[devin-ai-integration]

Summary

Header tabs can now open a dropdown menu (tab-menu) that lists other tabs, grouped into columns, plus external links. Each tab in the menu keeps its own sidebar and can have its own variants selector. Sites with many products can build a product switcher in the header instead of a long row of tabs, and restyle it with stable fern-tab-menu-* classes and --fern-tab-menu-* CSS variables. Variant selectors also gain group and link entries.

Implements docs for: feat(docs): header tab menus (tab-menu), nested member variants, grouped variant menus and links (fern-api/fern#18397), feat(docs): header tab menus, nested variants under menu entries, grouped variant menus and links (fern-api/fern-platform#15864)

Pages changed

• navigation/tabs.mdx (canonical home, /learn/docs/configuration/tabs)
  • New ## Tab menus section: setup steps, a full docs.yml example, URL nesting (/products/agents/...), default behavior, column layout, hover vs selection, and the sidebar fallback when tabs aren't in the header.
  • ### Tab menu entry properties: tab, display-name, subtitle, icon, slug, skip-slug, hidden, default, viewers, feature-flag, plus group and link entry shapes.
  • <llms-only> list of the valid-tab-menu fern check errors and warnings.
  • New tab-menu and tab-menu-column-height ParamFields under Tab properties.
  • New ### Grouped variants subsection under Tab variants (group + items, link entries, rendered as one stacked list in the sidebar).
• navigation/site-level-settings.mdx: ParamFields for layout.tab-menu.default-column-height and layout.tab-menu.interact-on-click-only after layout.tabs-placement, and both keys added to the layout example.
• customization/css-selectors.mdx: new ## Tab menu components section (between Header and Sidebar components) with the fern-tab-menu-* classes and data attributes, and the --fern-tab-menu-* custom properties with their defaults (from header/index.scss in fern-platform#15864). Also adds the classes to the complete selector index. This doesn't touch the Dropdown section or the fern-variant-* index rows that docs: document stable CSS selectors for navbar dropdowns and variant menus #7859 edits. The two PRs only meet in the index table, and their rows are far apart.
• home/pages/fern-instructions/docs/configure/navigation.mdx: two rows in the Options table for tab-menu and grouped variants.

I checked every key against fern/apis/docs-yml/definition/docs.yml in fern-api/fern main. I left out --fern-tab-menu-scrollbar-gutter, which exists in the SCSS but isn't in the PR's public list. No CLI changelog edits.

fern check --warnings reports 0 errors, and no warnings on the changed pages. Pre-commit (vale) passes.

Link to Devin session: https://app.devin.ai/sessions/ca6ad877db6744e4a9b4f15c325ac825
Open in Devin Desktop: https://app.devin.ai/desktop/session/ca6ad877db6744e4a9b4f15c325ac825?variant=devin

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🟢 Devin Review found nothing to fix · View findings

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

[github-actions]

🌿 Preview your docs: https://fern-preview-devin-1794676135-header-tab-menus.docs.buildwithfern.com/learn

Here are the markdown pages you've updated:

• learn/docs/customization/css-selectors-reference
• learn/docs/configuration/site-level-settings
• learn/docs/configuration/tabs
• learn/home/fern-instructions/docs/configure/navigation