot
-    /// redirect.
+    /// redirect. On macOS it is run once when written, with `--warm`: macOS checks a new
+    /// executable file on its first exec, which can take seconds while other tests start theirs,
+    /// and that time must not count against the launches it serves. Not on Linux, where the
+    /// check does not exist and running a file this process has just written can fail with
+    /// `ETXTBSY` (see `write_script` in `linux_sandbox`).
     fn stand_in(dir: &Path, name: &str, entry: &str, behavior: &str) -> PathBuf {
         let script = format!(
             r#"#!/bin/bash
+if [ "$1" = --warm ]; then exit 0; fi
 while [ "$1" != "--" ]; do
   case "$1" in
     --permit-fd) permit="$2" ;;
@@ -710,6 +715,13 @@ report() {{ eval "printf '%s\n' \"\$1\" >&$report"; }}
         let path = dir.join(name);
         std::fs::write(&path, script).unwrap();
         std::fs::set_permissions(&path, std::fs::Permissions::from_mode(0o700)).unwrap();
+        if cfg!(target_os = "macos") {
+            let warmed = std::process::Command::new(&path)
+                .arg("--warm")
+                .status()
+                .unwrap();
+            assert!(warmed.success(), "{warmed}");
+        }
         path
     }
 
diff --git a/crates/runner/src/linux_sandbox.rs b/crates/runner/src/linux_sandbox.rs
index 6b0e2d7..234b931 100644
--- a/crates/runner/src/linux_sandbox.rs
+++ b/crates/runner/src/linux_sandbox.rs
@@ -609,9 +609,11 @@ mod tests {
 
     #[test]
     fn prepare_stdout_flood_is_too_large() {
-        let dir = tempfile::tempdir().unwrap();
-        let helper = write_script(dir.path(), "#!/bin/sh\nwhile :; do printf x; done\n");
-        let spawned = Command::new(&helper)
+        // The system's `yes` floods in large writes, from a file executed before. Under load,
+        // a byte per write, or the first exec of a script written for the test, could take
+        // long enough to reach the deadline before the limit.
+        let helper = Path::new("/usr/bin/yes");
+        let spawned = Command::new(helper)
             .arg("prepare")
             .stdin(Stdio::piped())
             .stdout(Stdio::piped())
@@ -619,7 +621,7 @@ mod tests {
             .spawn()
             .unwrap();
         let start = Instant::now();
-        let err = prepare_from_child(&helper, spawned, b"{}", Duration::from_secs(2), 64 * 1024)
+        let err = prepare_from_child(helper, spawned, b"{}", Duration::from_secs(2), 64 * 1024)
             .unwrap_err();
         assert_eq!(err.code, ErrorCode::ProcessSpawnFailed);
         assert!(err.message.contains("output too large"), "{}", err.message);
diff --git a/crates/server/src/runtime.rs b/crates/server/src/runtime.rs
index a871f1a..07fbc1b 100644
--- a/crates/server/src/runtime.rs
+++ b/crates/server/src/runtime.rs
@@ -178,17 +178,25 @@ pub(crate) fn worker_command(bin: &Path, socket: &Path) -> Command {
     command
 }
 
+/// How long the gateway waits for a started worker's socket. A worker binary never run before
+/// can take macOS a few seconds to start, as it checks a new executable file on its first exec.
+const WORKER_READY_BOUND: Duration = Duration::from_secs(10);
+
+/// The worker's socket once it accepts; an error at once if the worker exits first.
 async fn wait_for_socket(socket: &Path, wait: &JoinHandle<()>) -> Result<UnixStream> {
-    for _ in 0..100 {
+    let deadline = tokio::time::Instant::now() + WORKER_READY_BOUND;
+    loop {
         if wait.is_finished() {
             return Err(anyhow!("worker exited before the runner socket was ready"));
         }
         match UnixStream::connect(socket).await {
             Ok(stream) => return Ok(stream),
-            Err(_) => tokio::time::sleep(Duration::from_millis(20)).await,
+            Err(_) if tokio::time::Instant::now() < deadline => {
+                tokio::time::sleep(Duration::from_millis(20)).await
+            }
+            Err(_) => return Err(anyhow!("worker socket not ready at {}", socket.display())),
         }
     }
-    Err(anyhow!("worker socket not ready at {}", socket.display()))
 }
 
 #[cfg(test)]
@@ -498,4 +506,26 @@ mod tests {
             .expect("process leases released after worker death");
         assert!(!dir.exists() || std::fs::read_dir(&dir).map(|d| d.count()).unwrap_or(0) == 0);
     }
+
+    /// The wait for a worker's socket is long enough for a first exec, but a worker that exits
+    /// first fails the start at once.
+    #[tokio::test]
+    async fn a_worker_that_exits_before_its_socket_fails_at_once() {
+        let store = Arc::new(Store::memory().unwrap());
+        let started = std::time::Instant::now();
+        let error =
+            RuntimeProcess::spawn(Path::new("/usr/bin/false"), None, Arc::new(|_| {}), store)
+                .await
+                .err()
+                .expect("a worker that exits cannot serve");
+        assert!(
+            format!("{error:#}").contains("worker exited before"),
+            "{error:#}"
+        );
+        assert!(
+            started.elapsed() < Duration::from_secs(5),
+            "{:?}",
+            started.elapsed()
+        );
+    }
 }