bernstein itself does not call an llm; the cli agents you configure do. you decide which models per role in bernstein.yaml. the contextual-bandit router picks among the models you allow for a given task class and learns from outcomes. typical configurations: claude opus 4.7 for architect, claude sonnet 4.6 for backend, claude haiku 4.5 for docs, gpt-5 for review, gemini 2.5 pro for ml. local-only setups can route everything through ollama. bernstein cost prints the realised mix after each run. routing source: src/bernstein/core/routing/.
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