`fetch-in-workflow`

This error occurs when you try to use fetch() directly in a workflow function, or when a library (like the AI SDK) tries to call fetch() under the hood.

Error Message

Global "fetch" is unavailable in workflow functions. Use the "fetch" step function from "workflow" to make HTTP requests.

Why This Happens

Workflow functions run in a sandboxed environment without direct access to fetch().

Many libraries make HTTP requests under the hood. For example, the AI SDK's generateText() function calls fetch() to make HTTP requests to AI providers. When these libraries run inside a workflow function, they fail because the global fetch is not available.

Quick Fix

Import the fetch step function from the workflow package and assign it to globalThis.fetch inside your workflow function. This version of fetch is a step function that wraps the standard fetch API, automatically handling serialization and providing retry capabilities. This will also make fetch() available to all functions and libraries in the current workflow function.

Before:

workflows/ai.ts

import { generateText } from 'ai';
import { openai } from '@ai-sdk/openai';

export async function chatWorkflow(prompt: string) {
  "use workflow";

  // Error - generateText() calls fetch() under the hood
  const result = await generateText({ 
    model: openai('gpt-4'), 
    prompt, 
  }); 

  return result.text;
}

After:

workflows/ai.ts

import { generateText } from 'ai';
import { openai } from '@ai-sdk/openai';
import { fetch } from 'workflow'; 

export async function chatWorkflow(prompt: string) {
  "use workflow";

  globalThis.fetch = fetch; 

  // Now generateText() can make HTTP requests via the fetch step
  const result = await generateText({
    model: openai('gpt-4'),
    prompt,
  });

  return result.text;
}

Common Scenarios

AI SDK Integration

This is the most common scenario - using AI SDK functions that make HTTP requests:

import { generateText, streamText } from 'ai';
import { openai } from '@ai-sdk/openai';
import { fetch } from 'workflow'; 

export async function aiWorkflow(userMessage: string) {
  "use workflow";

  globalThis.fetch = fetch; 

  // generateText makes HTTP requests to OpenAI
  const response = await generateText({
    model: openai('gpt-4'),
    prompt: userMessage,
  });

  return response.text;
}

Direct API Calls

You can also use the fetch step function directly for your own HTTP requests:

import { fetch } from 'workflow';

export async function dataWorkflow() {
  "use workflow";

  // Use fetch directly for HTTP requests
  const response = await fetch('https://api.example.com/data'); 
  const data = await response.json();

  return data;
}

For more details on the fetch step function, see the fetch API reference.