# 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": [
                    {
                        "id": "...",  // required only for mistral
                        "type": "function",
                        "function": {
                            "name": "...",
                            "arguments": {
                                "...": "...",
                            }
                        }
                    }
                ]
            },
            {
                "role": "tool",
                "tool_call_id": "...",  // required only for mistral
                "name": "...",
                "content": "..."
            },
        ],
    }

Note

Tools need to follow JSON schema.

Warning

If you have tool arguments with same name but different dtypes (like `"time": string` and `"time": number`), please save `arguments:` as JSON string to prevent `datasets` from having casting issues.

    "arguments": "{\"...\": \"...\"}"

Example config for Llama4:

    chat_template: llama4
    datasets:
      - path: Nanobit/text-tools-2k-test
        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": "..."}]}