Missing fields when using streaming API

[zoravur]

Tool calls don't contain "role": "assistant" in the completed ChatCompletionAccumulator.Choices[0].message. It does contain it for the non-streaming API responses though. Here is a direct comparison:

> What's the weather in NYC?

Tool call stream finished: 0 get_weather {"location":"New York City"}

streaming:  {
  "id": "chatcmpl-A8iJ5dT3WSaOoJJ1KTPGAyv94OgWY",
  "choices": [
    {
      "finish_reason": "tool_calls",
      "index": 0,
      "logprobs": {
        "content": null,
        "refusal": null
      },
      "message": {
        "role": "",
        "tool_calls": [
          {
            "function": {
              "arguments": "{\"location\":\"New York City\"}",
              "name": "get_weather"
            },
            "id": "",
            "type": ""
          }
        ]
      }
    }
  ],
  "created": 1726640303,
  "model": "gpt-4o-mini-2024-07-18",
  "object": "chat.completion.chunk",
  "service_tier": "",
  "system_fingerprint": "fp_483d39d857",
  "usage": {
    "completion_tokens": 0,
    "prompt_tokens": 0,
    "total_tokens": 0,
    "completion_tokens_details": {
      "reasoning_tokens": 0
    }
  }
}
nonstreaming:  {
  "id": "chatcmpl-A8iJ56XcjwlGPTtCZUkTIWpk2Wf89",
  "object": "chat.completion",
  "created": 1726640303,
  "model": "gpt-4o-mini-2024-07-18",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": null,
        "tool_calls": [
          {
            "id": "call_NK8PHa5XX4AVPYxdXBpHYvkm",
            "type": "function",
            "function": {
              "name": "get_weather",
              "arguments": "{\"location\":\"New York City\"}"
            }
          }
        ],
        "refusal": null
      },
      "logprobs": null,
      "finish_reason": "tool_calls"
    }
  ],
  "usage": {
    "prompt_tokens": 50,
    "completion_tokens": 16,
    "total_tokens": 66,
    "completion_tokens_details": {
      "reasoning_tokens": 0
    }
  },
  "system_fingerprint": "fp_483d39d857"
}

Here is the code to generate the above output:

package main

import (
	"context"
	"encoding/json"
	"github.com/openai/openai-go"
)

// Mock function to simulate weather data retrieval
func getWeather(location string) string {
	// In a real implementation, this function would call a weather API
	return "Sunny, 25°C"
}

func main() {
	client := openai.NewClient()
	ctx := context.Background()

	question := "What's the weather in NYC?"
	msgs := []openai.ChatCompletionMessageParamUnion{
		openai.UserMessage(question),
	}

	print("> ")
	println(question)
	println()

	params := openai.ChatCompletionNewParams{
		Messages: openai.F(msgs),
		Seed:     openai.Int(0),
		Model:    openai.F(openai.ChatModelGPT4oMini),
		Tools: openai.F([]openai.ChatCompletionToolParam{
			{
				Type: openai.F(openai.ChatCompletionToolTypeFunction),
				Function: openai.F(openai.FunctionDefinitionParam{
					Name:        openai.String("get_weather"),
					Description: openai.String("Get weather at the given location"),
					Parameters: openai.F(openai.FunctionParameters{
						"type": "object",
						"properties": map[string]interface{}{
							"location": map[string]string{
								"type": "string",
							},
						},
						"required": []string{"location"},
					}),
				}),
			},
		}),
	}

	stream := client.Chat.Completions.NewStreaming(ctx, params)

	acc := openai.ChatCompletionAccumulator{}

	for stream.Next() {
		chunk := stream.Current()
		acc.AddChunk(chunk)

		// When this fires, the current chunk value will not contain content data
		if content, ok := acc.JustFinishedContent(); ok {
			println("Content stream finished:", content)
			println()
		}

		if tool, ok := acc.JustFinishedToolCall(); ok {
			println("Tool call stream finished:", tool.Index, tool.Name, tool.Arguments)
			println()
		}

		if refusal, ok := acc.JustFinishedRefusal(); ok {
			println("Refusal stream finished:", refusal)
			println()
		}
	}

	if err := stream.Err(); err != nil {
		panic(err)
	}

	if data, err := json.MarshalIndent(acc, "", "    "); err != nil {
		panic(err)
	} else {
		println("streaming: ", string(data))
	}

	output, err := client.Chat.Completions.New(ctx, params)
	if err != nil {
		panic(err)
	}
	println("nonstreaming: ", output.JSON.RawJSON())
}

• This seems to happen for non-toolcalls as well.
• The id and type fields of the toolcalll are also missing. id is probably most critical because without it you can't respond to the model with a toolcall.

[zoravur]

I was able to get the tool ID and Type by making the following changes in a fork (the role is still not showing up):

diff --git a/streamaccumulator.go b/streamaccumulator.go
index 8d8832e..5fb4505 100644
--- a/streamaccumulator.go
+++ b/streamaccumulator.go
@@ -110,7 +110,6 @@ func (cc *ChatCompletion) accumulateDelta(chunk ChatCompletionChunk) bool {
                choice.Index = delta.Index
                choice.FinishReason = ChatCompletionChoicesFinishReason(delta.FinishReason)

-        choice.Message.Role += ChatCompletionMessageRole(delta.Delta.Role)
                choice.Message.Content += delta.Delta.Content
                choice.Message.Refusal += delta.Delta.Refusal

@@ -120,8 +119,8 @@ func (cc *ChatCompletion) accumulateDelta(chunk ChatCompletionChunk) bool {
                        choice.Message.ToolCalls = expandToFit(choice.Message.ToolCalls, int(deltaTool.Index))
                        tool := &choice.Message.ToolCalls[deltaTool.Index]

-                       tool.ID += deltaTool.ID
-                       tool.Type += ChatCompletionMessageToolCallType(deltaTool.Type)
+                       tool.ID = deltaTool.ID
+                       tool.Type = ChatCompletionMessageToolCallType(deltaTool.Type)
                        tool.Function.Name += deltaTool.Function.Name
                        tool.Function.Arguments += deltaTool.Function.Arguments
                }

[RobertCraigie]

Thanks for the report @zoravur, I can reproduce the error you're seeing. We're working on a fix.

[zoravur]

Thank you!

[RobertCraigie]

@zoravur this should be fixed in v0.1.0-alpha.19!