fix(llmobs): propagate llmobs_parent_id in _current_trace_context

ddtrace/llmobs/_llmobs.py

@@ -1959,6 +1959,7 @@ def _current_trace_context(self) -> Optional[Context]:
             context = active.context
             wire_trace_id = _trace_id_to_wire(get_llmobs_trace_id(active)) or str(active.trace_id)
             context._meta[PROPAGATED_LLMOBS_TRACE_ID_KEY] = wire_trace_id
+            context._meta[PROPAGATED_PARENT_ID_KEY] = str(active.span_id)
             return context
         return None
 

releasenotes/notes/llmobs-propagate-parent-id-401cc2c7a9274277.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    LLM Observability: Fixed an issue where ``_current_trace_context`` did not propagate
+    ``_dd.p.llmobs_parent_id`` into the trace context metadata. Without this value, downstream
+    consumers (e.g. dd-trace-go) could not locate the active LLMObs parent span and would create
+    orphaned child traces instead of correctly continuing the parent trace.

tests/llmobs/test_propagation.py

@@ -472,6 +472,19 @@ def _make_upstream_llmobs_context(trace_id_value, parent_id="987654321"):
     return ctx
 
 
+def test_current_trace_context_includes_parent_id(llmobs):
+    """_current_trace_context must set PROPAGATED_PARENT_ID_KEY so that HTTPPropagator.inject
+    (and any other consumer that reads _meta directly) propagates _dd.p.llmobs_parent_id to
+    subprocess / HTTP consumers. Without this, dd-trace-go's contextWithPropagatedLLMSpan
+    sees an empty parent_id and falls through to newLLMObsTraceID(), orphaning the child trace.
+    """
+    with llmobs.workflow("w") as span:
+        ctx = llmobs._instance._current_trace_context()
+    assert ctx is not None
+    assert ctx._meta.get(PROPAGATED_PARENT_ID_KEY) == str(span.span_id)
+    assert ctx._meta.get(PROPAGATED_LLMOBS_TRACE_ID_KEY) is not None
+
+
 def test_injected_trace_id_is_decimal_on_the_wire(llmobs):
     """Wire must stay decimal so older SDKs that do int(header) keep working."""
     with llmobs.workflow("w") as span: