Control Flow

Workflows run a sequence of predefined tasks, and you can control how that flow is executed. Tasks are divided into steps, which can be executed in different ways depending on your requirements. They can run sequentially, in parallel, or follow different paths based on conditions.

Each step connects to the next in the workflow through defined schemas that keep data controlled and consistent.

Core principles

• The first step’s inputSchema must match the workflow’s inputSchema.
• The final step’s outputSchema must match the workflow’s outputSchema.
• Each step’s outputSchema must match the next step’s inputSchema.
  • If it doesn’t, use Input data mapping to transform the data into the required shape.

Chaining steps with .then()

Use .then() to run steps in order, allowing each step to access the result of the step before it.

src/mastra/workflows/test-workflow.ts

const step1 = createStep({
  //...
  inputSchema: z.object({
    message: z.string()
  }),
  outputSchema: z.object({
    formatted: z.string()
  })
});

const step2 = createStep({
  // ...
  inputSchema: z.object({
    formatted: z.string()
  }),
  outputSchema: z.object({
    emphasized: z.string()
  })
});

export const testWorkflow = createWorkflow({
  // ...
  inputSchema: z.object({
    message: z.string()
  }),
  outputSchema: z.object({
    emphasized: z.string()
  })
})
  .then(step1)
  .then(step2)
  .commit();

Simultaneous steps with .parallel()

Use .parallel() to run steps at the same time. Each step's id is used when defining a following step's inputSchema and becomes the key on the inputData object used to access the previous step's values. The outputs of parallel steps can then be referenced or combined by a following step.

src/mastra/workflows/test-workflow.ts

const step1 = createStep({
  id: "step-1",
  // ...
});

const step2 = createStep({
  id: "step-2",
  // ...
});

const step3 = createStep({
  id: "step-3",
  inputSchema: z.object({
    "step-1": z.object({
      formatted: z.string()
    }),
    "step-2": z.object({
      emphasized: z.string()
    })
  }),
  outputSchema: z.object({
    combined: z.string()
  }),
  execute: async ({ inputData }) => {
    const { formatted } = inputData["step-1"];
    const { emphasized } = inputData["step-2"];
    return {
      combined: `${formatted} | ${emphasized}`
    };
  }
});

export const testWorkflow = createWorkflow({
  // ...
  inputSchema: z.object({
    message: z.string()
  }),
  outputSchema: z.object({
    combined: z.string()
  })
})
  .parallel([step1, step2])
  .then(step3)
  .commit();

📹 Watch: How to run steps in parallel and optimize your Mastra workflow → YouTube (3 minutes)

Conditional logic with .branch()

Use .branch() to choose which step to run based on a condition. All steps in a branch need the same inputSchema and outputSchema because branching requires consistent schemas so workflows can follow different paths.

src/mastra/workflows/test-workflow.ts

const step1 = createStep({...})

const stepA = createStep({
  // ...
  inputSchema: z.object({
    value: z.number()
  }),
  outputSchema: z.object({
    result: z.string()
  })
});

const stepB = createStep({
  // ...
  inputSchema: z.object({
    value: z.number()
  }),
  outputSchema: z.object({
    result: z.string()
  })
});

export const testWorkflow = createWorkflow({
  // ...
  inputSchema: z.object({
    value: z.number()
  }),
  outputSchema: z.object({
    result: z.string()
  })
})
  .then(step1)
  .branch([
    [async ({ inputData: { value } }) => value > 10, stepA],
    [async ({ inputData: { value } }) => value <= 10, stepB]
  ])
  .commit();

Input data mapping

When using .then(), .parallel(), or .branch(), it is sometimes necessary to transform the output of a previous step to match the input of the next. In these cases you can use .map() to access the inputData and transform it to create a suitable data shape for the next step.

src/mastra/workflows/test-workflow.ts

const step1 = createStep({...});
const step2 = createStep({...});

export const testWorkflow = createWorkflow({...})
  .then(step1)
  .map(async ({ inputData }) => {
    const { foo } = inputData;
    return {
      bar: `new ${foo}`,
    };
  })
  .then(step2)
  .commit();

The .map() method provides additional helper functions for more complex mapping scenarios.

Available helper functions:

• getStepResult(): Access a specific step's full output
• getInitData(): Access the workflow's initial input data
• mapVariable(): Use declarative object syntax to extract and rename fields

Looping steps

Workflows support different looping methods that let you repeat steps until or while a condition is met, or iterate over arrays. Loops can be combined with other control methods like .then().

Looping with .dountil()

Use .dountil() to run a step repeatedly until a condition becomes true.

src/mastra/workflows/test-workflow.ts

const step1 = createStep({...});

const step2 = createStep({
  // ...
  execute: async ({ inputData }) => {
    const { number } = inputData;
    return {
      number: number + 1
    };
  }
});

export const testWorkflow = createWorkflow({
  // ...
})
  .then(step1)
  .dountil(step2, async ({ inputData: { number } }) => number > 10)
  .commit();

Looping with .dowhile()

Use .dowhile() to run a step repeatedly while a condition remains true.

src/mastra/workflows/test-workflow.ts

const step1 = createStep({...});

const step2 = createStep({
  // ...
  execute: async ({ inputData }) => {
    const { number } = inputData;
    return {
      number: number + 1
    };
  }
});

export const testWorkflow = createWorkflow({
  // ...
})
  .then(step1)
  .dowhile(step2, async ({ inputData: { number } }) => number < 10)
  .commit();

Looping with .foreach()

Use .foreach() to run the same step for each item in an array. The input must be of type array so the loop can iterate over its values, applying the step’s logic to each one.

src/mastra/workflows/test-workflow.ts

const step1 = createStep({
  // ...
  inputSchema: z.string(),
  outputSchema: z.string(),
  execute: async ({ inputData }) => {
    return inputData.toUpperCase();
  }
});

const step2 = createStep({...});

export const testWorkflow = createWorkflow({
  // ...
  inputSchema: z.array(z.string()),
  outputSchema: z.array(z.string())
})
  .foreach(step1)
  .then(step2)
  .commit();

Concurrency limits

Use concurrency to control the number of array items processed at the same time. The default is 1, which runs steps sequentially. Increasing the value allows .foreach() to process multiple items simultaneously.

src/mastra/workflows/test-workflow.ts

const step1 = createStep({...})

export const testWorkflow = createWorkflow({...})
  .foreach(step1, { concurrency: 4 })
  .commit();

Loop management

Loop conditions can be implemented in different ways depending on how you want the loop to end. Common patterns include checking values returned in inputData, setting a maximum number of iterations, or aborting execution when a limit is reached.

Aborting loops

Use iterationCount to limit how many times a loop runs. If the count exceeds your threshold, throw an error to fail the step and stop the workflow.

src/mastra/workflows/test-workflow.ts

const step1 = createStep({...});

export const testWorkflow = createWorkflow({...})
  .dountil(step1, async ({ inputData: { userResponse, iterationCount } }) => {
    if (iterationCount >= 10) {
      throw new Error("Maximum iterations reached");
    }
    return userResponse === "yes";
  })
  .commit();