feat(llmobs): add tag if envar detected

ddtrace/_version.py

@@ -0,0 +1,34 @@
+# file generated by setuptools-scm
+# don't change, don't track in version control
+
+__all__ = [
+    "__version__",
+    "__version_tuple__",
+    "version",
+    "version_tuple",
+    "__commit_id__",
+    "commit_id",
+]
+
+TYPE_CHECKING = False
+if TYPE_CHECKING:
+    from typing import Tuple
+    from typing import Union
+
+    VERSION_TUPLE = Tuple[Union[int, str], ...]
+    COMMIT_ID = Union[str, None]
+else:
+    VERSION_TUPLE = object
+    COMMIT_ID = object
+
+version: str
+__version__: str
+__version_tuple__: VERSION_TUPLE
+version_tuple: VERSION_TUPLE
+commit_id: COMMIT_ID
+__commit_id__: COMMIT_ID
+
+__version__ = version = '4.1.0.dev7+g9e0f1f8dd.d20251204'
+__version_tuple__ = version_tuple = (4, 1, 0, 'dev7', 'g9e0f1f8dd.d20251204')
+
+__commit_id__ = commit_id = 'g9e0f1f8dd'

ddtrace/llmobs/_llmobs.py

@@ -1762,6 +1762,11 @@ def submit_evaluation(
                             "Failed to parse tags. Tags for evaluation metrics must be strings."
                         )
 
+            # Auto-add source:otel tag when OTel tracing is enabled
+            # This allows the backend to wait for OTel span conversion
+            if config._otel_trace_enabled:
+                evaluation_tags["source"] = "otel"
+
             evaluation_metric: LLMObsEvaluationMetricEvent = {
                 "join_on": join_on,
                 "label": str(label),

tests/llmobs/test_llmobs_otel_evaluation.py

@@ -0,0 +1,46 @@
+"""
+Tests for automatic source:otel tag on evaluations when OTel tracing is enabled.
+
+When DD_TRACE_OTEL_ENABLED=true, all evaluations should have `source:otel` tag
+to allow the backend to wait for OTel span conversion (~3 minutes) before
+discarding unmatched evaluations.
+"""
+
+import mock
+
+
+def test_submit_evaluation_adds_source_otel_when_otel_enabled(llmobs, mock_llmobs_eval_metric_writer):
+    """Verify source:otel tag is auto-added when DD_TRACE_OTEL_ENABLED=true."""
+    with mock.patch("ddtrace.llmobs._llmobs.config._otel_trace_enabled", True):
+        llmobs.submit_evaluation(
+            span={"span_id": "123", "trace_id": "456"},
+            label="quality",
+            metric_type="score",
+            value=0.9,
+            ml_app="test-app",
+        )
+
+    mock_llmobs_eval_metric_writer.enqueue.assert_called_once()
+    call_args = mock_llmobs_eval_metric_writer.enqueue.call_args[0][0]
+
+    assert "tags" in call_args
+    assert "source:otel" in call_args["tags"]
+
+
+def test_submit_evaluation_no_source_otel_when_otel_disabled(llmobs, mock_llmobs_eval_metric_writer):
+    """Verify source:otel tag is NOT added when DD_TRACE_OTEL_ENABLED=false (default)."""
+    with mock.patch("ddtrace.llmobs._llmobs.config._otel_trace_enabled", False):
+        llmobs.submit_evaluation(
+            span={"span_id": "123", "trace_id": "456"},
+            label="quality",
+            metric_type="score",
+            value=0.9,
+            ml_app="test-app",
+        )
+
+    mock_llmobs_eval_metric_writer.enqueue.assert_called_once()
+    call_args = mock_llmobs_eval_metric_writer.enqueue.call_args[0][0]
+
+    assert "tags" in call_args
+    assert "source:otel" not in call_args["tags"]
+