some fixes

python_app/gui/controllers/app_window_pipeline_mixin.py

@@ -142,6 +142,14 @@ class AppWindowPipelineMixin:
                     self._log("History reset because run settings changed")
                 self._history_run_signature = run_signature
 
+            # Open the single-capture acquisition window BEFORE the producer can emit:
+            # any collection the one-shot orchestrator publishes is then strictly newer
+            # than this timestamp and is recognized as the target. Reading the clock
+            # AFTER start() raced a fast (simulator) orchestrator that had already
+            # published — its collection.monotonic_ns < start_ns, so the capture never
+            # completed and the GUI hung.
+            single_capture_start_ns = time.monotonic_ns() if single_capture else None
+
             self._supervisor.start(config_path, allow_clean_orchestrator_exit=single_capture)
             self._close_readers()
             self._raw_reader = ShmRingReader(config.rings.raw_tap.name)
@@ -149,13 +157,16 @@ class AppWindowPipelineMixin:
             self._result_reader = ShmRingReader(config.rings.results.name)
             self._processor_run_signature = processor_signature
             self._single_capture_active = single_capture
-            self._single_capture_start_ns = None
+            self._single_capture_start_ns = single_capture_start_ns
             self._single_capture_seen_raw = False
             self._single_capture_target_collection_id = None
 
-            # Always drop unread payloads for all stages so single-capture starts
-            # from a clean boundary and does not retain stale results-only tail.
-            self._drop_pending_ring_payloads(include_results=True)
+            if not single_capture:
+                # Continuous start: discard any stale tail so rendering begins fresh.
+                # Single capture must NOT drop here — the drop races with (and can
+                # discard) the one-shot result; it instead filters stale data by the
+                # start timestamp recorded above.
+                self._drop_pending_ring_payloads(include_results=True)
             self._last_reader_error_signature = None
             self._reader_error_repeat_count = 0
             # Record what to relaunch if a child later dies unexpectedly. Only a
@@ -164,8 +175,6 @@ class AppWindowPipelineMixin:
             self._active_run_config_path = config_path
             self._pipeline_should_run = not single_capture
             self._pipeline_restart_count = 0
-            if single_capture:
-                self._single_capture_start_ns = time.monotonic_ns()
 
             pid_map = self._supervisor.pids()
             pid_text = ", ".join(f"{name}={pid}" for name, pid in sorted(pid_map.items())) or "none"