fix(plugins): report updates that completed, not ones that were queued

run_scheduled_updates_with_changes() snapshotted plugin_last_update,
called run_scheduled_updates(), and diffed the two to answer "whose data
just changed".

But run_scheduled_updates() only enqueues. The work runs on the update
worker and stamps plugin_last_update there, after this method has already
returned, so the two snapshots were always identical and the result was
always an empty list. The only path that ever worked was the synchronous
kill-switch, where update() runs inline.

Vegas is the caller. That empty list is what feeds mark_plugin_updated(),
which drops the cached content for a plugin whose data moved -- so a
segment kept scrolling whatever it was first built from. It is the
failure the coordinator's own comments describe: last night's live game
still drawn as live the next morning. On a live rig: zero update ticks in
twenty minutes, with weather, stocks and news all updating on schedule.

The worker now records each completed update in a ledger and the call
drains it, reporting what has finished since the previous poll rather
than what this call enqueued. That costs one tick of latency -- Vegas
polls every ~4s -- and is correct whichever side of the queue the work
lands on. Failure paths are excluded: they stamp the timestamp too, to
space out retries, but no fresh data exists.

Verified on the rig it was found on: 0 update ticks before, 208 in
twenty-five minutes after, naming real plugins.

The behavioural tests here would pass with both production call sites
deleted, which mutation testing caught -- they drive the ledger directly.
So there is also a structural test asserting the invariant at the source:
wherever a successful update stamps plugin_last_update, it must record
the completion. Writing it immediately caught that _record_update_failure
stamps the same field and must not be included.

Mutation-checked: removing either call site, removing both, and dropping
the drain's clear are all caught.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Udr6MfaFLUPhX5Fgo67Jf5

src/plugin_system/plugin_manager.py

@@ -116,6 +116,14 @@ class PluginManager:
         self._plugin_locks: Dict[str, threading.Lock] = {}
         self._plugin_locks_guard = threading.Lock()
         self._update_worker: Optional[threading.Thread] = None
+        # Plugin ids whose update() has finished since the last time anyone
+        # asked. Updates are dispatched to a worker thread, so a caller that
+        # wants to know "whose data just changed" cannot learn it by diffing
+        # plugin_last_update around run_scheduled_updates() -- that call only
+        # enqueues, and the timestamp is stamped later, on the worker. See
+        # run_scheduled_updates_with_changes().
+        self._completed_updates: set = set()
+        self._completed_updates_lock = threading.Lock()
         self._synchronous_updates = False
         if self.config_manager is not None:
             try:
@@ -940,6 +948,7 @@ class PluginManager:
                 if success:
                     with self._plugin_last_update_lock:
                         self.plugin_last_update[plugin_id] = scheduled_time
+                    self._note_update_completed(plugin_id)
                     self.state_manager.record_update(plugin_id)
                     self.state_manager.set_state(plugin_id, PluginState.ENABLED)
                     if self.health_tracker:
@@ -1006,28 +1015,41 @@ class PluginManager:
 
     def run_scheduled_updates_with_changes(self, current_time: Optional[float] = None) -> List[str]:
         """
-        Like run_scheduled_updates(), but also returns the plugin_ids whose
+        Like run_scheduled_updates(), but also reports which plugins have
-        plugin_last_update timestamp actually advanced during this call.
+        fresh data -- the ids whose update() has finished since the last
+        call, not necessarily the ones enqueued by this one.
 
-        The before/after snapshots and the update pass itself are each
+        That distinction is the whole point. This used to snapshot
-        individually lock-protected against concurrent plugin_last_update
+        plugin_last_update, call run_scheduled_updates(), and diff. But
-        mutation (Vegas mode calls this from its own background
+        run_scheduled_updates() only *enqueues*: the work runs on the
-        update-tick thread, racing the main render loop's plugin updates),
+        update worker and the timestamp is stamped there, after this method
-        so callers get an atomic "who got fresh data" answer without
+        has already returned. The two snapshots were therefore always
-        reaching into plugin_last_update themselves. The lock is not held
+        identical and the result was always empty, so Vegas never learned
-        across the update pass so slow/blocking plugin update() calls don't
+        that any plugin's data had changed and kept scrolling whatever a
-        serialize against other plugin_last_update readers.
+        segment was first built from -- last night's live game still drawn
+        as live the next morning. The only path that ever worked was the
+        synchronous kill-switch, where update() runs inline.
+
+        Reporting completions instead of enqueues costs a poll's worth of
+        latency (the Vegas tick runs every ~4s) and is correct regardless of
+        which side of the queue the work lands on.
         """
-        with self._plugin_last_update_lock:
-            old_times = dict(self.plugin_last_update)
-
         self.run_scheduled_updates(current_time)
+        return self.drain_completed_updates()
 
-        with self._plugin_last_update_lock:
+    def _note_update_completed(self, plugin_id: str) -> None:
-            return [
+        """Record that a plugin's update() finished, for the next poll."""
-                plugin_id for plugin_id, new_time in self.plugin_last_update.items()
+        with self._completed_updates_lock:
-                if new_time > old_times.get(plugin_id, 0.0)
+            self._completed_updates.add(plugin_id)
-            ]
+
+    def drain_completed_updates(self) -> List[str]:
+        """Return and clear the plugin ids whose update() has since finished."""
+        with self._completed_updates_lock:
+            if not self._completed_updates:
+                return []
+            done = sorted(self._completed_updates)
+            self._completed_updates.clear()
+            return done
 
     def update_all_plugins(self) -> None:
         """
@@ -1053,6 +1075,7 @@ class PluginManager:
                 if success:
                     with self._plugin_last_update_lock:
                         self.plugin_last_update[plugin_id] = time.time()
+                    self._note_update_completed(plugin_id)
                     self.state_manager.record_update(plugin_id)
                     self.state_manager.set_state(plugin_id, PluginState.ENABLED)
                 else:

test/test_update_change_reporting.py

@@ -0,0 +1,182 @@
+#!/usr/bin/env python3
+"""
+Tests that "which plugins have fresh data" survives the async update worker.
+
+Regression under test: run_scheduled_updates_with_changes() snapshotted
+plugin_last_update, called run_scheduled_updates(), and diffed the two. But
+run_scheduled_updates() only *enqueues* -- the work runs on the update worker
+and stamps the timestamp there, after the method has already returned. The
+snapshots were therefore always identical and the result always empty.
+
+Vegas depends on that result: it is what calls mark_plugin_updated(), which
+drops the cached content for a plugin whose data changed. With it always
+empty, a segment kept scrolling whatever it was first built from -- the
+"last night's live game still drawn as live the next morning" failure the
+coordinator comments describe. Observed on a live rig: zero update ticks in
+twenty minutes, with weather, stocks and news all updating.
+
+Run: python -m pytest test/test_update_change_reporting.py -v
+"""
+
+import ast
+import inspect
+import sys
+import threading
+import unittest
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+from src.plugin_system.plugin_manager import PluginManager  # noqa: E402
+
+
+def _manager():
+    """A PluginManager with only the update-reporting state initialised."""
+    manager = PluginManager.__new__(PluginManager)
+    manager._completed_updates = set()
+    manager._completed_updates_lock = threading.Lock()
+    return manager
+
+
+class DrainCompletedUpdates(unittest.TestCase):
+    def setUp(self):
+        self.manager = _manager()
+
+    def test_nothing_completed_reports_nothing(self):
+        self.assertEqual(self.manager.drain_completed_updates(), [])
+
+    def test_a_completed_update_is_reported(self):
+        self.manager._note_update_completed("news")
+        self.assertEqual(self.manager.drain_completed_updates(), ["news"])
+
+    def test_draining_clears_so_the_next_poll_is_empty(self):
+        self.manager._note_update_completed("news")
+        self.manager.drain_completed_updates()
+        self.assertEqual(
+            self.manager.drain_completed_updates(), [],
+            "a plugin must be reported once per update, not on every poll, "
+            "or Vegas would drop its cached content every few seconds")
+
+    def test_repeated_completions_between_polls_collapse(self):
+        for _ in range(5):
+            self.manager._note_update_completed("weather")
+        self.assertEqual(self.manager.drain_completed_updates(), ["weather"])
+
+    def test_multiple_plugins_are_all_reported(self):
+        for plugin_id in ("news", "weather", "ledmatrix-stocks"):
+            self.manager._note_update_completed(plugin_id)
+        self.assertEqual(self.manager.drain_completed_updates(),
+                         ["ledmatrix-stocks", "news", "weather"])
+
+
+class CompletionReportingIsAsyncSafe(unittest.TestCase):
+    """The point of the change: completion may land after the call returns."""
+
+    def setUp(self):
+        self.manager = _manager()
+
+    def test_an_update_completing_after_the_call_is_still_reported(self):
+        """The exact shape of the bug.
+
+        The enqueueing call sees nothing, because the worker has not run yet.
+        The next poll must report it -- under the old diff it was lost, since
+        the second snapshot was taken before the worker ever stamped.
+        """
+        first = self.manager.drain_completed_updates()
+        self.assertEqual(first, [], "nothing has finished yet")
+
+        # The worker finishes some time later, on its own thread.
+        worker = threading.Thread(
+            target=self.manager._note_update_completed, args=("news",))
+        worker.start()
+        worker.join()
+
+        self.assertEqual(
+            self.manager.drain_completed_updates(), ["news"],
+            "an update that finishes between polls must still be reported")
+
+    def test_concurrent_completions_are_not_lost(self):
+        ids = ["plugin-%02d" % i for i in range(40)]
+        threads = [threading.Thread(target=self.manager._note_update_completed,
+                                    args=(pid,)) for pid in ids]
+        for thread in threads:
+            thread.start()
+        for thread in threads:
+            thread.join()
+        self.assertEqual(self.manager.drain_completed_updates(), sorted(ids))
+
+    def test_a_completion_during_a_drain_is_not_swallowed(self):
+        """A drain must not clear an entry it did not report."""
+        self.manager._note_update_completed("news")
+        reported = self.manager.drain_completed_updates()
+        # ...worker finishes another one immediately afterwards
+        self.manager._note_update_completed("weather")
+        self.assertEqual(reported, ["news"])
+        self.assertEqual(self.manager.drain_completed_updates(), ["weather"])
+
+
+class EveryStampRecordsACompletion(unittest.TestCase):
+    """The ledger is only correct if the production paths actually fill it.
+
+    Asserting on the mechanics alone passes even when nothing calls
+    _note_update_completed -- verified by deleting the call sites, which the
+    behavioural tests above did not notice. This checks the invariant at the
+    source: wherever a successful update stamps plugin_last_update, it must
+    also record the completion, or Vegas silently stops being told.
+    """
+
+    def test_success_paths_record_the_completion(self):
+        import src.plugin_system.plugin_manager as pm
+
+        tree = ast.parse(inspect.getsource(pm))
+        stamps = []
+        for node in ast.walk(tree):
+            if not isinstance(node, ast.With):
+                continue
+            # `with self._plugin_last_update_lock:` blocks that stamp a real
+            # time on success. Two stamps are deliberately excluded: the 0.0
+            # written at registration, and the failure path, which backs the
+            # timestamp off to space out retries -- neither means fresh data.
+            assigns_time = any(
+                isinstance(stmt, ast.Assign)
+                and any(isinstance(t, ast.Subscript)
+                        and getattr(t.value, "attr", None) == "plugin_last_update"
+                        for t in stmt.targets)
+                and not (isinstance(stmt.value, ast.Constant)
+                         and stmt.value.value == 0.0)
+                and "failure" not in ast.dump(stmt.value)
+                for stmt in node.body
+            )
+            if assigns_time:
+                stamps.append(node)
+
+        self.assertGreaterEqual(
+            len(stamps), 2,
+            "expected the worker and inline success paths to stamp the time; "
+            "if this drops, the search below is looking at the wrong thing")
+
+        for stamp in stamps:
+            enclosing = self._enclosing_function(tree, stamp)
+            calls = [n for n in ast.walk(enclosing)
+                     if isinstance(n, ast.Call)
+                     and getattr(n.func, "attr", None) == "_note_update_completed"]
+            self.assertTrue(
+                calls,
+                "%s stamps plugin_last_update on success but never calls "
+                "_note_update_completed, so a plugin's fresh data would never "
+                "be reported and Vegas would keep its stale cached content"
+                % enclosing.name)
+
+    @staticmethod
+    def _enclosing_function(tree, target):
+        best = None
+        for node in ast.walk(tree):
+            if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef)):
+                if node.lineno <= target.lineno <= (node.end_lineno or node.lineno):
+                    if best is None or node.lineno > best.lineno:
+                        best = node
+        return best
+
+
+if __name__ == "__main__":
+    unittest.main(verbosity=2)