diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index dc5f51b..9b27ab6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -34,6 +34,12 @@ jobs:
       - name: Run release guard audit
         run: COMMON_PLAT="$GITHUB_WORKSPACE/learning_ai_common_plat" bash scripts/release-guard-audit.sh
 
+      - name: Run UI drift ratchet (one-way gate vs scripts/ui-drift-baseline.json)
+        run: bash scripts/ui-drift-ratchet.sh
+
+      - name: Run UI drift audit (report mode, informational)
+        run: bash scripts/ui-drift-audit.sh || true
+
   backend:
     name: Backend — typecheck + test + build
     runs-on: ubuntu-latest
diff --git a/docs/UI_UX_PLATFORM_CORE_ROADMAP.md b/docs/UI_UX_PLATFORM_CORE_ROADMAP.md
index 47c2986..ff0314a 100644
--- a/docs/UI_UX_PLATFORM_CORE_ROADMAP.md
+++ b/docs/UI_UX_PLATFORM_CORE_ROADMAP.md
@@ -190,13 +190,16 @@ The review surface is the highest-value pilot because it is operator-critical an
 
 ### Phase UI8 — Remove Legacy Globals
 
-- [ ] Remove or greatly reduce global `.surface-card`, `.surface-muted`, `.badge`, and `.input-shell` after migrated screens no longer depend on them.
-- [ ] Keep only truly global layout/accessibility utilities such as focus-visible, `sr-only`, skip link, and motion preferences.
-- [ ] Add CI guard for new raw UI drift:
-  - raw form controls outside approved primitives
-  - raw `.badge`/`.surface-*` usage
+- [x] **CI guard for new raw UI drift** — ratchet shipped May 23, 2026. `scripts/ui-drift-ratchet.sh` reads tracked counts from `scripts/ui-drift-baseline.json` and FAILS in CI (`release-guards` job) if any of the four categories regress above baseline:
+  - raw form controls (`<button|<input|<textarea|<select`) outside approved primitives
+  - raw `className="… (badge|surface-card|surface-muted|input-shell) …"` usage
   - hardcoded hex/rgb colors
-  - direct `@bytelyst/ui` imports outside the adapter unless explicitly allowed
+  - direct `@bytelyst/ui` imports outside `web/src/components/ui/Primitives.tsx`
+  Lower the baseline by running `pnpm run audit:ui:ratchet:update` alongside the migration commit that reduced the count.
+- [ ] Drive baseline counts to zero by completing UI5 remainder, UI6, and UI7. Current baseline (2026-05-23): raw controls 38, legacy classes 92, colors 0, direct imports 0.
+- [ ] Remove or greatly reduce global `.surface-card`, `.surface-muted`, `.badge`, and `.input-shell` from `web/src/app/globals.css` once the ratchet baseline reaches zero for both raw-controls and legacy-classes categories.
+- [ ] Keep only truly global layout/accessibility utilities such as focus-visible, `sr-only`, skip link, and motion preferences.
+- [ ] Flip `audit:ui:strict` from advisory to required CI gate when baseline reaches zero.
 - [ ] Verify full web test/typecheck/lint, E2E, and visual smoke.
 
 ## Proposed Component Ownership Matrix
diff --git a/package.json b/package.json
index 5d8279c..bf0fdd3 100644
--- a/package.json
+++ b/package.json
@@ -14,6 +14,8 @@
     "audit:release-guards": "bash scripts/release-guard-audit.sh",
     "audit:ui": "bash scripts/ui-drift-audit.sh",
     "audit:ui:strict": "bash scripts/ui-drift-audit.sh --strict",
+    "audit:ui:ratchet": "bash scripts/ui-drift-ratchet.sh",
+    "audit:ui:ratchet:update": "bash scripts/ui-drift-ratchet.sh --update",
     "dependency:health": "bash scripts/dependency-health.sh",
     "verify": "pnpm run typecheck && pnpm run test && pnpm run build",
     "prepare": "husky"
diff --git a/scripts/ui-drift-baseline.json b/scripts/ui-drift-baseline.json
new file mode 100644
index 0000000..6690054
--- /dev/null
+++ b/scripts/ui-drift-baseline.json
@@ -0,0 +1,7 @@
+{
+  "//": "Baseline UI drift counts captured 2026-05-23 after UI5 settings + modals slice. ui-drift-ratchet.sh compares current counts against these and FAILS if any category EXCEEDS its baseline. To lower the baseline after migrating screens, run scripts/ui-drift-ratchet.sh --update.",
+  "raw_interactive_controls": 38,
+  "legacy_global_surface_classes": 92,
+  "hardcoded_color_literals": 0,
+  "direct_bytelyst_ui_imports_outside_adapter": 0
+}
diff --git a/scripts/ui-drift-ratchet.sh b/scripts/ui-drift-ratchet.sh
new file mode 100755
index 0000000..c5e1c1a
--- /dev/null
+++ b/scripts/ui-drift-ratchet.sh
@@ -0,0 +1,128 @@
+#!/usr/bin/env bash
+# UI drift ratchet — a one-way gate that prevents UI legacy patterns from
+# growing while UI5–UI8 migrations are still in flight.
+#
+# How it works:
+#   - Reads tracked baseline counts from scripts/ui-drift-baseline.json
+#   - Counts current matches per category by re-using the same patterns
+#     as scripts/ui-drift-audit.sh
+#   - FAILS if any category COUNT is GREATER than its baseline
+#   - PASSES (and reports the delta) if counts equal or fall below baseline
+#
+# Usage:
+#   ./scripts/ui-drift-ratchet.sh            # check against baseline (CI mode)
+#   ./scripts/ui-drift-ratchet.sh --update   # rewrite baseline to current counts
+#                                            #   (commit the result with a UI
+#                                            #    migration that lowered them)
+
+set -euo pipefail
+
+ROOT="$(git rev-parse --show-toplevel)"
+cd "$ROOT"
+
+BASELINE_FILE="scripts/ui-drift-baseline.json"
+
+if [[ ! -f "$BASELINE_FILE" ]]; then
+  echo "FAIL: missing $BASELINE_FILE" >&2
+  exit 2
+fi
+
+MODE="check"
+if [[ "${1:-}" == "--update" ]]; then
+  MODE="update"
+fi
+
+# Detect ripgrep availability with a grep fallback (same logic as ui-drift-audit.sh).
+if command -v rg >/dev/null 2>&1; then
+  SEARCH_BACKEND="rg"
+else
+  SEARCH_BACKEND="grep"
+fi
+
+count_matches() {
+  local pattern="$1"
+  shift
+  local n
+  if [[ "$SEARCH_BACKEND" == "rg" ]]; then
+    n=$(rg -n "$pattern" "$@" --glob '!**/*.test.*' 2>/dev/null | wc -l | tr -d ' ')
+  else
+    n=$(grep -rnE "$pattern" "$@" \
+      --include="*.ts" --include="*.tsx" --include="*.js" --include="*.jsx" \
+      --exclude="*.test.*" --exclude="*.spec.*" \
+      --exclude-dir=node_modules --exclude-dir=.next 2>/dev/null | wc -l | tr -d ' ')
+  fi
+  echo "$n"
+}
+
+# Read baseline values. Avoid jq dependency by using grep + sed.
+read_baseline() {
+  local key="$1"
+  grep -E "\"$key\"" "$BASELINE_FILE" | head -1 | sed -E 's/.*: *([0-9]+).*/\1/'
+}
+
+BASE_RAW=$(read_baseline raw_interactive_controls)
+BASE_LEGACY=$(read_baseline legacy_global_surface_classes)
+BASE_COLORS=$(read_baseline hardcoded_color_literals)
+BASE_IMPORTS=$(read_baseline direct_bytelyst_ui_imports_outside_adapter)
+
+CUR_RAW=$(count_matches '<button|<input|<textarea|<select' web/src/app web/src/components)
+CUR_LEGACY=$(count_matches 'className="[^"]*(badge|surface-card|surface-muted|input-shell)' web/src/app web/src/components)
+CUR_COLORS=$(count_matches '#[0-9a-fA-F]{3,8}|rgba?\(' web/src/app web/src/components)
+# For the adapter exclusion, filter out the adapter file post-hoc since we
+# want a stable raw count.
+CUR_IMPORTS_RAW=$(count_matches 'from "@bytelyst/ui"|from '\''@bytelyst/ui'\''' web/src/app web/src/components)
+# Adapter file is allowed to import @bytelyst/ui; subtract one line per
+# import line in Primitives.tsx so the ratchet doesn't drift just because
+# the adapter grows its re-export list.
+ADAPTER_LINES=$(grep -cE 'from "@bytelyst/ui"|from '\''@bytelyst/ui'\''' web/src/components/ui/Primitives.tsx 2>/dev/null || echo 0)
+CUR_IMPORTS=$((CUR_IMPORTS_RAW - ADAPTER_LINES))
+if [[ "$CUR_IMPORTS" -lt 0 ]]; then CUR_IMPORTS=0; fi
+
+if [[ "$MODE" == "update" ]]; then
+  cat >"$BASELINE_FILE" <<JSON
+{
+  "//": "Baseline UI drift counts. Updated $(date -u +%Y-%m-%dT%H:%M:%SZ) by scripts/ui-drift-ratchet.sh --update. Commit alongside the migration that lowered the counts.",
+  "raw_interactive_controls": $CUR_RAW,
+  "legacy_global_surface_classes": $CUR_LEGACY,
+  "hardcoded_color_literals": $CUR_COLORS,
+  "direct_bytelyst_ui_imports_outside_adapter": $CUR_IMPORTS
+}
+JSON
+  echo "Wrote new baseline to $BASELINE_FILE"
+  cat "$BASELINE_FILE"
+  exit 0
+fi
+
+# Compare and report.
+failures=0
+report() {
+  local title="$1"
+  local cur="$2"
+  local base="$3"
+  if [[ "$cur" -gt "$base" ]]; then
+    printf "  ✗ %-50s %4d (baseline %d, +%d) — REGRESSION\n" "$title" "$cur" "$base" "$((cur - base))"
+    failures=$((failures + 1))
+  elif [[ "$cur" -lt "$base" ]]; then
+    printf "  ↓ %-50s %4d (baseline %d, -%d) — progress, run --update\n" "$title" "$cur" "$base" "$((base - cur))"
+  else
+    printf "  = %-50s %4d (at baseline)\n" "$title" "$cur"
+  fi
+}
+
+echo "UI drift ratchet (baseline: $BASELINE_FILE)"
+report "raw interactive controls"               "$CUR_RAW"     "$BASE_RAW"
+report "legacy global surface classes"          "$CUR_LEGACY"  "$BASE_LEGACY"
+report "hardcoded color literals"               "$CUR_COLORS"  "$BASE_COLORS"
+report "direct @bytelyst/ui imports outside adapter" "$CUR_IMPORTS" "$BASE_IMPORTS"
+
+if [[ "$failures" -gt 0 ]]; then
+  echo
+  echo "FAIL: $failures category/categories regressed above baseline." >&2
+  echo "      Migrate the new call site(s) to @bytelyst/ui primitives via" >&2
+  echo "      @/components/ui/Primitives, or — if migration lowered other" >&2
+  echo "      counts — run 'pnpm run audit:ui:ratchet:update' and commit." >&2
+  exit 1
+fi
+
+echo
+echo "OK — no UI drift regressions above baseline."