Design Vision Loop

AI-consumed reference. This skill verifies rendered UI; it does not generate taste (that's frontend-aesthetics) or enforce statically (that's the design-conformance hook + theme-consistency rule). Close the loop: build → see → critique → fix.

Design Vision Loop

Open-loop text guidance is why "correct" UI still looks off — nobody looked at it. This skill adds the eyes: render → screenshot → critique → iterate, the pattern Anthropic endorses for UI agents (Building agents with the Claude Agent SDK: "visual feedback… can be helpful"; computer-use docs: "after each step, take a screenshot and carefully evaluate… only when you confirm a step was executed correctly should you move on").

Precondition

The UI must be renderable: a running dev server URL/route, or a static HTML artifact. If nothing renders (component with no harness), say so and either spin up a preview or fall back to static review — don't pretend to have looked.

The loop (max 3 iterations by default)

loop[4]{step,action,tools}:
  1,Render + capture,"navigate → resize each viewport → screenshot; emulate dark mode, screenshot again"
  2,Tier-1 deterministic gates,"run the design-conformance check + read console errors — cheap, run FIRST"
  3,Tier-2 vision critique,"read the screenshots, score against references/critique-rubric.md"
  4,Verdict,"PASS → done · defects → fix → re-enter step 1 (until pass or budget hit)"

Two-tier verification is deliberate (Anthropic ranks rules-based feedback above LLM-as-judge): the deterministic gate is the strong signal and it's nearly free, so run it before spending a vision call. Only screenshot-critique what already passes the lint-level gate.

Step 1 — capture (Playwright MCP)

• browser_navigate to the route → for each viewport in references/viewport-matrix.md (browser_resize 375 → 768 → 1440) → browser_take_screenshot.
• Dark mode: emulate prefers-color-scheme: dark (via browser_evaluate / an emulation call) and re-screenshot at the primary viewport. If the design system declares no dark mode, skip and note it.
• Save PNGs under .claude/workflow/vision/<route>-<viewport>[-dark].png.

Step 2 — deterministic gates (tier 1)

• Run the design-conformance check over the changed files (hardcoded hex/px vs tokens, mixed component libraries, missing prefers-reduced-motion). Any FAIL → fix before wasting a vision call.
• Read browser_console_messages — runtime errors / failed asset loads are defects regardless of looks.

Step 3 — vision critique (tier 2)

Read the captured screenshots and score against references/critique-rubric.md. Conformance target is .claude/design/design-system.md (palette / type scale / spacing / signature). If a Stitch screen PNG or Figma frame exists, compare at the layout level (structure, hierarchy, spacing rhythm) — not pixel-diff.

Output a verdict, not vibes:

verdict[2]{field,form}:
  status,"PASS | ITERATE"
  defects[]{element,viewport,expected,actual}"

Step 4 — iterate

Fix each defect, re-render, re-capture. Stop at PASS or after the iteration budget (default 3 — raise only if the user asks). If still failing at budget, report the remaining defects honestly rather than looping.

Step 5 — teardown (mandatory)

Call browser_close as soon as you reach PASS or the iteration cap. Do not leave the browser open. The @playwright/mcp Chrome does not close itself — an unclosed browser survives the task and, if the session later exits ungracefully, is orphaned and runs for days (the playwright-reaper SessionStart hook is only the backstop for that leak; closing here is what prevents it). Use the browser, then dispose it.

Output

Write the verdict + screenshot paths + defect log to .claude/workflow/vision-report-<route>.md so a Phase-4 reviewer (or the user) has the visual evidence. Never claim "looks good" without an attached shot.

Budget & honesty

• Screenshots and vision calls cost tokens; the iteration cap and the tier-1-first ordering keep it bounded.
• If you couldn't render, couldn't reach dark mode, or hit the cap — say which. A skipped check reported as passed is the failure mode this skill exists to prevent.

See also: references/critique-rubric.md, references/viewport-matrix.md, rules/agent/design-system-persistence.md (conformance target), skills/frontend-aesthetics/SKILL.md (taste), hooks/design-conformance.cjs (tier-1 gate), skills/stitch-design/SKILL.md (screen PNG targets).