Lei Zhao

On four trailer-editing task types built from 49 real films and their released trailers, decaying an LLM-judged turn-level process reward to zero within the same GRPO setup gives a 45.4% relative gain over outcome-only GRPO on Fine Cut, while the fixed-weight variant scores below outcome-only GRPO on the three shorter task types and truncates 44.1% of rollouts. Process rewards do encourage visual inspection and reasoning early, but continued optimization drives redundant tool calls without a committed result; token-level on-policy self-distillation proves highly sensitive to the teacher's privileged information.

On four trailer-editing task types built from 49 real films and their released trailers, decaying an LLM-judged turn-level process reward to zero within the same GRPO setup gives a 45.4% relative gain over outcome-only GRPO on Fine Cut, while the fixed-weight variant scores below outcome-only GRPO on the three shorter task types and truncates 44.1% of rollouts. Process rewards do encourage visual inspection and reasoning early, but continued optimization drives redundant tool calls without a committed result; token-level on-policy self-distillation proves highly sensitive to the teacher's privileged information.