onBeforeStep

The onBeforeStep event fires at the beginning of each iteration of the agent's execution loop, right before a request is sent to the model.

Usage

Because an agent can loop multiple times within a single userMessage() call (e.g., to process multiple tool calls sequentially), this event may fire multiple times.

It is useful for:

• Checking the remaining step budget.
• Modifying the step parameters.
• Aborting the execution early if specific conditions are met.

Payload Details

agent.onBeforeStep(({ params, context }) => {
    // `params` contains the current step parameters, including the remaining step budget
    console.log(`Starting step ${context.state.stepCount}. Remaining budget: ${params.maxStep}`);
    
    // You must return the parameters
    return params;
});