Set up local SDK previews

Once you configure your SDK, you can use the --preview flag to test generated SDK code locally before publishing. This allows quick iteration on your SDK as you develop:

# Preview all SDKs
fern generate --preview
# Preview SDK for a specific language
fern generate --group <language>-sdk --preview

--preview generates your SDK code into a local .preview/ folder within your fern folder. No changes are published to package managers or GitHub.

Example usage

Here’s an example of how you can preview a Python SDK.

api: 
  path: ./path/to/openapi.yml
groups:
  python-sdk:
    generators:
      - name: fern-python-sdk
        version: 5.30.2
        output:
          location: pypi
          package-name: imdb
          token: ${PYPI_TOKEN}
        github:
          repository: imdb/imdb-python
        config:
          client_class_name: imdb

fern generate --group python-sdk --preview