feat(cli): propagate collapsed config from API reference to child package nodes

[cadesark]

Description

Setting collapsed: open-by-default or collapsed: true on an - api entry in docs.yml now cascades to all auto-generated endpoint group sections (API package nodes) in the sidebar.

Previously, the collapsed value was only set on the top-level ApiReferenceNode but not propagated to child ApiPackageNodes — every child had collapsed: undefined hardcoded. The frontend already handles collapsed on any node via getInitiallyCollapsedNodes / getInitiallyOpenByDefaultNodes, so the only gap was the CLI not passing the value through.

Changes Made

• In ApiReferenceNodeConverter.ts, changed 7 locations where apiPackage nodes had collapsed: undefined to inherit this.apiSection.collapsed
• Explicit section entries in the layout that set their own collapsed are unchanged (line 464)
• Added unreleased changelog entry

Testing

• pnpm --filter @fern-api/docs-resolver test — 44/44 passed
• pnpm --filter @fern-api/configuration-loader test -- --testPathPattern collapsible — 13/13 collapsed tests + 252 total passed
• pnpm check — biome lint clean

Link to Devin session: https://app.devin.ai/sessions/f50b384f315b4bb8975f66c337f5fdb4
Requested by: @cade-fern

[devin-ai-integration]

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[github-actions]

Docs Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-06-04T05:35:26Z).

Fixture	main	PR	Delta
docs	230.6s (n=5)	225.6s (35 versions)	-5.0s (-2.2%)

Docs generation runs fern generate --docs --preview end-to-end against the benchmark fixture with 35 API versions (each version: markdown processing + OpenAPI-to-IR + FDR upload).
Delta is computed against the nightly baseline on main.
Baseline from nightly run(s) on main (latest: 2026-06-04T05:35:26Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-06-04 16:47 UTC

[devin-ai-integration]

Test Results: collapsed propagation to child apiPackage nodes

All 3 programmatic tests passed ✅

Test Output

 ✓ collapsed-propagation.test.ts (3 tests) 860ms
   ✓ propagates collapsed: open-by-default to all child apiPackage nodes  580ms
   ✓ propagates collapsed: true to all child apiPackage nodes  154ms
   ✓ preserves default behavior when collapsed is undefined  123ms

 Test Files  1 passed (1)
      Tests  3 passed (3)

What was tested

Used the availability-inheritance fixture (Fern native definitions with multiple subpackages → multiple apiPackage child nodes) to verify:

1. collapsed: "open-by-default" — set on apiSection, verified ALL child apiPackage nodes inherit it
2. collapsed: true — same propagation for boolean value
3. collapsed: undefined (default) — no regression, children remain undefined

All 8 apiPackage creation sites in ApiReferenceNodeConverter.ts now use this.apiSection.collapsed instead of undefined.

Visual context — current sidebar (before feature)

The live Natural docs site currently shows all 16 endpoint groups collapsed:

With this PR + collapsed: open-by-default in docs.yml, all groups would start expanded showing individual endpoints.

Note: Could not generate a live docs preview (token lacks FDR access to natural org). The programmatic test directly verifies the navigation tree output, which is more rigorous than a visual check.

Devin session

[cadesark]

Tested locally on demo site, API Ref page opens with all endpoint groups expanded after adding

collapsed: open-by-default under -api:

[devin-ai-integration]

Awesome — looks great! All 16 endpoint groups expanded by default, exactly as intended. Thanks for verifying on the live site.