ADR 0005: Use Basecoat and one OpenAgents component system

Date: 2026-08-20

Status: Accepted

Context

The application previously combined DaisyUI, hand-written classes, and persona-named component wrappers. Conflicting cascade layers made variants render incorrectly and created multiple ways to build the same control.

Decision

Use the pinned, vendored Basecoat component CSS as the structural foundation and one OpenAgents style pack for product identity. Import only the Basecoat component files that a surface uses. Wrap the system in one Phoenix component module and use those components before adding surface-specific markup.

Do not add DaisyUI, another component library, remote fonts, icon fonts, or a second Markdown presentation stack. The generic component module is OpenAgentsWeb.UI, and the product style pack is assets/css/openagents.css. Keep Sarah-specific visual copy only where it identifies the persona.

Consequences

• Components share one variant, accessibility, token, and interaction model.
• Vendored Basecoat remains separately licensed and must not be patched in place.
• The application owns its identity in the style pack rather than in vendored source.
• Component and screenshot regression tests can target one catalog.