---

name: headless-component description: Author or extend unstyled Fluent UI v9 primitives in @fluentui/react-headless-components-preview, including stable hooks, render functions, state data attributes, compound context wiring, tests, exports, and CSS Module stories. Use for any change that adds a headless component or component family to the preview library. argument-hint: disable-model-invocation: true allowed-tools: Bash Read Write Edit Grep Glob

Author a Headless Component

Author $ARGUMENTS in:

• packages/react-components/react-headless-components-preview/library
• packages/react-components/react-headless-components-preview/stories

Headless components provide Fluent behavior, accessibility, semantic slots, and stable state selectors without Fluent styling. They must remain usable with plain CSS, CSS Modules, Tailwind, or another styling system.

If $ARGUMENTS is empty or is not a PascalCase component name, ask for a valid component name before searching or editing.

Source Of Truth And References

This skill is the operational source of truth for authoring a headless component. Do not require the RFC to be loaded for routine work: the normative package contract, state-attribute rules, packaging requirements, stacked-PR workflow, and validation bar are fully stated here.

Always inspect current code before editing:

1. The corresponding styled v9 package under packages/react-components/react-<name>/library/src/
2. The nearest headless implementation with the same shape:
   • simple primitive: library/src/components/Button/
   • compound primitive using upstream base hooks: library/src/components/Accordion/
   • composite/context/positioning primitive: library/src/components/Menu/
3. The current package manifests, export barrels, API reports, bundle fixtures, tests, and stories touched by the change

Consult these documents only when changing the package-wide contract, resolving an ambiguity not answered here, or updating their documentation:

• packages/react-components/react-headless-components-preview/library/docs/Spec.md
• packages/react-components/react-headless-components-preview/stories/README.md
• docs/react-v9/contributing/rfcs/react-components/convergence/headless-components.md

The RFC provides decision history and rationale; it is not a per-component checklist and may describe the intended stable package name rather than the current preview package.

Use current implementations as structural references, not as permission to copy legacy violations. Repository instructions override existing code.

Preflight

Before writing code:

1. Search the headless library and stories for the component and its family. Extend an existing implementation instead of creating a competing one.
2. Inspect the corresponding styled v9 package and its public API docs. Inventory:
   • public components and subcomponents
   • slots, props, state, refs, and polymorphic as behavior
   • controlled and uncontrolled state
   • context values
   • ARIA semantics and keyboard/focus behavior
   • positioning, portals, and mount-node behavior
3. Verify the upstream package's actual exports before reimplementing logic. Search for use<Name>Base_unstable, render<Name>_unstable, use<Name>ContextValues_unstable, context hooks, and shared utilities.
4. Classify the work:
   • simple — one hook, renderer, component, and state attributes
   • compound — parent plus child primitives and context-value wiring
   • composite — substantial focus, selection, positioning, portal, or nested-component behavior
5. Define the stable data-* contract before implementation. Include only behavior/base state, never visual design state.
6. Record every inventory row as implemented, intentionally excluded with a source-backed reason, or unresolved. Trace implemented rows through: types/exports -> hook/context -> rendered DOM/slots -> test or story.
7. Plan the change as three stacked PRs before editing:
   • bottom PR — regression test: lock down the existing behavior that the base extraction must preserve; do not change production code
   • middle PR — component package: base hook/types/renderer/context exports and their package-local tests, API docs, bundle-size coverage, manifest updates, and change file
   • top PR — headless package: stable headless primitive, data-* contract, headless tests, stories, public subpath, headless bundle-size coverage, API docs, manifest updates, and change file

Do not mix component-package and headless-package changes in one PR. The headless layer depends on the base APIs introduced or confirmed by the component package, so the component-package PR is always below the headless PR.

Do not broaden the component API with styled-only props such as appearance, size, shape, or other visual variants.

Use an existing repository generator for the component family when one is available. Otherwise, follow the file structure and validation requirements below rather than creating a parallel scaffold.

Package Contract

Every public headless primitive exposes stable, unsuffixed names:

Component
useComponent
renderComponent
ComponentProps
ComponentSlots
ComponentState

Compound families additionally expose their public children, context types, and context hooks when consumers need them for advanced composition.

Internally, these APIs normally wrap the corresponding package's _unstable base hook and renderer:

useComponentBase_unstable
        ↓
useComponent
        ↓
renderComponent
        ↓
Component

The headless layer must not add styling, design props, motion, default icons, or new interaction behavior.

File Structure

For a simple component:

library/src/components/ComponentName/
  ComponentName.tsx
  ComponentName.types.ts
  ComponentName.test.tsx
  index.ts
  renderComponentName.ts
  useComponentName.ts

library/src/component-name.ts

stories/src/ComponentName/
  ComponentNameDescription.md
  ComponentNameDefault.stories.tsx
  component-name.module.css
  index.stories.tsx

For a compound family, place child primitives beneath the root folder:

library/src/components/ComponentName/
  ComponentName.tsx
  ...
  ComponentPart/
    ComponentPart.tsx
    ComponentPart.types.ts
    ComponentPart.test.tsx
    index.ts
    renderComponentPart.ts
    useComponentPart.ts

Add *.cy.tsx integration coverage when behavior depends on real browser focus, Tabster, positioning, portals, native popovers, or nested trigger composition.

Implementation

Component

• Add 'use client'; to component and hook modules that use React client APIs.
• Use ForwardRefComponent<Props> with React.forwardRef for ref-capable primitives. Never use React.FC.
• For provider-only components with no meaningful DOM ref, use a normally typed function returning JSXElement; do not invent a fake ref and do not use React.FC.
• Keep the component thin: state hook, optional context-values hook, renderer.
• Set displayName on every exported React component.
• Add concise JSDoc describing purpose and any required accessibility contract.
• Do not import icons or add default icons in base hooks or headless renderers. If an icon is needed in a styled wrapper or story, import it there and define bundleIcon at module scope, never inside a hook or render function.

'use client';

import * as React from 'react';
import type { ForwardRefComponent } from '@fluentui/react-utilities';

export const ComponentName: ForwardRefComponent<ComponentNameProps> = React.forwardRef((props, ref) => {
  const state = useComponentName(props, ref);
  return renderComponentName(state);
});

ComponentName.displayName = 'ComponentName';

For compound roots, derive and pass context values between the state hook and renderer.

Hook

• Prefer the upstream useComponentNameBase_unstable hook.
• When adding a new v9 base hook, follow the repository-enforced signature: useComponentNameBase_unstable(props, ref?), with an explicitly typed props parameter and ref typed as React.Ref<...>.
• Keep base hooks free of Tabster and other forbidden focus/keyboard runtimes. Logic requiring those runtimes stays in the styled package's wrapping useComponentName_unstable hook. Run the component-package lint target so base-hook-signature and base-hook-no-forbidden-runtime validate the split.
• Preserve upstream behavior rather than copying the styled component's main hook, which may include design defaults and styling concerns.
• Reuse exported context-value hooks and utilities. Do not reconstruct their return objects manually.
• Reimplement behavior only after proving the required base API is not exported. In that case, port only behavior/accessibility logic and preserve parity with the styled package's tests.
• Use useFluent_unstable() for targetDocument and its defaultView; never access window, document, or navigator directly.

Stable data-* Attributes

State attributes are the supported CSS targeting contract.

• Boolean and presence state: emit '' when true and omit when false. Reserve explicit string values for enum or tri-state contracts.
• Enum or tri-state: emit the documented string value.
• Put attributes on the root slot unless a documented exception makes another slot the semantic state owner.
• Type every attribute on ComponentState so it appears in generated API docs.
• Apply reserved attributes after the base hook resolves consumer root props. The headless state must win if a consumer supplies a conflicting reserved attribute.
• Removal or rename is breaking. Additions require tests and documentation.

Use toDataAttributeValue from library/src/utils for presence and string attributes:

const state: ComponentNameState = useComponentNameBase_unstable(props, ref);

// Applied after consumer props so base state cannot be misrepresented.
state.root['data-disabled'] = toDataAttributeValue(state.disabled);

return state;

Good attributes describe behavior: data-disabled, data-open, data-expanded, data-checked, data-selected, data-orientation, data-icon-only.

Do not expose design attributes such as data-appearance, data-size, data-shape, or styling-specific class names.

Types

• Derive props, slots, and state from the upstream base types, not the styled public types when those include design props.
• Alias unchanged base types directly.
• Extend state only for public headless additions such as typed data-* attributes.
• Keep exact attribute value unions when known instead of widening to string.
• Export event and context types required by consumers of compound components.
• Do not use any or unnecessary type assertions to hide an API mismatch.

Renderer and Context

• Re-export or alias the upstream unstable renderer when its slot structure is already correct.

  export { renderComponentName_unstable as renderComponentName } from '@fluentui/react-component';
  

• Compound renderers must provide the same behavior contexts as the styled component while omitting style contexts.

• Keep portal and positioning behavior semantic. Inline rendering is allowed only when it is the intended headless contract, not as a test shortcut.

Public Exports

Component-Package PR

When the headless primitive needs new base APIs from the corresponding @fluentui/react-* component package, update all applicable surfaces in the middle PR:

1. Export base types from the component implementation barrel, for example ComponentBaseProps, ComponentBaseState, and the existing slots type.
2. Export useComponentBase_unstable from the component implementation barrel.
3. Export the renderer and context/context-values hooks needed by the headless composition. Reuse existing exports; do not create a second equivalent API.
4. Re-export every new public symbol from the component package root library/src/index.ts.
5. Run generate-api and commit the updated library/etc/*.api.md files.
6. Update the component package library/package.json when runtime imports or public entry points change:
   • add every new runtime package to dependencies
   • use the version range already established for that dependency in the workspace; when it is new, derive it from the dependency package's current package.json rather than inventing a range
   • add type-only tooling/test packages to the existing appropriate dependency section only when the repository convention requires it
   • keep dependency keys alphabetized
   • do not add headless-package dependencies to a component package
   • do not introduce dependencies between Tier 3 component packages; move genuinely shared behavior to the appropriate utility/shared-context layer
   • preserve the existing root export map unless adding an intentional new package subpath
   • if a new subpath is added, add matching types, node, import, and require entries and ensure its built files are included by files
   • do not hand-edit package versions
7. If package.json changes, run Yarn through the repository workflow and commit yarn.lock only when Yarn updates it. Never hand-edit yarn.lock.

Adding only a base hook/type export to an existing root entry normally does not require a new package.json export-map entry. It does require root barrel and generated API updates.

Headless-Package PR

Update every required surface in the top PR:

1. library/src/components/ComponentName/index.ts
2. library/src/component-name.ts
3. Parent-family indexes for all public subcomponents, types, events, contexts, hooks, and renderers
4. library/package.json:
   • add the corresponding @fluentui/react-* package to dependencies if it is not already present
   • add any other new runtime dependency used by library source
   • use the dependency version range established elsewhere in the workspace; for a newly referenced workspace package, derive it from that package's current version
   • keep dependency keys alphabetized
   • add exports["./component-name"] with matching types, node, import, and require paths
   • keep component subpath export keys alphabetized, with "./package.json" retained in the package's established position
   • preserve exports["./package.json"]
   • confirm the generic files entries still publish the generated declaration and JavaScript files; update files only if the new artifact falls outside those patterns
   • preserve sideEffects: false only while the new modules remain free of import-time side effects
   • do not add story-only packages, icons, or styling dependencies to the library manifest
   • do not hand-edit the package version
5. Run generate-api and commit the new or updated library/etc/component-name.api.md plus any aggregate API report changed by the export.
6. If package.json changes, run Yarn through the repository workflow and commit yarn.lock only when Yarn updates it. Never hand-edit yarn.lock.

The stories package is private and normally needs no package.json change. Change it only when the story runtime truly needs a new direct dependency or script; do not duplicate dependencies that are already supplied by the workspace's established Storybook setup.

The package intentionally uses kebab-case subpath exports. Keep library/src/index.ts unchanged unless the package's root-export policy changes.

The colocated conformance helper verifies the top-level source file and export map for components that run isConformant.

Bundle-Size Requirements

Bundle-size coverage is required in both PR layers and must be reviewable in the PR that introduces the relevant public API.

Component-Package PR

• Inspect packages/react-components/react-<name>/library/bundle-size/.
• Bundle fixtures are component-level. For a newly public styled component, add a focused <ComponentName>.fixture.js that imports the component from the package root, references it (normally with console.log), and exports a stable fixture name.
• Do not create standalone fixtures for base hooks, renderers, context helpers, or type-only exports.
• For a new public member of an existing family, add a fixture when it can be consumed independently or when the existing family fixture does not import it. Do not assume a nearby fixture covers a new export.
• Type-only exports do not need a bundle fixture because they are erased.
• Keep fixtures focused on public imports. Never import private source paths to make a bundle check pass.
• Run the component package's Nx bundle-size target and inspect the generated report for unexpected growth.

Headless-Package PR

Update library/bundle-size/AllComponents.fixture.js for every new public component subpath:

1. Add import * as ComponentName from '@fluentui/react-headless-components-preview/component-name';.
2. Add ComponentName to the logged object.
3. Keep both lists alphabetized and exactly in sync.

The namespace import intentionally measures the complete public subpath: component, hook, renderer, types erased at compile time, and compound-family exports. A package.json subpath without a matching fixture entry is incomplete, even when build and tests pass.

Run:

yarn nx run react-<name>:bundle-size
yarn nx run react-headless-components-preview:bundle-size

Use yarn nx show project <project> to confirm the component project name. Commit source fixtures, not generated dist/bundle-size or dist/bundle-analyze output.

Tests

Add focused tests beside every public primitive.

Required Coverage

• isConformant for every ref-capable component
• default semantic render and native element behavior
• ref, className, style, as, and slot forwarding where applicable
• every stable data-* attribute:
  • positive state
  • false/absent state
  • exact string value for enum/tri-state attributes
  • consumer override cannot misrepresent reserved state
• ARIA role, state, relationships, and accessible name
• controlled and uncontrolled behavior
• primary interaction and its inverse: open/close, expand/collapse, select/deselect, check/uncheck
• compound context and parent-child coordination
• disabled and disabled-focusable behavior
• keyboard and focus behavior at the appropriate unit or Cypress layer

Prefer Testing Library role/name queries and assert observable behavior. A count or snapshot alone does not prove the contract.

Use the real browser Cypress layer for behavior that jsdom cannot validate reliably, such as focus restoration, arrow navigation, Escape dismissal, positioning, native popovers, and portal composition.

Stories

Stories demonstrate that the unstyled primitive can support an independent design system. Styling belongs only in the stories package.

1. Import from the public package subpath, never a relative library path.
2. Add a short, behavior-accurate ComponentNameDescription.md.
3. Put metadata and exports in index.stories.tsx.
4. Import every CSS Module used by the story family from a story or index.stories.tsx, and import the primary module in index.stories.tsx so the custom "Show code" panel includes the CSS source. No manual source-panel configuration is needed.
5. Include the component family as subcomponents for compound APIs.
6. Add a default story plus stories for important behavioral states.
7. Exercise the primary interaction instead of rendering only static variants. Keep stories demonstrable and cover the resulting role, ARIA, and data state in unit or Cypress tests. Cover the inverse action too; use Cypress when the behavior requires a real browser primitive unavailable to the unit test environment.
8. Use CSS Modules only: no Griffel, inline styles, or Tailwind.
9. Use variables from stories/.storybook/tokens.css; do not hardcode colors, spacing, sizing, typography, radii, shadows, or motion values.
10. Style state through documented data-* selectors and semantic ARIA/native selectors.
11. Preserve native inputs and semantic DOM. Visual indicators may be layered around them, but must not replace them.
12. Use logical properties and verify RTL-sensitive layout; avoid physical left/right properties unless the behavior is intentionally physical.
13. If the story adds transitions or animation, use motion tokens and provide a prefers-reduced-motion override.
14. Preserve visible focus and state affordances in forced-colors mode when the component needs custom borders, indicators, or overlays.
15. Verify focus-visible, disabled-focusable, light theme, and dark theme.

Before finishing story CSS, search the changed modules for raw color functions and un-tokenized pixel/rem values. Reuse an existing token; if a component-local calculation is unavoidable, derive a named CSS custom property from tokens instead of repeating a magic value.

Stories are visual consumers, not part of the headless behavior implementation. Never move story styles or design defaults into library/.

Build both Storybooks, open the new story in a browser, verify the primary interaction and focus behavior, switch light/dark themes, and confirm the custom "Show code" panel displays both the TSX and every referenced CSS Module.

Documentation

Update the component's Storybook description with:

• purpose and composition model
• required parent/child relationships
• accessibility naming requirements
• stable data-* attributes and their values
• any important semantic-slot exception

If the package-level attribute contract changes, update both:

• library/docs/Spec.md
• docs/react-v9/contributing/rfcs/react-components/convergence/headless-components.md

Do not edit an accepted RFC merely to document one component that follows the existing contract.

Three-PR Workflow With gh stack

Use gh stack so reviewers see package-layer changes separately while the headless PR can build against the component base APIs below it.

Stack Shape

master
 └── <prefix>/<component>-test
      └── <prefix>/<component>-base
           └── <prefix>/<component>-headless

• <component>-test PR (base: master) — only regression tests that lock down existing behavior; no production code and no Beachball change file.
• <component>-base PR (base: <component>-test) — only the corresponding @fluentui/react-* component package, its tests/API/bundle fixture, its manifest/lockfile changes, and its Beachball change file.
• <component>-headless PR (base: <component>-base) — only react-headless-components-preview library/stories/docsite-facing changes, its manifest/lockfile changes, its bundle fixture, generated API docs, and its Beachball change file.

If no component-package code change is required because every needed base API is already published, do not create empty test or base PRs. Use one PR for the headless change and state that the upstream export inventory was verified. If a base extraction does not need new regression coverage, omit only the test PR and use a two-PR base/headless stack.

Stack Remote

Select <stack-remote> before initializing: the Git remote whose GitHub repository should host the PRs. Do not assume origin is correct. In a fork checkout, origin often points to the fork while review belongs in microsoft/fluentui. gh stack submit creates PRs in the selected remote's repository and has no separate --repo/base-repository flag.

Verify the selected remote URL and push permission before initializing the stack. If the intended repository is upstream but the contributor can push only to a fork, surface that limitation rather than silently creating PRs in the fork; use the repository's approved cross-fork PR workflow instead.

Drive gh stack non-interactively: always pass explicit branch names, use gh stack submit --auto and gh stack view --json, and pass --remote <stack-remote> to submit/push/sync because this repository normally has more than one remote configured.

Change Files

Each publishable layer generates its own change file against the trunk with an explicit --package, so an inherited down-stack change never leaks into the wrong file:

# middle branch, after editing only the component package and its tests
yarn beachball change --no-commit --branch master \
  --package @fluentui/react-<name> --type minor \
  --message "feat: expose headless base APIs"

# top branch, after editing only the headless library and stories
yarn beachball change --no-commit --branch master \
  --package @fluentui/react-headless-components-preview --type patch \
  --message "feat: add <ComponentName>"

Commit each change file with the files it describes, plus yarn.lock only when Yarn updated it.

The test-only bottom PR does not receive a Beachball change file because it does not alter published output.

Change-File Ownership

• Each published package gets its own Beachball change file in the PR that changes that package.
• The test-only PR must not include a change file.
• The component-package PR must not include the headless package change file.
• The top PR must not include the component package change file.
• Story-only files need no separate change file, but when shipped with a headless library addition they stay in the headless PR.
• Generate change files with yarn change or the non-interactive yarn beachball change form; never create or edit them manually.
• After generation, inspect the new JSON file and verify it contains exactly the owning package and no inherited package from another stack layer.
• New public base exports in stable component packages are normally minor changes. The headless preview package follows zero-semver, so additive headless primitives and exports use patch until that package is stable. Use patch for corrections without new public API as well, and never use major without explicit approval.

Validation

Run tasks through Nx and use the narrowest checks that cover the change:

# bottom test-only PR
yarn nx run react-<name>:test

# middle component-package PR
yarn nx run react-<name>:test
yarn nx run react-<name>:lint
yarn nx run react-<name>:type-check
yarn nx run react-<name>:build
yarn nx run react-<name>:generate-api
yarn nx run react-<name>:bundle-size

# top PR
yarn nx run react-headless-components-preview:test --runTestsByPath \
  packages/react-components/react-headless-components-preview/library/src/components/ComponentName/ComponentName.test.tsx

yarn nx run react-headless-components-preview:lint
yarn nx run react-headless-components-preview:type-check
yarn nx run react-headless-components-preview:build
yarn nx run react-headless-components-preview:generate-api
yarn nx run react-headless-components-preview:bundle-size
yarn nx run react-headless-components-preview:e2e
yarn nx run react-headless-components-preview:test-rit
yarn nx run react-headless-components-preview-stories:lint
yarn nx run react-headless-components-preview-stories:type-check
yarn nx run react-headless-components-preview-stories:build-storybook
yarn nx run react-headless-components-preview-stories:test-ssr
yarn nx run public-docsite-v9-headless:build-storybook

Run e2e when adding or changing browser-dependent interaction tests. Run cross-version React and SSR targets when the component, renderer, portal, or story composition changes. Use yarn nx show project <project> to confirm target names before invoking a target not listed above.

Inspect generated API files and confirm the new stable subpath, hook, renderer, types, context exports, and data-* attributes are present.

Final Checklist

• The implementation contains behavior and accessibility, but no styles, design props, motion, or default icons.
• Upstream base hooks/renderers/context helpers were reused where available.
• Public APIs use stable unsuffixed names.
• Every behavior state intended for styling has a typed, tested, documented data-* attribute.
• Reserved attributes cannot be overridden into a false representation.
• Compound context, refs, controlled state, focus, and keyboard behavior match the styled v9 counterpart.
• Component, family, top-level subpath, package export map, and API docs agree.
• Component-package and headless-package manifest updates are complete, alphabetized, and owned by the correct stacked PR.
• Every newly measured public styled export has component-package bundle coverage, and every new headless subpath is present in AllComponents.fixture.js.
• Unit tests, applicable browser tests, and Storybook stories cover the primary interaction in both directions.
• Story styling uses CSS Modules and token variables only, includes reduced motion/forced-colors handling where applicable, and appears in "Show code".
• The stack contains separate regression-test, component-package, and headless PRs unless a layer is demonstrably unnecessary.
• Each published package has a Beachball change file in its owning PR.