diff --git a/.github/workflows/quality-gate.yml b/.github/workflows/quality-gate.yml
new file mode 100644
index 00000000..a2eb43ad
--- /dev/null
+++ b/.github/workflows/quality-gate.yml
@@ -0,0 +1,166 @@
+name: Quality Gate
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: quality-gate-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  changes:
+    name: Detect changed areas
+    runs-on: ubuntu-latest
+    outputs:
+      frontend: ${{ steps.changed.outputs.frontend }}
+      backend: ${{ steps.changed.outputs.backend }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Detect frontend and backend changes
+        id: changed
+        env:
+          EVENT_NAME: ${{ github.event_name }}
+          PR_BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          PR_HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+          PUSH_BASE_SHA: ${{ github.event.before }}
+          PUSH_HEAD_SHA: ${{ github.sha }}
+        run: |
+          set -euo pipefail
+
+          if [ "$EVENT_NAME" = "pull_request" ]; then
+            base_sha="$PR_BASE_SHA"
+            head_sha="$PR_HEAD_SHA"
+          elif [ "$EVENT_NAME" = "push" ] && [ -n "$PUSH_BASE_SHA" ]; then
+            base_sha="$PUSH_BASE_SHA"
+            head_sha="$PUSH_HEAD_SHA"
+          else
+            base_sha=""
+            head_sha=""
+          fi
+
+          if [ -n "$base_sha" ] && [ "$base_sha" != "0000000000000000000000000000000000000000" ]; then
+            changed_files=$(git diff --name-only "$base_sha" "$head_sha")
+          else
+            changed_files=$(git ls-files)
+          fi
+
+          frontend=false
+          backend=false
+
+          if printf '%s\n' "$changed_files" | grep -Eq '^frontend/'; then
+            frontend=true
+          fi
+          if printf '%s\n' "$changed_files" | grep -Eq '^backend/'; then
+            backend=true
+          fi
+
+          {
+            echo "frontend=$frontend"
+            echo "backend=$backend"
+          } >> "$GITHUB_OUTPUT"
+
+          echo "frontend=$frontend backend=$backend"
+
+  frontend:
+    name: Frontend checks
+    needs: changes
+    if: needs.changes.outputs.frontend == 'true'
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    env:
+      CI: 'true'
+    defaults:
+      run:
+        working-directory: frontend
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 24
+          cache: npm
+          cache-dependency-path: frontend/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Check formatting
+        run: npm run format:check
+
+      - name: Lint
+        run: npm run lint
+
+      - name: Typecheck
+        run: npm run typecheck
+
+      - name: Test
+        run: npm run test
+
+      - name: Build
+        run: npm run build
+
+  backend:
+    name: Backend checks
+    needs: changes
+    if: needs.changes.outputs.backend == 'true'
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    defaults:
+      run:
+        working-directory: backend
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v8.3.2
+        with:
+          enable-cache: true
+
+      - name: Setup Python
+        run: uv python install 3.12
+
+      - name: Install dependencies
+        run: uv sync --frozen
+
+      - name: Ruff
+        run: uv run ruff check .
+
+      - name: Import-linter
+        run: uv run lint-imports
+
+      - name: Pytest
+        run: uv run pytest -q
+
+  quality-gate:
+    name: Quality gate
+    if: always()
+    needs: [changes, frontend, backend]
+    runs-on: ubuntu-latest
+    steps:
+      - name: Require all relevant checks
+        env:
+          CHANGES_RESULT: ${{ needs.changes.result }}
+          FRONTEND_RESULT: ${{ needs.frontend.result }}
+          BACKEND_RESULT: ${{ needs.backend.result }}
+        run: |
+          set -euo pipefail
+          for result in "$CHANGES_RESULT" "$FRONTEND_RESULT" "$BACKEND_RESULT"; do
+            case "$result" in
+              success|skipped) ;;
+              *) echo "::error::A required CI job ended with result: $result"; exit 1 ;;
+            esac
+          done
diff --git a/vercel.json b/vercel.json
new file mode 100644
index 00000000..b61f0735
--- /dev/null
+++ b/vercel.json
@@ -0,0 +1,14 @@
+{
+  "$schema": "https://openapi.vercel.sh/vercel.json",
+  "framework": "vite",
+  "installCommand": "npm --prefix frontend ci",
+  "buildCommand": "npm --prefix frontend run build",
+  "outputDirectory": "frontend/dist",
+  "ignoreCommand": "test ! -d frontend || git diff --quiet HEAD^ HEAD -- frontend/ vercel.json",
+  "rewrites": [
+    {
+      "source": "/(.*)",
+      "destination": "/index.html"
+    }
+  ]
+}