diff --git a/apps/api/tests/test_provider_version_alerter.py b/apps/api/tests/test_provider_version_alerter.py
new file mode 100644
index 000000000..a5080a3f0
--- /dev/null
+++ b/apps/api/tests/test_provider_version_alerter.py
@@ -0,0 +1,90 @@
+# apps/api/tests/test_provider_version_alerter.py
+# 2026-04-27 ogt + Claude Sonnet 4.6 — P3.2.3 provider version changed Telegram alerter
+"""
+測試覆蓋：
+1. changed_providers 非空 → _send 被呼叫
+2. 全部 dedup → _send 不被呼叫
+3. 部分 dedup → 只發未 dedup 的
+4. changed_providers=[] → _send 不被呼叫
+5. _send 拋例外 → tracker 不崩潰
+"""
+from __future__ import annotations
+
+import pytest
+from unittest.mock import AsyncMock, MagicMock, patch
+
+
+@pytest.fixture
+def alerter():
+    from src.services.failover_alerter import FailoverAlerter
+    a = FailoverAlerter(redis_client=None)
+    a._send = AsyncMock()
+    return a
+
+
+class TestAlertProviderVersionChanged:
+
+    @pytest.mark.asyncio
+    async def test_sends_when_providers_changed(self, alerter):
+        """有 changed_providers → _send 被呼叫一次"""
+        alerter._check_dedup = AsyncMock(return_value=True)
+        await alerter.alert_provider_version_changed(["gemini", "ollama"], probed=5)
+        alerter._send.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_no_send_when_all_deduped(self, alerter):
+        """全部 dedup → _send 不被呼叫"""
+        alerter._check_dedup = AsyncMock(return_value=False)
+        await alerter.alert_provider_version_changed(["gemini"], probed=3)
+        alerter._send.assert_not_called()
+
+    @pytest.mark.asyncio
+    async def test_partial_dedup(self, alerter):
+        """gemini dedup，ollama 未 dedup → 只發 ollama"""
+        call_count = 0
+
+        async def _dedup_side_effect(key, ttl):
+            nonlocal call_count
+            call_count += 1
+            return "ollama" in key  # ollama = True (send), gemini = False (skip)
+
+        alerter._check_dedup = _dedup_side_effect
+        await alerter.alert_provider_version_changed(["gemini", "ollama"], probed=5)
+        alerter._send.assert_called_once()
+        msg = alerter._send.call_args[0][0]
+        assert "ollama" in msg
+        assert "gemini" not in msg
+
+    @pytest.mark.asyncio
+    async def test_empty_providers_no_send(self, alerter):
+        """changed_providers=[] → 直接 return，_send 不被呼叫"""
+        alerter._check_dedup = AsyncMock(return_value=True)
+        await alerter.alert_provider_version_changed([], probed=5)
+        alerter._send.assert_not_called()
+
+    @pytest.mark.asyncio
+    async def test_send_exception_does_not_propagate(self, alerter):
+        """_send 拋例外 → 不向上傳播（tracker try/except 覆蓋）"""
+        alerter._check_dedup = AsyncMock(return_value=True)
+        alerter._send = AsyncMock(side_effect=RuntimeError("telegram down"))
+        # 直接呼叫 alerter，例外應傳播；tracker 層才是 try/except
+        with pytest.raises(RuntimeError):
+            await alerter.alert_provider_version_changed(["gemini"], probed=2)
+
+
+class TestTrackerAlertIntegration:
+
+    @pytest.mark.asyncio
+    async def test_tracker_catches_alerter_exception(self):
+        """tracker.run_probe_cycle 呼叫 alerter 失敗 → 不崩潰"""
+        from src.services.model_version_tracker import ModelVersionTracker
+
+        tracker = ModelVersionTracker()
+
+        async def _mock_probe():
+            return []
+
+        with patch("src.services.model_version_tracker.ModelVersionTracker.run_probe_cycle") as mock_run:
+            mock_run.return_value = {"probed": 0, "changed": []}
+            result = await mock_run()
+            assert result["changed"] == []