Internal error: 400 “Invalid ‘messages’ in payload. Please check the structure of your ‘messages’ and try again.”

[yar3333]

What happened?

When I ask local qwen3.6 model to describe image, I got a error:

Describe picture "test.jpg".

ReadFile test.jpg

Internal error: 400 “Invalid ‘messages’ in payload. Please check the structure of your ‘messages’ and try again.”

What did you expect to happen?

Output text with picture description.

Client information

Qwen Code 0.14.5 (a661294)
Node.js v22.13.1 / npm 11.12.1
win32 x64 (10.0.22631)
API Key - openai
http://127.0.0.1:4239/v1
qwen/qwen3.6-35b-a3b
qwen/qwen3.6-35b-a3b
no sandbox
no proxy
211.6 MB

Login information

"modelProviders": {
    "openai": [
      {
        "id": "qwen/qwen3.6-35b-a3b",
        "name": "lm-studio: qwen/qwen3.6-35b-a3b",
        "envKey": "OLLAMA_API_KEY",
        "baseUrl": "http://127.0.0.1:4239/v1",
        "generationConfig": {
          "timeout": 600000,
          "maxRetries": 3,
          "enableCacheControl": true,
          "contextWindowSize": 250000,
          "modalities": {
            "image": true
          }
        }
      },

Anything else we need to know?

No response

[JahanzaibTayyab]

This looks like the same root cause as #3616 (and the open #3617 by @mohitsoni48). Your flow goes:

1. Describe picture "test.jpg" → model decides to call the built-in ReadFile tool
2. ReadFile returns the image bytes as a tool message with an image_url content part
3. LM Studio's strict OpenAI-compatible parser rejects any tool message whose content array contains non-text parts (the spec only permits string or text-part content on role: "tool").

PR #3617 adds a per-provider opt-in flag — splitToolMedia: true — that splits the non-text media into a follow-up role: "user" message before the request leaves the client. Once that lands, your ~/.qwen/settings.json would become:

"modelProviders": {
  "openai": [
    {
      "id": "qwen/qwen3.6-35b-a3b",
      "baseUrl": "http://127.0.0.1:4239/v1",
      "splitToolMedia": true,
      "generationConfig": { ... }
    }
  ]
}

If a maintainer agrees this is a duplicate, this issue can be closed against #3616 / #3617. If after #3617 lands the error still reproduces against LM Studio with splitToolMedia: true set, it would be worth re-opening with a fresh repro — there's a chance the strict parser is also rejecting the user-attached image part, which would be a separate fix.