diff --git a/client/package.json b/client/package.json
index c1a9f6d3..d2c72c09 100644
--- a/client/package.json
+++ b/client/package.json
@@ -17,6 +17,8 @@
     "lint": "eslint .",
     "lint:check": "eslint .",
     "lint:pages": "node scripts/check-page-pattern.mjs",
+    "theme:lint": "node scripts/theme-lint.mjs",
+    "theme:lint:strict": "node scripts/theme-lint.mjs --strict",
     "e2e": "playwright test",
     "e2e:report": "playwright show-report",
     "format": "prettier --write \"src/**/*.tsx\" \"src/**/*.css\"",
diff --git a/client/scripts/theme-lint.mjs b/client/scripts/theme-lint.mjs
new file mode 100644
index 00000000..adb72e0e
--- /dev/null
+++ b/client/scripts/theme-lint.mjs
@@ -0,0 +1,73 @@
+#!/usr/bin/env node
+/*
+ * theme:lint — guards the appearance token system.
+ *
+ * Flags styling that bypasses the design tokens and therefore won't follow a
+ * user's chosen scheme / transparency / text-size:
+ *   - inline color literals  (color: '#111', background: 'rgba(...)', boxShadow: '...rgba...')
+ *   - inline numeric fontSize (fontSize: 13)
+ *   - arbitrary-value Tailwind color classes (bg-[#..], text-[rgba(..)])
+ *
+ * ALLOWED (never flagged): var(--token) inline styles, bg-[var(--..)] classes,
+ * and genuinely dynamic values (data-driven colors, computed sizes/positions).
+ *
+ * Mirrors the i18n:parity gate. Default mode reports a baseline and exits 0;
+ * `--strict` exits non-zero when any violations remain (for once the backlog is
+ * burned down, or wired to changed files only). Add `theme-lint-disable` in a
+ * line comment to suppress an intentional exception (map/PDF/brand colors).
+ */
+import { readdirSync, readFileSync, statSync } from 'node:fs';
+import { join, relative } from 'node:path';
+
+let SRC = new URL('../src', import.meta.url).pathname;
+if (process.platform === 'win32' && SRC.startsWith('/')) SRC = SRC.slice(1);
+
+// Surfaces where CSS variables genuinely cannot reach (injected map HTML, WebGL
+// paint, standalone PDF documents) — colors there must stay literal.
+const EXEMPT = [
+  /Mapbox/i, /placePopup/i, /marker/i, /popup/i, /TripPDF/, /JourneyBookPDF/,
+  /MapViewGL/, /MapView\./, /JourneyMapGL/, /reservationsMapbox/, /useAtlas/,
+  /ReservationOverlay/, /\.test\./, /\.spec\./,
+];
+
+const ARB_CLASS = /\b(?:bg|text|border|ring|fill|stroke|from|via|to|shadow|outline|decoration|divide|caret)-\[\s*(?:#|rgba?\(|hsla?\(|oklch\()/;
+const INLINE_COLOR = /(?:color|background|backgroundColor|borderColor|border|borderTop|borderBottom|borderLeft|borderRight|boxShadow|fill|stroke|outline|textDecorationColor)\s*:\s*['"`]?\s*(?:#[0-9a-fA-F]{3,8}\b|rgba?\(|hsla?\(|oklch\()/;
+const INLINE_FONTSIZE = /fontSize\s*:\s*['"`]?\d/;
+
+function walk(dir, files = []) {
+  for (const name of readdirSync(dir)) {
+    const p = join(dir, name);
+    if (statSync(p).isDirectory()) walk(p, files);
+    else if (/\.(ts|tsx)$/.test(name)) files.push(p);
+  }
+  return files;
+}
+
+const strict = process.argv.includes('--strict');
+const offenders = [];
+let total = 0;
+
+for (const f of walk(SRC)) {
+  if (EXEMPT.some((re) => re.test(f))) continue;
+  let count = 0;
+  for (const line of readFileSync(f, 'utf8').split('\n')) {
+    if (line.includes('theme-lint-disable')) continue;
+    if (ARB_CLASS.test(line) || INLINE_COLOR.test(line) || INLINE_FONTSIZE.test(line)) count++;
+  }
+  if (count) {
+    offenders.push([relative(SRC, f).replace(/\\/g, '/'), count]);
+    total += count;
+  }
+}
+
+offenders.sort((a, b) => b[1] - a[1]);
+console.log(`theme:lint — ${total} hardcoded-style hits across ${offenders.length} files (map/PDF excluded).`);
+for (const [f, c] of offenders.slice(0, 20)) console.log(`  ${String(c).padStart(4)}  ${f}`);
+if (offenders.length > 20) console.log(`  … and ${offenders.length - 20} more files.`);
+console.log('\nNew/changed code must use tokens (bg-surface / text-content / bg-accent / var(--..)) and the');
+console.log('text-title/subtitle/body/caption tiers — never inline #hex, never bg-[#..]. See src/theme/README.md.');
+
+if (strict && total > 0) {
+  console.error(`\n✖ theme:lint:strict — ${total} violations remain.`);
+  process.exit(1);
+}