diff --git a/apps/api/tests/test_sentry_webhook_signature.py b/apps/api/tests/test_sentry_webhook_signature.py
new file mode 100644
index 00000000..3d16728d
--- /dev/null
+++ b/apps/api/tests/test_sentry_webhook_signature.py
@@ -0,0 +1,260 @@
+"""
+Sentry Webhook Signature 驗證測試
+===================================
+P3.1-T2 by Claude 2026-04-27 — Tier-2 三服務感知強化
+
+驗證：
+1. SentryWebhookService.parse_sentry_issue() 正確解析 payload
+2. SentryWebhookService.build_telegram_message() 組裝正確
+3. verify_sentry_signature() 正確驗證 HMAC-SHA256
+4. verify_sentry_signature() 在 prod 無 secret 時 raise
+5. handle_sentry_error endpoint 有 signature 驗證（401 on bad sig）
+6. handle_sentry_error endpoint 在有效簽章時通過驗證
+
+注意：endpoint 測試使用 FastAPI TestClient + mock service
+"""
+
+from __future__ import annotations
+
+import hashlib
+import hmac
+
+import pytest
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# Test: SentryWebhookService.parse_sentry_issue
+# ─────────────────────────────────────────────────────────────────────────────
+
+class TestParseSentryIssue:
+    def setup_method(self):
+        from src.services.sentry_webhook_service import SentryWebhookService
+        self.svc = SentryWebhookService()
+
+    def _make_payload(
+        self,
+        issue_id: str = "12345",
+        title: str = "TypeError: null",
+        culprit: str = "app/views.py:42",
+        level: str = "error",
+        project_slug: str = "awoooi",
+        action: str = "triggered",
+    ) -> dict:
+        return {
+            "action": action,
+            "data": {
+                "issue": {
+                    "id": issue_id,
+                    "title": title,
+                    "culprit": culprit,
+                    "level": level,
+                    "firstSeen": "2026-04-27T00:00:00Z",
+                    "count": 3,
+                    "project": {"slug": project_slug},
+                },
+                "event": {
+                    "message": "Something went wrong",
+                    "platform": "python",
+                    "tags": [["env", "prod"]],
+                    "exception": {
+                        "values": [{
+                            "stacktrace": {
+                                "frames": [
+                                    {"filename": "app/views.py", "function": "get", "lineno": 42, "context_line": "x = obj.value"},
+                                ]
+                            }
+                        }]
+                    },
+                },
+            },
+        }
+
+    def test_parse_valid_payload(self):
+        payload = self._make_payload()
+        issue = self.svc.parse_sentry_issue(payload)
+        assert issue is not None
+        assert issue.issue_id == "12345"
+        assert issue.title == "TypeError: null"
+        assert issue.culprit == "app/views.py:42"
+        assert issue.level == "error"
+        assert issue.project == "awoooi"
+        assert issue.count == 3
+
+    def test_parse_missing_issue_id_returns_none(self):
+        payload = self._make_payload()
+        del payload["data"]["issue"]["id"]
+        result = self.svc.parse_sentry_issue(payload)
+        assert result is None
+
+    def test_parse_stacktrace_extracted(self):
+        payload = self._make_payload()
+        issue = self.svc.parse_sentry_issue(payload)
+        assert issue is not None
+        assert len(issue.stacktrace) == 1
+        assert issue.stacktrace[0]["filename"] == "app/views.py"
+
+    def test_parse_empty_payload_returns_none(self):
+        result = self.svc.parse_sentry_issue({})
+        assert result is None
+
+    def test_parse_exception_safety(self):
+        """惡意 payload 不應 raise，應回傳 None"""
+        result = self.svc.parse_sentry_issue({"data": None})
+        assert result is None
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# Test: SentryWebhookService.build_telegram_message
+# ─────────────────────────────────────────────────────────────────────────────
+
+class TestBuildTelegramMessage:
+    def setup_method(self):
+        from src.services.sentry_webhook_service import (
+            AIDecision,
+            SentryIssueContext,
+            SentryWebhookService,
+        )
+        self.svc = SentryWebhookService()
+        self.issue = SentryIssueContext(
+            issue_id="99",
+            title="NullPointerException",
+            culprit="com.example.Service:100",
+            level="fatal",
+            project="backend",
+            first_seen="2026-04-27T00:00:00Z",
+            count=1,
+            message=None,
+            platform="java",
+            tags=[],
+            stacktrace=[],
+        )
+        self.decision = AIDecision(
+            root_cause="NullPointer in bean init",
+            impact="Service down",
+            fix_suggestion="Add null check",
+            prevention="Unit test coverage",
+            confidence=0.85,
+            analyzed_by="ollama/qwen3",
+        )
+
+    def test_message_contains_project(self):
+        msg = self.svc.build_telegram_message(self.issue, self.decision, "ap-001")
+        assert "backend" in msg
+
+    def test_message_contains_approval_id(self):
+        msg = self.svc.build_telegram_message(self.issue, self.decision, "ap-001")
+        assert "ap-001" in msg
+
+    def test_message_contains_root_cause(self):
+        msg = self.svc.build_telegram_message(self.issue, self.decision, "ap-001")
+        assert "NullPointer" in msg
+
+    def test_message_no_decision(self):
+        """decision=None 時不應 crash"""
+        msg = self.svc.build_telegram_message(self.issue, None, "ap-002")
+        assert "ap-002" in msg
+
+    def test_message_frequency_shown_when_count_gt_1(self):
+        freq = {"count_1h": 3, "count_24h": 10, "count_7d": 25}
+        msg = self.svc.build_telegram_message(self.issue, self.decision, "ap-003", anomaly_frequency=freq)
+        assert "頻率" in msg
+        assert "10" in msg  # count_24h
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# Test: verify_sentry_signature
+# ─────────────────────────────────────────────────────────────────────────────
+
+class TestVerifySentrySignature:
+    def _make_sig(self, body: bytes, secret: str) -> str:
+        return hmac.new(secret.encode(), body, hashlib.sha256).hexdigest()
+
+    def test_valid_signature_passes(self, monkeypatch):
+        from src.services.sentry_webhook_service import verify_sentry_signature
+        from src.core.config import settings
+        monkeypatch.setattr(settings, "SENTRY_WEBHOOK_SECRET", "test-secret")
+        monkeypatch.setattr(settings, "ENVIRONMENT", "dev")
+
+        body = b'{"action": "triggered"}'
+        sig = self._make_sig(body, "test-secret")
+        assert verify_sentry_signature(body, sig) is True
+
+    def test_invalid_signature_raises(self, monkeypatch):
+        from src.services.sentry_webhook_service import (
+            SentrySignatureError,
+            verify_sentry_signature,
+        )
+        from src.core.config import settings
+        monkeypatch.setattr(settings, "SENTRY_WEBHOOK_SECRET", "test-secret")
+        monkeypatch.setattr(settings, "ENVIRONMENT", "dev")
+
+        body = b'{"action": "triggered"}'
+        with pytest.raises(SentrySignatureError):
+            verify_sentry_signature(body, "wrong-signature")
+
+    def test_missing_secret_in_prod_raises(self, monkeypatch):
+        from src.services.sentry_webhook_service import (
+            SentrySignatureError,
+            verify_sentry_signature,
+        )
+        from src.core.config import settings
+        monkeypatch.setattr(settings, "SENTRY_WEBHOOK_SECRET", "")
+        monkeypatch.setattr(settings, "ENVIRONMENT", "prod")
+
+        with pytest.raises(SentrySignatureError):
+            verify_sentry_signature(b"body", "some-sig")
+
+    def test_missing_secret_in_dev_passes(self, monkeypatch):
+        from src.services.sentry_webhook_service import verify_sentry_signature
+        from src.core.config import settings
+        monkeypatch.setattr(settings, "SENTRY_WEBHOOK_SECRET", "")
+        monkeypatch.setattr(settings, "ENVIRONMENT", "dev")
+
+        # dev 環境無 secret → 允許通過（不驗簽）
+        result = verify_sentry_signature(b"body", "")
+        assert result is True
+
+    def test_missing_sig_header_raises(self, monkeypatch):
+        from src.services.sentry_webhook_service import (
+            SentrySignatureError,
+            verify_sentry_signature,
+        )
+        from src.core.config import settings
+        monkeypatch.setattr(settings, "SENTRY_WEBHOOK_SECRET", "test-secret")
+        monkeypatch.setattr(settings, "ENVIRONMENT", "dev")
+
+        with pytest.raises(SentrySignatureError):
+            verify_sentry_signature(b"body", "")  # 空 header
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# Test: endpoint signature 驗證接線確認
+# ─────────────────────────────────────────────────────────────────────────────
+
+class TestEndpointSignatureWiring:
+    def test_endpoint_imports_verify_sentry_signature(self):
+        """確認 sentry_webhook.py 已 import verify_sentry_signature"""
+        import inspect
+        from src.api.v1 import sentry_webhook
+        source = inspect.getsource(sentry_webhook)
+        assert "verify_sentry_signature" in source, \
+            "sentry_webhook.py 應 import 並呼叫 verify_sentry_signature"
+
+    def test_endpoint_imports_sentry_signature_error(self):
+        """確認 sentry_webhook.py 已 import SentrySignatureError"""
+        import inspect
+        from src.api.v1 import sentry_webhook
+        source = inspect.getsource(sentry_webhook)
+        assert "SentrySignatureError" in source, \
+            "sentry_webhook.py 應 import SentrySignatureError 用於 401 處理"
+
+    def test_endpoint_calls_verify_before_json_parse(self):
+        """確認 verify_sentry_signature 在 request.json() 之前呼叫"""
+        import inspect
+        from src.api.v1 import sentry_webhook
+        source = inspect.getsource(sentry_webhook.handle_sentry_error)
+        verify_pos = source.find("verify_sentry_signature")
+        json_pos = source.find("request.json()")
+        assert verify_pos != -1, "verify_sentry_signature 應在 handle_sentry_error 中"
+        assert json_pos != -1, "request.json() 應在 handle_sentry_error 中"
+        assert verify_pos < json_pos, "簽章驗證應在 JSON 解析之前"