# Paper-style joint sequence (pi0.5 §IV-B): one sample supervises the subtask
# text with CE and, because the assistant turn is part of the prefix, conditions
# the FAST and flow action losses on the same annotated subtask in one forward.
# The supervised span is attended causally; the action losses see task + subtask.
#
# Training-only for now: the runtime does not yet rebuild this joint prefix at
# inference, so checkpoints trained with it cannot be deployed through it.
# Samples without a `subtask` annotation fall back to a plain task-prompt
# low-level sample via `if_present`.

messages:
  - {role: user, content: "${task}", stream: low_level}
  - {role: assistant, content: "${subtask}", stream: low_level, target: true, if_present: subtask}
