diff --git a/lua/avante/providers/openai.lua b/lua/avante/providers/openai.lua
index 42f207e..5f70aaa 100644
--- a/lua/avante/providers/openai.lua
+++ b/lua/avante/providers/openai.lua
@@ -246,17 +246,10 @@ function M:parse_response(ctx, data_stream, _, opts)
   if choice.finish_reason == "stop" or choice.finish_reason == "eos_token" then
     if choice.delta.content and choice.delta.content ~= vim.NIL then
       self:add_text_message(ctx, choice.delta.content, "generated", opts)
-      opts.on_chunk(choice.delta.content)
+      if opts.on_chunk then opts.on_chunk(choice.delta.content) end
     end
     self:finish_pending_messages(ctx, opts)
     opts.on_stop({ reason = "complete" })
-  elseif choice.finish_reason == "tool_calls" then
-    self:finish_pending_messages(ctx, opts)
-    opts.on_stop({
-      reason = "tool_use",
-      -- tool_use_list = ctx.tool_use_list,
-      usage = jsn.usage,
-    })
   elseif choice.delta.reasoning_content and choice.delta.reasoning_content ~= vim.NIL then
     if ctx.returned_think_start_tag == nil or not ctx.returned_think_start_tag then
       ctx.returned_think_start_tag = true
@@ -284,7 +277,7 @@ function M:parse_response(ctx, data_stream, _, opts)
         local tool_use = {
           name = tool_call["function"].name,
           id = tool_call.id,
-          input_json = "",
+          input_json = type(tool_call["function"].arguments) == "string" and tool_call["function"].arguments or "",
         }
         ctx.tool_use_list[tool_call.index + 1] = tool_use
         self:add_tool_use_message(tool_use, "generating", opts)
@@ -313,6 +306,13 @@ function M:parse_response(ctx, data_stream, _, opts)
       self:add_text_message(ctx, choice.delta.content, "generating", opts)
     end
   end
+  if choice.finish_reason == "tool_calls" then
+    self:finish_pending_messages(ctx, opts)
+    opts.on_stop({
+      reason = "tool_use",
+      usage = jsn.usage,
+    })
+  end
 end
 
 function M:parse_response_without_stream(data, _, opts)