fix(llmobs): apply tracer.set_tags() tags to LLM Observability spans

ddtrace/llmobs/_llmobs.py

@@ -2573,7 +2573,7 @@ def _activate_llmobs_span(self, span: Span) -> None:
             resolved_name = span.resource
 
         initial_tags = {
-            **config.tags,
+            **self.tracer._tags,
             "version": config.version or "",
             "env": config.env or "",
             "service": span.service or "",

releasenotes/notes/llmobs-tracer-set-tags-fae850aeca55cdb5.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    LLM Observability: Tags set with ``tracer.set_tags()`` are now applied to LLM Observability spans. Previously only tags from ``DD_TAGS`` were applied.

tests/llmobs/test_llmobs_service.py

@@ -1312,6 +1312,14 @@ def test_tags(ddtrace_global_config, llmobs, monkeypatch):
     )
 
 
+def test_tracer_set_tags_applied_to_llmobs_spans(llmobs, tracer, monkeypatch):
+    monkeypatch.setattr(tracer, "_tags", {})
+    tracer.set_tags({"airid": "air-123"})
+    with llmobs.workflow(name="test_workflow") as span:
+        pass
+    assert get_llmobs_tags(span)["airid"] == "air-123"
+
+
 @pytest.mark.subprocess(
     env={
         "DD_API_KEY": "<not-a-real-key>",