diff --git a/lua/CopilotChat/client.lua b/lua/CopilotChat/client.lua
index e2801844..e8383b8c 100644
--- a/lua/CopilotChat/client.lua
+++ b/lua/CopilotChat/client.lua
@@ -445,12 +445,22 @@ function Client:ask(opts)
 
     if out.tool_calls then
       for _, tool_call in ipairs(out.tool_calls) do
-        local key = tool_call.id or tool_call.index
-        local val = tool_calls:get(key)
-        if not val then
+        local key = tool_call.id or tool_call.index or tool_call.name or (#tool_calls:values() + 1)
+        local existing = tool_calls:get(key)
+
+        if not existing then
           tool_calls:set(key, tool_call)
         else
-          val.arguments = val.arguments .. tool_call.arguments
+          existing.arguments = existing.arguments .. tool_call.arguments
+          if tool_call.id then
+            existing.id = tool_call.id
+          end
+          if tool_call.index then
+            existing.index = tool_call.index
+          end
+          if tool_call.name then
+            existing.name = tool_call.name
+          end
         end
       end
     end
@@ -597,12 +607,17 @@ function Client:ask(opts)
     response_reasoning = response_reasoning_buffer:tostring()
   end
 
+  -- Filter out tool calls that don't have names (streaming deltas used only for accumulation)
+  local final_tool_calls = vim.tbl_filter(function(tc)
+    return tc.name ~= nil
+  end, tool_calls:values())
+
   return {
     message = {
       role = constants.ROLE.ASSISTANT,
       content = response_text,
       reasoning = response_reasoning,
-      tool_calls = #tool_calls:values() > 0 and tool_calls:values() or nil,
+      tool_calls = #final_tool_calls > 0 and final_tool_calls or nil,
       model = out_model,
     },
     token_count = token_count,
diff --git a/lua/CopilotChat/config/providers.lua b/lua/CopilotChat/config/providers.lua
index c817f6f8..548f6abd 100644
--- a/lua/CopilotChat/config/providers.lua
+++ b/lua/CopilotChat/config/providers.lua
@@ -397,14 +397,12 @@ local function prepare_responses_output(output)
         content = output.delta.text
       end
     elseif output.type == 'response.output_item.done' then
-      -- Complete output item (including tool calls)
       local item = output.item
       if item and item.type == 'function_call' then
-        local index = output.output_index or (#tool_calls + 1)
         table.insert(tool_calls, {
-          id = item.call_id or ('tooluse_' .. index),
-          index = index,
-          name = item.name or '',
+          id = item.call_id,
+          index = output.output_index,
+          name = item.name,
           arguments = item.arguments or '',
         })
       end
@@ -436,9 +434,9 @@ local function prepare_responses_output(output)
         if msg.tool_calls then
           for i, tool_call in ipairs(msg.tool_calls) do
             table.insert(tool_calls, {
-              id = tool_call.call_id or ('tooluse_' .. i),
+              id = tool_call.call_id,
               index = i,
-              name = tool_call.name or '',
+              name = tool_call.name,
               arguments = tool_call.arguments or '',
             })
           end
@@ -481,11 +479,9 @@ local function prepare_chat_output(output)
         for i, tool_call in ipairs(message.tool_calls) do
           local fn = tool_call['function']
           if fn then
-            local index = tool_call.index or i
-            local id = utils.empty(tool_call.id) and ('tooluse_' .. index) or tool_call.id
             table.insert(tool_calls, {
-              id = id,
-              index = index,
+              id = tool_call.id,
+              index = tool_call.index or i,
               name = fn.name,
               arguments = fn.arguments or '',
             })
diff --git a/lua/CopilotChat/init.lua b/lua/CopilotChat/init.lua
index 9cea5d2d..1b7d0570 100644
--- a/lua/CopilotChat/init.lua
+++ b/lua/CopilotChat/init.lua
@@ -546,6 +546,7 @@ function M.ask(prompt, config)
         M.chat:add_message(response, true)
         M.chat.token_count = token_count
         M.chat.token_max_count = token_max_count
+
         finish()
       end
     end))