fix: add project_id to urls returned by langfuse_context.get_current_…

…trace_url (#1056)

langfuse/client.py

@@ -342,20 +342,28 @@ def _get_release_value(self, release: Optional[str] = None) -> Optional[str]:
         else:
             return get_common_release_envs()
 
+    def _get_project_id(self) -> Optional[str]:
+        """Fetch and return the current project id. Persisted across requests. Returns None if no project id is found for api keys."""
+        if not self.project_id:
+            proj = self.client.projects.get()
+            if not proj.data or not proj.data[0].id:
+                return None
+
+            self.project_id = proj.data[0].id
+
+        return self.project_id
+
     def get_trace_id(self) -> str:
         """Get the current trace id."""
         return self.trace_id
 
     def get_trace_url(self) -> str:
         """Get the URL of the current trace to view it in the Langfuse UI."""
-        if not self.project_id:
-            proj = self.client.projects.get()
-            if not proj.data or not proj.data[0].id:
-                return f"{self.base_url}/trace/{self.trace_id}"
-
-            self.project_id = proj.data[0].id
+        project_id = self._get_project_id()
+        if not project_id:
+            return f"{self.base_url}/trace/{self.trace_id}"
 
-        return f"{self.base_url}/project/{self.project_id}/traces/{self.trace_id}"
+        return f"{self.base_url}/project/{project_id}/traces/{self.trace_id}"
 
     def get_dataset(
         self, name: str, *, fetch_items_page_size: Optional[int] = 50

langfuse/decorators/langfuse_decorator.py

@@ -713,7 +713,12 @@ def get_current_trace_url(self) -> Optional[str]:
             if not trace_id:
                 raise ValueError("No trace found in the current context")
 
-            return f"{self.client_instance.client._client_wrapper._base_url}/trace/{trace_id}"
+            project_id = self.client_instance._get_project_id()
+
+            if not project_id:
+                return f"{self.client_instance.client._client_wrapper._base_url}/trace/{trace_id}"
+
+            return f"{self.client_instance.client._client_wrapper._base_url}/project/{project_id}/traces/{trace_id}"
 
         except Exception as e:
             self._log.error(f"Failed to get current trace URL: {e}")

tests/test_core_sdk.py

@@ -1538,6 +1538,13 @@ def faulty_mask_func(data):
     assert fetched_trace["output"] == "<fully masked due to failed mask function>"
 
 
+def test_get_project_id():
+    langfuse = Langfuse(debug=False)
+    res = langfuse._get_project_id()
+    assert res is not None
+    assert res == "7a88fb47-b4e2-43b8-a06c-a5ce950dc53a"
+
+
 def test_generate_trace_id():
     langfuse = Langfuse(debug=False)
     trace_id = create_uuid()

tests/test_decorators.py

@@ -608,6 +608,30 @@ def level_1_function(*args, **kwargs):
     )
 
 
+def test_get_current_trace_url():
+    mock_trace_id = create_uuid()
+
+    @observe()
+    def level_3_function():
+        return langfuse_context.get_current_trace_url()
+
+    @observe()
+    def level_2_function():
+        return level_3_function()
+
+    @observe()
+    def level_1_function(*args, **kwargs):
+        return level_2_function()
+
+    result = level_1_function(
+        *mock_args, **mock_kwargs, langfuse_observation_id=mock_trace_id
+    )
+    langfuse_context.flush()
+
+    expected_url = f"http://localhost:3000/project/7a88fb47-b4e2-43b8-a06c-a5ce950dc53a/traces/{mock_trace_id}"
+    assert result == expected_url
+
+
 def test_scoring_observations():
     mock_name = "test_scoring_observations"
     mock_trace_id = create_uuid()