diff --git a/app/main.py b/app/main.py
index 8ef60fff..535f0535 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1681,7 +1681,6 @@ async def _check_stale_workers() -> None:
         logger.warning("Stale worker check error: %s", exc)
         return
     now = datetime.now(UTC)
-    cutoff = now - timedelta(seconds=STALE_WORKER_SECONDS)
     purge_cutoff = now - timedelta(hours=1)
     global _collector_alerts
     for w in workers:
@@ -1691,6 +1690,7 @@ async def _check_stale_workers() -> None:
                 continue
             cid = w.get("client_id") or w["name"]
             last = datetime.fromisoformat(last_hb).replace(tzinfo=UTC)
+            cutoff = now - timedelta(seconds=_stale_after_seconds(w))
             if w["status"] == "online" and last < cutoff:
                 _worker_online_streak.pop(cid, None)
                 # Conditional on the heartbeat the decision was based on: a
@@ -1871,7 +1871,7 @@ async def _raise_worker_offline_alert(w: dict[str, Any]) -> None:
     """
     cid = w.get("client_id") or w["name"]
     msg = (
-        f"Worker '{w['name']}': no heartbeat for over {STALE_WORKER_SECONDS // 60} minutes. Its "
+        f"Worker '{w['name']}': no heartbeat for over {_stale_after_seconds(w) // 60} minutes. Its "
         "containers keep running and earning, but CashPilot cannot see or manage them until it reconnects."
     )
     if alert_id := await database.record_alert("worker", cid, msg):
@@ -1909,6 +1909,20 @@ async def _raise_worker_offline_alert(w: dict[str, Any]) -> None:
 HOSTNAME_PREFIX = os.getenv("CASHPILOT_HOSTNAME_PREFIX", "cashpilot")
 COLLECT_INTERVAL_MIN = int(os.getenv("CASHPILOT_COLLECT_INTERVAL", "60"))
 STALE_WORKER_SECONDS = 180  # Mark worker offline after 3 missed heartbeats
+# A phone reports from Android's WorkManager, whose shortest period is 15
+# minutes, so 180 s would show every phone offline between two reports.
+# Three missed periods, the same rule as the 60 s Docker workers.
+STALE_ANDROID_WORKER_SECONDS = 45 * 60
+
+
+def _stale_after_seconds(w: dict[str, Any]) -> int:
+    """How long this worker may stay silent before it is marked offline."""
+    info = w.get("system_info") or {}
+    if not isinstance(info, dict):  # raw DB rows carry it as JSON text
+        info = _safe_json(info, {})
+    if placement.is_android(info):
+        return STALE_ANDROID_WORKER_SECONDS
+    return STALE_WORKER_SECONDS
 
 
 async def _warm_session_epochs() -> None:
diff --git a/docs/fleet.md b/docs/fleet.md
index ca1e2869..6dc265b9 100644
--- a/docs/fleet.md
+++ b/docs/fleet.md
@@ -206,7 +206,7 @@ If the worker and UI are on different subnets (e.g., connected via Tailscale):
 
 ## Offline Handling
 
-If a worker goes offline (no heartbeat for 180 seconds):
+If a worker goes offline (no heartbeat for 180 seconds; 45 minutes for an Android phone, which reports every 15 minutes):
 
 - The UI marks the worker as offline
 - Historical earnings and health data is retained
diff --git a/tests/test_android_worker_stale.py b/tests/test_android_worker_stale.py
new file mode 100644
index 00000000..5b076d1c
--- /dev/null
+++ b/tests/test_android_worker_stale.py
@@ -0,0 +1,112 @@
+"""A phone is offline after three missed reports, not after three minutes.
+
+The Android client reports from WorkManager, whose shortest period is 15
+minutes. With the Docker workers' 180 s threshold every phone would be marked
+offline, and alerted on, between two ordinary reports. Phones get three missed
+periods (45 min); Docker workers keep 180 s.
+"""
+
+import asyncio
+import os
+from datetime import UTC, datetime, timedelta
+
+os.environ.setdefault("CASHPILOT_API_KEY", "test-fleet-key")
+
+import pytest  # noqa: E402
+
+try:
+    from app.main import _check_stale_workers  # noqa: E402
+except ImportError:
+    pytest.skip(
+        "Requires full app dependencies (fastapi, httpx, etc.) — runs in CI",
+        allow_module_level=True,
+    )
+
+from unittest.mock import AsyncMock, patch  # noqa: E402
+
+from app import main  # noqa: E402
+
+DOCKER = '{"docker_available": true}'
+PHONE = '{"os": "Android", "device_type": "android"}'
+# CashPilot-android 0.3.0 sends only os, no device_type.
+OLD_PHONE = '{"os": "Android"}'
+
+
+def _silent_for(minutes: float) -> str:
+    return (datetime.now(UTC) - timedelta(minutes=minutes)).replace(tzinfo=None).isoformat()
+
+
+def _row(system_info: str, silent_min: float) -> dict:
+    return {
+        "id": 7,
+        "client_id": "cid-pixel",
+        "name": "pixel",
+        "url": "",
+        "status": "online",
+        "containers": "[]",
+        "apps": "[]",
+        "system_info": system_info,
+        "last_heartbeat": _silent_for(silent_min),
+        "registered_at": "2026-04-01T00:00:00",
+        "api_key_enc": "enc",
+    }
+
+
+@pytest.fixture(autouse=True)
+def _isolate():
+    before = main._collector_alerts
+    main._collector_alerts = []
+    main._worker_online_streak.clear()
+    main._worker_last_offline_push.clear()
+    yield
+    main._collector_alerts = before
+    main._worker_online_streak.clear()
+    main._worker_last_offline_push.clear()
+
+
+def _sweep(row: dict):
+    record = AsyncMock(return_value=True)
+    mark = AsyncMock(return_value=True)
+
+    async def _send(*a, **kw):
+        return 1
+
+    with (
+        patch("app.main.database.list_workers", new_callable=AsyncMock, return_value=[row]),
+        patch("app.main.database.mark_worker_offline_if_unchanged", mark),
+        patch("app.main.database.delete_worker", new_callable=AsyncMock),
+        patch("app.main.database.record_alert", record),
+        patch("app.main.database.clear_alerts", AsyncMock()),
+        patch("app.main.notify.send", _send),
+    ):
+        asyncio.run(_check_stale_workers())
+    return mark, record
+
+
+@pytest.mark.parametrize("info", [PHONE, OLD_PHONE])
+def test_phone_between_two_reports_stays_online(info):
+    mark, record = _sweep(_row(info, silent_min=16))
+    mark.assert_not_awaited()
+    record.assert_not_awaited()
+
+
+def test_phone_after_three_missed_reports_goes_offline_with_its_own_minutes():
+    mark, record = _sweep(_row(PHONE, silent_min=46))
+    mark.assert_awaited_once()
+    msg = record.await_args.args[2]
+    assert "over 45 minutes" in msg, msg
+
+
+def test_docker_worker_keeps_the_three_minute_threshold():
+    # Control: the same sweep, a Docker worker silent for 4 minutes, still goes
+    # offline, so the phone tests above are not passing because nothing fires.
+    mark, record = _sweep(_row(DOCKER, silent_min=4))
+    mark.assert_awaited_once()
+    assert "over 3 minutes" in record.await_args.args[2]
+
+
+def test_threshold_reads_decoded_and_raw_system_info():
+    assert main._stale_after_seconds({"system_info": PHONE}) == 45 * 60
+    assert main._stale_after_seconds({"system_info": {"device_type": "android"}}) == 45 * 60
+    assert main._stale_after_seconds({"system_info": "not json"}) == main.STALE_WORKER_SECONDS
+    assert main._stale_after_seconds({}) == main.STALE_WORKER_SECONDS