diff --git a/src/gentrace/__init__.py b/src/gentrace/__init__.py
index b7da1e46..04001b86 100644
--- a/src/gentrace/__init__.py
+++ b/src/gentrace/__init__.py
@@ -107,6 +107,7 @@ def __getattr__(self, name: str) -> _t.Any:
     ATTR_GENTRACE_PIPELINE_ID,
     ATTR_GENTRACE_TEST_CASE_ID,
     ATTR_GENTRACE_EXPERIMENT_ID,
+    ATTR_GENTRACE_IN_EXPERIMENT,
     ATTR_GENTRACE_TEST_CASE_NAME,
     ATTR_GENTRACE_FN_ARGS_EVENT_NAME,
     ATTR_GENTRACE_FN_OUTPUT_EVENT_NAME,
@@ -160,7 +161,6 @@ def __getattr__(self, name: str) -> _t.Any:
     "DefaultHttpxClient",
     "DefaultAsyncHttpxClient",
     "DefaultAioHttpClient",
-
     # Start custom Gentrace exports
     "init",
     "setup",
@@ -170,6 +170,8 @@ def __getattr__(self, name: str) -> _t.Any:
     "eval",
     "eval_dataset",
     "TestInput",
+    "ATTR_GENTRACE_SAMPLE_KEY",
+    "ATTR_GENTRACE_IN_EXPERIMENT",
     "ATTR_GENTRACE_PIPELINE_ID",
     "ATTR_GENTRACE_TEST_CASE_ID",
     "ATTR_GENTRACE_EXPERIMENT_ID",
diff --git a/src/gentrace/lib/constants.py b/src/gentrace/lib/constants.py
index 6f96ea2b..7ecff51a 100644
--- a/src/gentrace/lib/constants.py
+++ b/src/gentrace/lib/constants.py
@@ -12,6 +12,7 @@
 ATTR_GENTRACE_TEST_CASE_ID = "gentrace.test_case_id"
 
 ATTR_GENTRACE_SAMPLE_KEY = "gentrace.sample"
+ATTR_GENTRACE_IN_EXPERIMENT = "gentrace.in_experiment"
 
 # Maximum allowed concurrency for eval_dataset
 MAX_EVAL_DATASET_CONCURRENCY = 100
@@ -25,5 +26,6 @@
     "ATTR_GENTRACE_TEST_CASE_ID",
     "ATTR_GENTRACE_PIPELINE_ID",
     "ATTR_GENTRACE_SAMPLE_KEY",
+    "ATTR_GENTRACE_IN_EXPERIMENT",
     "MAX_EVAL_DATASET_CONCURRENCY",
 ]
diff --git a/src/gentrace/lib/eval.py b/src/gentrace/lib/eval.py
index a5ca3e7a..7e375d00 100644
--- a/src/gentrace/lib/eval.py
+++ b/src/gentrace/lib/eval.py
@@ -13,6 +13,7 @@
     ANONYMOUS_SPAN_NAME,
     ATTR_GENTRACE_SAMPLE_KEY,
     ATTR_GENTRACE_EXPERIMENT_ID,
+    ATTR_GENTRACE_IN_EXPERIMENT,
     ATTR_GENTRACE_TEST_CASE_NAME,
     ATTR_GENTRACE_FN_ARGS_EVENT_NAME,
     ATTR_GENTRACE_FN_OUTPUT_EVENT_NAME,
@@ -90,6 +91,9 @@ async def wrapper(*args: P.args, **kwargs: P.kwargs) -> Any:
             context_with_modified_baggage = otel_baggage.set_baggage(
                 ATTR_GENTRACE_SAMPLE_KEY, "true", context=current_context
             )
+            context_with_modified_baggage = otel_baggage.set_baggage(
+                ATTR_GENTRACE_IN_EXPERIMENT, "true", context=context_with_modified_baggage
+            )
 
             token = otel_context.attach(context_with_modified_baggage)
             try:
diff --git a/src/gentrace/lib/eval_dataset.py b/src/gentrace/lib/eval_dataset.py
index dff60f2a..0e7f310f 100644
--- a/src/gentrace/lib/eval_dataset.py
+++ b/src/gentrace/lib/eval_dataset.py
@@ -43,6 +43,7 @@
     ATTR_GENTRACE_SAMPLE_KEY,
     ATTR_GENTRACE_TEST_CASE_ID,
     ATTR_GENTRACE_EXPERIMENT_ID,
+    ATTR_GENTRACE_IN_EXPERIMENT,
     ATTR_GENTRACE_TEST_CASE_NAME,
     MAX_EVAL_DATASET_CONCURRENCY,
     ATTR_GENTRACE_FN_ARGS_EVENT_NAME,
@@ -215,6 +216,9 @@ async def _run_single_test_case_for_dataset(
     # Set up baggage context similar to @interaction()
     current_context = otel_context.get_current()
     context_with_modified_baggage = otel_baggage.set_baggage(ATTR_GENTRACE_SAMPLE_KEY, "true", context=current_context)
+    context_with_modified_baggage = otel_baggage.set_baggage(
+        ATTR_GENTRACE_IN_EXPERIMENT, "true", context=context_with_modified_baggage
+    )
 
     token = otel_context.attach(context_with_modified_baggage)
     try:
diff --git a/src/gentrace/lib/span_processor.py b/src/gentrace/lib/span_processor.py
index b3e7ae70..ef7ef426 100644
--- a/src/gentrace/lib/span_processor.py
+++ b/src/gentrace/lib/span_processor.py
@@ -6,7 +6,7 @@
 from opentelemetry.context import Context
 from opentelemetry.sdk.trace import ReadableSpan, SpanProcessor
 
-from gentrace.lib.constants import ATTR_GENTRACE_SAMPLE_KEY
+from gentrace.lib.constants import ATTR_GENTRACE_SAMPLE_KEY, ATTR_GENTRACE_IN_EXPERIMENT
 
 
 class GentraceSpanProcessor(SpanProcessor):
@@ -35,6 +35,11 @@ def on_start(self, span: Span, parent_context: Optional[Context] = None) -> None
             if isinstance(sample_value, str):
                 span.set_attribute(ATTR_GENTRACE_SAMPLE_KEY, sample_value)
 
+        in_experiment_value = baggage.get_baggage(ATTR_GENTRACE_IN_EXPERIMENT, context=parent_context)
+        if in_experiment_value is not None:
+            if isinstance(in_experiment_value, str):
+                span.set_attribute(ATTR_GENTRACE_IN_EXPERIMENT, in_experiment_value)
+
     @override
     def on_end(self, span: ReadableSpan) -> None:
         """