Revert #10192: _template_context must unset template.max_length in GRPO/GKD - #10221
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tastelikefeet
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Sep 21, 2026
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What does this PR do?
Reverts #10192, restoring the original default of
RolloutTrainerMixin._template_context:max_length: Optional[int] = Nonewithtemplate.max_length = max_length, and drops the_TEMPLATE_CONTEXT_USE_ORIGINALsentinel.Why
max_lengthbounds the prompt in GRPO/GKD/inference (max_prompt_length), and the completion isbounded separately by
max_completion_length/ the rolloutgeneration_config. The training-timere-encode of prompt + completion therefore must not be truncated again: a legal sample can be up to
max_length + max_completion_length.#10192 made the default "preserve
template.max_length", which silently re-enabled truncation at everycall site (GRPO
_prepare_batch_inputs/ SP logps / MLLM chunk re-encode, GKD_encode_samples).The Megatron trainers (
_template_context/_disable_maxlength_template_context) were never changedand still unset
max_length; this revert restores the same semantics for the HF path.