fix(llmobs): mark artificially added gen_ai tags on APM spans

ddtrace/llmobs/_constants.py

@@ -97,6 +97,7 @@ class LLMObsSamplingDecision(str, Enum):
 LLMOBS_APM_SHADOW_MODEL_NAME_TAG_KEY = "_dd.llmobs.model_name"
 LLMOBS_APM_SHADOW_MODEL_PROVIDER_TAG_KEY = "_dd.llmobs.model_provider"
 LLMOBS_APM_SHADOW_ENABLED_METRIC_KEY = "_dd.llmobs.enabled"
+LLMOBS_ARTIFICIAL_GEN_AI_TAGS_KEY = "_dd.llmobs.artificial_gen_ai_tags"
 
 GEN_AI_OPERATION_NAME_TAG_KEY = "gen_ai.operation.name"
 GEN_AI_REQUEST_MODEL_TAG_KEY = "gen_ai.request.model"

ddtrace/llmobs/_utils.py

@@ -41,6 +41,7 @@
 from ddtrace.llmobs._constants import INPUT_TOKENS_METRIC_KEY
 from ddtrace.llmobs._constants import INTERNAL_CONTEXT_VARIABLE_KEYS
 from ddtrace.llmobs._constants import INTERNAL_QUERY_VARIABLE_KEYS
+from ddtrace.llmobs._constants import LLMOBS_ARTIFICIAL_GEN_AI_TAGS_KEY
 from ddtrace.llmobs._constants import LLMOBS_STRUCT
 from ddtrace.llmobs._constants import ML_APP
 from ddtrace.llmobs._constants import ML_APP_DEFAULT
@@ -1127,3 +1128,6 @@ def set_gen_ai_apm_tags(span: Span, llmobs_data: Mapping[str, Any], span_kind: O
             value = metrics.get(llmobs_key)
             if value is not None:
                 span._set_attribute(gen_ai_key, value)
+    # Without this tag, the backend processor identifies gen_ai tags on the APM span and creates
+    # a duplicate LLMObs span.
+    span.set_tag(LLMOBS_ARTIFICIAL_GEN_AI_TAGS_KEY, "true")

releasenotes/notes/mark-artificial-gen-ai-tags-03f6dab36ff3c8ca.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    LLM Observability: Fixes an issue where APM spans annotated with gen_ai attributes could
+    cause a duplicate LLM Observability span to be created.

tests/llmobs/test_llmobs_gen_ai_apm_tags.py

@@ -14,6 +14,7 @@
 from ddtrace.llmobs._constants import GEN_AI_USAGE_OUTPUT_TOKENS_METRIC_KEY
 from ddtrace.llmobs._constants import GEN_AI_USAGE_REASONING_OUTPUT_TOKENS_METRIC_KEY
 from ddtrace.llmobs._constants import GEN_AI_USAGE_TOTAL_TOKENS_METRIC_KEY
+from ddtrace.llmobs._constants import LLMOBS_ARTIFICIAL_GEN_AI_TAGS_KEY
 from ddtrace.llmobs._constants import LLMOBS_STRUCT
 from ddtrace.llmobs._constants import UNKNOWN_MODEL_NAME
 from ddtrace.llmobs._constants import UNKNOWN_MODEL_PROVIDER
@@ -58,6 +59,7 @@ def test_llm_span_emits_all_scalars(llmobs, test_spans):
     assert span.get_tag(GEN_AI_PROVIDER_NAME_TAG_KEY) == "openai"
     assert span.get_tag(GEN_AI_CONVERSATION_ID_TAG_KEY) == "sess-1"
     assert span.get_tag(GEN_AI_APPLICATION_NAME_TAG_KEY) is not None
+    assert span.get_tag(LLMOBS_ARTIFICIAL_GEN_AI_TAGS_KEY) == "true"
     assert _usage(span) == {
         GEN_AI_USAGE_INPUT_TOKENS_METRIC_KEY: 10,
         GEN_AI_USAGE_OUTPUT_TOKENS_METRIC_KEY: 20,

tests/utils.py

@@ -74,6 +74,7 @@
     "meta._dd.llmobs.span_kind",
     "meta._dd.llmobs.model_name",
     "meta._dd.llmobs.model_provider",
+    "meta._dd.llmobs.artificial_gen_ai_tags",
     "meta._dd.p.llmobs_trace_id",
     "meta._dd.p.llmobs_parent_id",
     "meta._dd.p.llmobs_ml_app",