Components: Generate Toast

[JasonVMo]

Summary

Generate Toast with its canonical contract, implementation, tests, stories, platform validation, and explicit package export so transient status feedback is available. The local spec is missing, and delivery also depends on shared overlay placement plus the cross-platform status-icon source established by MessageBar.

Observed. toast is entry toast in the canonical catalog and has no
implementation in packages/agentic/components. Upstream describes it as: Floating notification surfacing a brief, primarily self-dismissing message on a neutral elevated surface. Status is carried by a swappable icon rather than the surface, only the title is required, and an optional progress bar doubles as the auto-dismiss countdown or an action's loading state. Composes ProgressBar, Link, and Button.

Goal

Generate the toast component in
packages/agentic/components/src/components against the
canonical Fluent Flex spec, with the colocated coverage, stories, and platform
validation the package requires, and export it explicitly from
src/index.ts.

Stage

Stage 2 (beta). Wave 2 - overlay and popover stack.

Why it matters

Observed. The canonical catalog has 50 components and the agentic library has
generated 18. toast is one of the 32 in the gap, enumerated in
the missing-components index.

Inferred. It belongs to the overlay stack, which is the largest single cluster of blocked components. Delivering the cluster converts a broad "not implementable" state into ordinary component work.

Observed current state

Canonical spec and source

Field	Value
Canonical spec	plugins/components/skills/toast/SKILL.md with usage.md, web/tokens.yaml, web/accessibility.md, and web/interaction.md, at x3-design/fluent-design @ d334acf
Upstream tier	molecule
Upstream catalog key	toast in component-map.yaml
Local staged spec	None. No specs/toast folder exists; the spec must be ingested first
Local implementation	None. No src/components/toast directory exists

Closest existing FURN or V1 implementation

• packages/components/Notification - Notification.tsx, Notification.styling.ts, Notification.helper.tsx, and NotificationTokens.ts - the closest legacy equivalent. NotificationTokens.ts is the cross-platform and desktop path; NotificationTokens.ios.ts is a mobile-only override.

Note on platform canon. Where a legacy package has platform-specific files, the
desktop path (.win32, .windows, .macos, or the unsuffixed cross-platform file)
is the compatibility reference. .ios, .android, and .mobile variants are not
treated as the cross-platform canonical implementation.

Local dependencies

• src/components/progress-bar - Observed present (component).
• src/components/button - Observed present (component).

Known blockers

Observed. There is no recorded blocker, because there is no local spec folder and therefore no
blockers.md. The absence of an ingested spec is itself the first blocker; see
spec-ingestion-and-generation.md.

Scope

• Ingest or promote the spec into the component directory in the generated shape
  (SPEC.md plus a spec/ folder), per
  spec-ingestion-and-generation.md.
• Establish the public contract first: variants, slots, native props, accessibility,
  interaction states, and platform behavior.
• Implement the required file structure from
  src/components/AGENTS.md:
  toast.types.ts, toast.styles.ts, use*.ts, use*Styles.ts, render*.tsx, and
  the assembly module with a displayName.
• Style from Flex tokens first and record genuine token gaps rather than substituting
  unrelated values.
• Export the component, its public types, and the state, style, and render stages
  explicitly from src/index.ts under component-qualified unstable names.
• Decide the host model: toasts need a positioned, stacked container that outlives any single component, which is a different overlay shape from an anchored popover.
• Consume the cross-platform status icon source owned by
  message-bar; do not solve it twice.
• Depends on link for the inline action link described upstream.

Out of scope

• Changing the contract of an existing generated component, unless this task explicitly
  calls for it above; raise it as its own item.
• Building shared infrastructure owned by another task: overlay hosting
  (popover), roving focus (focus-zone.md), spec
  ingestion (spec-ingestion-and-generation.md),
  or the coverage contract (component-test-strategy.md).
• Migrating any legacy FURN consumer onto this component.
• Mobile platform support; the applicable upstream companion is web, retargeted to
  React Native for Windows and macOS.

Deliverables

• src/components/toast/ implementing the full required file structure.
• SPEC.md and a spec/ companion folder with provenance recording the upstream path,
  SHA, and ingestion date.
• Colocated toast.test.tsx, toast.types.test.ts, and toast.stories.tsx.
• Snapshot coverage where the visual contract is state-dependent, or a recorded
  exemption.
• Explicit exports from src/index.ts, with src/index.test.ts updated.
• A changeset, per the repository's version management rules.
• A recorded readiness level with its supporting evidence.

Required coverage, stories, and platform validation

Runtime and type coverage:

• Title only, and title with body, action, and dismiss.
• Each status icon.
• Auto-dismiss countdown driven by the progress bar, asserted with fake timers.
• Manual dismiss cancels the countdown.
• Announcement semantics appropriate to a transient notification.
• Stacking of multiple toasts, if the host model supports it.
• User style and handler forwarding, and that user styles are applied after component
  styles.
• Compile-time slot acceptance and any mutually exclusive props.

Stories: a typed Meta titled Components/Toast, an args-driven Default, a
grouped Overview when the contract has several axes, one focused story per variant
axis, and an interactive story for each stateful axis. Self-driving axes expose
default<State> as the control; externally driven selection is owned by the story with
React.useState. Identity-changing axes are not exposed as controls.

Platform validation: the component's stories render and behave correctly on macOS
and on React Native Windows Fabric through apps/storybook,
including hover, pressed, disabled, focus, optional-slot, and constrained-content
scenarios. Add a stable root testID if the component joins the automated smoke set.

Acceptance criteria

• src/components/toast exists with the required file structure and a displayName.
• Every variant axis in the component's SPEC.md is implemented, or a deviation is recorded in the spec.
• The component styles from Flex tokens, with any genuine token gap recorded rather than approximated.
• Focus feedback renders through FocusVisual; no outline* props and no React Native Windows native focus visuals are introduced.
• State precedence is explicit: disabled wins over pressed, which wins over hovered.
• Every stateful axis is classified as self-driving or externally driven, and both paths are covered.
• Runtime, type, and story coverage satisfy the package coverage contract.
• The component, its public types, and its pipeline stages are exported explicitly from src/index.ts, and src/index.test.ts covers them.
• The component's stories render on macOS and on React Native Windows Fabric.
• yarn workspace @fluentui-react-native/components format, lint, build, and test pass, and the Storybook bundle succeeds for both desktop platforms.
• A readiness level is recorded with its supporting evidence.
• A changeset is included.

Dependencies and ordering

• Blocked by spec-ingestion-and-generation.md: the spec must be pulled from the pinned upstream revision before generation can start.
• Blocked by popover for the overlay host, anchoring, light dismiss, and focus return.
• Gated by component-test-strategy.md: the component must satisfy the coverage contract on arrival rather than being retrofitted.
• Gated by readiness-model.md: the target readiness level must be stated before the work starts.
• Consumes the Infrastructure workstream (storybook-e2e.md) for automated macOS and Windows Fabric validation; until it lands, platform validation is manual.

Risks and open decisions

1. A toast host is app-level state, which sits uneasily with a component library whose source boundary excludes app infrastructure. Decide whether FURN ships the host or only the surface.
2. Auto-dismiss timing plus screen-reader announcement is an accessibility hazard; the dismiss duration should be caller-controllable.

Evidence and references

• Upstream spec: plugins/components/skills/toast/SKILL.md and
  components-index/SKILL.md
  at x3-design/fluent-design @ d334acf.
• Canonical implementations to follow: src/components/button
  for a styled higher-order component and src/primitives/icon
  for a primitive.
• Authoring rules: src/components/AGENTS.md and the
  agentic component authoring skill.
• Workstream context: Components README and
  the missing-components index.

Sources retrieved 2026-08-20.