diff --git a/tests/unit/vertexai/genai/replays/conftest.py b/tests/unit/vertexai/genai/replays/conftest.py
index 7b7e41d0ce..94e0004316 100644
--- a/tests/unit/vertexai/genai/replays/conftest.py
+++ b/tests/unit/vertexai/genai/replays/conftest.py
@@ -25,6 +25,7 @@
 from vertexai._genai import _agent_engines_utils
 from google.cloud import storage, bigquery
 from google.genai import _replay_api_client
+from google.genai import types as genai_types
 from google.genai import client as google_genai_client_module
 from vertexai._genai import _gcs_utils
 from vertexai._genai import prompt_optimizer
@@ -249,6 +250,13 @@ def client(use_vertex, replays_prefix, http_options, request):
             )
         )
         os.environ["GOOGLE_GENAI_REPLAYS_DIRECTORY"] = replays_root_directory
+
+    if http_options is None:
+        http_options = genai_types.HttpOptions()
+    if http_options.headers is None:
+        http_options.headers = {}
+    http_options.headers["x-goog-vertex-sdk"] = "true"
+
     replay_client = _replay_api_client.ReplayApiClient(
         mode=mode,
         replay_id=replay_id,
diff --git a/vertexai/_genai/client.py b/vertexai/_genai/client.py
index 8a9a9ff135..29f81d2e0f 100644
--- a/vertexai/_genai/client.py
+++ b/vertexai/_genai/client.py
@@ -41,19 +41,23 @@
 
 _GENAI_MODULES_TELEMETRY_HEADER = "vertex-genai-modules"
 
+genai_append_method = _api_client.append_library_version_headers
 
-def _add_tracking_headers(headers: dict[str, str]) -> None:
-    """Appends Vertex Gen AI modules tracking information to the request headers."""
 
-    tracking_label = f"{_GENAI_MODULES_TELEMETRY_HEADER}/{aip_version.__version__}"
+def _add_tracking_headers(headers: dict[str, str]) -> None:
+    """Adds Vertex Gen AI tracking headers."""
+    is_vertex = headers.get(
+        "x-goog-vertex-sdk"
+    ) == "true" or "vertex-genai-modules" in headers.get("user-agent", "")
+    if is_vertex:
+        tracking_label = f"{_GENAI_MODULES_TELEMETRY_HEADER}/{aip_version.__version__}"
 
-    user_agent = headers.get("user-agent", "")
-    if tracking_label not in user_agent:
-        headers["user-agent"] = f"{user_agent} {tracking_label}".strip()
+        headers["user-agent"] = tracking_label
+        headers["x-goog-api-client"] = tracking_label
 
-    api_client = headers.get("x-goog-api-client", "")
-    if tracking_label not in api_client:
-        headers["x-goog-api-client"] = f"{api_client} {tracking_label}".strip()
+        headers.pop("x-goog-vertex-sdk", None)
+    else:
+        genai_append_method(headers)
 
 
 _api_client.append_library_version_headers = _add_tracking_headers
@@ -221,6 +225,11 @@ def __init__(
         self._debug_config = debug_config or genai_client.DebugConfig()
         if isinstance(http_options, dict):
             http_options = types.HttpOptions(**http_options)
+        if http_options is None:
+            http_options = types.HttpOptions()
+        if http_options.headers is None:
+            http_options.headers = {}
+        http_options.headers["x-goog-vertex-sdk"] = "true"
 
         self._api_client = genai_client.Client._get_api_client(
             vertexai=True,