chore: fix phantom user creation in posthog

api/services/posthog_client.py

@@ -6,6 +6,7 @@ from posthog import Posthog
 from api.constants import POSTHOG_API_KEY, POSTHOG_HOST
 
 _posthog_client: Posthog | None = None
+POSTHOG_SERVER_GROUP_IDENTIFY_DISTINCT_ID = "server-group-identify"
 
 
 def get_posthog() -> Posthog | None:
@@ -77,7 +78,7 @@ def group_identify(
             group_type,
             group_key,
             properties,
-            distinct_id=distinct_id,
+            distinct_id=distinct_id or POSTHOG_SERVER_GROUP_IDENTIFY_DISTINCT_ID,
         )
     except Exception:
         logger.exception("Failed to identify PostHog group")

api/tests/test_posthog_client.py

@@ -0,0 +1,34 @@
+from api.services import posthog_client
+
+
+class FakePostHog:
+    def __init__(self):
+        self.group_identify_calls = []
+
+    def group_identify(self, *args, **kwargs):
+        self.group_identify_calls.append((args, kwargs))
+
+
+def test_group_identify_uses_stable_server_distinct_id(monkeypatch):
+    fake_posthog = FakePostHog()
+    monkeypatch.setattr(posthog_client, "get_posthog", lambda: fake_posthog)
+
+    posthog_client.group_identify("organization", "42", {})
+
+    _, kwargs = fake_posthog.group_identify_calls[0]
+    assert kwargs["distinct_id"] == "server-group-identify"
+
+
+def test_group_identify_preserves_real_distinct_id(monkeypatch):
+    fake_posthog = FakePostHog()
+    monkeypatch.setattr(posthog_client, "get_posthog", lambda: fake_posthog)
+
+    posthog_client.group_identify(
+        "organization",
+        "42",
+        {},
+        distinct_id="stack-user-1",
+    )
+
+    _, kwargs = fake_posthog.group_identify_calls[0]
+    assert kwargs["distinct_id"] == "stack-user-1"