Dynamic turns

Dynamic callbacks recalculate model parameters from the current run state before each model request.

$agent = AgentSdk::createAgent(new AgentDefinition(
    id: "support-agent",
    model: fn ($turn) => $turn->run->stepCount > 3
        ? "openai/gpt-5.4"
        : "openai/gpt-5.4-nano",
    instructions: fn ($turn) => "Resolve the request using the current context."
));

Dynamic tools and sampling values can use the same turn context. A tool can also set nextTurnParams to modify only the immediately following request. These overrides are persisted when the run pauses for approval and expire after the next turn. Use dynamic callbacks for policy that should be recomputed every turn. Use nextTurnParams for a tool-specific handoff.

Last modified on July 26, 2026

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