Context

PR #25530 revives only the lower-risk per-call model/provider override from #3719/#3794. The delegation pool / strengths-per-model half remains separate follow-up work.

Work

• Design a delegation pool config with model strengths/capabilities.
• Teach delegate_task selection to choose from the pool when explicit override is not provided.
• Preserve deterministic per-call override behavior.
• Add tests for selection, fallback, and invalid pool entries.

Source

Follow-up from #25530.

Referenced by #25530.