Dynamic turns

Callable agent fields recalculate request parameters from the current run state before each model turn.

agent = PhaseoAgentSdk.create_agent(
  id: "support-agent",
  model: ->(turn) {
    turn.run.step_count > 3 ? "openai/gpt-5.4" : "openai/gpt-5.4-nano"
  },
  instructions: ->(turn) {
    "Resolve the request using the current context."
  }
)

Dynamic tools and sampling values can follow the same pattern. A tool may set next_turn_params to change only the immediately following request. These overrides survive an approval checkpoint and expire after the next turn. Use callables for policy that should be recomputed every turn. Use next_turn_params for a tool-specific handoff.

Last modified on July 26, 2026

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