vaadin-skills - SKILL.md Agent Skill

name: vaadin-skills description: "Use when: writing, styling, fixing, or reviewing Vaadin UI code in owlcms_67 (Vaadin Flow, Java server-side) — layouts, forms/Binder, Grid/ComboBox data providers, theming, routing/navigation, security, or Vaadin tests. Keywords: Vaadin, Flow, Vaadin 25, HorizontalLayout, VerticalLayout, FlexLayout, AppLayout, Binder, GridField, Grid, ComboBox, data provider, Lumo, Aura theme, route, TestBench, Browserless. This skill points to the official Vaadin agent-skills and the Vaadin MCP server."

Vaadin Skills (pointer)

owlcms is a Vaadin Flow application (server-side Java, package app.owlcms.nui.*). For Vaadin-specific work, prefer the authoritative Vaadin guidance over guessing.

1. Vaadin MCP server (already available in this workspace)

This workspace already exposes the Vaadin MCP tools. Use them first for version-accurate component APIs, styling, and docs (load them with tool_search if they are deferred):

mcp_vaadin_get_component_java_api — Flow (Java) component API
mcp_vaadin_get_component_web_component_api — underlying web component API
mcp_vaadin_get_component_styling / mcp_vaadin_get_theme_css_properties — styling/theme tokens
mcp_vaadin_search_vaadin_docs / mcp_vaadin_get_full_document — docs search/fetch
mcp_vaadin_get_vaadin_primer — high-level primer
mcp_vaadin_get_components_by_version / mcp_vaadin_get_latest_vaadin_version — version info

Because owlcms is Flow / Java, prefer the Java API tools. Ignore React/Hilla client-side guidance unless a task is explicitly about a client-side view.

2. Official Vaadin agent-skills

Source of truth: https://github.com/vaadin/agent-skills

These are designed for Vaadin 25 apps and installed with the vercel-labs/skills CLI. To pull the full skill content locally (creates/updates a skills folder):

# all skills
npx skills add vaadin/agent-skills

# only the ones relevant to a Flow/server-side app like owlcms
npx skills add vaadin/agent-skills \
  --skill forms-and-validation \
  --skill data-providers \
  --skill vaadin-layouts \
  --skill responsive-layouts \
  --skill reusable-components \
  --skill views-and-navigation \
  --skill theming \
  --skill frontend-design \
  --skill security \
  --skill third-party-components \
  --skill ui-unit-testing \
  --skill testbench-testing

Available skills and when to use them

Relevant to owlcms (Vaadin Flow):

vaadin-layouts — HorizontalLayout, VerticalLayout, FlexLayout, AppLayout, spacing, sizing, alignment. Note: be careful with setFlexGrow / setFlexShrink.
responsive-layouts — responsive desktop/mobile layouts.
forms-and-validation — Binder-based forms, validation, converters, submission.
data-providers — Grid/ComboBox data providers, lazy loading, filtering, sorting, pagination.
reusable-components — splitting large Flow views into focused reusable components.
views-and-navigation — views, routes, router layouts, navigation menus, URL parameters.
theming / aura-theme — Aura and Lumo theme customization.
frontend-design — polished UI beyond default theme styling.
security — Spring Security, route access control, login/logout, roles, OAuth2.
third-party-components — integrating third-party web/React components into Flow.
ui-unit-testing — fast browser-free Browserless view tests.
testbench-testing — end-to-end browser tests with TestBench.
signals — Vaadin Signals reactive state (mostly client-side; rarely needed in owlcms Flow code).

Mostly NOT relevant to owlcms (client-side React/Hilla):

client-side-views — React/Hilla views, file-based routes (owlcms uses Flow, not Hilla).

3. owlcms-specific Vaadin guidance

Do not create Vaadin UI objects in unit tests — see the add-test-case skill.
OwlcmsSession.getLocale() / OwlcmsSession.withFop() rely on UI.getCurrent(); capture values on the UI thread before entering background threads/callbacks (see copilot-instructions).
After editing Java, validate with the verify-java-fix skill (get_errors), do not run Maven without explicit consent.