feat(canary): auto-rebase pe layout change (2↔1 ferestre)

Când canary drift coincide cu schimbare strip-count pe același frame
(ex: TS comută 2→1 chart-uri și mută menu-ul peste care e ancorat ROI),
sistemul rescrie automat baseline_phash în TOML, commit layout change
și trimite o singură alertă combinată — fără pauză, fără /rebase manual.

Drift fără strip-count change rămâne pauză ca azi (drift real).
Gate pe două semnale independente previne fals-pozitive.

Canary.check() despărțit în măsurare pură + commit_pause/rebase
explicit; tick-loop-ul orchestrează decizia.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/atm/canary.py

@@ -24,8 +24,10 @@ class CanaryResult:
 class Canary:
     """Compare live canary ROI phash against a known-good baseline.
 
-    Once drift is detected the instance stays paused until resume() is called,
+    ``check()`` is pure measurement — it never mutates ``_paused`` or fires
-    even if subsequent frames look clean again.
+    side-effects. Callers decide whether to ``commit_pause()`` (real drift) or
+    ``rebase()`` (legitimate layout change). This split exists so the tick loop
+    can use a second signal (strip-count change) to disambiguate before pausing.
     """
 
     def __init__(
@@ -47,8 +49,12 @@ class Canary:
         current_hash = phash(roi_img)
         distance = hamming_hex(current_hash, self._cfg.canary.baseline_phash)
         drifted = distance > self._cfg.canary.drift_threshold
+        return CanaryResult(distance=distance, drifted=drifted, paused=self._paused)
 
-        if drifted and not self._paused:
+    def commit_pause(self, distance: int) -> None:
+        """Transition to paused state. Idempotent — no-op if already paused."""
+        if self._paused:
+            return
         self._paused = True
         if self._pause_flag_path is not None:
             self._pause_flag_path.write_text("paused", encoding="utf-8")
@@ -59,7 +65,13 @@ class Canary:
                 # Never let a notifier hiccup abort the detection cycle.
                 logger.warning("canary on_pause_callback raised: %s", exc)
 
-        return CanaryResult(distance=distance, drifted=drifted, paused=self._paused)
+    def rebase(self, new_phash: str) -> None:
+        """Replace baseline_phash in the live cfg (in-memory mirror).
+
+        Caller is responsible for persisting to TOML separately. Does NOT touch
+        ``_paused`` — used in the auto-rebase path where we never paused.
+        """
+        object.__setattr__(self._cfg.canary, "baseline_phash", new_phash)
 
     @property
     def is_paused(self) -> bool:

src/atm/main.py

@@ -603,6 +603,43 @@ def _rewrite_baseline_phash(config_path: Path, new_phash: str) -> str:
     return old_phash
 
 
+def _auto_rebase_canary(
+    ctx: "RunContext", frame, now: float
+) -> "tuple[str, str] | None":
+    """Compute new canary phash from frame, persist to TOML, mirror in-memory.
+
+    Used by the tick loop when canary drift coincides with a strip-count change
+    (legitimate layout transition like 2↔1 chart windows). Returns (old_phash,
+    new_phash) on success. Returns None on TOML rewrite failure or when
+    config_version is unknown — caller falls back to commit_pause().
+    """
+    from atm.vision import crop_roi, phash as _phash
+
+    cfg = ctx.cfg
+    config_name = getattr(cfg, "config_version", None) or "unknown"
+    if config_name in ("", "unknown"):
+        ctx.audit.log({
+            "ts": now, "event": "auto_rebase_failed",
+            "error": "config_version unknown",
+        })
+        return None
+    config_path = Path("configs") / f"{config_name}.toml"
+    try:
+        new_phash = _phash(crop_roi(frame, cfg.canary.roi))
+    except Exception as exc:
+        ctx.audit.log({"ts": now, "event": "auto_rebase_failed",
+                       "error": f"phash compute: {exc}"})
+        return None
+    try:
+        old_phash = _rewrite_baseline_phash(config_path, new_phash)
+    except Exception as exc:
+        ctx.audit.log({"ts": now, "event": "auto_rebase_failed",
+                       "error": str(exc), "config": str(config_path)})
+        return None
+    ctx.canary.rebase(new_phash)
+    return old_phash, new_phash
+
+
 def _save_rebase_frame(
     frame, cfg, fires_dir: Path, now: float, audit: "_AuditLike | None" = None,
 ) -> "Path | None":
@@ -1396,12 +1433,21 @@ def _chart_id_for_index(i: int, n: int) -> str:
     return f"chart_{i}"
 
 
-def _commit_layout_change(ctx: RunContext, new_strips: list, now: float) -> None:
+def _commit_layout_change(
+    ctx: RunContext,
+    new_strips: list,
+    now: float,
+    suppress_alert: bool = False,
+) -> None:
     """Replace ctx.charts with fresh ChartState objects for new_strips.
 
     Resets per-chart FSM (StateMachine(lockout_s)) and Detector (with
     dot_roi_override=strip), zeroes n_primed_global, stops scheduler if running,
     audits the layout_change event, sends a status Alert.
+
+    ``suppress_alert=True`` skips the status Alert (caller will send a combined
+    one — used by the auto-rebase path so the user gets a single notification
+    covering both the layout change and the canary rebase).
     """
     from atm.detector import Detector
     from atm.state_machine import StateMachine
@@ -1433,8 +1479,9 @@ def _commit_layout_change(ctx: RunContext, new_strips: list, now: float) -> None
         "strips": [{"x": s.x, "w": s.w} for s in new_strips],
     })
     # Suppress notification on first-ever detection (old_n=0 = startup bootstrap,
-    # not a real layout change).
+    # not a real layout change). Also suppress when caller (auto-rebase path)
-    if old_n > 0:
+    # will send a combined alert.
+    if old_n > 0 and not suppress_alert:
         ctx.notifier.send(Alert(
             kind="status",
             title=f"🔄 Layout TS schimbat: {old_n} → {new_n} ferestre. FSM resetat.",
@@ -1503,12 +1550,60 @@ async def _run_multi_tick(ctx: RunContext) -> "list[_TickSyncResult]":
 
     cr = ctx.canary.check(frame)
     if ctx.canary.is_paused:
+        # Already paused from a prior tick — short-circuit. Auto-rebase only
+        # runs on the not_paused→drifted edge; once paused, only /resume or
+        # /rebase confirm clears it.
         ctx.audit.log({"ts": now, "event": "paused", "drift": cr.distance})
         return []
 
     new_strips = await asyncio.to_thread(_detect_strips_for_ctx, ctx, frame)
     current_strips = [c.sub_roi for c in ctx.charts]
-    if new_strips:
+
+    if cr.drifted:
+        # Two-signal gate: drift ALONE could be a real anomaly (window occluded,
+        # screen blackout) OR a layout transition that moved the canary anchor
+        # within the frame (e.g. 2→1 chart split shifts the menu chrome). We
+        # disambiguate by checking strip count on the same frame. If strip count
+        # changed, treat as legitimate layout change → silently rebase canary +
+        # commit layout change + single combined alert. Otherwise pause as before.
+        count_changed = bool(new_strips) and len(new_strips) != len(current_strips)
+        if count_changed:
+            rebase_result = _auto_rebase_canary(ctx, frame, now)
+            if rebase_result is not None:
+                old_phash, new_phash = rebase_result
+                old_n = len(current_strips)
+                new_n = len(new_strips)
+                _commit_layout_change(ctx, new_strips, now, suppress_alert=True)
+                ctx.audit.log({
+                    "ts": now, "event": "layout_change_with_rebase",
+                    "old_n": old_n, "new_n": new_n,
+                    "old_phash": old_phash, "new_phash": new_phash,
+                    "distance": cr.distance,
+                })
+                shot = await asyncio.to_thread(
+                    _save_rebase_frame, frame, ctx.cfg, ctx.fires_dir, now, ctx.audit,
+                )
+                ctx.notifier.send(Alert(
+                    kind="status",
+                    title=f"🔄 Layout TS schimbat: {old_n}→{new_n} ferestre + canary auto-rebased",
+                    body=f"distance={cr.distance}, old={old_phash[:12]}…, new={new_phash[:12]}…",
+                    image_path=shot,
+                    silent=True,
+                ))
+                # Fall through to per-chart tick loop with new charts.
+            else:
+                # Rebase failed (TOML malformed / config_version unknown) →
+                # fall back to standard drift-pause behavior.
+                ctx.canary.commit_pause(cr.distance)
+                ctx.audit.log({"ts": now, "event": "paused", "drift": cr.distance,
+                               "reason": "auto_rebase_failed"})
+                return []
+        else:
+            # Drift without strip-count change → real drift. Pause.
+            ctx.canary.commit_pause(cr.distance)
+            ctx.audit.log({"ts": now, "event": "paused", "drift": cr.distance})
+            return []
+    elif new_strips:
         if len(new_strips) != len(current_strips):
             # Real count change (1↔2 ferestre) → rebuild charts.
             _commit_layout_change(ctx, new_strips, now)
@@ -2078,6 +2173,8 @@ async def run_live_async(cfg, duration_s=None, capture_stub: bool = False) -> No
         canary_status = f"drift={first_check.distance}/{cfg.canary.drift_threshold}"
         if first_check.drifted:
             print(f"WARN: canary drift at startup ({canary_status}). Wrong window in front?", flush=True)
+            # check() no longer auto-pauses; resume() kept defensively in case
+            # an earlier startup path or a future change pauses before this.
             canary.resume()
         senzor_label = "deviat" if first_check.drifted else "ok"
         senzor_info = f"senzor: {senzor_label} ({canary_status.replace('drift=', '')})"

tests/test_canary.py

@@ -91,24 +91,37 @@ def test_no_drift() -> None:
     assert canary.is_paused is False
 
 
-def test_drift_triggers_pause() -> None:
+def test_check_does_not_auto_pause() -> None:
-    """Drastically different canary ROI → drifted=True, paused=True."""
+    """check() is pure measurement — never transitions to paused on its own."""
     cfg = _cfg_with_baseline(BASELINE_FRAME)
     canary = Canary(cfg)
 
     result = canary.check(DRIFTED_FRAME)
 
     assert result.drifted is True
-    assert result.paused is True
+    assert result.paused is False  # not committed
+    assert canary.is_paused is False
+
+
+def test_drift_triggers_pause() -> None:
+    """check() detects drift; commit_pause() transitions state."""
+    cfg = _cfg_with_baseline(BASELINE_FRAME)
+    canary = Canary(cfg)
+
+    result = canary.check(DRIFTED_FRAME)
+    assert result.drifted is True
+    canary.commit_pause(result.distance)
+
     assert canary.is_paused is True
 
 
 def test_persists_paused() -> None:
-    """After drift, feeding back a clean frame keeps paused=True."""
+    """After commit_pause, feeding back a clean frame keeps paused=True."""
     cfg = _cfg_with_baseline(BASELINE_FRAME)
     canary = Canary(cfg)
 
-    canary.check(DRIFTED_FRAME)       # trigger pause
+    r1 = canary.check(DRIFTED_FRAME)
+    canary.commit_pause(r1.distance)
     result = canary.check(BASELINE_FRAME)  # clean frame, but still paused
 
     assert result.paused is True
@@ -120,7 +133,8 @@ def test_resume_clears() -> None:
     cfg = _cfg_with_baseline(BASELINE_FRAME)
     canary = Canary(cfg)
 
-    canary.check(DRIFTED_FRAME)   # pause
+    r = canary.check(DRIFTED_FRAME)
+    canary.commit_pause(r.distance)
     canary.resume()
 
     assert canary.is_paused is False
@@ -130,13 +144,15 @@ def test_resume_clears() -> None:
 
 
 def test_pause_file_written(tmp_path: Path) -> None:
-    """When pause_flag_path is provided, the file is created on drift."""
+    """When pause_flag_path is provided, the file is created on commit_pause."""
     flag = tmp_path / "paused.flag"
     cfg = _cfg_with_baseline(BASELINE_FRAME)
     canary = Canary(cfg, pause_flag_path=flag)
 
     assert not flag.exists()
-    canary.check(DRIFTED_FRAME)
+    r = canary.check(DRIFTED_FRAME)
+    assert not flag.exists()  # check() alone does NOT write the flag
+    canary.commit_pause(r.distance)
     assert flag.exists()
 
 
@@ -147,14 +163,32 @@ def test_canary_pause_callback_fires_once() -> None:
 
     canary = Canary(cfg, on_pause_callback=lambda d: calls.append(d))
 
-    canary.check(DRIFTED_FRAME)   # transition → callback fires
+    r1 = canary.check(DRIFTED_FRAME)
-    canary.check(DRIFTED_FRAME)   # still paused → no new callback
+    canary.commit_pause(r1.distance)   # transition → callback fires
+    canary.commit_pause(r1.distance)   # idempotent → no new callback
+    r2 = canary.check(DRIFTED_FRAME)
+    canary.commit_pause(r2.distance)   # still paused → no new callback
     canary.check(BASELINE_FRAME)       # clean but still paused → no new callback
 
     assert len(calls) == 1
     assert calls[0] > 0  # distance should be positive
 
 
+def test_commit_pause_idempotent() -> None:
+    """commit_pause is no-op when already paused — no flag re-write, no callback."""
+    cfg = _cfg_with_baseline(BASELINE_FRAME)
+    calls: list[int] = []
+
+    canary = Canary(cfg, on_pause_callback=lambda d: calls.append(d))
+
+    canary.commit_pause(100)
+    canary.commit_pause(200)
+    canary.commit_pause(300)
+
+    assert len(calls) == 1
+    assert calls[0] == 100
+
+
 def test_canary_resume_allows_new_pause_notification() -> None:
     """After resume, a fresh drift must re-fire the callback."""
     cfg = _cfg_with_baseline(BASELINE_FRAME)
@@ -162,17 +196,19 @@ def test_canary_resume_allows_new_pause_notification() -> None:
 
     canary = Canary(cfg, on_pause_callback=lambda d: calls.append(d))
 
-    canary.check(DRIFTED_FRAME)
+    r1 = canary.check(DRIFTED_FRAME)
+    canary.commit_pause(r1.distance)
     assert len(calls) == 1
 
     canary.resume()
-    canary.check(DRIFTED_FRAME)  # new pause transition
+    r2 = canary.check(DRIFTED_FRAME)
+    canary.commit_pause(r2.distance)  # new pause transition
 
     assert len(calls) == 2
 
 
-def test_canary_pause_callback_exception_does_not_crash_check() -> None:
+def test_canary_pause_callback_exception_does_not_crash_commit_pause() -> None:
-    """A failing callback must not break canary.check (detection cycle safety)."""
+    """A failing callback must not break commit_pause (detection cycle safety)."""
     cfg = _cfg_with_baseline(BASELINE_FRAME)
 
     def _boom(_d: int) -> None:
@@ -181,8 +217,8 @@ def test_canary_pause_callback_exception_does_not_crash_check() -> None:
     canary = Canary(cfg, on_pause_callback=_boom)
 
     # Must not raise — exception is swallowed + logged.
-    result = canary.check(DRIFTED_FRAME)
+    r = canary.check(DRIFTED_FRAME)
-    assert result.paused is True
+    canary.commit_pause(r.distance)
     assert canary.is_paused is True
 
 
@@ -192,7 +228,26 @@ def test_resume_deletes_pause_file(tmp_path: Path) -> None:
     cfg = _cfg_with_baseline(BASELINE_FRAME)
     canary = Canary(cfg, pause_flag_path=flag)
 
-    canary.check(DRIFTED_FRAME)
+    r = canary.check(DRIFTED_FRAME)
+    canary.commit_pause(r.distance)
     assert flag.exists()
     canary.resume()
     assert not flag.exists()
+
+
+def test_rebase_updates_baseline_in_memory() -> None:
+    """rebase(new_h) mirrors hash into cfg.canary; subsequent check uses it."""
+    cfg = _cfg_with_baseline(BASELINE_FRAME)
+    canary = Canary(cfg)
+
+    # Compute the phash of the drifted frame; rebase to it.
+    drifted_hash = phash(crop_roi(DRIFTED_FRAME, CANARY_ROI))
+    assert cfg.canary.baseline_phash != drifted_hash
+
+    canary.rebase(drifted_hash)
+
+    assert cfg.canary.baseline_phash == drifted_hash
+    # Now the drifted frame reads as clean.
+    result = canary.check(DRIFTED_FRAME)
+    assert result.drifted is False
+    assert result.paused is False

tests/test_main.py

@@ -2089,3 +2089,379 @@ def test_commit_layout_change_alert_is_silent(monkeypatch):
     layout_alerts = [a for a in notifier_alerts if "Layout TS schimbat" in a.title]
     assert len(layout_alerts) == 1
     assert layout_alerts[0].silent is True
+
+
+# ---------------------------------------------------------------------------
+# Auto-rebase on layout change (two-signal gate: drift + strip-count change)
+# ---------------------------------------------------------------------------
+
+class _FakeCanary:
+    """Stand-in for atm.canary.Canary that lets tests drive drift state.
+
+    Mirrors the new split API (check pure, commit_pause + rebase explicit).
+    """
+
+    def __init__(self, drift_distance: int = 0):
+        self.drift_distance = drift_distance
+        self.is_paused = False
+        self.commit_pause_calls: list[int] = []
+        self.rebase_calls: list[str] = []
+        self.resume_calls = 0
+
+    def check(self, _frame):
+        return types.SimpleNamespace(
+            distance=self.drift_distance,
+            drifted=self.drift_distance > 0,
+            paused=self.is_paused,
+        )
+
+    def commit_pause(self, distance: int) -> None:
+        if self.is_paused:
+            return
+        self.is_paused = True
+        self.commit_pause_calls.append(distance)
+
+    def rebase(self, new_phash: str) -> None:
+        self.rebase_calls.append(new_phash)
+
+    def resume(self) -> None:
+        self.is_paused = False
+        self.resume_calls += 1
+
+
+def _build_multi_tick_ctx(tmp_path, cfg, canary, initial_strips):
+    """Construct a RunContext suitable for driving _run_multi_tick.
+
+    Returns (ctx, notifier_alerts, audit_events, detector_stubs).
+    Charts are seeded with stub Detectors that record dot_roi updates.
+    """
+    import atm.main as _main
+    from atm.detector import DetectionResult
+
+    notifier_alerts: list = []
+    audit_events: list = []
+
+    class _Det:
+        def __init__(self):
+            self.last_roi = None
+
+        def step(self, ts, frame=None):
+            return DetectionResult(
+                ts=ts, window_found=True, dot_found=False,
+                rgb=None, match=None, accepted=False, color=None,
+            )
+
+        def update_dot_roi(self, roi):
+            self.last_roi = roi
+
+    class _FSM:
+        state = types.SimpleNamespace(value="IDLE")
+        _last_fire: dict = {}
+
+    class _N:
+        def send(self, a): notifier_alerts.append(a)
+
+    class _A:
+        def log(self, e): audit_events.append(e)
+
+    class _S:
+        is_running = False
+        def start(self, s): pass
+        def stop(self): pass
+
+    state_obj = _main._LoopState()
+    detectors = [_Det() for _ in initial_strips]
+    charts = [
+        _main.ChartState(
+            chart_id=("left" if i == 0 else "right") if len(initial_strips) == 2 else "only",
+            sub_roi=strip, detector=detectors[i], fsm=_FSM(),
+        )
+        for i, strip in enumerate(initial_strips)
+    ]
+    ctx = _main.RunContext(
+        cfg=cfg, capture=lambda: np.zeros((200, 1800, 3), dtype=np.uint8),
+        canary=canary, detector=MagicMock(), fsm=_FSM(),
+        notifier=_N(), audit=_A(), detection_log=_A(),
+        scheduler=_S(), samples_dir=tmp_path, fires_dir=tmp_path,
+        cmd_queue=MagicMock(), state=state_obj,
+        levels_extractor_factory=lambda *a, **kw: None,
+        lifecycle=None,
+    )
+    ctx.charts = charts
+    return ctx, notifier_alerts, audit_events, detectors
+
+
+def _make_minimal_cfg_for_multi_tick():
+    """Minimal cfg that satisfies _run_multi_tick + _commit_layout_change paths."""
+    from atm.config import ROI
+    cfg = MagicMock()
+    cfg.lockout_s = 60
+    cfg.colors = {}
+    cfg.debounce_depth = 3
+    cfg.confidence_min = 0.5
+    cfg.dot_roi = ROI(x=0, y=0, w=600, h=35)
+    cfg.window_title = None
+    cfg.attach_screenshots = types.SimpleNamespace(
+        arm=False, prime=False, trigger=False, late_start=False,
+        catchup=False, opposite_rearm=False, rearm=False, phase_skip=False,
+    )
+    cfg.config_version = "test-cfg"
+    cfg.canary = types.SimpleNamespace(
+        roi=ROI(x=0, y=0, w=50, h=50),
+        baseline_phash="0" * 64,
+        drift_threshold=8,
+    )
+    return cfg
+
+
+@pytest.mark.asyncio
+async def test_multi_tick_drift_with_strip_count_change_auto_rebases(monkeypatch, tmp_path):
+    """Drift + strip count 2→1 → silent auto-rebase, no pause, single combined alert."""
+    import atm.main as _main
+    from atm.config import ROI
+
+    monkeypatch.chdir(tmp_path)
+
+    cfg = _make_minimal_cfg_for_multi_tick()
+    canary = _FakeCanary(drift_distance=156)
+    initial = [ROI(x=0, y=0, w=400, h=35), ROI(x=500, y=0, w=400, h=35)]
+    new_strips = [ROI(x=0, y=0, w=900, h=35)]  # 2 → 1
+    ctx, notifier_alerts, audit_events, _ = _build_multi_tick_ctx(
+        tmp_path, cfg, canary, initial,
+    )
+
+    monkeypatch.setattr(_main, "_detect_strips_for_ctx", lambda c, f: new_strips)
+    rewrite_calls: list = []
+    def _stub_rewrite(path, new_phash):
+        rewrite_calls.append((path, new_phash))
+        return "OLD_PHASH"
+    monkeypatch.setattr(_main, "_rewrite_baseline_phash", _stub_rewrite)
+
+    await _main._run_multi_tick(ctx)
+
+    # Layout committed: charts shrank to 1.
+    assert len(ctx.charts) == 1
+    assert ctx.charts[0].sub_roi == new_strips[0]
+    # Canary NOT paused (auto-rebase path).
+    assert canary.is_paused is False
+    assert canary.commit_pause_calls == []
+    # rebase() called with the new phash that was also passed to _rewrite_baseline_phash.
+    assert len(canary.rebase_calls) == 1
+    assert len(rewrite_calls) == 1
+    new_phash = canary.rebase_calls[0]
+    assert rewrite_calls[0][1] == new_phash
+    # Audit: layout_change_with_rebase + standard layout_change (from _commit_layout_change).
+    rebase_events = [e for e in audit_events if e.get("event") == "layout_change_with_rebase"]
+    assert len(rebase_events) == 1
+    assert rebase_events[0]["old_n"] == 2
+    assert rebase_events[0]["new_n"] == 1
+    assert rebase_events[0]["distance"] == 156
+    assert rebase_events[0]["old_phash"] == "OLD_PHASH"
+    assert rebase_events[0]["new_phash"] == new_phash
+    # No "paused" audit event.
+    assert not any(e.get("event") == "paused" for e in audit_events)
+    # Exactly one combined alert. Generic layout_change alert was suppressed.
+    combined = [a for a in notifier_alerts if "auto-rebased" in a.title]
+    assert len(combined) == 1
+    assert "2→1" in combined[0].title
+    plain_layout = [a for a in notifier_alerts
+                    if "Layout TS schimbat" in a.title and "auto-rebased" not in a.title]
+    assert plain_layout == []
+
+
+@pytest.mark.asyncio
+async def test_multi_tick_drift_with_same_strip_count_pauses(monkeypatch, tmp_path):
+    """Drift without strip count change → real drift → pause as before."""
+    import atm.main as _main
+    from atm.config import ROI
+
+    monkeypatch.chdir(tmp_path)
+
+    cfg = _make_minimal_cfg_for_multi_tick()
+    canary = _FakeCanary(drift_distance=156)
+    initial = [ROI(x=0, y=0, w=400, h=35), ROI(x=500, y=0, w=400, h=35)]
+    same_count = [ROI(x=0, y=0, w=400, h=35), ROI(x=500, y=0, w=400, h=35)]
+    ctx, notifier_alerts, audit_events, _ = _build_multi_tick_ctx(
+        tmp_path, cfg, canary, initial,
+    )
+
+    monkeypatch.setattr(_main, "_detect_strips_for_ctx", lambda c, f: same_count)
+    monkeypatch.setattr(_main, "_rewrite_baseline_phash",
+                        lambda *a, **kw: pytest.fail("should not be called"))
+
+    results = await _main._run_multi_tick(ctx)
+
+    assert results == []
+    assert canary.is_paused is True
+    assert canary.commit_pause_calls == [156]
+    assert len(ctx.charts) == 2  # unchanged
+    paused_events = [e for e in audit_events if e.get("event") == "paused"]
+    assert len(paused_events) == 1
+    assert paused_events[0]["drift"] == 156
+    assert canary.rebase_calls == []
+
+
+@pytest.mark.asyncio
+async def test_multi_tick_drift_with_zero_strips_pauses(monkeypatch, tmp_path):
+    """Strip detection returns [] (chart blackout) → pause, do NOT auto-rebase."""
+    import atm.main as _main
+    from atm.config import ROI
+
+    monkeypatch.chdir(tmp_path)
+
+    cfg = _make_minimal_cfg_for_multi_tick()
+    canary = _FakeCanary(drift_distance=156)
+    initial = [ROI(x=0, y=0, w=400, h=35), ROI(x=500, y=0, w=400, h=35)]
+    ctx, _alerts, audit_events, _ = _build_multi_tick_ctx(
+        tmp_path, cfg, canary, initial,
+    )
+
+    monkeypatch.setattr(_main, "_detect_strips_for_ctx", lambda c, f: [])
+    monkeypatch.setattr(_main, "_rewrite_baseline_phash",
+                        lambda *a, **kw: pytest.fail("should not be called"))
+
+    results = await _main._run_multi_tick(ctx)
+
+    assert results == []
+    assert canary.is_paused is True
+    assert canary.commit_pause_calls == [156]
+    assert canary.rebase_calls == []
+    assert any(e.get("event") == "paused" for e in audit_events)
+
+
+@pytest.mark.asyncio
+async def test_multi_tick_no_drift_strip_count_change_unchanged_path(monkeypatch, tmp_path):
+    """Strip count change without drift → existing _commit_layout_change path,
+    canary baseline untouched, silent layout-change alert."""
+    import atm.main as _main
+    from atm.config import ROI
+
+    monkeypatch.chdir(tmp_path)
+
+    cfg = _make_minimal_cfg_for_multi_tick()
+    canary = _FakeCanary(drift_distance=0)  # no drift
+    initial = [ROI(x=0, y=0, w=400, h=35), ROI(x=500, y=0, w=400, h=35)]
+    new_strips = [ROI(x=0, y=0, w=900, h=35)]
+    ctx, notifier_alerts, audit_events, _ = _build_multi_tick_ctx(
+        tmp_path, cfg, canary, initial,
+    )
+
+    monkeypatch.setattr(_main, "_detect_strips_for_ctx", lambda c, f: new_strips)
+    monkeypatch.setattr(_main, "_rewrite_baseline_phash",
+                        lambda *a, **kw: pytest.fail("should not be called"))
+
+    await _main._run_multi_tick(ctx)
+
+    assert len(ctx.charts) == 1
+    assert canary.rebase_calls == []
+    # Standard layout_change alert (not suppressed).
+    layout_alerts = [a for a in notifier_alerts if "Layout TS schimbat" in a.title]
+    assert len(layout_alerts) == 1
+    assert "auto-rebased" not in layout_alerts[0].title
+    assert any(e.get("event") == "layout_change" for e in audit_events)
+    assert not any(e.get("event") == "layout_change_with_rebase" for e in audit_events)
+
+
+@pytest.mark.asyncio
+async def test_multi_tick_auto_rebase_toml_failure_falls_back_to_pause(monkeypatch, tmp_path):
+    """When _rewrite_baseline_phash raises, fall back to commit_pause + audit."""
+    import atm.main as _main
+    from atm.config import ROI
+
+    monkeypatch.chdir(tmp_path)
+
+    cfg = _make_minimal_cfg_for_multi_tick()
+    canary = _FakeCanary(drift_distance=156)
+    initial = [ROI(x=0, y=0, w=400, h=35), ROI(x=500, y=0, w=400, h=35)]
+    new_strips = [ROI(x=0, y=0, w=900, h=35)]
+    ctx, notifier_alerts, audit_events, _ = _build_multi_tick_ctx(
+        tmp_path, cfg, canary, initial,
+    )
+
+    monkeypatch.setattr(_main, "_detect_strips_for_ctx", lambda c, f: new_strips)
+    def _boom(_path, _new):
+        raise ValueError("expected exactly 1 baseline_phash line, found 0")
+    monkeypatch.setattr(_main, "_rewrite_baseline_phash", _boom)
+
+    results = await _main._run_multi_tick(ctx)
+
+    assert results == []
+    assert canary.is_paused is True
+    assert canary.commit_pause_calls == [156]
+    # Charts NOT mutated.
+    assert len(ctx.charts) == 2
+    fail_events = [e for e in audit_events if e.get("event") == "auto_rebase_failed"]
+    assert len(fail_events) == 1
+    paused_events = [e for e in audit_events
+                     if e.get("event") == "paused" and e.get("reason") == "auto_rebase_failed"]
+    assert len(paused_events) == 1
+
+
+@pytest.mark.asyncio
+async def test_multi_tick_symmetric_1_to_2(monkeypatch, tmp_path):
+    """1→2 transition is symmetric: same auto-rebase + layout commit path."""
+    import atm.main as _main
+    from atm.config import ROI
+
+    monkeypatch.chdir(tmp_path)
+
+    cfg = _make_minimal_cfg_for_multi_tick()
+    canary = _FakeCanary(drift_distance=120)
+    initial = [ROI(x=0, y=0, w=900, h=35)]
+    new_strips = [ROI(x=0, y=0, w=400, h=35), ROI(x=500, y=0, w=400, h=35)]
+    ctx, notifier_alerts, audit_events, _ = _build_multi_tick_ctx(
+        tmp_path, cfg, canary, initial,
+    )
+
+    monkeypatch.setattr(_main, "_detect_strips_for_ctx", lambda c, f: new_strips)
+    monkeypatch.setattr(_main, "_rewrite_baseline_phash",
+                        lambda path, new_phash: "OLD")
+
+    await _main._run_multi_tick(ctx)
+
+    assert len(ctx.charts) == 2
+    assert canary.is_paused is False
+    assert len(canary.rebase_calls) == 1
+    rebase_events = [e for e in audit_events if e.get("event") == "layout_change_with_rebase"]
+    assert len(rebase_events) == 1
+    assert rebase_events[0]["old_n"] == 1
+    assert rebase_events[0]["new_n"] == 2
+    combined = [a for a in notifier_alerts if "auto-rebased" in a.title]
+    assert len(combined) == 1
+    assert "1→2" in combined[0].title
+
+
+@pytest.mark.asyncio
+async def test_multi_tick_already_paused_short_circuits(monkeypatch, tmp_path):
+    """is_paused=True at tick start → return [], no auto-rebase attempted."""
+    import atm.main as _main
+    from atm.config import ROI
+
+    monkeypatch.chdir(tmp_path)
+
+    cfg = _make_minimal_cfg_for_multi_tick()
+    canary = _FakeCanary(drift_distance=156)
+    canary.is_paused = True  # already paused from a prior tick
+    initial = [ROI(x=0, y=0, w=400, h=35), ROI(x=500, y=0, w=400, h=35)]
+    new_strips = [ROI(x=0, y=0, w=900, h=35)]
+    ctx, _alerts, audit_events, _ = _build_multi_tick_ctx(
+        tmp_path, cfg, canary, initial,
+    )
+
+    # Strip detection should NOT run on the already-paused short-circuit path.
+    detect_calls: list = []
+    def _detect(c, f):
+        detect_calls.append((c, f))
+        return new_strips
+    monkeypatch.setattr(_main, "_detect_strips_for_ctx", _detect)
+    monkeypatch.setattr(_main, "_rewrite_baseline_phash",
+                        lambda *a, **kw: pytest.fail("should not be called"))
+
+    results = await _main._run_multi_tick(ctx)
+
+    assert results == []
+    assert detect_calls == []  # short-circuited before strip detection
+    assert canary.rebase_calls == []
+    assert canary.commit_pause_calls == []  # already paused; no new commit
+    assert len(ctx.charts) == 2
+    assert any(e.get("event") == "paused" for e in audit_events)