Workflow.while()

The .while() method repeats a step as long as a specified condition remains true. This creates a loop that continues executing the specified step until the condition becomes false.

Usage

workflow.step(incrementStep).while(condition, incrementStep).then(finalStep);

Parameters

condition:

Function | ReferenceCondition

A function or reference condition that determines when to continue looping

step:

Step

The step to repeat while the condition is true

Condition Types

Function Condition

You can use a function that returns a boolean:

workflow
  .step(incrementStep)
  .while(async ({ context }) => {
    const result = context.getStepResult<{ value: number }>("increment");
    return (result?.value ?? 0) < 10; // Continue as long as value is less than 10
  }, incrementStep)
  .then(finalStep);

Reference Condition

You can use a reference-based condition with comparison operators:

workflow
  .step(incrementStep)
  .while(
    {
      ref: { step: incrementStep, path: "value" },
      query: { $lt: 10 }, // Continue as long as value is less than 10
    },
    incrementStep,
  )
  .then(finalStep);

Comparison Operators

When using reference-based conditions, you can use these comparison operators:

Operator	Description	Example
$eq	Equal to	{ $eq: 10 }
$ne	Not equal to	{ $ne: 0 }
$gt	Greater than	{ $gt: 5 }
$gte	Greater than or equal to	{ $gte: 10 }
$lt	Less than	{ $lt: 20 }
$lte	Less than or equal to	{ $lte: 15 }

Returns

workflow:

LegacyWorkflow

The workflow instance for chaining

Example

import { LegacyWorkflow, LegacyStep } from "@mastra/core/workflows/legacy";
import { z } from "zod";

// Create a step that increments a counter
const incrementStep = new LegacyStep({
  id: "increment",
  description: "Increments the counter by 1",
  outputSchema: z.object({
    value: z.number(),
  }),
  execute: async ({ context }) => {
    // Get current value from previous execution or start at 0
    const currentValue =
      context.getStepResult<{ value: number }>("increment")?.value ||
      context.getStepResult<{ startValue: number }>("trigger")?.startValue ||
      0;

    // Increment the value
    const value = currentValue + 1;
    console.log(`Incrementing to ${value}`);

    return { value };
  },
});

// Create a final step
const finalStep = new LegacyStep({
  id: "final",
  description: "Final step after loop completes",
  execute: async ({ context }) => {
    const finalValue = context.getStepResult<{ value: number }>(
      "increment",
    )?.value;
    console.log(`Loop completed with final value: ${finalValue}`);
    return { finalValue };
  },
});

// Create the workflow
const counterWorkflow = new LegacyWorkflow({
  name: "counter-workflow",
  triggerSchema: z.object({
    startValue: z.number(),
    targetValue: z.number(),
  }),
});

// Configure the workflow with a while loop
counterWorkflow
  .step(incrementStep)
  .while(async ({ context }) => {
    const targetValue = context.triggerData.targetValue;
    const currentValue =
      context.getStepResult<{ value: number }>("increment")?.value ?? 0;
    return currentValue < targetValue;
  }, incrementStep)
  .then(finalStep)
  .commit();

// Execute the workflow
const run = counterWorkflow.createRun();
const result = await run.start({
  triggerData: { startValue: 0, targetValue: 5 },
});
// Will increment from 0 to 4, then stop and execute finalStep

Related

• .until() - Loop until a condition becomes true
• Control Flow Guide
• Workflow Class Reference