Troubleshooting of Ollama API

Troubleshooting of Ollama API

If you have any questions about the Ollama API, you can post them on the Ollama GitHub Repository.

How to fix "json: cannot unmarshal object ..."

Error message:

HTTP Error 400: {"error": "json: cannot unmarshal object into Go struct field ChatRequest.messages of type []api.Message"}

Applicable Model:

• gpt-oss:120b

Solution

Root Cause: Incorrect `messages` format. The API expects an array format, but a single object was being sent.

Incorrect Format in PHP: ❌ This is an object

'messages' => ['role' => 'user', 'content' => $message]

Correct Format in PHP: ✅ This is an array containing an object

'messages' => [['role' => 'user', 'content' => $message]]  

Explanation: The `messages` parameter must be an array of message objects, not a single message object. Each message object should contain `role` and `content` properties. The extra square brackets `[]` wrap the message object into an array, which matches the API's expected format.

This fix resolves the `"cannot unmarshal object into Go struct field ChatRequest.messages"` error.

Related links

• Forum: ollama