First live pick after #893 chose claude-sonnet-4-5 at 0.23 over claude-sonnet-4-6: same-family models split the probability for a mid-weight task, and "prefer newer" is a policy, not a judgment. New scripts/ci/choose-model.sh applies it to the distribution: among candidates within CHOOSE_MODEL_MARGIN (0.7) of the best probability the most recently released wins; a clear best stays; NONE yields nothing. The picker logs the top probabilities. Four policy tests added. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>