From 1d267375f9bda3167a3f3e349ee7aa27b123e32d Mon Sep 17 00:00:00 2001
From: wyzula-jan <jan.wyzula@psi.ch>
Date: Thu, 2 Jul 2026 23:45:47 +0200
Subject: [PATCH] fix(rpc): isolate broadcast callbacks and retry delivery
 after failures

---
 bec_widgets/utils/rpc_register.py     | 12 ++++++++++-
 tests/unit_tests/test_rpc_register.py | 31 +++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/bec_widgets/utils/rpc_register.py b/bec_widgets/utils/rpc_register.py
index e126683c..6493769b 100644
--- a/bec_widgets/utils/rpc_register.py
+++ b/bec_widgets/utils/rpc_register.py
@@ -182,6 +182,7 @@ class RPCRegister:
         self._broadcast_pending = False
         connections = self.list_all_connections()
         dead_refs = []
+        delivery_failed = False
         for callback_ref in list(self.callbacks):
             callback = callback_ref()
             if callback is None:
@@ -193,12 +194,21 @@ class RPCRegister:
                 # e.g. during shutdown): calling it would raise on any Qt access.
                 dead_refs.append(callback_ref)
                 continue
-            callback(connections)
+            try:
+                callback(connections)
+            except Exception:
+                delivery_failed = True
+                logger.exception(f"RPC registry broadcast callback {callback!r} failed")
         for ref in dead_refs:
             try:
                 self.callbacks.remove(ref)
             except ValueError:
                 pass
+        if delivery_failed:
+            # The state change must not be lost: leave the registry dirty so the
+            # next broadcast retries delivery (duplicates are safe, the payload
+            # is the full state).
+            self._broadcast_pending = True
 
     def object_is_registered(self, obj: BECConnector) -> bool:
         """
diff --git a/tests/unit_tests/test_rpc_register.py b/tests/unit_tests/test_rpc_register.py
index 40d3f6ee..6d9dcb9e 100644
--- a/tests/unit_tests/test_rpc_register.py
+++ b/tests/unit_tests/test_rpc_register.py
@@ -189,3 +189,34 @@ def test_broadcast_without_callbacks_skips_registry_walk(rpc_register, monkeypat
     rpc_register.broadcast()
     walk.assert_called_once()
     assert len(received) == 1
+
+
+def test_broadcast_prunes_callbacks_of_destroyed_qobjects(rpc_register, qapp):
+    """A bound-method callback whose QObject was destroyed (Python wrapper still
+    referenced, C++ side gone — the shutdown scenario) must be pruned, not called."""
+    import shiboken6
+    from qtpy.QtCore import QObject
+
+    class Listener(QObject):
+        def __init__(self):
+            super().__init__()
+            self.received = []
+
+        def on_update(self, connections):
+            self.received.append(connections)
+
+    listener = Listener()
+    rpc_register.add_callback(listener.on_update)
+    rpc_register.mark_broadcast_pending()
+    rpc_register.broadcast()
+    assert len(listener.received) == 1
+    callbacks_before = len(rpc_register.callbacks)
+
+    shiboken6.delete(listener)
+    assert not shiboken6.isValid(listener)
+
+    rpc_register.mark_broadcast_pending()
+    rpc_register.broadcast()  # must neither call the dead callback nor raise
+
+    assert len(listener.received) == 1
+    assert len(rpc_register.callbacks) == callbacks_before - 1