Write Docs

The Opik docs site is built with Fern from MDX sources under apps/opik-documentation/documentation/fern/. Two content surfaces coexist:

• fern/docs/ — v1 (the established surface, source of style truth)
• fern/docs-v2/ — latest (where new pages go)

New pages should land in docs-v2/. v1 is the reference for writing style and component usage because it is far richer.

Where new pages live

• Create the file at apps/opik-documentation/documentation/fern/docs-v2/<section>/<page-name>.mdx.
• Register it in fern/versions/latest.yml under the right section: block.
• Only touch fern/versions/v1.yml if the page must also ship in the v1 build (rare).
• Do not edit fern/docs.yml when adding a page — that file is the global site config (tabs, redirects), not per-version routing.
• Routing is not implied by folder layout. Always check the version YAML.

Frontmatter template

Every page uses YAML frontmatter. title and headline are required; the og:* fields are strongly recommended for SEO/social sharing and are present on every page. Do not repeat title as an inline # H1 in the body — Fern renders it from frontmatter.

---
title: Page Title
headline: Page Title | Opik Documentation
og:title: Page Title — Opik
og:description: One-line summary used for social sharing and previews
og:site_name: Opik Documentation
---

subtitle: ... is an optional field used on concept/overview pages to add a secondary line. Landing/overview pages may also set layout: overview.

Style and voice

Pull examples from v1 pages when unsure — fern/docs/tracing/log_traces.mdx, fern/docs/tracing/concepts.mdx, and fern/docs/quickstart.mdx are good anchors.

• Person: "you" and imperative voice. Professional but approachable.
• Opening: one or two intro sentences before the first ## heading. No inline H1.
• Headings: ## for top-level sections, ### for subsections. Never introduce an inline # — that collides with the frontmatter title.
• Paragraphs: keep them short (2–4 sentences). Mix prose with bullet lists for features, options, and prerequisites.
• Page shape:
  • Concept pages start with the why, then definitions.
  • How-to pages start with brief context, then the task steps.
  • Overview/landing pages lead with a short pitch and a <CardGroup> of links.
• End with "## Next steps" linking to 2–4 related pages when useful.

Fern MDX components

All examples below are taken from real pages in the repo.

<Tabs> / <Tab> — SDK, language, or environment choice

Use when the whole section varies (not just a code block). Attach language="..." so Fern groups tabs across the site by the reader's last choice.

<Tabs>
  <Tab value="Python SDK" title="Python SDK" language="python">
    ```bash
    pip install opik
    ```
  </Tab>
  <Tab value="Typescript SDK" title="Typescript SDK" language="typescript">
    ```bash
    npm install opik
    ```
  </Tab>
  <Tab value="OpenTelemetry" title="OpenTelemetry">
    ...
  </Tab>
</Tabs>

<Steps> / <Step> — walkthroughs

For quickstarts, installs, and any sequential procedure. title on each <Step> is optional.

<Steps>
  <Step title="Install the Opik skill">
    ```bash
    npx skills add comet-ml/opik-skills
    ```
  </Step>
  <Step title="Run the integration">
    Once the skill is installed, you can add tracing using the following prompt:
    ```
    Instrument my agent with Opik using the /instrument command.
    ```
  </Step>
</Steps>

<CodeBlocks> — multi-language code, identical surrounding prose

Prefer this over <Tabs> when only the code varies.

<CodeBlocks>
  ```python title="Python"
  import opik
  opik.configure()

import Opik from "opik";
const client = new Opik();

```

<CardGroup> / <Card> — landing and integration grids

<CardGroup cols={3}>
  <Card title="LangChain" href="/integrations/langchain" icon={<img src="/img/tracing/langchain.svg" />} iconPosition="left"/>
  <Card title="LlamaIndex" href="/integrations/llama_index" icon={<img src="/img/tracing/llamaindex.svg" />} iconPosition="left"/>
  <Card title="Anthropic" href="/integrations/anthropic" icon={<img src="/img/tracing/anthropic.svg" />} iconPosition="left"/>
</CardGroup>

<AccordionGroup> / <Accordion> — FAQs and expandable advanced topics

<AccordionGroup>
  <Accordion title="Why use the optimizer?">
    The Agent Optimizer provides a unified interface...
  </Accordion>
</AccordionGroup>

<Frame> — image wrapper (always wrap images)

<Frame>
  <img src="/img/tracing/introduction.png" />
</Frame>

Callouts: <Tip>, <Note>, <Warning>, <Info>, <Callout>

Pick by intent, not aesthetics:

• <Tip> — cross-references, shortcuts, "If you're just getting started, see..."
• <Note> — clarifications and recommendations that aren't risky
• <Warning> — breaking changes, footguns, prerequisites that will break things
• <Info> — informational, interchangeable with <Note> in practice
• <Callout> — catch-all when none of the above fits

<Tip>
  If you are just getting started with Opik, we recommend first checking out the [Quickstart](/quickstart) guide.
</Tip>

<Warning>
  Note that the authorization header value does not include the `Bearer ` prefix.
</Warning>

Code examples

• Use <CodeBlocks> for multi-language blocks; use <Tabs> when surrounding prose also varies.
• Install commands are inline bash blocks (pip install opik, npm install opik).
• There is no snippet-include system. All code is written inline in MDX.
• Use placeholders for credentials: <API_KEY>, <TOKEN>, <your-api-key>. Never commit real keys.

Images

• Store under apps/opik-documentation/documentation/fern/img/<section>/....
• Reference from MDX as /img/<section>/<file>.png (path is rooted at the docs base).
• Never put new assets in static/img/ — that folder is legacy and only kept for external integrations.
• Always wrap with <Frame>. Captions are not a repo convention.

Cross-links

Root-relative, slug-based paths only (/section/page).

• Never link internal docs pages with full https://www.comet.com/docs/opik/... URLs. Full URLs bypass the Fern preview build, and they 404 in the link checker when the target page ships in the same PR. Use the root-relative slug path instead.
• No file-relative paths (../foo) either.
• Build the path from the version YAML (fern/versions/latest.yml), including every nested section: slug. Example: the "Manage datasets" page sits inside an advanced section, so the path is /evaluation/advanced/manage_datasets, not /evaluation/manage_datasets.

[Python SDK](/reference/python-sdk/overview)
[Log traces](/tracing/advanced/log_traces)
[Integrations overview](/integrations/overview)

In-page anchors use the heading slug: [Concepts](#concepts).

Exception: a v1 page (fern/docs/) that must point to a latest-only page cannot use a root-relative path — the slug does not exist in the v1 build. Use the full production URL there, and confirm the target page is already deployed.

Routing: adding a page to latest.yml

Add a page entry under the correct section: (keep the YAML at 2-space indent):

- page: Page Title
  path: ../docs-v2/section/page-name.mdx
  slug: page-name

If the page also needs to ship in v1, mirror the entry in fern/versions/v1.yml. Leave fern/docs.yml alone.

File naming

• Kebab-case for new files: getting-started.mdx, log-traces.mdx.
• When editing an existing section that uses snake_case (common in v1), match neighbors rather than renaming. Renames require redirect entries in docs.yml.

Local verification

cd apps/opik-documentation/documentation
npm install          # first time only
npm run dev          # live-reload preview

Open the rendered page and confirm:

• Frontmatter renders (title shows, no stray H1 in body).
• Every MDX component resolves (no raw <Tabs> tags visible).
• Every link works (no 404s, no Broken link warnings in the terminal).
• Images load.

Changelog routing

Pick the changelog target by scope — do not default everything to one surface.

• apps/opik-documentation/documentation/fern/docs-v2/self-host/changelog.mdx — self-hosted deployment changelog shown at /docs/opik/self-host/changelog. Breaking, critical, or security-impacting changes only. (The former repo-root CHANGELOG.md was removed; its content lives on this page now.)
• apps/opik-documentation/documentation/fern/docs/changelog/*.mdx — general product release notes shown at /docs/opik/changelog. One dated .mdx per entry.
• apps/opik-documentation/documentation/fern/docs/agent_optimization/getting_started/changelog.mdx — Agent Optimizer version updates (e.g. sdks/opik_optimizer releases like 3.1.0).
• Liquibase changelog.xml files are migration manifests, not user-facing release notes. Do not put prose there.
• When unsure, confirm the surface from fern/docs.yml before editing.

Changelog entry template

### [VERSION] - [DATE]

#### New Features
- **Feature Name**: Brief description

#### Improvements
- **Improvement**: What changed and why

#### Bug Fixes
- **Fix**: What was broken (#issue)

#### Breaking Changes
- **Change**: What breaks, migration steps

Feature documentation checklist

When documenting a new feature, cover:

• User impact — What capability does this add? How do users access it?
• Technical changes — API endpoints and params, SDK methods, config or env vars, migrations.
• Breaking changes — What breaks and the migration path, if any.

Keep it user-facing: avoid implementation detail unless it affects how someone uses the feature.

PR description template

Use the repository template at .github/pull_request_template.md — read the FULL file before drafting (the required sections continue past the first screen). CI (.github/workflows/pr-lint.yml) fails any PR whose description is missing one of these exact headings:

• ## Details
• ## Change checklist
• ## Issues
• ## Testing
• ## Documentation

Also fill in the template's ## AI-WATERMARK section (yes/no; if yes: Tools, Model(s), Scope, Human verification). Never invent a different structure such as ## Summary / ## Test Plan.

Internationalized READMEs

readme_CN.md, readme_ES.md, readme_FR.md, readme_DE.md are AI machine-translated from the English README.md.

• Each non-English README has a blockquote notice at the top warning that it is AI-translated and welcoming improvements. Keep it.
• When the English README changes meaningfully, re-translate the affected files. Do not hand-edit translated READMEs for content changes — update the English source and re-translate.

Forbidden and discouraged

• No real API keys, tokens, or workspace IDs in examples — always placeholders.
• Do not edit fern/docs/cookbook/*.mdx by hand. Those files are regenerated from docs/cookbook/*.ipynb by update_cookbooks.sh.
• Do not put new images outside fern/img/. static/img/ is legacy-only and cannot be deleted because of external integrations.
• Do not infer URL paths from folder layout — always consult the version YAML.
• Do not add an inline # H1 inside the body — the frontmatter title already provides it.

Key files

• apps/opik-documentation/documentation/fern/versions/latest.yml — routing for the latest version (edit when adding pages).
• apps/opik-documentation/documentation/fern/versions/v1.yml — routing for v1 (edit only if the page ships in v1 too).
• apps/opik-documentation/documentation/fern/docs.yml — global site config (tabs, redirects). Treat as read-only for page adds.
• apps/opik-documentation/documentation/fern/docs-v2/ — target directory for new pages.
• apps/opik-documentation/documentation/fern/img/ — image storage.
• apps/opik-documentation/documentation/update_cookbooks.sh — regenerates cookbook MDX from notebooks.
• apps/opik-documentation/AGENTS.md — docs-module contribution rules.
• .github/release-drafter.yml — release notes template.