fix(providers): preserve tool-provided fingerprint when dedup rule uses only the fingerprint field

keep/providers/base/base_provider.py

@@ -520,6 +520,12 @@ def get_alert_fingerprint(alert: AlertDto, fingerprint_fields: list = []) -> str
         """
         if not fingerprint_fields:
             return alert.name
+        # if the only fingerprint field is the fingerprint itself, the alert
+        # already carries a fingerprint provided by the monitoring tool -
+        # preserve it as-is instead of hashing it, so Keep's fingerprint stays
+        # aligned with the tool's (e.g. Grafana/Prometheus)
+        if fingerprint_fields == ["fingerprint"] and alert.fingerprint:
+            return alert.fingerprint
         fingerprint = hashlib.sha256()
         event_dict = alert.dict()
         for fingerprint_field in fingerprint_fields:

tests/test_get_alerts_custom_dedup.py

@@ -105,6 +105,33 @@ def test_no_custom_rule_keeps_original_fingerprint(self, mock_get_rule):
 
         self.assertEqual(alerts[0].fingerprint, "original-fp")
 
+    @patch("keep.providers.base.base_provider.get_custom_deduplication_rule")
+    def test_custom_dedup_on_fingerprint_field_preserves_tool_fingerprint(
+        self, mock_get_rule
+    ):
+        """A custom rule whose only field is "fingerprint" should keep the
+        tool-provided fingerprint verbatim instead of hashing it."""
+        alert = _make_alert(
+            "HighCPU",
+            labels={"alertname": "HighCPU"},
+            fingerprint="grafana-native-fp",
+        )
+
+        rule = MagicMock()
+        rule.fingerprint_fields = ["fingerprint"]
+        mock_get_rule.return_value = rule
+
+        provider = _make_provider([alert])
+
+        with patch(
+            "keep.providers.base.base_provider.tracer"
+        ) as mock_tracer:
+            mock_tracer.start_as_current_span.return_value.__enter__ = MagicMock()
+            mock_tracer.start_as_current_span.return_value.__exit__ = MagicMock()
+            alerts = provider.get_alerts()
+
+        self.assertEqual(alerts[0].fingerprint, "grafana-native-fp")
+
     @patch("keep.providers.base.base_provider.get_custom_deduplication_rule")
     def test_custom_dedup_with_dot_notation_fields(self, mock_get_rule):
         """Custom dedup should support dot-notation to access nested dict fields."""