fern-docs

name	fern-docs
description	Maintain the NeMo AutoModel Fern docs site under docs/ (MDX content) + docs/fern/ (infra) — add, update, move, or remove pages; manage redirects, slugs, navigation, and version aliases; run validation and previews.
when_to_use	Editing or adding documentation pages, fixing broken links, renaming a slug, updating the sidebar, adding a redirect, regenerating the API library reference, debugging fern check / broken-link errors, cutting a new version train, 'edit docs', 'add doc page', 'fern check failing', 'preview fails locally'.

Fern Docs Maintenance — NeMo AutoModel

Unified skill for adding, updating, moving, and removing pages on the NeMo AutoModel Fern documentation site at docs.nvidia.com/nemo/automodel.

Scope rule

Nightly MDX content lives at the top level of docs/ (e.g. docs/index.mdx, docs/guides/llm/finetune.mdx). docs/fern/ holds only Fern build infrastructure — config, theme, and components. New pages, release notes, migration guides → add as a top-level .mdx under docs/.

Only the nightly tree is kept on main. Frozen backward-version snapshots live on the docs-archive branch and are restored at build time — see Archived backward versions below.

Two real content trees, plus a GA alias YAML.

• docs/ — bleeding-edge (nightly) tree. Every PR lands here. Mounted at the nightly URL slug via docs/fern/versions/nightly.yml (paths reach back up via ../../<rel>.mdx).
• docs/fern/versions/v0.4/pages/ — frozen 0.4.0 GA snapshot. Not on main: it lives on the docs-archive branch and is restored under this path by make docs-stitch (local) or the stitch-fern-versions CI action (build). Mounted at the v0.4 URL slug via v0.4.yml. Only changes via deliberate back-port (on docs-archive).
• docs/fern/versions/latest.yml — GA alias. Its path: lines mount the current GA's content (today: ./v0.4/pages/...). Repointed at the next GA's tree when one is cut.

The nightly and v0.4 trees were byte-for-byte identical at the moment 0.4.0 shipped, but they will diverge as nightly accumulates post-release edits and v0.4 stays frozen. Default editing target is docs/ top-level. Back-ports to a frozen version happen on the docs-archive branch, not here — call out the divergence in the PR description.

Archived backward versions

Fern has no native way to source a version train's prose from another git ref: fern generate --docs reads the single local working tree, and publish is a full-site snapshot (a train missing from the tree is unpublished). So frozen GA pages are kept off main on the docs-archive branch and restored before every Fern build.

• The registry lives inline in each fern-docs-* workflow as archived-versions: | lines of <version-dir>=<git-ref> (today: v0.4=docs-archive). The <git-ref> is opaque: a branch (default — all frozen versions in one place, easy back-ports) or a tag like docs/v0.4.0 (immutable snapshot). latest is an alias of an existing pages tree and needs no entry.
• The mechanism is the .github/actions/stitch-fern-versions composite action: git fetch --depth=1 origin <ref> then git restore --source=FETCH_HEAD -- docs/fern/versions/<vdir>/pages. It runs in publish-fern-docs.yml, fern-docs-ci.yml, and fern-docs-preview-build.yml. docs.yml + the nav YAMLs always come from the live checkout, never the archive ref, so frozen prose can't drift into the wrong train.
• Locally, make docs / docs-check / docs-preview depend on make docs-stitch, which does the same restore. Override the ref with make docs-check ARCHIVE_REF=docs/v0.4.0.
• The restored path is gitignored on main, so a local stitch won't show the pages as untracked.

Sidebar fidelity rule. Section captions, page titles, and Model Coverage child ordering must match the published v0.4.0 sidebar at docs.nvidia.com/nemo/automodel/latest verbatim. Don't silently shorten a title or reorder siblings — the docs PM and content engineers diff against the published site and any drift is treated as a regression. If you want a shorter sidebar label, change the toctree-derived display name in the source — never just retitle in the MDX.

Layout at a glance

docs/                                ← nightly MDX (top level)
├── index.mdx, breaking-changes.mdx, release-notes.mdx, ...
├── about/, guides/, model-coverage/, launcher/, api-reference/
├── *.png / *.jpg                    ← page-scoped images
└── fern/                            ← infra only
    ├── fern.config.json             # Org slug + Fern CLI pin (5.29.0+)
    ├── docs.yml                     # Site config + global-theme: nvidia (inherits
    │                                #   logos / footer / theme CSS / fonts / OneTrust JS
    │                                #   from NVIDIA/fern-components)
    ├── components/                  # BadgeLinks.tsx, Tag.tsx
    │                                #   (repo-specific; NVIDIA footer ships in global theme)
    ├── versions/
    │   ├── nightly.yml              # Nav for nightly — paths → ../../<rel>.mdx (up into docs/)
    │   ├── v0.4.yml                 # Nav for frozen 0.4.0 — paths → ./v0.4/pages/
    │   ├── v0.4/pages/              # Frozen 0.4.0 MDX (back-ports only)
    │   └── latest.yml               # GA alias — paths → ./v0.4/pages/ today; repointed at next GA cut
    └── product-docs/                # GENERATED Python API reference (gitignored)

File                                                          URL
─────────────────────────────────────────────────────────────  ────────────────────────────────────────────
docs/get-started/installation.mdx                              /nightly/get-started/installation
docs/fern/versions/v0.4/pages/get-started/installation.mdx     /latest/get-started/installation
                                                               /v0.4/get-started/installation

Operations

Add a page

1. Gather: title, target section, filename (kebab-case .mdx), subdirectory under docs/.

2. Create the MDX at docs/<subdir>/<filename>.mdx with frontmatter:

   ---
   title: "<Page Title>"
   description: "One-line SEO description (or empty string)"
   position: 4
   ---
   
   <body — typically no leading `# H1`; Fern renders the title automatically>
   

3. Add a - page: entry to docs/fern/versions/nightly.yml under the right section:, with path: reaching up into docs/ via ../../:

   - page: "<Page Title>"
     path: ../../<subdir>/<filename>.mdx
     slug: <short-url-segment>
   

4. make docs-check (runs fern check) and verify URL resolves on make docs preview. There is no nightly.yml ↔ latest.yml alias-sync step under this layout — latest.yml mounts the frozen v0.4 tree, not nightly, so it's intentionally out of sync.

Update a page

1. Locate by path, title, or keyword: grep -rn "<keyword>" docs/ --include="*.mdx" --exclude-dir=fern.
2. Content only — edit the single MDX file at docs/<...>.mdx.
3. Title change — update the frontmatter title: and update the - page: entry's display label in docs/fern/versions/nightly.yml.
4. Section move — git mv the file within docs/, update path: in nightly.yml, fix incoming links.
5. Slug change — change slug: in the YAML (or rename the file and let the default slug update). Add a redirects: entry in docs/fern/docs.yml so the old URL keeps working.

Redirect quirks

Four things to watch when editing redirects: in docs/fern/docs.yml:

1. :path* does NOT match the empty-path case. /<basepath>/v0.4/:path*/index.html will not match /<basepath>/v0.4/index.html (where :path* would have to be empty). Each version-root index.html needs its own explicit rule. NeMo Curator (NVIDIA-NeMo/Curator#1938) discovered this when their version-root URLs 404'd. AutoModel ships explicit rules for latest, v0.4, nightly, and the legacy 0.4 form — when you add a new version slug, add four new explicit rules: <slug>/index.html, <slug>/index, plus the same two for any legacy form (e.g. 0.5 → v0.5).
2. Older un-migrated versions need a fallback. Whatever versions the published Sphinx site exposed (check the version-switcher dropdown on docs.nvidia.com/nemo/<product>/latest/) but you didn't migrate into Fern still need to resolve. The pattern: redirect each old slug's URLs to the equivalent path under /latest/ so external bookmarks and search results land on the closest current page instead of 404ing. Five rules per old version: <slug>/index.html, <slug>/index, <slug>/:path*/index.html, <slug>/:path*, <slug>/:path*.html — all destinations /latest/.... AutoModel ships these for 0.3.0, 0.2.0, 0.1.0.
3. Order matters. Specific rules must come before catch-alls — Fern uses first-match. Slot new rules before the :path*/index.html and :path*.html catch-alls.
4. Don't ship redirects: [] then re-run the redirect generator on top — it replaces the whole redirects: block. Edit by hand or back up the existing rules first.

Remove a page

1. Find incoming links: grep -rn "<filename>" docs/ --include="*.mdx" --exclude-dir=fern.
2. git rm docs/<...>.mdx.
3. Remove the - page: block from docs/fern/versions/nightly.yml.
4. Fix or delete incoming links.
5. Add a redirect in docs/fern/docs.yml if the URL was public.

Worked example: add a guide

Request: "Add a fine-tuning guide for Qwen3.6 under Recipes & E2E Examples."

1. Create docs/guides/llm/qwen3-6-finetune.mdx:

   ---
   title: "Fine-Tune Qwen3.6"
   description: "End-to-end SFT and PEFT recipes for Qwen3.6 on NeMo AutoModel"
   ---
   
   This guide walks through fine-tuning Qwen3.6 with NeMo AutoModel...
   

2. Add to docs/fern/versions/nightly.yml under the Recipes & E2E Examples section, slotted in publication-order with the other fine-tune entries:

   - page: "Fine-Tune Qwen3.6"
     path: ../../guides/llm/qwen3-6-finetune.mdx
     slug: qwen3-6-finetune
   

3. make docs-check then make docs to preview at http://localhost:3002/nightly/recipes-e2e-examples/qwen3-6-finetune.

Worked example: rename a slug with a redirect

Request: "Rename /recipes-e2e-examples/sft-peft to /recipes-e2e-examples/fine-tuning."

1. Edit docs/fern/versions/nightly.yml, change the slug: on the SFT & PEFT entry from sft-peft to fine-tuning.

2. Add a redirect to docs/fern/docs.yml:

   redirects:
     - source: "/:version/recipes-e2e-examples/sft-peft"
       destination: "/:version/recipes-e2e-examples/fine-tuning"
   

3. grep -rn "/recipes-e2e-examples/sft-peft" docs/ --include="*.mdx" --exclude-dir=fern and update incoming body links.

Content guidelines

NeMo AutoModel uses Fern-native MDX components. Don't use GitHub > [!NOTE] syntax — it doesn't render in MDX.

Purpose	Component
Neutral aside	<Note>...</Note>
Helpful tip	<Tip>...</Tip>
Informational callout	<Info>...</Info>
Warning	<Warning>...</Warning>
Error / danger	<Error>...</Error>
Card grid on landing pages	<Cards> with <Card title="..." href="..."> children
Card chips ("start here", "5 min")	<Tag variant="primary">label</Tag> — sphinx-design {bdg-*} mapping
Header badge rows (PyPI, license, GitHub)	<BadgeLinks badges={[{href, src, alt}, ...]} />

Required imports when using <Tag> or <BadgeLinks> (landing_badges.py adds these in the post stage; in hand-written pages add them yourself):

import { Tag } from "@/components/Tag";
import { BadgeLinks } from "@/components/BadgeLinks";

<Tag variant="..."> accepts: primary, secondary, success, warning, danger, info, light, dark (1:1 with sphinx-design {bdg-*} variants).

Page-scoped images live alongside the MDX file (e.g. docs/guides/audio/qwen_omni_asr.png). Reference them with relative paths (./image.png), not absolute (/image.png) — Fern's path resolver doesn't normalize root-relative image paths the same way as link targets. The NVIDIA logos and favicon come from the nvidia global theme; do not add them locally.

Frontmatter

---
title: "<Page Title>"        # required — Fern renders this as the page H1
description: ""              # required (may be "") — SEO meta description
position: 1                  # optional — orders auto-discovered pages within a folder
---

Don't repeat the title as a leading # H1 in the body. Fern already renders title: at the top of the page, and a duplicate creates a double heading. The post-stage remove_duplicate_h1.py strips them when title and H1 match exactly, but it can't catch near-duplicates (e.g. title: "About" vs # About NeMo AutoModel) — keep the body H1-free, or promote the descriptive form to subtitle: if you want both visible.

Internal links

Use version-agnostic paths — no /latest/, /v0.4/, or /nightly/ prefix:

[Install NeMo AutoModel](/get-started/installation)
[Llama coverage](/model-coverage/large-language-models/llama)

The same MDX backs every version slug; a hard-coded prefix sends readers across versions unintentionally. URL slugs come from explicit slug: overrides in the version YAML (set during the migration so URLs stay short while sidebar titles match the verbose published H1s) — so Install NeMo AutoModel is at /get-started/installation, not /get-started/install-nemo-automodel.

For cross-repo references (yaml configs, Python source), use absolute GitHub URLs:

[mistral4_medpix.yaml](https://github.com/NVIDIA-NeMo/Automodel/blob/main/examples/vlm_finetune/mistral4/mistral4_medpix.yaml)

Validate

make docs-check          # MDX syntax validation + `fern check`

Run from docs/fern/ (cd docs/fern && make docs-check) or anywhere with make -C docs/fern docs-check.

make docs-check must pass before commit. It runs a no-secret MDX parser before fern check, so raw HTML must be valid JSX (for example, use <img ... />, not <img ...>). The dev server's broken-link warnings for version-prefixed routes (e.g. /latest/get-started/installation from MDX that uses /get-started/installation) are false positives — Fern's strict validator doesn't resolve version-agnostic links. The published site renders them correctly. The URLMap-based validate_fern_internal_links.py (under the convert-to-fern toolkit) is authoritative.

To regenerate the autodoc library reference (gitignored under docs/fern/product-docs/):

make docs                # runs `fern docs md generate` then `fern docs dev`

fern docs md generate populates docs/fern/product-docs/ from the nemo_automodel package source declared in docs.yml libraries: block. Without this step, a cold fern docs dev fails with Folder not found: ./product-docs/....

Preview and publish

Goal	Command
Local preview at http://localhost:3002	make docs
Validation only (no server)	make docs-check
Shared preview URL on *.docs.buildwithfern.com (needs DOCS_FERN_TOKEN)	make docs-preview
Trigger production publish workflow on origin/main	make docs-publish

PRs that touch docs/** get an automatic Fern preview URL posted as a 🌿 comment by fern-docs-preview-comment.yml. No manual step.

Every job below first runs the stitch-fern-versions action to restore the archived backward-version pages (the docs-archive branch) into the working copy — the frozen trees are not on main.

                    ┌─ fern-docs-ci.yml                  → stitch → MDX syntax → fern check (push to pull-request/<n>)
PR (touches docs/) ─┼─ fern-docs-preview-build.yml       → stitch → upload docs/ artifact (no secrets)
                    └─ fern-docs-preview-comment.yml     → 🌿 preview URL comment (consumes artifact)

Push to main (touches docs/) → publish-fern-docs.yml → stitch → docs.nvidia.com/nemo/automodel
Tag push (docs/v*)           → publish-fern-docs.yml → stitch → docs.nvidia.com/nemo/automodel
Manual dispatch              → publish-fern-docs.yml → stitch → docs.nvidia.com/nemo/automodel

The preview-comment + publish jobs require the DOCS_FERN_TOKEN org secret (already wired for build-docs.yml).

Cutting a new version train

When NeMo AutoModel ships a new GA (e.g. v0.5):

1. mkdir -p docs/fern/versions/v0.5/pages && rsync -a --exclude='fern' docs/ docs/fern/versions/v0.5/pages/ — fresh frozen snapshot of nightly at release time.
2. cp docs/fern/versions/nightly.yml docs/fern/versions/v0.5.yml and rewrite ../../ path prefixes to ./v0.5/pages/.
3. Update docs/fern/versions/latest.yml to point at the new train: cp docs/fern/versions/v0.5.yml docs/fern/versions/latest.yml. (latest is the auto-bumping GA alias.)
4. In docs/fern/docs.yml versions:, add a new frozen-pin entry (display-name: "0.5.0 · 26.07", slug: v0.5, availability: stable) and keep the previous pin (v0.4) for permalink stability.
5. Archive the frozen tree off main (see Archived backward versions): commit docs/fern/versions/v0.5/pages/ onto the docs-archive branch and push it, then git rm -r docs/fern/versions/v0.5/pages from main and add that path to .gitignore. The v0.5.yml/latest.yml/docs.yml config stays on main.
6. Add v0.5=docs-archive to the archived-versions: registry in publish-fern-docs.yml, fern-docs-ci.yml, and fern-docs-preview-build.yml (and the .gitignore line). docs/ keeps moving forward as the bleeding-edge tree; the new frozen snapshot only changes via deliberate back-port on docs-archive.
7. Promote nightly to availability: stable if and when its content tree gets cut over.
8. Tag docs/v0.5.0 and push to publish.

Commits and DCO

Every commit needs a Signed-off-by: trailer:

git commit -s -m "docs: add fine-tuning guide for Qwen3.6"

If sign-off is missing on a recent commit, amend with git commit --amend -s. PR titles follow Conventional Commits: docs(fern): <short summary>. See AGENTS.md for the full repo commit convention.

Debugging

Symptom	Fix
fern check YAML error	2-space indent; - page: inside contents:; path: is relative to nightly.yml's location (so nightly entries reach back up via ../../); slug: must not collide with siblings
Page 404 in preview	Missing slug: override (default slugifies the long display title) or position: collision in an auto-discovered folder
Folder not found: ./product-docs/... on fern docs dev	Run make docs once to populate the library reference
[ERR_PNPM_IGNORED_BUILDS] on first fern docs dev	pnpm 10+ blocks esbuild's postinstall — pnpm config set onlyBuiltDependencies '["esbuild"]' --location global, then rm -rf ~/.fern/app-preview and retry
Broken-link warning on version-agnostic path	fern docs broken-links false-positives; URLMap-based validator is authoritative
JSX expressions must have one parent element	Wrap multi-element JSX in <>...</> or a <div>
Old Sphinx URL breaks	Add a redirects: entry in docs/fern/docs.yml; the redirect generator already handles /index.html and .html legacy forms
Image not rendering	Use relative path (./image.png) for page-scoped images, not root-relative (/image.png)
Sidebar caption looks shortened vs published site	Compare against docs.nvidia.com/nemo/automodel/latest and restore the verbatim title in docs/fern/versions/nightly.yml
path: ../../foo.mdx doesn't resolve	Confirm the MDX file is at docs/foo.mdx (top level), not still under docs/fern/versions/nightly/pages/ — that legacy tree no longer exists
fatals on missing paths

Key references

File	Purpose
docs/fern/docs.yml	Site config — instances, versions, redirects, libraries, theme
docs/fern/versions/nightly.yml	Canonical nav tree — paths reach up into docs/ via ../../
docs/fern/versions/{latest,v0.4}.yml	Frozen GA nav (mount ./v0.4/pages/...)
docs/ (top-level *.mdx)	Nightly MDX content (~140 pages + page-scoped images)
docs/fern/versions/v0.4/pages/	Frozen 0.4.0 snapshot — on the docs-archive branch, not main; stitched in at build time
docs-archive branch	Holds all frozen backward-version pages/ trees; restored by stitch-fern-versions / make docs-stitch
.github/actions/stitch-fern-versions/	Composite action that restores archived version pages before any Fern build
docs/fern/components/	BadgeLinks.tsx, Tag.tsx (repo-specific; NVIDIA footer ships via global-theme: nvidia)
docs/fern/README.md	Human-facing orientation
docs/fern/Makefile	make docs / docs-check / docs-preview / docs-publish (run from docs/fern/ or via make -C docs/fern)
.github/workflows/fern-docs-*.yml	CI: check, preview build, preview comment
.github/workflows/publish-fern-docs.yml	CI: publish to docs.nvidia.com/nemo/automodel