Document layout.api-reference-layout

[devin-ai-integration]

Summary

Documents the new site-level layout.api-reference-layout key, which selects how nested object fields render in the API Reference: indented (default, connector-line tree with a path breadcrumb per level) or cards (the previous bordered-card nesting).

layout:
  api-reference-layout: cards # opt back into nested cards

Two edits:

• navigation/site-level-settings.mdx — canonical <ParamField> for the key, plus the key in the layout example block.
• api-references/customize-api-ref.mdx — short Nested object fields section pointing at the canonical field, since a reader customizing the API Reference is the one most likely to want the opt-out.

Depends on the implementation PRs, so this should land after them:

• fern-platform: https://github.com/fern-api/fern-platform/pull/13441 (resolves the key, defaults to indented)
• fern CLI: docs.yml schema support for the key (see the companion fern-api/fern PR)

No changelog entry here — the feature isn't shipped yet; worth adding one with the release.

Link to Devin session: https://app.devin.ai/sessions/1f176e5bc4fc49f480e0be1183283042

[devin-ai-integration]

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[github-actions]

🌿 Preview your docs: https://fern-preview-devin-1786478198-api-reference-layout.docs.buildwithfern.com/learn

Here are the markdown pages you've updated:

• learn/docs/api-references/customize-api-reference-layout
• learn/docs/configuration/site-level-settings