Conversation

Conversation format for supervised fine-tuning.

chat_template

Chat Template strategy uses a jinja2 template that converts a list of messages into a prompt. Support using tokenizer’s template, a supported template, or custom jinja2.

data.jsonl

{"messages": [{"role": "...", "content": "..."}, {"role": "...", "content": "..."}, ...]}

See configs for full configs and supported templates.

Migrating from sharegpt

Most configs can be adapted as follows:

# old
chat_template: chatml
datasets:
  - path: ...
    type: sharegpt
    conversation: chatml

# new (if using tokenizer's chat_template)
datasets:
  - path: ...
    type: chat_template

    field_messages: conversations
    message_property_mappings:
      role: from
      content: value

# new (if setting a new chat_template like chatml, gemma, etc)
chat_template: chatml
datasets:
  - path: ...
    type: chat_template

    field_messages: conversations
    message_property_mappings:
      role: from
      content: value

We recommend checking the below examples for other usecases.

Examples

Training on last message

(Legacy) Using the default chat template in the tokenizer_config.json on OpenAI messages format, training on only last message.

datasets:
  - path: ...
    type: chat_template
    roles_to_train:
    train_on_eos:

Tip

If you receive an error like “chat_template choice is tokenizer_default but tokenizer’s chat_template is null.”, it means the tokenizer does not have a default chat_template. Follow the examples below instead to set a custom chat_template.

Overriding default chat template

Using the gemma chat template to override the tokenizer_config.json’s chat template on OpenAI messages format, training on all assistant messages.

chat_template: gemma # this overwrites the tokenizer's chat_template
datasets:
  - path: ...
    type: chat_template
    roles_to_train: ["assistant"]  # default value

Note

If you want to use built-in chat_template, use chat_template: tokenizer_default (this is set by default).

Using default chat template with fallback

Using the tokenizer_config.json’s chat template or chatml as fallback if the former’s chat template does not exist, on OpenAI messages format, training on all assistant messages.

chat_template: tokenizer_default_fallback_chatml # this overwrites the tokenizer's chat_template
datasets:
  - path: ...
    type: chat_template

Custom Jinja template

Using a custom jinja template on OpenAI messages format, training on all assistant messages.

# chat_template: jinja # `jinja` will be implied if the `chat_template_jinja` is set and this field is empty
chat_template_jinja: "{{ bos_token }}{% for message in messages %}{% if (message['role'] == 'system') %}{{'<|system|>' + '\n' + message['content'] + '<|end|>' + '\n'}}{% elif (message['role'] == 'user') %}{{'<|user|>' + '\n' + message['content'] + '<|end|>' + '\n' + '<|assistant|>' + '\n'}}{% elif message['role'] == 'assistant' %}{{message['content'] + '<|end|>' + '\n'}}{% endif %}{% endfor %}"

datasets:
  - path: ...
    type: chat_template

Important

Please make sure that your tokenizer.eos_token is same as EOS (End-of-Sequence) token in template. Otherwise, set eos_token under special_tokens:.

Using template with different token for EOT and EOS

• If you are using a template that has a different EOT (End-of-Turn) token from EOS token or multiple EOT tokens (like Mistral V7 Tekken), set the eot_tokens: config. The handling of EOT tokens follows train_on_eos: which defaults to turn.

eot_tokens:
  - "[/INST]"
  # - "[/SYSTEM_PROMPT]"

datasets:
  - path: ...
    type: chat_template

    # optional
    train_on_eot: turn  # defaults read from train_on_eos (which defaults to turn)

Tip

See config documentation for detailed explanations of “turn”, “last”, and “all” options for training on tokens.

Note

Using eot_tokens requires each token that exists in chat_template to be a single token in the tokenizer. Otherwise, the tokenizer will split the token and cause unexpected behavior.

You can add those tokens as new tokens under tokens: or (recommended) override unused added_tokens via added_tokens_overrides:. See config for more details.

• Continuing from the previous example, if you want to train on all EOT token trainable turns but only last EOS token, set train_on_eos: last.

eot_tokens:
  - "[/INST]"
  # ...

datasets:
  - path: ...
    type: chat_template

    train_on_eos: last
    train_on_eot: turn

Tip

If EOS token only appears at the end of a prompt, train_on_eos: last is equivalent to train_on_eos: turn. Therefore, generally, you can leave them to their defaults and omit them.

Using tool use

Instead of passing tools via the system prompt, an alternative method would be to have the tools in a separate column and loaded via chat_template to let the template dynamically build it.

{
    "tools": [
        {
            "type": "...",
            "function": {
                "name": "...",
                "description": "...",
                "parameters": {
                    "type": "...",
                    "properties": {
                        // ...
                    },
                    "required": ["..."],
                },
            },
        },
    ],
    "messages": [
        // ...
        {
            "role": "assistant", // call the function via assistant
            "tool_calls": [
                {
                    "type": "function",
                    "function": {
                        "name": "...",
                        "arguments": {
                            "...": "...",
                        }
                    }
                }
            ]
        },
        {
            "role": "tool",
            "name": "...",
            "content": "..."
        },
    ],
}

Note

Tools need to follow JSON schema.

chat_template: llama4
datasets:
  - path: ...
    type: chat_template
    # field_tools: tools # default is `tools`

Tip

Look into the chat_template you are using to see if it supports tools and what the expected role is for the tool answer. In the example above, the tool answer is expected to be in the tool or ipython role for llama4 template.

Using fine-grained control over token masking

(Advanced) Using fine-grained control over tokens and turns to train in a conversation

For a data sample that looks like:

data.jsonl

{
  "conversations": [
    {"from": "system", "value": "You are an AI assistant.", "train": false},
    {"from": "human", "value": "Hello", "train": false},
    {"from": "assistant", "value": "Hello", "train": true},
    {"from": "human", "value": "How are you?", "train": true},
    {
      "from": "assistant",
      "value": "I'm doing very well, thank you!",
      "train_detail": [
        {"begin_offset": 0, "end_offset": 8, "train": false},
        {"begin_offset": 9, "end_offset": 18, "train": true},
        {"begin_offset": 19, "end_offset": 30, "train": false},
      ],
    },
    {
        "from": "human",
        "value": "I'm doing very well, thank you!",
        "train": true,
    },
    {"from": "assistant", "value": "Hi there!", "train": true}
  ]
}

The configuration would look like:

datasets:
  - path: ...
    type: chat_template
    chat_template: tokenizer_default
    field_messages: conversations
    message_property_mappings:
      role: from
      content: value
    roles_to_train: []
    train_on_eos: turn
    message_field_training: train
    message_field_training_detail: train_detail

Tip

It is not necessary to set both message_field_training and message_field_training_detail at once.

Reasoning split

(For Qwen3 template only) Enable reasoning split, where the reasoning is split from the content and passed as a separate field into the template.

datasets:
  - path: ...
    type: chat_template
    chat_template: qwen3
    split_thinking: true

For example, a content can look like:

{
  "content": "<think>Some thinking outputs</think>Output after thinking."
}

After split, it will look like:

{
  "reasoning_content": "Some thinking outputs",
  "content": "Output after thinking..."
}

sharegpt

Important

ShareGPT is deprecated!. Please see chat_template section.

pygmalion

data.jsonl

{"conversations": [{"role": "...", "value": "..."}]}