diff --git a/backend-python/routes/state_cache.py b/backend-python/routes/state_cache.py
index c58cf08..a150419 100644
--- a/backend-python/routes/state_cache.py
+++ b/backend-python/routes/state_cache.py
@@ -47,32 +47,36 @@ def add_state(body: AddStateBody):
     if trie is None:
         raise HTTPException(status.HTTP_400_BAD_REQUEST, "trie not loaded")
 
-    if len(trie) >= max_trie_len:
-        del_prompt = trie[loop_del_trie_id]
-        trie.remove(del_prompt)
-        dtrie[loop_del_trie_id] = None
-        loop_del_trie_id = loop_del_trie_id + 1
-        if loop_del_trie_id >= max_trie_len:
-            loop_del_trie_id = loop_start_id
+    try:
+        id = trie.insert(body.prompt)
+        device = body.state[0].device
+        dtrie[id] = {
+            "tokens": copy.deepcopy(body.tokens),
+            "state": [tensor.cpu() for tensor in body.state]
+            if device != torch.device("cpu")
+            else copy.deepcopy(body.state),
+            "logits": copy.deepcopy(body.logits),
+            "device": device,
+        }
 
-    id = trie.insert(body.prompt)
-    device = body.state[0].device
-    dtrie[id] = {
-        "tokens": copy.deepcopy(body.tokens),
-        "state": [tensor.cpu() for tensor in body.state]
-        if device != torch.device("cpu")
-        else copy.deepcopy(body.state),
-        "logits": copy.deepcopy(body.logits),
-        "device": device,
-    }
+        if len(trie) >= max_trie_len:
+            del_prompt = trie[loop_del_trie_id]
+            trie.remove(del_prompt)
+            dtrie[loop_del_trie_id] = None
+            loop_del_trie_id = loop_del_trie_id + 1
+            if loop_del_trie_id >= max_trie_len:
+                loop_del_trie_id = loop_start_id
 
-    quick_log(
-        None,
-        None,
-        f"New Trie Id: {id}\nTrie Len: {len(trie)}\nTrie Buff Size: {trie.buff_size()}\nDtrie Buff Size Of Id: {_get_a_dtrie_buff_size(dtrie[id])}",
-    )
-
-    return "success"
+        quick_log(
+            None,
+            None,
+            f"New Trie Id: {id}\nTrie Len: {len(trie)}\nTrie Buff Size: {trie.buff_size()}\nDtrie Buff Size Of Id: {_get_a_dtrie_buff_size(dtrie[id])}",
+        )
+        return "success"
+    except Exception as e:
+        raise HTTPException(
+            status.HTTP_400_BAD_REQUEST, f"insert failed, bad prompt.\n{e}"
+        )
 
 
 @router.post("/reset-state")
@@ -116,7 +120,10 @@ def longest_prefix_state(body: LongestPrefixStateBody, request: Request):
         raise HTTPException(status.HTTP_400_BAD_REQUEST, "trie not loaded")
 
     id = -1
-    for id, len in trie.prefix(body.prompt):
+    try:
+        for id, len in trie.prefix(body.prompt):
+            pass
+    except:
         pass
     if id != -1:
         v = dtrie[id]