fix(shared-runtime): guard shutdown() against Tokio TLS destruction

libdd-shared-runtime/src/shared_runtime/fork_safe.rs

@@ -131,6 +131,17 @@ impl ForkSafeRuntime {
     /// exceeded.
     pub fn shutdown(&self, timeout: Option<std::time::Duration>) -> Result<(), SharedRuntimeError> {
         debug!(?timeout, "Shutting down ForkSafeRuntime");
+        // block_on calls context::enter() which accesses Tokio's CONTEXT thread-local.
+        // During CPython interpreter finalization, TLS is destroyed before atexit handlers
+        // fire, causing a panic. Detect this via try_current() and bail out early —
+        // the OS will clean up remaining threads on process exit.
+        if matches!(
+            tokio::runtime::Handle::try_current(),
+            Err(ref e) if e.is_thread_local_destroyed()
+        ) {
+            debug!("Tokio TLS destroyed during interpreter finalization, skipping shutdown");
+            return Ok(());
+        }
         match self.runtime.lock_or_panic().take() {
             Some(runtime) => {
                 if let Some(timeout) = timeout {
@@ -421,4 +432,24 @@ mod tests {
             "worker should not run or shut down after fork in child when restart_on_fork is false"
         );
     }
+
+    #[test]
+    fn test_shutdown_is_idempotent() {
+        // Calling shutdown() twice must not panic or error. The second call hits the
+        // None-guard (runtime already taken). This covers the same early-return path as
+        // the TLS-destroyed guard added for CPython atexit finalization ordering.
+        let shared_runtime = ForkSafeRuntime::new().unwrap();
+        let (worker, receiver) = make_test_worker();
+
+        let _ = shared_runtime.spawn_worker(worker, true).unwrap();
+        receiver
+            .recv_timeout(Duration::from_secs(1))
+            .expect("worker did not run");
+
+        assert!(shared_runtime.shutdown(None).is_ok());
+        assert!(
+            shared_runtime.shutdown(None).is_ok(),
+            "second shutdown must not panic"
+        );
+    }
 }