fix:

sdks/python/src/agent_control/control_decorators.py

@@ -36,6 +36,7 @@ async def chat(message: str) -> str:
 from typing import Any, TypeVar
 
 from agent_control_models import Step, normalize_action
+from agent_control_telemetry import get_trace_context_from_provider
 
 from agent_control import AgentControlClient
 from agent_control.evaluation import check_evaluation_with_local
@@ -53,6 +54,25 @@ async def chat(message: str) -> str:
 F = TypeVar("F", bound=Callable[..., Any])
 
 
+def _resolve_control_trace_context() -> tuple[str, str]:
+    """Resolve trace/span IDs for a decorated control site.
+
+    External providers, such as the Galileo bridge, are authoritative because
+    they may reserve the concrete span ID that the eventual LLM/tool call will
+    use. Without a provider, keep the existing behavior: share an active trace
+    but create a fresh function span for this decorated call.
+    """
+    provider_context = get_trace_context_from_provider()
+    if provider_context is not None:
+        return provider_context["trace_id"], provider_context["span_id"]
+
+    existing_trace_id = get_current_trace_id()
+    if existing_trace_id:
+        return existing_trace_id, _generate_span_id()
+
+    return get_trace_and_span_ids()
+
+
 @dataclass
 class ControlContext:
     """
@@ -697,14 +717,7 @@ async def _execute_with_control(
     # Get cached controls for local evaluation support
     controls = _get_server_controls()
 
-    # Get trace context: inherit trace_id if set, always generate new span_id
-    # This allows multiple @control() calls to share the same trace but have unique spans
-    existing_trace_id = get_current_trace_id()
-    if existing_trace_id:
-        trace_id = existing_trace_id
-        span_id = _generate_span_id()  # New span for this function
-    else:
-        trace_id, span_id = get_trace_and_span_ids()  # New trace and span
+    trace_id, span_id = _resolve_control_trace_context()
 
     ctx = ControlContext(
         agent_name=agent.agent_name,

sdks/python/tests/test_control_decorators.py

@@ -3,9 +3,9 @@
 from unittest.mock import MagicMock, patch
 
 import pytest
+from agent_control_telemetry import clear_trace_context_provider, set_trace_context_provider
 
-from agent_control.control_decorators import ControlViolationError, ControlSteerError, control
-
+from agent_control.control_decorators import ControlSteerError, ControlViolationError, control
 
 # =============================================================================
 # FIXTURES
@@ -255,6 +255,54 @@ async def chat(message: str) -> str:
 class TestPrePostExecution:
     """Tests for pre and post execution checks."""
 
+    @pytest.mark.asyncio
+    async def test_uses_external_provider_trace_context(self, mock_agent, mock_safe_response):
+        """Test that an external provider supplies both trace and span IDs."""
+        # Given: an external telemetry provider that owns the active trace/span IDs
+        provided_trace_id = "6c4e3f7e-4a9a-4e7e-8c1f-3a9a3a9a3a9d"
+        provided_span_id = "8d30272e-23f7-4a4c-80d8-2decb2f3f9f8"
+        captured_contexts = []
+
+        async def mock_evaluate(
+            agent_name,
+            step,
+            stage,
+            server_url,
+            trace_id=None,
+            span_id=None,
+            controls=None,
+            event_agent_name=None,
+        ):
+            captured_contexts.append((trace_id, span_id))
+            return mock_safe_response
+
+        set_trace_context_provider(
+            lambda: {"trace_id": provided_trace_id, "span_id": provided_span_id}
+        )
+        try:
+            with (
+                patch(
+                    "agent_control.control_decorators._get_current_agent",
+                    return_value=mock_agent,
+                ),
+                patch("agent_control.control_decorators._evaluate", side_effect=mock_evaluate),
+            ):
+
+                @control()
+                async def chat(message: str) -> str:
+                    return f"Response to: {message}"
+
+                # When: a protected function runs pre and post checks
+                await chat("Hello!")
+        finally:
+            clear_trace_context_provider()
+
+        # Then: Agent Control preserves the provider's concrete target span ID
+        assert captured_contexts == [
+            (provided_trace_id, provided_span_id),
+            (provided_trace_id, provided_span_id),
+        ]
+
     @pytest.mark.asyncio
     async def test_calls_pre_and_post(self, mock_agent, mock_safe_response):
         """Test that both pre and post checks are called."""