Before anything else: read $HOME/.agentic-workflow/toolkit/skills/_preamble.md and follow it (skill index, provider capability map, bootstrap check, session context). Run its Session Close section when this skill finishes.

Design context: read $HOME/.agentic-workflow/toolkit/skills/_design-preamble.md and follow it before continuing.

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Design Evolve — Merge New Reference into Design Language

Analyze a new reference site mid-project and selectively merge its design elements into the existing design language. Shows a diff of what would change, lets the user choose what to adopt.

Step 1: Validate Prerequisites

Both .impeccable.md and design-tokens.json must exist. If either is missing:

"No existing design language found. Run /design-analyze and /design-language first to establish a baseline before evolving."

Step 2: Validate URL

Validate that the <url> argument starts with http:// or https:// and contains only URL-safe characters: letters, digits, :, /, ., -, _, ~, ?, =, %, +, @, ,.

Reject any URL containing characters outside this allowlist.

If validation fails:

"Invalid URL: <url>. URLs must start with http:// or https:// and may only contain URL-safe characters (a-zA-Z0-9 and :/.\\-_~?=%+@,). Offending characters: <list of disallowed characters found>."

Step 3: Run Dembrandt on New URL

Pin the extractor output to a known path so the diff reads an exact file — never a guessed filename. <host> is the URL's hostname (e.g. https://linear.app/features → linear.app). One Bash invocation (shell state does not persist between calls):

SHARED_DIR="$HOME/.agentic-workflow/toolkit/skills/_shared"
source "$SHARED_DIR/repo-slug.sh"
mkdir -p "$AW_DIR/design/raw"
npx dembrandt <url> --dtcg --out "$AW_DIR/design/raw/<host>.json"

Verify the pinned file exists and is non-empty; if not, report the dembrandt error and stop. Then Read ~/.agentic-workflow/<repo-slug>/design/raw/<host>.json — this exact file is the merge input.

Step 4: Merge (shared algorithm)

Read $SHARED_DIR/token-merge.md and follow it exactly:

• Step A — category diff table (NEW / DIFFERENT / UNCHANGED) against current design-tokens.json
• Step B — Ask the user Adopt / Adapt / Ignore per group; Adapt requires the follow-up Ask the user capturing the literal replacement value
• Step C — write merged design-tokens.json; unconditionally append the consultation to .impeccable.md ## Sources; set baseline_stale in screens.json when anything was adopted or adapted
• Step D — report counts and exact before→after values

The pinned design/raw/<host>.json is kept — do not delete it.

Next steps

• /design-mockup-web — rebuild mockups with the updated tokens (existing baselines are now marked stale)
• /design-refine — apply the evolved language to existing screens