iterative-training

Proposes BIRD, a two-stage self-reasoning distillation method that bootstraps concise reasoning trajectories before on-policy training, achieving stronger accuracy-efficiency trade-offs on MATH-500 and AIME benchmarks. On Qwen3-8B, accuracy improves from 86.2% to 92.0% while average response length drops from 3,099 to 1,115 tokens.