[Feature Request] Configurable Body Parser Limits for Large JSON Payloads

[AvinashDalvi89]

Summary

Currently, Motia's Express server uses the default body parser limits (~100kb), which prevents uploading larger base64-encoded images through JSON API endpoints. This limitation affects use cases that require processing larger files through JSON APIs.

Problem Description

When attempting to upload base64-encoded images larger than ~100kb through a JSON API endpoint, the server returns:

PayloadTooLargeError: request entity too large
    at readStream (/path/to/node_modules/raw-body/index.js:163:17)
    at getRawBody (/path/to/node_modules/raw-body/index.js:116:12)
    at read (/path/to/node_modules/body-parser/lib/read.js:79:3)
    at jsonParser (/path/to/node_modules/body-parser/lib/types/json.js:138:5)

Use Case

• Image Processing API: Uploading base64-encoded images for processing (resize, optimization, etc.)
• Document Processing: Handling large JSON payloads with embedded file data
• Data Import APIs: Processing large datasets through JSON endpoints

Current Workaround

Currently limited to very small images (< 100kb base64-encoded) for testing.

Proposed Solution

Add configuration options to control Express body parser limits, either through:

Option 1: Configuration File

// motia.config.js or similar
module.exports = {
  server: {
    bodyParser: {
      json: { limit: '50mb' },
      urlencoded: { limit: '50mb', extended: true }
    }
  }
}

Option 2: Environment Variables

MOTIA_BODY_PARSER_JSON_LIMIT=50mb
MOTIA_BODY_PARSER_URLENCODED_LIMIT=50mb

Option 3: CLI Options

motia dev --body-limit 50mb

Technical Details

• Framework: Motia (using Express.js internally)
• Current Default: ~100kb (Express default)
• Desired Limit: Configurable (e.g., 50mb for image processing)
• Body Parser: Uses body-parser package internally

Example API Endpoint

// steps/upload-image.step.ts
export const config: ApiRouteConfig = {
  method: 'POST',
  path: '/upload-image',
  bodySchema: z.object({
    filename: z.string(),
    data: z.string() // base64 encoded image - can be large
  })
}

Impact

• High: Blocks image processing and file upload use cases
• Workaround Complexity: Requires splitting large payloads or alternative upload methods
• User Experience: Prevents straightforward JSON API design for file handling

Additional Context

• Base64 encoding increases file size by ~33%
• A 1MB image becomes ~1.3MB when base64-encoded
• Common image sizes (2-5MB) easily exceed current limits
• This is a common pattern in modern web APIs

Environment

• Motia Version: 0.5.2-beta.102-976525
• Node.js: 18.19.0
• Platform: macOS (darwin)

Related

• Express.js body-parser documentation: https://expressjs.com/en/resources/middleware/body-parser.html
• Similar issues in other frameworks that provide configurable limits

[nobodyn0se]

I would like to work on a fix, please assign this to me