diff --git a/CHANGELOG.md b/CHANGELOG.md
index 85217a6..c0bf56f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,22 @@
 # Stream-Mapparr CHANGELOG
 
+## 1.26.2571153 (2026-09-14)
+
+### Changed
+
+- **A scheduled run now stands aside when IPTV Checker is mid-scan and Run After
+  IPTV Checker Scan is on.** On the first morning the trigger fired, the fixed-time
+  run had been waiting for that same scan under Wait for IPTV Checker Completion,
+  saw the scan end, and sorted the same channels one second after the triggered run,
+  in a different worker process, while that run was still writing. Nothing was
+  damaged, but two delete-and-recreate passes over the same rows at once is not a
+  state to leave open. The fixed-time run now checks, before it waits, whether a
+  scan is running and the trigger will cover the day; if both are true it logs that
+  it is standing aside and returns without running. A missing or unreadable
+  progress file counts as not running, so an installation without IPTV Checker
+  keeps its schedule exactly as before. The scheduled-run timestamp behind
+  Validate Settings is not written for a run that stood aside.
+
 ## 1.26.2561754 (2026-09-13)
 
 ### Added
diff --git a/Stream-Mapparr/__init__.py b/Stream-Mapparr/__init__.py
index cb08636..1416582 100644
--- a/Stream-Mapparr/__init__.py
+++ b/Stream-Mapparr/__init__.py
@@ -5,5 +5,5 @@
 
 from .plugin import Plugin
 
-__version__ = "1.26.2561754"
+__version__ = "1.26.2571153"
 __all__ = ["Plugin"]
\ No newline at end of file
diff --git a/Stream-Mapparr/plugin.json b/Stream-Mapparr/plugin.json
index ee72c50..df97357 100644
--- a/Stream-Mapparr/plugin.json
+++ b/Stream-Mapparr/plugin.json
@@ -1,6 +1,6 @@
 {
   "name": "Stream-Mapparr",
-  "version": "1.26.2561754",
+  "version": "1.26.2571153",
   "description": "Automatically add matching streams to channels based on name similarity and quality precedence. Supports unlimited stream matching, channel visibility management, and CSV export cleanup.",
   "author": "PiratesIRC",
   "license": "MIT",
diff --git a/Stream-Mapparr/plugin.py b/Stream-Mapparr/plugin.py
index 8ee8a8c..88de673 100644
--- a/Stream-Mapparr/plugin.py
+++ b/Stream-Mapparr/plugin.py
@@ -303,7 +303,7 @@ class PluginConfig:
     """
 
     # === PLUGIN METADATA ===
-    PLUGIN_VERSION = "1.26.2561754"
+    PLUGIN_VERSION = "1.26.2571153"
     FUZZY_MATCHER_MIN_VERSION = "25.358.0200"  # Requires custom ignore tags Unicode fix
 
     # Match sensitivity presets (maps select value to threshold number)
@@ -8091,6 +8091,18 @@ def _run_scheduled_sequence(self, settings, logger, trigger=None):
         and the timestamp means "the timer fired".
         """
         if trigger is None:
+            # Measured 2026-09-14: with the trigger on, a timer run that waited
+            # for the checker and the run the checker then triggered sorted the
+            # same channels concurrently, one second apart, in two workers.
+            # When the trigger will cover the day, the timer stands aside. The
+            # slot is already claimed, so nothing re-runs; the scheduled-run
+            # timestamp is not written, because no run happened here.
+            if (self._should_run_after_iptv_checker_scan(settings)
+                    and self._iptv_checker_is_running(logger)):
+                logger.info("[Stream-Mapparr] IPTV Checker is running and 'Run After IPTV Checker Scan' "
+                            "is on, so this scheduled run stands aside; the scan will trigger the steps when it finishes")
+                return {"status": "skipped",
+                        "message": "Left to the IPTV Checker trigger, because a scan is in progress"}
             if not self._wait_for_iptv_checker_completion(settings, logger):
                 logger.warning("[Stream-Mapparr] IPTV Checker wait timed out, proceeding anyway")
         else:
@@ -8143,6 +8155,19 @@ def _run_scheduled_sequence(self, settings, logger, trigger=None):
         logger.info("[Stream-Mapparr] Scheduled run completed successfully")
         return {"status": "success"}
 
+    def _iptv_checker_is_running(self, logger):
+        """True only when the IPTV Checker progress file says a check is running.
+
+        Fails open to False: a missing, unreadable or unparseable file means the
+        timer run proceeds as it always did, so a checker that is not installed
+        can never silence the schedule.
+        """
+        try:
+            with open(PluginConfig.IPTV_CHECKER_PROGRESS_FILE, 'r') as fh:
+                return json.load(fh).get('status') == 'running'
+        except (OSError, ValueError, AttributeError):
+            return False
+
     def _should_run_after_iptv_checker_scan(self, settings):
         """Pure gate for the IPTV Checker trigger: the setting alone, no ORM."""
         return self._get_bool_setting(settings, "run_after_iptv_checker_scan",
diff --git a/tests/test_iptv_checker_trigger.py b/tests/test_iptv_checker_trigger.py
index a183ee4..8fc7d9c 100644
--- a/tests/test_iptv_checker_trigger.py
+++ b/tests/test_iptv_checker_trigger.py
@@ -206,3 +206,82 @@ def test_a_triggered_run_names_its_trigger_in_the_header(plugin_module):
 def test_a_timer_run_does_not_mention_a_trigger(plugin_module):
     line = _mode_line(plugin_module, is_scheduled=True)
     assert "Scheduled" in line and "after" not in line
+
+
+# --------------------------------------------------------------------------- #
+# The timer run stands aside when the trigger will cover the day (2026-09-14)
+# --------------------------------------------------------------------------- #
+def _wire_running(monkeypatch, p, running):
+    monkeypatch.setattr(p, "_iptv_checker_is_running", lambda logger: running)
+
+
+def test_the_timer_skips_when_the_trigger_is_on_and_the_checker_is_running(plugin_module, monkeypatch):
+    """Measured 2026-09-14: the waiting timer run and the triggered run sorted
+    the same channels concurrently, one second apart, in two workers."""
+    p = _plugin(plugin_module)
+    calls, stamps = _wire_sequence(monkeypatch, p)
+    _wire_running(monkeypatch, p, True)
+    settings = {"run_after_iptv_checker_scan": True, "scheduled_sort_streams": True,
+                "scheduled_match_streams": False}
+    result = p._run_scheduled_sequence(settings, log)
+    assert result["status"] == "skipped"
+    assert calls == []
+    assert stamps == []
+
+
+def test_the_timer_still_waits_when_the_trigger_is_off(plugin_module, monkeypatch):
+    p = _plugin(plugin_module)
+    calls, _ = _wire_sequence(monkeypatch, p)
+    _wire_running(monkeypatch, p, True)
+    settings = {"run_after_iptv_checker_scan": False, "scheduled_sort_streams": True,
+                "scheduled_match_streams": False}
+    p._run_scheduled_sequence(settings, log)
+    assert calls == ["wait", "load", ("sort", True, None)]
+
+
+def test_the_timer_runs_normally_when_the_checker_is_idle(plugin_module, monkeypatch):
+    p = _plugin(plugin_module)
+    calls, _ = _wire_sequence(monkeypatch, p)
+    _wire_running(monkeypatch, p, False)
+    settings = {"run_after_iptv_checker_scan": True, "scheduled_sort_streams": True,
+                "scheduled_match_streams": False}
+    p._run_scheduled_sequence(settings, log)
+    assert calls == ["wait", "load", ("sort", True, None)]
+
+
+def test_the_triggered_path_never_consults_the_running_check(plugin_module, monkeypatch):
+    p = _plugin(plugin_module)
+    calls, _ = _wire_sequence(monkeypatch, p)
+
+    def boom(logger):
+        raise AssertionError("the triggered path must not ask whether the checker is running")
+    monkeypatch.setattr(p, "_iptv_checker_is_running", boom)
+    settings = {"run_after_iptv_checker_scan": True, "scheduled_sort_streams": True,
+                "scheduled_match_streams": False}
+    p._run_scheduled_sequence(settings, log, trigger=TRIGGER)
+    assert calls == ["load", ("sort", True, TRIGGER)]
+
+
+def _progress(plugin_module, monkeypatch, tmp_path, content):
+    path = tmp_path / "iptv_checker_progress.json"
+    if content is not None:
+        path.write_text(content, encoding="utf-8")
+    monkeypatch.setattr(plugin_module.PluginConfig, "IPTV_CHECKER_PROGRESS_FILE", str(path))
+
+
+def test_running_check_reads_the_progress_file(plugin_module, monkeypatch, tmp_path):
+    p = _plugin(plugin_module)
+    _progress(plugin_module, monkeypatch, tmp_path, '{"status": "running", "current": 3, "total": 9}')
+    assert p._iptv_checker_is_running(log) is True
+    _progress(plugin_module, monkeypatch, tmp_path, '{"status": "idle"}')
+    assert p._iptv_checker_is_running(log) is False
+
+
+def test_running_check_fails_open_to_not_running(plugin_module, monkeypatch, tmp_path):
+    """A missing or unreadable file must not make the timer stand aside, or a
+    checker that is not installed would silence the schedule forever."""
+    p = _plugin(plugin_module)
+    _progress(plugin_module, monkeypatch, tmp_path, None)
+    assert p._iptv_checker_is_running(log) is False
+    _progress(plugin_module, monkeypatch, tmp_path, "{not json")
+    assert p._iptv_checker_is_running(log) is False