Commonly Design

This skill is a thin pointer — the actual design system lives in the commonly repo at frontend/design-system/. Always read those files when invoked, then apply.

Workflow

1. Read first — every time this skill triggers:
   • docs/design/signal-identity.md — the identity as a system (Signal, chosen 2026-09-03): five rules, the complete grey ramp, state grammar, component grammar with exact values, copy rules, the process that made it land, how to add a screen. Read this FIRST for anything visual.
   • frontend/design-system/README.md — voice, content rules, visual fundamentals, iconography, layout, animation; § Identity: Signal is the short form of the doc above
   • frontend/design-system/tokens.css — the canonical token set as portable CSS
   • frontend/src/v2/v2.css (top of file, the .v2-root { ... } block) — the production tokens that ship today
2. Match tokens to use case — pick the smallest set of tokens that fit. Don't introduce new colors, sizes, or radii without strong reason; the system is intentionally tight.
3. Apply through var(--v2-*) — never hardcode hex values in v2 components. If a hex appears in a diff, that's almost always a bug.
4. Cross-check brand voice — read the "Content fundamentals" section in the README. Sentence case, no emoji, em-dashes, agents-by-name.

The two sources of truth and how they relate

File	What it is	Who reads it
frontend/src/v2/v2.css	Production tokens — what actually ships, scoped under .v2-root	The browser
frontend/design-system/tokens.css	Same tokens as portable --c-* CSS — for HTML mocks, design-review pages, cross-tool skill use	Designers, mocks, this skill
frontend/design-system/README.md	The system's spec — voice, visual fundamentals, layout (incl. the .v2-root app-shell scroll-containment rule), iconography	Humans + agents during design work
frontend/design-system/preview/*.html	One-card-per-concept review pages — open in a browser to see live samples	Anyone reviewing the system
frontend/design-system/assets/commonly-mark.svg	Brand mark — uses currentColor so it inherits the surface	V2NavRail, marketing, login

Hard rule: when one moves, the other moves in the same PR. If you change a token in v2.css, change it in tokens.css too (and vice versa). If they drift, v2.css is what the user sees but the system has lost its source of truth — fix it immediately.

What the system says (read the README for the full version)

One colour, two volumes. Cobalt #1d3fd1 is the only accent. Front door (landing, connect, create account, invite): cobalt as BLOCKS. Inside the app: cobalt as MARKS — live dot, agent name in mono, link, focus edge, the 2px ring on the card that needs you. Per docs/design/signal-identity.md §1–3, an open decision card's primary option is cobalt; secondary options are bordered and Other… is cobalt text. Ordinary filled actions use ink #101828; this does not make every action a filled button. Match the screen artboard's control hierarchy (Activity Reply/Open are bordered).

Three faces, one job each. Bricolage Grotesque 700/800 for display (−0.03em), IBM Plex Sans 400/500/600 for body and controls (14/20), IBM Plex Mono 500 for meta (ids, times, counts, status, commands). Self-hosted via @fontsource; the pre-Signal SF-first stack is gone.

Hard edges, no shadows. Radius 4 on controls, rows, chips, avatars (4px squares, never circles); 6 on cards and panels. No shadow anywhere; a pending card is a 2px cobalt ring, not a lift.

No emoji in chrome. Emoji are user-generated content only.

No gradients in chrome. Solid surfaces, only.

Tight letter-spacing on big text. Feature titles -0.03em at weight 850. Body stays at 0.

Sentence case for buttons, nav, section titles. UPPERCASE only for kickers (NOW, LEAD, CURRENT TASK).

Calm motion. 80ms hover, 120ms card hover, 300ms layout. No bounces, no springs, no entrance animations.

Before you draw or build a screen (the process that made Signal land)

1. Canvas first. The artboard exists and Sam has seen it before any component work starts. Copy the nearest artboard, change only the content, keep the helmet block.
2. Directions, when a direction is open: three named candidates, the same product moment, the same fixed copy, so the only variable is the design. Then the chosen one gets clickable on the screen people live in.
3. One system, two volumes. A new screen never needs a new colour, radius or face. If it seems to, the screen is wrong.
4. Ship with proof. The PR carries 1440 and 390 screenshots of the real screen beside its artboard; load-bearing CSS is re-pinned in v2-layout-invariants.test.ts.
5. Survey what is left every few weeks: screenshot every live route into one sheet and give each uncovered screen a call — draw, fold, or delete (Sam rules on deletes).

When you ship a change

1. Tokens — update frontend/src/v2/v2.css + frontend/design-system/tokens.css in the same commit.
2. Brand asset — update both frontend/design-system/assets/ and any in-component reference (e.g. inline SVG in V2NavRail.tsx).
3. README rule change — if you're deviating from a documented rule, update the README in the same PR. The README is the spec; if the spec is outdated, fix the spec.
4. Preview card — if the change is shape-altering (a new component pattern, a new color role), add or update a preview HTML card under frontend/design-system/preview/.

Improving the system

The design system is meant to evolve. The way to evolve it:

• Propose changes through the same files. Don't keep design rules in your head or in scratch docs.
• Document the why in the README when adding a token or rule, not just the what. Someone in 6 months should understand the trade-off.
• Kill old patterns explicitly. When a token is replaced, remove it from both files. Don't leave deprecated values around — agents will pick them up.
• Preview before merge. For any visual change, open the relevant frontend/design-system/preview/*.html in a browser to see it in isolation, plus a v2 page in the app to see it in context.

When in doubt

• For mocks / throwaway prototypes, use frontend/design-system/tokens.css + lucide icons via CDN. Output static HTML the user can open.
• For production v2 code, use var(--v2-*) tokens from v2.css. Match the existing component patterns (V2PodChat, V2PodInspector, V2MessageBubble).
• For new component types, draft a preview card first under frontend/design-system/preview/, then implement against tokens.

Related skills

• frontend-design — Anthropic's public design-judgment skill. Pull it alongside this skill for any new surface or redesign work; this skill carries Commonly's tokens and rules, while frontend-design carries the process that stops templated output.