From 0eb33e8e1289c87ab1783ba9ddd9cd396e4dab94 Mon Sep 17 00:00:00 2001
From: Timothy Jaeryang Baek <tim@openwebui.com>
Date: Tue, 16 Dec 2025 13:49:00 -0500
Subject: [PATCH] refac: logit bias handling

---
 backend/open_webui/routers/openai.py   |  9 +++++----
 backend/open_webui/utils/middleware.py |  7 ++++---
 backend/open_webui/utils/misc.py       | 22 ++++++++++++----------
 3 files changed, 21 insertions(+), 17 deletions(-)

diff --git a/backend/open_webui/routers/openai.py b/backend/open_webui/routers/openai.py
index a74a59ca1f..eb8a93c8e2 100644
--- a/backend/open_webui/routers/openai.py
+++ b/backend/open_webui/routers/openai.py
@@ -891,10 +891,11 @@ async def generate_chat_completion(
         del payload["max_tokens"]
 
     # Convert the modified body back to JSON
-    if "logit_bias" in payload:
-        payload["logit_bias"] = json.loads(
-            convert_logit_bias_input_to_json(payload["logit_bias"])
-        )
+    if "logit_bias" in payload and payload["logit_bias"]:
+        logit_bias = convert_logit_bias_input_to_json(payload["logit_bias"])
+
+        if logit_bias:
+            payload["logit_bias"] = json.loads(logit_bias)
 
     headers, cookies = await get_headers_and_cookies(
         request, url, key, api_config, metadata, user=user
diff --git a/backend/open_webui/utils/middleware.py b/backend/open_webui/utils/middleware.py
index 6c285b9367..aafa3879ff 100644
--- a/backend/open_webui/utils/middleware.py
+++ b/backend/open_webui/utils/middleware.py
@@ -1100,9 +1100,10 @@ def apply_params_to_form_data(form_data, model):
 
         if "logit_bias" in params and params["logit_bias"] is not None:
             try:
-                form_data["logit_bias"] = json.loads(
-                    convert_logit_bias_input_to_json(params["logit_bias"])
-                )
+                logit_bias = convert_logit_bias_input_to_json(params["logit_bias"])
+
+                if logit_bias:
+                    form_data["logit_bias"] = json.loads(logit_bias)
             except Exception as e:
                 log.exception(f"Error parsing logit_bias: {e}")
 
diff --git a/backend/open_webui/utils/misc.py b/backend/open_webui/utils/misc.py
index e0e21249f6..4501dfaf07 100644
--- a/backend/open_webui/utils/misc.py
+++ b/backend/open_webui/utils/misc.py
@@ -523,16 +523,18 @@ def parse_ollama_modelfile(model_text):
     return data
 
 
-def convert_logit_bias_input_to_json(user_input):
-    logit_bias_pairs = user_input.split(",")
-    logit_bias_json = {}
-    for pair in logit_bias_pairs:
-        token, bias = pair.split(":")
-        token = str(token.strip())
-        bias = int(bias.strip())
-        bias = 100 if bias > 100 else -100 if bias < -100 else bias
-        logit_bias_json[token] = bias
-    return json.dumps(logit_bias_json)
+def convert_logit_bias_input_to_json(user_input) -> Optional[str]:
+    if user_input:
+        logit_bias_pairs = user_input.split(",")
+        logit_bias_json = {}
+        for pair in logit_bias_pairs:
+            token, bias = pair.split(":")
+            token = str(token.strip())
+            bias = int(bias.strip())
+            bias = 100 if bias > 100 else -100 if bias < -100 else bias
+            logit_bias_json[token] = bias
+        return json.dumps(logit_bias_json)
+    return None
 
 
 def freeze(value):