diff --git a/backend/agents.py b/backend/agents.py
index 155ce0a..03a8865 100644
--- a/backend/agents.py
+++ b/backend/agents.py
@@ -63,9 +63,10 @@ def _require_llm_creds() -> None:
 
 
 _GENAI_CLIENT = None
+_GENAI_CLIENT_LOCK = asyncio.Lock()
 
 
-def _get_genai_client():
+async def _get_genai_client():
     """
     Build a google.genai client for either Vertex (ADC or creds file) or API-key mode.
     """
@@ -73,17 +74,28 @@ def _get_genai_client():
     if _GENAI_CLIENT is not None:
         return _GENAI_CLIENT
 
-    if _use_vertex():
-        project = os.getenv("GCP_PROJECT_ID")
-        location = os.getenv("GCP_REGION") or "europe-west4"
-        _ensure_google_creds_for_vertex()
-        _GENAI_CLIENT = genai.Client(vertexai=True, project=project, location=location)
-    else:
-        _GENAI_CLIENT = genai.Client(api_key=os.getenv("GOOGLE_API_KEY"))
+    async with _GENAI_CLIENT_LOCK:
+        #Double-check inside lock
+        if _GENAI_CLIENT is not None:
+            return _GENAI_CLIENT
+
+        if _use_vertex():
+            project = os.getenv("GCP_PROJECT_ID")
+            location = os.getenv("GCP_REGION") or "europe-west4"
+            _ensure_google_creds_for_vertex()
+            _GENAI_CLIENT = genai.Client(
+                vertexai=True,
+                project=project,
+                location=location
+            )
+        
+        else:
+            _GENAI_CLIENT = genai.Client(
+                api_key=os.getenv("GOOGLE_API_KEY")
+            )
 
     return _GENAI_CLIENT
 
-
 FLASH_MODEL = os.getenv("GEMINI_FLASH_MODEL", "gemini-2.5-flash")
 FLASH_LITE_MODEL = os.getenv("GEMINI_FLASH_LITE_MODEL", "gemini-2.5-flash-lite")
 
@@ -124,7 +136,7 @@ async def call_gemini_for_keywords(query: str) -> List[str]:
     No local greeting filters — prompt handles exclusions. Minimal trim+dedupe here.
     """
     _require_llm_creds()
-    client = _get_genai_client()
+    client = await _get_genai_client()
     prompt = (
         "Extract important search keywords and multi-word phrases from a neuroscience *data* query.\n"
         "Return STRICT JSON only:\n"
@@ -166,7 +178,7 @@ async def call_gemini_rewrite_with_history(query: str, history: List[str]) -> st
     Keeps exact tokens and multi-word phrases intact.
     """
     _require_llm_creds()
-    client = _get_genai_client()
+    client = await _get_genai_client()
     last_user_turns = [h for h in history if h.startswith("User: ")]
     ctx = "\n".join(last_user_turns[-6:])
     prompt = (
@@ -201,7 +213,7 @@ async def call_gemini_detect_intents(query: str, history: List[str]) -> List[str
     - If any data-related tokens exist, prefer data_discovery.
     """
     _require_llm_creds()
-    client = _get_genai_client()
+    client = await _get_genai_client()
     allowed = [i.value for i in QueryIntent]
     last_user_turns = [h for h in history if h.startswith("User: ")]
     ctx = "\n".join(last_user_turns[-6:])
@@ -242,7 +254,7 @@ async def call_gemini_for_final_synthesis(
 ) -> str:
 
     _require_llm_creds()
-    client = _get_genai_client()
+    client = await _get_genai_client()
 
     extras = []
     if QueryIntent.ACCESS_DOWNLOAD.value in intents: