Imported from equinor/fusion-skills (skills/fusion-developer-app/SKILL.md) via skills.sh. Install upstream with npx skills add equinor/fusion-skills --skill fusion-developer-app. Copyright stays with the author (MIT).

Fusion App Development

When to use

Use this skill when developing features, components, hooks, services, or types for a Fusion Framework React application.

Typical triggers:

• "Add a component / hook / service / page for ..."
• "Wire up the API"
• "Configure a Fusion module"
• "Which Fusion Framework hook / package should this app use?"
• "Persist this preference as an app setting"
• "Add bookmark / analytics / feature flag support"
• "Add a chart / people picker / person column to AG Grid"
• "How do I write a custom Fusion Framework module?"
• "Should this be a Fusion module or a React context?"
• "Write tests for this Fusion component / hook / route"
• "Mock auth, context, feature flags, or HTTP in this test"

Implicit triggers:

• Building in src/
• References Fusion Framework modules, EDS, @equinor/fusion-react-*, or styled-components
• References app settings, bookmarks, analytics, app.config.ts
• Adding route, page, or data-fetching layer
• Adding or updating *.test.ts / *.test.tsx, vitest.config.ts, or Fusion test fixtures
• References charting: @equinor/fusion-framework-react-ag-charts, chart.js, react-chartjs-2

When not to use

Do not use this skill for:

• Issue authoring/triage → fusion-issue-authoring
• Skill authoring → fusion-skill-authoring
• Backend/service changes (separate repo)
• CI/CD or deployment config
• Architecture docs (use ADR template)

For Fusion Framework package ownership, hook behavior, or example discovery → use fusion-research first.

Required inputs

Mandatory

• What to build: feature, component, hook, or service description
• Where it fits: layer (component, hook, service, type) and parent/sibling context

For ambiguous requests, consult assets/follow-up-questions.md before implementing.

Conditional

• API endpoint details when the feature involves data fetching
• Design/layout specifics when building visual components
• Fusion module name when extending module configuration
• Whether state should persist per-user, be shareable via bookmark, or stay runtime-only
• Expected test layer: pure logic, hook, component, route, complete app, or module graph
• External boundaries tests must seed: auth, context, services, feature flags, bookmarks, or HTTP

Instructions

Step 1 — Discover project conventions

Inspect target repo before writing code:

1. Read package.json — package manager (bun/pnpm/npm), scripts, dependencies.
2. Read tsconfig.json — TypeScript settings, path aliases.
3. Scan src/ — directory layout, layer structure.
4. Check docs/adr/ or contribute/ for project-specific code standards.
5. Check formatter/linter config (biome.json, .eslintrc, prettier).
6. Read app.config.ts and app.manifest.ts — endpoints, environment setup.
7. Delegate uncertain Fusion Framework behavior, package ownership, or cookbook examples to fusion-research before writing code.

Adapt to discovered conventions. references/ patterns are defaults — defer to project-specific rules when they differ.

Step 2 — Plan the implementation

New app from scratch → use assets/new-app-checklist.md.

1. Break into discrete files/changes.
2. Map to correct directory. Typical Fusion app:
   • src/components/ — React components (presentation layer)
   • src/hooks/ — Custom React hooks (state and side-effect logic)
   • src/api/ — API clients, data transforms, business logic
   • src/types/ — TypeScript interfaces, type aliases, enums
   • src/routes.ts — Route definitions (when using Fusion Router)
   • src/config.ts — Fusion module configuration
   • src/App.tsx — Root component, layout shell
3. Identify shared types early — define before referencing.
4. Project uses routing → follow references/using-router.md for DSL + page patterns.
5. Different structure → follow it.

Step 3 — Implement following code conventions

Follow project code standards from Step 1. For naming, TSDoc, inline comments, type patterns, code style, error handling → defer to fusion-code-conventions.

For convention questions during implementation, invoke fusion-code-conventions directly.

Step 4 — Style with styled-components, EDS, and Fusion React components

Follow references/styled-components.md, references/styling-with-eds.md, references/using-fusion-react-components.md:

• Use styled-components for custom styling (Fusion convention).
• No CSS Modules, global CSS, Tailwind, or alternative CSS-in-JS unless project uses them.
• Use Styled object pattern for co-located styled components.
• Prefer EDS (@equinor/eds-core-react) for standard UI.
• Use EDS design tokens (@equinor/eds-tokens) for colors, spacing, typography.
• Extend EDS with styled() for customization.
• Use @equinor/fusion-react-* for domain needs not in EDS (person display/selection, side sheets, progress).
• Inline style props: one-off tweaks only.
• For page/view structure (shell composition, layout zones, empty/loading states), invoke agents/design.md. For component-level EDS styling, invoke agents/styling.md.

Step 5 — Wire up data fetching (when applicable)

Follow references/configure-services.md, references/using-react-query.md, references/configure-mocking.md:

• Register HTTP clients via configureHttpClient in config.ts or app.config.ts.
• Access clients with useHttpClient(name) from @equinor/fusion-framework-react-app/http.
• Prefer @equinor/fusion-framework-react-app/* hooks over direct module access. Reserve framework.modules.* for non-React contexts.
• React Query: wrap useQuery in thin custom hooks.
• Query keys: derived from API path + parameters.
• Keep client UI state in React state/context, not server-state libs.

Step 6 — Configure Fusion modules (when applicable)

Identify which module the user needs, then read only the matching reference:

• Module setup in config.ts via AppModuleInitiator callback.
• Access modules via hooks: useAppModule, useHttpClient, useCurrentContext.
• Register HTTP endpoints in app.config.ts for new API integrations.
• Enable navigation with enableNavigation in config.ts when app uses routing.
• Define routes via Fusion Router DSL (layout, index, route, prefix) for auto code splitting.
• Unclear framework API → use fusion-research before choosing implementation pattern.

Step 7 — Add or update tests

Follow references/testing.md. Use agents/testing.md for focused test creation, maintenance, and execution. It routes framework setup/rendering to fusion-framework-testing and module/HTTP state to fusion-framework-mocking.

Step 8 — Validate

Use assets/review-checklist.md as post-generation checklist.

1. Run typecheck (bun run typecheck or pnpm typecheck) — zero errors.
2. Run lint/format check — zero violations.
3. Every new exported symbol has TSDoc.
4. Styling follows project conventions.
5. No new dependencies unless justified/approved.

Expected output

• New/modified src/ files following project layer structure.
• All files pass typecheck + lint.
• Every exported function, component, hook, and type has TSDoc.
• Styling follows project conventions.
• Tests cover changed behavior using fusion-framework-testing; test-time Fusion state uses fusion-framework-mocking where needed.
• Brief summary of what changed and why.

Helper agents

Optional helpers in agents/. Use for focused review or mid-implementation guidance. Runtimes without skill-local agents apply criteria inline.

Companion skills:

• fusion-research for source-backed Fusion ecosystem research when implementation is blocked by uncertainty.

• fusion-framework-testing for Fusion Framework React test setup, fixtures, rendering, and troubleshooting.

• fusion-framework-mocking for deterministic module state and HTTP/OpenAPI boundaries in tests.

• agents/testing.md — creates, maintains, and executes app tests; routes to testing/mocking companion skills. Use for changed behavior, test files, fixtures, config, or failures.

• agents/framework.md — Fusion Framework integration: modules, HTTP clients, bootstrap, runtime config, settings, bookmarks, analytics. Prefers mcp_fusion_search_framework; falls back to mcp_fusion_search_docs. Consult when wiring config.ts, app.config.ts, or framework module access.

• agents/styling.md — EDS component selection, styled-components, design tokens, accessibility. Prefers mcp_fusion_search_eds. Consult when building/modifying visual components.

• agents/design.md — page/view structure: Fusion Portal shell composition, layout zones, side panel usage, empty/loading state patterns. References equinor-design-system for layout ground truth. Delegates component-level checks to agents/styling.md. Consult when scaffolding new pages or layout wrappers.

• agents/data-display.md — AG Grid vs AG Charts, module setup, column defs, chart options, integrated charting. Prefers mcp_fusion_search_framework. Consult for grids, charts, dashboards. Use assets/charts-decision-matrix.md for library selection.

• agents/person-components.md — @equinor/fusion-react-person: PersonAvatar, PersonCard, PersonListItem, PersonPicker, PeoplePicker, PeopleViewer, PersonCell (AG Grid). DOM event pattern, valueGetter setup, pitfalls. Consult for any person display, search, or selection UI.

• agents/code-quality.md — delegates convention checks (naming, TSDoc, TS strictness, intent comments) to fusion-code-conventions, aggregates findings. Run on every new/modified file before finalizing.

Safety & constraints

• No new dependencies without explicit approval.
• No direct DOM manipulation — use React patterns.
• No any types — TypeScript strict mode standard.
• No secrets or credentials in source files.
• Conventional commits (feat:, fix:, refactor:, etc.).
• No infrastructure files (docker-compose, CI config) unless explicitly asked.