For AI agents: a documentation index is available at the root level at /llms.txt and /llms-full.txt. Append /llms.txt to any URL for a page-level index, or .md for the markdown version of any page.
Book a demoLog inStart for free
  • Overview
    • Introduction
    • How it works
    • Quickstart
    • Customer showcase
  • Working with SDKs
    • Project structure
    • Adding custom code
    • Migrating to Replay
    • Capabilities
  • Generators
      • Generating an SDK
      • Publishing to PyPI
      • Configuration
      • Adding custom code
      • Dynamic authentication
      • aiohttp support
      • Changelog
      • Customer showcase
  • Reference
    • generators.yml
Checking status...
SOC2Soc 2 Type II
© 2026 Fern • Birch Solutions, Inc., a Postman company

Documentation

SDKsDocsAsk FernCLI Reference

API Definitions

OpenAPIAsyncAPIOpenRPCgRPC

Resources

BlogSupportPricing

Company

Brand KitPrivacy PolicyTerms of Service
LogoLogo
Book a demoLog inStart for free
GeneratorsPython

Changelog

March 18, 2026
March 18, 2026

5.0.4

(fix): Fix optional complex-type parameters in multipart file upload requests being sent as "null" instead of being omitted. When an optional body property (e.g., Optional[List[str]], Optional[Any]) defaults to OMIT, json.dumps(jsonable_encoder(OMIT)) was evaluating to the string "null", destroying the OMIT sentinel before remove_omit_from_dict could strip it. Optional non-primitive body properties now emit a ternary guard (json.dumps(...) if prop is not OMIT else OMIT) so that the OMIT sentinel is preserved and correctly removed from the request data.

Was this page helpful?
Edit this page
Previous

March 20, 2026

Next

March 17, 2026