Interception

An InterceptionHandler inspects or rewrites a loop transition before that state runs. Pass it as the optional fourth argument to runLoop:

interface InterceptionHandler {
  isSatisfiedBy(transition: ExecutableTransition): boolean;
  handle(transition: ExecutableTransition): Promise<ExecutableTransition>;
}

When isSatisfiedBy is true, the loop publishes interception.started, awaits handle (which may change nextStateId and input), publishes interception.finished, then executes the returned transition.

import { type InterceptionHandler } from '@mozaik-ai/core';

const inspectFunctionCalls: InterceptionHandler = {
  isSatisfiedBy(transition) {
    return transition.nextStateId === 'function_call';
  },
  async handle(transition) {
    if (transition.nextStateId === 'function_call') {
      console.log('about to call', transition.input.call.name);
    }
    return transition;
  },
};

runLoop(agent.getId(), message, inferenceInput, inspectFunctionCalls);

Use it to steer loop execution by rewriting the next state — for example, swapping a tool call’s input — without putting that logic inside the agent’s situation handlers. That is how you keep a human in the loop, or another agent, to control what runs next.

A transition is { nextStateId, input }. nextStateId is one of context_update, inference, inference_streaming, function_call, or model_message. The input shape matches that state (for function_call, { call, inferenceInput }).

Unlike situation processors, handle is awaited. The loop does not continue until the handler returns.