20
30
40
50
60
70
80
Rollout step
0.70
0.75
0.80
0.85
0.90
0.95
Strict reward
A Fixed validation set · 400 tasks
Bare validation
Random-mask gate
0
10
20
30
40
Difference
Initial skill
Base + S0 − Base
Final skill
Iter80 + ST − Iter80
Training, skill-free
Iter80 − Base
B Paired test differences · 95% CI
Reward ×100
Success (pp)