Hooks for document changes to trigger custom logic and automation

Yes! Sanity provides exactly what you're looking for through Sanity Functions - a serverless compute environment that lets you hook into document content changes and run custom logic in response to those events.

How it works

Sanity Functions allow you to create event-driven workflows that react to document changes (create, update, delete, publish, etc.). You can:

1. Listen to specific events - React when documents are created, updated, deleted, or published
2. Filter which documents trigger your function - Use GROQ queries to only run logic for specific document types or conditions
3. Access full document context - Read and write to your dataset with full Sanity API access
4. Automate document creation - Create new documents based on changes to other documents

Your use case: Boolean field triggers new document creation

Here's how you'd implement your specific scenario:

Example: When a boolean field changes on a document, automatically create another document

// functions/auto-create-doc/index.ts
import { type DocumentEventHandler } from "@sanity/functions";
import { createClient } from "@sanity/client";

interface MyDocData {
  _id: string;
  myBooleanField: boolean;
}

export const handler: DocumentEventHandler<MyDocData> = async ({
  context,
  event,
}) => {
  const client = createClient({
    ...context.clientOptions,
    apiVersion: "2025-01-01",
  });

  // Check if the boolean field was changed to true
  if (event.data.myBooleanField === true) {
    // Create a new document of another type
    await client.create({
      _type: 'anotherDocumentType',
      title: `Auto-created from ${event.data._id}`,
      sourceDocument: {
        _type: 'reference',
        _ref: event.data._id
      },
      createdAt: new Date().toISOString()
    });
    
    console.log(`Created new document triggered by ${event.data._id}`);
  }
};

Configure your function in blueprint.json:

{
  "blueprintVersion": "2024-10-01",
  "resources": [
    {
      "displayName": "auto-create-on-boolean-change",
      "name": "auto-create-doc",
      "src": "functions/auto-create-doc",
      "type": "sanity.function.document",
      "event": {
        "on": ["update", "publish"],
        "filter": "_type == 'myDocType' && defined(myBooleanField)",
        "projection": "{_id, myBooleanField}"
      }
    }
  ]
}

Getting started

1. Initialize a Blueprint (Sanity's infrastructure-as-code config):

   npx sanity@latest blueprints init

2. Add a function:

   npx sanity@latest blueprints add function

3. Deploy:

   npx sanity@latest blueprints deploy

Why Functions over Webhooks?

While webhooks are also available, Sanity Functions are the modern, recommended approach because they:

• Run natively within Sanity (no external hosting needed)
• Have built-in access to your Sanity client and dataset
• Scale automatically
• Are easier to set up and maintain
• Have better security (no need to expose public endpoints)

Check out the complete guide in the blog post and official documentation for more details!