hiyouga/LlamaFactory · error · ValueError

Cannot inject {% generation %} into chat template: no `{% el

Error message

Cannot inject {% generation %} into chat template: no `{% elif message['role'] == 'assistant' %}` block found.

What it means

Error "Cannot inject {% generation %} into chat template: no `{% elif message['role'] == 'assistant' %}` block found." thrown in hiyouga/LlamaFactory.

Source

Thrown at src/llamafactory/train/megatron_bridge/dataset_export.py:57

def supports_hf_chat_template() -> bool:
    r"""Return whether the installed Megatron Bridge supports HF chat templates."""
    try:
        from megatron.bridge.data.datasets.sft import GPTSFTChatDataset

        return "use_hf_tokenizer_chat_template" in inspect.signature(GPTSFTChatDataset.__init__).parameters
    except Exception:
        return False


def _inject_generation_block(chat_template: str) -> str:
    r"""Wrap assistant content with ``{% generation %}`` when missing."""
    if _GENERATION_REGEX.search(chat_template):
        return chat_template

    match = _ASSISTANT_ELIF_REGEX.search(chat_template)
    if match is None:
        raise ValueError(
            "Cannot inject {% generation %} into chat template: "
            "no `{% elif message['role'] == 'assistant' %}` block found."
        )

    body = match.group(2)
    if _END_GENERATION_REGEX.search(body):
        return chat_template

    patched = (
        chat_template[: match.start()]
        + match.group(1)
        + "{% generation %}"
        + body
        + "{% endgeneration %}"
        + match.group(3)
        + chat_template[match.end() :]
    )
    if not _GENERATION_REGEX.search(patched):

View on GitHub (pinned to f28afaf635)

Solutions

1. Use a chat template that contains a standard `{% elif message['role'] == 'assistant' %}` block, or manually add `{% generation %}...{% endgeneration %}` around the assistant content in the template.

Example fix

{% elif message['role'] == 'assistant' %}{% generation %}{{ message['content'] }}{% endgeneration %}

When it happens

Trigger: Thrown at src/llamafactory/train/megatron_bridge/dataset_export.py:57 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of hiyouga/LlamaFactory@f28afaf635 (2026-08-14). Data as JSON: /api/errors/e0b7d5565e87f301. Report an issue: GitHub.