fix(auth): revert store_id to uuid.UUID in user schemas

CTO review feedback: store_id must remain uuid.UUID since Store
model still uses UUIDPrimaryKeyMixin. Only user_id changes to str.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/workflows/ci.yml

@@ -11,16 +11,17 @@ concurrency:
   cancel-in-progress: true
 
 permissions:
-  contents: read
+  contents: write
   packages: write
 
 env:
   REGISTRY: ghcr.io
   IMAGE_NAME: cartsnitch/cartsnitch
+  AUTH_IMAGE_NAME: cartsnitch/auth
 
 jobs:
   lint:
-    runs-on: local-ubuntu-latest-cartsnitch
+    runs-on: runners-cartsnitch
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
@@ -34,7 +35,7 @@ jobs:
         run: npx tsc --noEmit
 
   test:
-    runs-on: local-ubuntu-latest-cartsnitch
+    runs-on: runners-cartsnitch
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
@@ -45,17 +46,57 @@ jobs:
       - name: Run tests
         run: npx vitest run
 
-  build-and-push:
-    runs-on: local-ubuntu-latest-cartsnitch
-    needs: [lint, test]
+  lighthouse:
+    runs-on: runners-cartsnitch
+    needs: [test]
     steps:
       - uses: actions/checkout@v4
-
-      - name: Log in to Docker Hub
-        uses: docker/login-action@v3
+      - uses: actions/setup-node@v4
         with:
-          username: ${{ secrets.DOCKERHUB_USERNAME }}
-          password: ${{ secrets.DOCKERHUB_TOKEN }}
+          node-version: "20"
+          cache: npm
+      - run: npm ci
+      - run: npm run build
+      - name: Install Chromium for Lighthouse
+        run: |
+          npm install -g playwright
+          npx playwright install --with-deps chromium
+      - name: Start preview server
+        run: |
+          npm run preview &
+          npx wait-on http://localhost:4173/ --timeout 30000
+      - name: Run Lighthouse CI
+        run: |
+          CHROME_PATH=$(find /home/runner/.cache/ms-playwright -name chrome -type f 2>/dev/null | head -1)
+          npm install -g @lhci/cli
+          LHCI_CHROME_PATH="$CHROME_PATH" lhci autorun
+
+  build-and-push:
+    runs-on: runners-cartsnitch
+    needs: [lint, test]
+    outputs:
+      calver_tag: ${{ steps.calver.outputs.version }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Generate CalVer tag
+        id: calver
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        run: |
+          DATE_TAG=$(date -u +%Y.%m.%d)
+          EXISTING=$(git tag -l "v${DATE_TAG}*" | sort -V | tail -1)
+          if [ -z "$EXISTING" ]; then
+            VERSION="$DATE_TAG"
+          elif [ "$EXISTING" = "v${DATE_TAG}" ]; then
+            VERSION="${DATE_TAG}.2"
+          else
+            BUILD_NUM=$(echo "$EXISTING" | sed "s/v${DATE_TAG}\.//")
+            VERSION="${DATE_TAG}.$((BUILD_NUM + 1))"
+          fi
+          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
+          echo "CalVer tag: $VERSION"
 
       - name: Log in to GHCR
         if: github.event_name == 'push' && github.ref == 'refs/heads/main'
@@ -72,6 +113,7 @@ jobs:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           tags: |
             type=sha,prefix=sha-
+            type=raw,value=${{ steps.calver.outputs.version }},enable=${{ github.ref == 'refs/heads/main' }}
             type=raw,value=latest,enable=${{ github.ref == 'refs/heads/main' }}
 
       - name: Build and push Docker image
@@ -82,3 +124,107 @@ jobs:
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           target: prod
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
+      - name: Create git tag
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        run: |
+          git tag "v${{ steps.calver.outputs.version }}"
+          git push origin "v${{ steps.calver.outputs.version }}"
+
+  build-and-push-auth:
+    runs-on: runners-cartsnitch
+    needs: [lint, test]
+    outputs:
+      calver_tag: ${{ steps.calver.outputs.version }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Generate CalVer tag
+        id: calver
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        run: |
+          DATE_TAG=$(date -u +%Y.%m.%d)
+          EXISTING=$(git tag -l "v${DATE_TAG}*" | sort -V | tail -1)
+          if [ -z "$EXISTING" ]; then
+            VERSION="$DATE_TAG"
+          elif [ "$EXISTING" = "v${DATE_TAG}" ]; then
+            VERSION="${DATE_TAG}.2"
+          else
+            BUILD_NUM=$(echo "$EXISTING" | sed "s/v${DATE_TAG}\.//")
+            VERSION="${DATE_TAG}.$((BUILD_NUM + 1))"
+          fi
+          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
+
+      - name: Log in to GHCR
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (auth)
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.AUTH_IMAGE_NAME }}
+          tags: |
+            type=sha,prefix=sha-
+            type=raw,value=${{ steps.calver.outputs.version }},enable=${{ github.ref == 'refs/heads/main' }}
+            type=raw,value=latest,enable=${{ github.ref == 'refs/heads/main' }}
+
+      - name: Build and push auth Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: ./auth
+          file: ./auth/Dockerfile
+          push: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+
+  deploy-dev:
+    runs-on: runners-cartsnitch
+    needs: [build-and-push, build-and-push-auth]
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+    steps:
+      - name: Generate GitHub App token
+        id: app-token
+        uses: actions/create-github-app-token@v1
+        with:
+          app-id: ${{ secrets.CARTSNITCH_APP_ID }}
+          private-key: ${{ secrets.CARTSNITCH_APP_PRIVATE_KEY }}
+          owner: ${{ github.repository_owner }}
+          repositories: infra
+
+      - name: Checkout infra repo
+        uses: actions/checkout@v4
+        with:
+          repository: cartsnitch/infra
+          token: ${{ steps.app-token.outputs.token }}
+          ref: main
+          path: infra
+
+      - name: Install kubectl
+        uses: azure/setup-kubectl@v4
+
+      - name: Install kustomize
+        uses: imranismail/setup-kustomize@v2
+
+      - name: Update dev overlay image tag
+        run: |
+          cd infra/apps/overlays/dev
+          kustomize edit set image ghcr.io/cartsnitch/cartsnitch:${{ needs.build-and-push.outputs.calver_tag }}
+          kustomize edit set image ghcr.io/cartsnitch/auth:${{ needs.build-and-push-auth.outputs.calver_tag }}
+
+      - name: Commit and push to infra
+        run: |
+          cd infra
+          git config user.name "cartsnitch-ci[bot]"
+          git config user.email "cartsnitch-ci[bot]@users.noreply.github.com"
+          git add apps/overlays/dev/kustomization.yaml
+          git commit -m "ci(dev): update cartsnitch and auth images to ${{ needs.build-and-push.outputs.calver_tag }}"
+          git push origin main

.gitignore

@@ -11,6 +11,7 @@ node_modules
 dist
 dist-ssr
 *.local
+.env
 
 # Editor directories and files
 .vscode/*

CLAUDE.md

@@ -1,20 +1,26 @@
-# CartSnitch Frontend
+# CartSnitch Monorepo
 
 ## Project Context
 
-CartSnitch is a self-hosted grocery price intelligence platform built as a polyrepo microservices architecture. This repo (`cartsnitch/cartsnitch`) is the mobile-first Progressive Web App — the flagship repo and primary user interface.
+CartSnitch is a self-hosted grocery price intelligence platform. This repo (`cartsnitch/cartsnitch`) is the **monorepo** containing the flagship frontend PWA and core backend services.
 
 **GitHub org:** github.com/cartsnitch
 **Domain:** cartsnitch.com
 
-### CartSnitch Services
+### Monorepo Layout
+
+| Directory | Service | Purpose |
+|-----------|---------|---------|
+| `/` (root) | Frontend | React PWA, mobile-first (this directory) |
+| `auth/` | Auth | Better-Auth Node.js service (session management, email/password, OAuth) |
+| `api/` | API Gateway | Frontend-facing REST API |
+| `common/` | Common | Shared Python models, schemas, Alembic migrations |
+| `receiptwitness/` | ReceiptWitness | Purchase data ingestion via retailer scrapers |
+
+### Other CartSnitch Repos (still separate)
 
 | Repo | Service | Purpose |
 |------|---------|---------|
-| `cartsnitch/common` | — | Shared models, schemas, utilities |
-| `cartsnitch/receiptwitness` | ReceiptWitness | Purchase data ingestion via retailer scrapers |
-| `cartsnitch/api` | API Gateway | Frontend-facing REST API |
-| `cartsnitch/cartsnitch` | Frontend | React PWA, mobile-first (this repo) |
 | `cartsnitch/stickershock` | StickerShock | Price increase detection & CPI comparison |
 | `cartsnitch/shrinkray` | ShrinkRay | Shrinkflation monitoring |
 | `cartsnitch/clipartist` | ClipArtist | Coupon/deal watching & shopping optimization |
@@ -161,9 +167,13 @@ frontend/
 
 All data comes from the CartSnitch API gateway (`cartsnitch/api`). Base URL configured via environment variable `VITE_API_URL`.
 
-- JWT auth: store access token in memory (not localStorage), refresh token in httpOnly cookie if possible, or secure storage.
+- **Authentication via Better-Auth** (`auth/` service). Sessions are managed via httpOnly cookies — no tokens in localStorage or memory.
+  - Auth service URL configured via `VITE_AUTH_URL` (default: `http://localhost:3001`)
+  - Frontend uses `better-auth/react` client for sign-in, sign-up, sign-out, and `useSession()` hook
+  - API gateway validates sessions by querying the shared `sessions` table in Postgres
+  - Both cookie-based and Bearer token auth are supported (cookies for web, Bearer for API clients)
 - TanStack Query handles caching, background refetching, and optimistic updates.
-- API client should handle 401 responses by attempting token refresh before retrying.
+- API client sends `credentials: 'include'` on all requests to forward session cookies.
 
 ## Development Workflow
 

Dockerfile

@@ -9,13 +9,14 @@ RUN npm ci
 COPY . .
 RUN npm run build
 
-# Stage 2: Production
-FROM nginx:stable-alpine AS prod
+# Stage 2: Production — uses nginxinc/nginx-unprivileged which runs as non-root (UID 101)
+FROM nginxinc/nginx-unprivileged:stable-alpine AS prod
 
 COPY --from=build /app/dist /usr/share/nginx/html
 COPY nginx.conf /etc/nginx/conf.d/default.conf
 
-EXPOSE 80
+USER 101
+EXPOSE 8080
 
 HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
-  CMD wget -qO- http://localhost/health || exit 1
+  CMD wget -qO- http://localhost:8080/health || exit 1

README.md

@@ -1,73 +1 @@
-# React + TypeScript + Vite
-
-This template provides a minimal setup to get React working in Vite with HMR and some ESLint rules.
-
-Currently, two official plugins are available:
-
-- [@vitejs/plugin-react](https://github.com/vitejs/vite-plugin-react/blob/main/packages/plugin-react) uses [Oxc](https://oxc.rs)
-- [@vitejs/plugin-react-swc](https://github.com/vitejs/vite-plugin-react/blob/main/packages/plugin-react-swc) uses [SWC](https://swc.rs/)
-
-## React Compiler
-
-The React Compiler is not enabled on this template because of its impact on dev & build performances. To add it, see [this documentation](https://react.dev/learn/react-compiler/installation).
-
-## Expanding the ESLint configuration
-
-If you are developing a production application, we recommend updating the configuration to enable type-aware lint rules:
-
-```js
-export default defineConfig([
-  globalIgnores(['dist']),
-  {
-    files: ['**/*.{ts,tsx}'],
-    extends: [
-      // Other configs...
-
-      // Remove tseslint.configs.recommended and replace with this
-      tseslint.configs.recommendedTypeChecked,
-      // Alternatively, use this for stricter rules
-      tseslint.configs.strictTypeChecked,
-      // Optionally, add this for stylistic rules
-      tseslint.configs.stylisticTypeChecked,
-
-      // Other configs...
-    ],
-    languageOptions: {
-      parserOptions: {
-        project: ['./tsconfig.node.json', './tsconfig.app.json'],
-        tsconfigRootDir: import.meta.dirname,
-      },
-      // other options...
-    },
-  },
-])
-```
-
-You can also install [eslint-plugin-react-x](https://github.com/Rel1cx/eslint-react/tree/main/packages/plugins/eslint-plugin-react-x) and [eslint-plugin-react-dom](https://github.com/Rel1cx/eslint-react/tree/main/packages/plugins/eslint-plugin-react-dom) for React-specific lint rules:
-
-```js
-// eslint.config.js
-import reactX from 'eslint-plugin-react-x'
-import reactDom from 'eslint-plugin-react-dom'
-
-export default defineConfig([
-  globalIgnores(['dist']),
-  {
-    files: ['**/*.{ts,tsx}'],
-    extends: [
-      // Other configs...
-      // Enable lint rules for React
-      reactX.configs['recommended-typescript'],
-      // Enable lint rules for React DOM
-      reactDom.configs.recommended,
-    ],
-    languageOptions: {
-      parserOptions: {
-        project: ['./tsconfig.node.json', './tsconfig.app.json'],
-        tsconfigRootDir: import.meta.dirname,
-      },
-      // other options...
-    },
-  },
-])
-```
+# CartSnitch

api/.dockerignore

@@ -0,0 +1,14 @@
+.git
+.github
+.pytest_cache
+.ruff_cache
+__pycache__
+*.py[cod]
+*.egg-info
+dist
+.venv
+.env
+tests
+openapi.json
+CLAUDE.md
+README.md

api/.github/workflows/ci.yml

@@ -0,0 +1,164 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: write
+  packages: write
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: cartsnitch/api
+
+jobs:
+  lint:
+    runs-on: runners-cartsnitch
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+          cache: pip
+      - run: pip install ruff
+      - name: Ruff lint
+        run: ruff check .
+      - name: Ruff format check
+        run: ruff format --check .
+
+  typecheck:
+    runs-on: runners-cartsnitch
+    continue-on-error: true
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+          cache: pip
+      - name: Install system dependencies
+        run: sudo apt-get update && sudo apt-get install -y libpq-dev build-essential
+      - name: Install cartsnitch-common from GitHub
+        run: pip install "cartsnitch-common @ git+https://github.com/cartsnitch/common.git"
+      - run: pip install -e ".[dev]" mypy
+      - name: Type check
+        run: mypy src/cartsnitch_api
+
+  test:
+    runs-on: runners-cartsnitch
+    services:
+      postgres:
+        image: postgres:15-alpine
+        credentials:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+        env:
+          POSTGRES_USER: cartsnitch
+          POSTGRES_PASSWORD: cartsnitch_test
+          POSTGRES_DB: cartsnitch_test
+        ports:
+          - 5432:5432
+        options: >-
+          --health-cmd pg_isready
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+      redis:
+        image: redis:7-alpine
+        credentials:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+        ports:
+          - 6379:6379
+        options: >-
+          --health-cmd "redis-cli ping"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+    env:
+      CARTSNITCH_DATABASE_URL: postgresql+asyncpg://cartsnitch:cartsnitch_test@localhost:5432/cartsnitch_test
+      CARTSNITCH_REDIS_URL: redis://localhost:6379/0
+      CARTSNITCH_JWT_SECRET_KEY: test-secret-do-not-use-in-prod
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+          cache: pip
+      - name: Install system dependencies
+        run: sudo apt-get update && sudo apt-get install -y libpq-dev build-essential
+      - name: Install cartsnitch-common from GitHub
+        run: pip install "cartsnitch-common @ git+https://github.com/cartsnitch/common.git"
+      - run: pip install -e ".[dev]"
+      - name: Run tests
+        run: pytest --tb=short -q
+
+  build-and-push:
+    runs-on: runners-cartsnitch
+    needs: [lint, test]
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Generate CalVer tag
+        id: calver
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        run: |
+          DATE_TAG=$(date -u +%Y.%m.%d)
+          EXISTING=$(git tag -l "v${DATE_TAG}*" | sort -V | tail -1)
+          if [ -z "$EXISTING" ]; then
+            VERSION="$DATE_TAG"
+          elif [ "$EXISTING" = "v${DATE_TAG}" ]; then
+            VERSION="${DATE_TAG}.2"
+          else
+            BUILD_NUM=$(echo "$EXISTING" | sed "s/v${DATE_TAG}\.//")
+            VERSION="${DATE_TAG}.$((BUILD_NUM + 1))"
+          fi
+          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
+          echo "CalVer tag: $VERSION"
+
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Log in to GHCR
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=sha,prefix=sha-
+            type=raw,value=${{ steps.calver.outputs.version }},enable=${{ github.ref == 'refs/heads/main' }}
+            type=raw,value=latest,enable=${{ github.ref == 'refs/heads/main' }}
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          target: prod
+
+      - name: Create git tag
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        run: |
+          git tag "v${{ steps.calver.outputs.version }}"
+          git push origin "v${{ steps.calver.outputs.version }}"

api/.gitignore

@@ -0,0 +1,9 @@
+__pycache__/
+*.py[cod]
+*.egg-info/
+dist/
+.venv/
+.env
+.pytest_cache/
+.ruff_cache/
+openapi.json

api/CLAUDE.md

@@ -0,0 +1,175 @@
+# CartSnitch API Gateway
+
+## Project Context
+
+CartSnitch is a self-hosted grocery price intelligence platform built as a polyrepo microservices architecture. This repo (`cartsnitch/api`) is the public-facing API gateway that serves the frontend and proxies requests to internal services.
+
+**GitHub org:** github.com/cartsnitch
+**Domain:** cartsnitch.com
+
+### CartSnitch Services
+
+| Repo | Service | Purpose |
+|------|---------|---------|
+| `cartsnitch/common` | — | Shared models, schemas, utilities |
+| `cartsnitch/receiptwitness` | ReceiptWitness | Purchase data ingestion via retailer scrapers |
+| `cartsnitch/api` | API Gateway | Frontend-facing REST API (this repo) |
+| `cartsnitch/cartsnitch` | Frontend | React PWA (mobile-first) |
+| `cartsnitch/stickershock` | StickerShock | Price increase detection & CPI comparison |
+| `cartsnitch/shrinkray` | ShrinkRay | Shrinkflation monitoring |
+| `cartsnitch/clipartist` | ClipArtist | Coupon/deal watching & shopping optimization |
+| `cartsnitch/infra` | — | K8s manifests, Flux kustomizations |
+
+### Architecture Decisions
+
+- **Polyrepo:** Each service has its own repo, Dockerfile, CI/CD pipeline.
+- **Shared DB:** One PostgreSQL cluster. This service reads from all tables for serving frontend queries. Models come from `cartsnitch-common`.
+- **Inter-service comms:** REST to internal services, Redis pub/sub for event subscriptions.
+- **Target scale:** 500–1,000 users initially.
+
+## What This Service Does
+
+The API Gateway is the single entry point for the frontend PWA and any external consumers. It:
+
+1. **Handles user authentication** — registration, login, JWT token management
+2. **Serves purchase/product/price data** — reads from the shared DB
+3. **Proxies scraping operations** — forwards scrape triggers to ReceiptWitness
+4. **Serves coupon/deal data** — reads from shared DB (written by ClipArtist)
+5. **Serves alerts** — price increase alerts (StickerShock), shrinkflation alerts (ShrinkRay)
+6. **Provides public data endpoints** — aggregate price trends for the transparency/shaming features
+
+## Tech Stack
+
+- Python 3.12+
+- FastAPI (async)
+- SQLAlchemy 2.0 (via `cartsnitch-common`, read-heavy)
+- Pydantic v2 (request/response validation)
+- python-jose or PyJWT (JWT auth)
+- passlib + bcrypt (password hashing)
+- httpx (async HTTP client for proxying to internal services)
+- Redis (subscribe to events for websocket push, caching)
+- uvicorn (ASGI server)
+
+## Repo Structure
+
+```
+api/
+├── CLAUDE.md
+├── README.md
+├── pyproject.toml
+├── Dockerfile
+├── docker-compose.yml
+├── src/
+│   └── cartsnitch_api/
+│       ├── __init__.py
+│       ├── config.py           # Service-specific settings
+│       ├── main.py             # FastAPI app factory, lifespan, middleware
+│       ├── auth/
+│       │   ├── __init__.py
+│       │   ├── jwt.py          # JWT creation/validation
+│       │   ├── passwords.py    # Hashing, verification
+│       │   ├── dependencies.py # FastAPI dependency injection (get_current_user)
+│       │   └── routes.py       # /auth/register, /auth/login, /auth/refresh
+│       ├── routes/
+│       │   ├── __init__.py
+│       │   ├── purchases.py    # Purchase history endpoints
+│       │   ├── products.py     # Normalized product catalog
+│       │   ├── prices.py       # Price history and trends
+│       │   ├── coupons.py      # Active coupons and deals
+│       │   ├── alerts.py       # Price increase / shrinkflation alerts
+│       │   ├── stores.py       # Store info, user store account management
+│       │   ├── scraping.py     # Proxy to ReceiptWitness (trigger scrape, status)
+│       │   ├── shopping.py     # Optimized shopping list (proxy to ClipArtist)
+│       │   ├── public.py       # Public price transparency endpoints (no auth)
+│       │   └── health.py
+│       ├── services/
+│       │   ├── __init__.py
+│       │   ├── receiptwitness.py   # HTTP client for ReceiptWitness internal API
+│       │   ├── stickershock.py     # HTTP client for StickerShock internal API
+│       │   ├── clipartist.py       # HTTP client for ClipArtist internal API
+│       │   └── shrinkray.py        # HTTP client for ShrinkRay internal API
+│       ├── middleware/
+│       │   ├── __init__.py
+│       │   ├── cors.py
+│       │   └── rate_limit.py
+│       └── cache.py            # Redis caching helpers
+└── tests/
+    ├── conftest.py
+    ├── test_auth/
+    ├── test_routes/
+    └── test_services/
+```
+
+## API Endpoint Design
+
+### Auth
+- `POST /auth/register` — create account
+- `POST /auth/login` — get JWT access + refresh tokens
+- `POST /auth/refresh` — refresh access token
+- `GET /auth/me` — current user profile
+
+### Store Accounts
+- `GET /stores` — list supported stores
+- `GET /me/stores` — list user's connected store accounts + sync status
+- `POST /me/stores/{store_slug}/connect` — initiate store connection flow
+- `DELETE /me/stores/{store_slug}` — disconnect store account
+
+### Purchases
+- `GET /purchases` — list user's purchases (paginated, filterable by store/date)
+- `GET /purchases/{id}` — purchase detail with line items
+- `GET /purchases/stats` — spending summary (by store, by category, by period)
+
+### Products
+- `GET /products` — normalized product catalog (search, filter)
+- `GET /products/{id}` — product detail with cross-store price comparison
+- `GET /products/{id}/prices` — price history for a product across stores
+
+### Prices
+- `GET /prices/trends` — aggregate price trends (public-capable)
+- `GET /prices/increases` — recent significant price increases
+- `GET /prices/comparison` — compare specific items across stores
+
+### Coupons
+- `GET /coupons` — active coupons/deals (filterable by store)
+- `GET /coupons/relevant` — coupons relevant to user's purchase history
+
+### Shopping
+- `POST /shopping/optimize` — input: shopping list → output: store-split + coupons
+- `GET /shopping/lists` — user's saved shopping lists
+
+### Alerts
+- `GET /alerts` — user's price increase and shrinkflation alerts
+- `PUT /alerts/settings` — configure alert thresholds
+
+### Public (No Auth)
+- `GET /public/trends/{product_id}` — public price trend for a product
+- `GET /public/store-comparison` — public store-vs-store price comparison
+- `GET /public/inflation` — price changes vs CPI baseline
+
+### Scraping (Proxy to ReceiptWitness)
+- `POST /scraping/{store_slug}/sync` — trigger a sync for the current user
+- `GET /scraping/status` — sync status across all stores
+
+## Authentication
+
+- JWT-based auth with short-lived access tokens (15 min) and longer refresh tokens (7 days).
+- Passwords hashed with bcrypt via passlib.
+- All user-specific endpoints require a valid JWT in the `Authorization: Bearer` header.
+- Public endpoints under `/public/` do not require auth.
+- Internal service-to-service calls (ReceiptWitness, etc.) use a shared API key in the `X-Service-Key` header — not user JWTs.
+
+## Development Workflow
+
+- **Never push directly to main.** Always create feature branches and open PRs.
+- Branch naming: `feature/<description>` or `fix/<description>`
+- Use conventional commits: `feat:`, `fix:`, `refactor:`, `docs:`, `chore:`
+- OpenAPI docs auto-generated at `/docs` (Swagger) and `/redoc`.
+- Write tests for all routes. Use httpx.AsyncClient with FastAPI's TestClient pattern.
+
+## Important Notes
+
+- This service is read-heavy on the shared DB. Use async SQLAlchemy sessions.
+- Consider Redis caching for expensive queries (price trends, product comparisons). Cache invalidation via Redis pub/sub events from other services.
+- Rate limiting on public endpoints is important — these could get hammered if the price transparency features get attention.
+- CORS must allow the frontend origin (cartsnitch.com and localhost for dev).
+- The store connection flow is the trickiest UX challenge: the user needs to authenticate with each retailer, and we need to capture the resulting session. This likely involves a controlled Playwright browser session that the user can see/interact with, or an OAuth-like redirect flow if the retailer supports it (Kroger does for its public API, but not for purchase history access).

api/Dockerfile

@@ -0,0 +1,26 @@
+FROM python:3.12-slim AS build
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    libpq-dev \
+    build-essential \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+COPY pyproject.toml ./
+COPY src/ ./src/
+RUN pip install --no-cache-dir --prefix=/install .
+
+FROM python:3.12-slim AS prod
+
+WORKDIR /app
+RUN adduser --system --group --uid 1000 app
+COPY --from=build /install /usr/local
+COPY src/ ./src/
+
+USER 1000
+EXPOSE 8000
+
+HEALTHCHECK --interval=30s --timeout=3s \
+    CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8000/health')"
+
+CMD ["uvicorn", "cartsnitch_api.main:app", "--host", "0.0.0.0", "--port", "8000"]

api/alembic.ini

@@ -0,0 +1,36 @@
+[alembic]
+script_location = alembic
+sqlalchemy.url = postgresql://OVERRIDE_VIA_ENV_VAR
+
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

api/alembic/env.py

@@ -0,0 +1,55 @@
+"""Alembic environment configuration for CartSnitch."""
+
+import os
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config, pool
+
+from alembic import context
+from cartsnitch_api.models import Base  # noqa: F401 — imports all models for autogenerate
+
+config = context.config
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+db_url = os.environ.get("CARTSNITCH_DATABASE_URL_SYNC")
+if not db_url:
+    raise RuntimeError(
+        "CARTSNITCH_DATABASE_URL_SYNC must be set. "
+        "Example: postgresql://user:pass@localhost:5432/cartsnitch"
+    )
+config.set_main_option("sqlalchemy.url", db_url)
+
+target_metadata = Base.metadata
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode."""
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode."""
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+    with connectable.connect() as connection:
+        context.configure(connection=connection, target_metadata=target_metadata)
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

api/alembic/script.py.mako

@@ -0,0 +1,25 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+${imports if imports else ""}
+
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}

api/alembic/versions/001_encrypt_session_data.py

@@ -0,0 +1,89 @@
+"""Encrypt existing plaintext session_data with Fernet.
+
+Revision ID: 001_encrypt_session_data
+Revises:
+Create Date: 2026-03-19
+"""
+
+import json
+import os
+
+import sqlalchemy as sa
+from cryptography.fernet import Fernet
+from sqlalchemy import text
+
+from alembic import op
+
+revision = "001_encrypt_session_data"
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def _get_fernet() -> Fernet:
+    key = os.environ.get("CARTSNITCH_FERNET_KEY")
+    if not key:
+        raise RuntimeError("CARTSNITCH_FERNET_KEY must be set to run this migration")
+    return Fernet(key.encode())
+
+
+def _is_fernet_token(value: str) -> bool:
+    """Check if a string looks like a Fernet token (base64 starting with gAAAAA)."""
+    return value.startswith("gAAAAA")
+
+
+def upgrade() -> None:
+    # Change column type from JSON to TEXT to hold Fernet ciphertext
+    op.alter_column(
+        "user_store_accounts",
+        "session_data",
+        type_=sa.Text(),
+        existing_type=sa.JSON(),
+        existing_nullable=True,
+        postgresql_using="session_data::text",
+    )
+
+    conn = op.get_bind()
+    rows = conn.execute(
+        text("SELECT id, session_data FROM user_store_accounts WHERE session_data IS NOT NULL")
+    ).fetchall()
+
+    f = _get_fernet()
+    for row_id, session_data in rows:
+        raw = str(session_data)
+        if _is_fernet_token(raw):
+            continue
+        plaintext = raw if isinstance(session_data, str) else json.dumps(session_data)
+        encrypted = f.encrypt(plaintext.encode()).decode()
+        conn.execute(
+            text("UPDATE user_store_accounts SET session_data = :data WHERE id = :id"),
+            {"data": encrypted, "id": row_id},
+        )
+
+
+def downgrade() -> None:
+    conn = op.get_bind()
+    rows = conn.execute(
+        text("SELECT id, session_data FROM user_store_accounts WHERE session_data IS NOT NULL")
+    ).fetchall()
+
+    f = _get_fernet()
+    for row_id, session_data in rows:
+        raw = str(session_data)
+        if not _is_fernet_token(raw):
+            continue
+        decrypted = f.decrypt(raw.encode()).decode()
+        conn.execute(
+            text("UPDATE user_store_accounts SET session_data = :data WHERE id = :id"),
+            {"data": decrypted, "id": row_id},
+        )
+
+    # Revert column type from TEXT back to JSON
+    op.alter_column(
+        "user_store_accounts",
+        "session_data",
+        type_=sa.JSON(),
+        existing_type=sa.Text(),
+        existing_nullable=True,
+        postgresql_using="session_data::json",
+    )

api/alembic/versions/002_better_auth_tables.py

@@ -0,0 +1,101 @@
+"""Add Better-Auth tables and extend users table.
+
+Creates sessions, accounts, and verifications tables for Better-Auth.
+Adds email_verified and image columns to existing users table.
+Migrates password hashes from users.hashed_password to accounts.password.
+
+Revision ID: 002_better_auth_tables
+Revises: 001_encrypt_session_data
+Create Date: 2026-03-28
+"""
+
+import sqlalchemy as sa
+from sqlalchemy import text
+
+from alembic import op
+
+revision = "002_better_auth_tables"
+down_revision = "001_encrypt_session_data"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # --- Extend users table for Better-Auth compatibility ---
+    op.add_column("users", sa.Column("email_verified", sa.Boolean(), nullable=False, server_default="false"))
+    op.add_column("users", sa.Column("image", sa.Text(), nullable=True))
+
+    # --- Create sessions table ---
+    op.create_table(
+        "sessions",
+        sa.Column("id", sa.Text(), nullable=False),
+        sa.Column("token", sa.Text(), nullable=False),
+        sa.Column("user_id", sa.Text(), nullable=False),
+        sa.Column("expires_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("ip_address", sa.Text(), nullable=True),
+        sa.Column("user_agent", sa.Text(), nullable=True),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.PrimaryKeyConstraint("id"),
+    )
+    op.create_index("ix_sessions_token", "sessions", ["token"], unique=True)
+    op.create_index("ix_sessions_user_id", "sessions", ["user_id"])
+
+    # --- Create accounts table ---
+    op.create_table(
+        "accounts",
+        sa.Column("id", sa.Text(), nullable=False),
+        sa.Column("user_id", sa.Text(), nullable=False),
+        sa.Column("account_id", sa.Text(), nullable=False),
+        sa.Column("provider_id", sa.Text(), nullable=False),
+        sa.Column("access_token", sa.Text(), nullable=True),
+        sa.Column("refresh_token", sa.Text(), nullable=True),
+        sa.Column("access_token_expires_at", sa.DateTime(timezone=True), nullable=True),
+        sa.Column("refresh_token_expires_at", sa.DateTime(timezone=True), nullable=True),
+        sa.Column("scope", sa.Text(), nullable=True),
+        sa.Column("id_token", sa.Text(), nullable=True),
+        sa.Column("password", sa.Text(), nullable=True),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.PrimaryKeyConstraint("id"),
+    )
+    op.create_index("ix_accounts_user_id", "accounts", ["user_id"])
+
+    # --- Create verifications table ---
+    op.create_table(
+        "verifications",
+        sa.Column("id", sa.Text(), nullable=False),
+        sa.Column("identifier", sa.Text(), nullable=False),
+        sa.Column("value", sa.Text(), nullable=False),
+        sa.Column("expires_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.PrimaryKeyConstraint("id"),
+    )
+
+    # --- Migrate existing password hashes to accounts table ---
+    # For each user with a hashed_password, create a 'credential' account row
+    conn = op.get_bind()
+    users = conn.execute(
+        text("SELECT id, hashed_password FROM users WHERE hashed_password IS NOT NULL")
+    ).fetchall()
+
+    for user_id, hashed_password in users:
+        user_id_str = str(user_id)
+        conn.execute(
+            text(
+                "INSERT INTO accounts (id, user_id, account_id, provider_id, password, created_at, updated_at) "
+                "VALUES (gen_random_uuid()::text, :user_id, :account_id, 'credential', :password, now(), now())"
+            ),
+            {"user_id": user_id_str, "account_id": user_id_str, "password": hashed_password},
+        )
+
+
+def downgrade() -> None:
+    op.drop_table("verifications")
+    op.drop_table("accounts")
+    op.drop_index("ix_sessions_user_id", table_name="sessions")
+    op.drop_index("ix_sessions_token", table_name="sessions")
+    op.drop_table("sessions")
+    op.drop_column("users", "image")
+    op.drop_column("users", "email_verified")

api/alembic/versions/003_fix_user_id_text.py

@@ -0,0 +1,53 @@
+"""Change users.id and FK columns from uuid to text.
+
+Better-Auth generates nanoid-style text IDs (e.g. pGud2ln2WAFHC0KYjBVKR4Rc7mM8OcTI),
+but the users table was using PostgreSQL uuid type, causing INSERT failures.
+
+Revision ID: 003_fix_user_id_text
+Revises: 002_better_auth_tables
+Create Date: 2026-03-31
+"""
+
+import sqlalchemy as sa
+from sqlalchemy import text
+
+from alembic import op
+
+revision = "003_fix_user_id_text"
+down_revision = "002_better_auth_tables"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # Step 1: Drop FK constraints that reference users.id
+    op.execute(text("ALTER TABLE user_store_accounts DROP CONSTRAINT IF EXISTS user_store_accounts_user_id_fkey"))
+    op.execute(text("ALTER TABLE purchases DROP CONSTRAINT IF EXISTS purchases_user_id_fkey"))
+
+    # Step 2: Alter users.id from uuid to text
+    op.alter_column("users", "id", existing_type=sa.UUID(), type_=sa.Text(), existing_nullable=False, postgresql_using="id::text")
+
+    # Step 3: Alter user_store_accounts.user_id from uuid to text
+    op.alter_column("user_store_accounts", "user_id", existing_type=sa.UUID(), type_=sa.Text(), existing_nullable=False, postgresql_using="user_id::text")
+
+    # Step 4: Alter purchases.user_id from uuid to text
+    op.alter_column("purchases", "user_id", existing_type=sa.UUID(), type_=sa.Text(), existing_nullable=False, postgresql_using="user_id::text")
+
+    # Step 5: Re-add FK constraints
+    op.execute(text("ALTER TABLE user_store_accounts ADD CONSTRAINT user_store_accounts_user_id_fkey FOREIGN KEY (user_id) REFERENCES users(id)"))
+    op.execute(text("ALTER TABLE purchases ADD CONSTRAINT purchases_user_id_fkey FOREIGN KEY (user_id) REFERENCES users(id)"))
+
+
+def downgrade() -> None:
+    # Drop FK constraints
+    op.execute(text("ALTER TABLE purchases DROP CONSTRAINT IF EXISTS purchases_user_id_fkey"))
+    op.execute(text("ALTER TABLE user_store_accounts DROP CONSTRAINT IF EXISTS user_store_accounts_user_id_fkey"))
+
+    # Alter back to UUID
+    op.alter_column("purchases", "user_id", existing_type=sa.Text(), type_=sa.UUID(), existing_nullable=False, postgresql_using="user_id::uuid")
+    op.alter_column("user_store_accounts", "user_id", existing_type=sa.Text(), type_=sa.UUID(), existing_nullable=False, postgresql_using="user_id::uuid")
+    op.alter_column("users", "id", existing_type=sa.Text(), type_=sa.UUID(), existing_nullable=False, postgresql_using="id::uuid")
+
+    # Re-add FK constraints
+    op.execute(text("ALTER TABLE user_store_accounts ADD CONSTRAINT user_store_accounts_user_id_fkey FOREIGN KEY (user_id) REFERENCES users(id)"))
+    op.execute(text("ALTER TABLE purchases ADD CONSTRAINT purchases_user_id_fkey FOREIGN KEY (user_id) REFERENCES users(id)"))

api/pyproject.toml

@@ -0,0 +1,58 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "cartsnitch-api"
+version = "0.1.0"
+description = "CartSnitch API Gateway — public-facing REST API"
+requires-python = ">=3.12"
+dependencies = [
+    "fastapi>=0.115.0",
+    "uvicorn[standard]>=0.30.0",
+    "pydantic[email]>=2.9.0",
+    "pydantic-settings>=2.5.0",
+    "sqlalchemy[asyncio]>=2.0.35",
+    "asyncpg>=0.30.0",
+    "alembic>=1.13,<2.0",
+    "psycopg2>=2.9,<3.0",
+    "python-jose[cryptography]>=3.3.0",
+    "passlib[bcrypt]>=1.7.4",
+    "httpx>=0.27.0",
+    "redis[hiredis]>=5.2.0",
+    "cryptography>=43.0.0",
+]
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=8.3.0",
+    "pytest-asyncio>=0.24.0",
+    "aiosqlite>=0.20.0",
+    "httpx>=0.27.0",
+    "ruff>=0.7.0",
+    "psycopg2-binary>=2.9,<3.0",
+]
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/cartsnitch_api"]
+
+[tool.pytest.ini_options]
+asyncio_mode = "auto"
+testpaths = ["tests"]
+
+[tool.ruff]
+target-version = "py312"
+line-length = 100
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "N", "UP", "B"]
+
+[tool.ruff.lint.per-file-ignores]
+"src/cartsnitch_api/**/routes*.py" = ["B008"]
+"src/cartsnitch_api/**/dependencies.py" = ["B008"]
+
+[tool.mypy]
+python_version = "3.12"
+ignore_missing_imports = true
+warn_return_any = true
+warn_unused_configs = true

api/renovate.json

@@ -0,0 +1,4 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": ["local>cartsnitch/.github:renovate-config"]
+}

api/src/cartsnitch_api/auth/dependencies.py

@@ -0,0 +1,93 @@
+"""FastAPI dependency injection for authentication.
+
+Validates Better-Auth session tokens from cookies or Bearer header.
+Sessions are verified by querying the shared sessions table directly.
+"""
+
+from datetime import UTC, datetime
+from uuid import UUID
+
+from fastapi import Cookie, Depends, Header, HTTPException, Request, status
+from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
+from sqlalchemy import text
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from cartsnitch_api.config import settings
+from cartsnitch_api.database import get_db
+
+# Keep Bearer scheme as optional — Better-Auth primarily uses cookies,
+# but we support Bearer tokens for service-to-service or mobile clients.
+bearer_scheme = HTTPBearer(auto_error=False)
+
+# Better-Auth session cookie name
+SESSION_COOKIE_NAME = "better-auth.session_token"
+
+
+async def _validate_session_token(token: str, db: AsyncSession) -> UUID:
+    """Validate a Better-Auth session token against the sessions table.
+
+    Returns the user_id (as UUID) if the session is valid and not expired.
+    """
+    result = await db.execute(
+        text("SELECT user_id, expires_at FROM sessions WHERE token = :token"),
+        {"token": token},
+    )
+    row = result.first()
+
+    if not row:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid session token",
+        )
+
+    user_id, expires_at = row
+    if expires_at.tzinfo is None:
+        # Treat naive datetimes as UTC
+        expires_at = expires_at.replace(tzinfo=UTC)
+
+    if expires_at < datetime.now(UTC):
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Session expired",
+        )
+
+    return UUID(str(user_id))
+
+
+async def get_current_user(
+    request: Request,
+    credentials: HTTPAuthorizationCredentials | None = Depends(bearer_scheme),
+    db: AsyncSession = Depends(get_db),
+) -> UUID:
+    """Extract and validate the session token from cookie or Authorization header.
+
+    Checks in order:
+    1. Better-Auth session cookie (primary — web clients)
+    2. Bearer token in Authorization header (fallback — API clients)
+    """
+    token: str | None = None
+
+    # 1. Check session cookie
+    cookie_token = request.cookies.get(SESSION_COOKIE_NAME)
+    if cookie_token:
+        token = cookie_token
+
+    # 2. Fall back to Bearer header
+    if not token and credentials:
+        token = credentials.credentials
+
+    if not token:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Authentication required",
+        )
+
+    return await _validate_session_token(token, db)
+
+
+async def verify_service_key(x_service_key: str = Header()) -> None:
+    if x_service_key != settings.service_key:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Invalid service key",
+        )

api/src/cartsnitch_api/auth/jwt.py

@@ -0,0 +1,31 @@
+"""JWT token creation and validation."""
+
+from datetime import UTC, datetime, timedelta
+from typing import Any, cast
+from uuid import UUID
+
+from jose import JWTError, jwt
+
+from cartsnitch_api.config import settings
+
+
+def create_access_token(user_id: UUID) -> str:
+    expire = datetime.now(UTC) + timedelta(minutes=settings.jwt_access_token_expire_minutes)
+    payload = {"sub": str(user_id), "exp": expire, "type": "access"}
+    return cast(str, jwt.encode(payload, settings.jwt_secret_key, algorithm=settings.jwt_algorithm))
+
+
+def create_refresh_token(user_id: UUID) -> str:
+    expire = datetime.now(UTC) + timedelta(days=settings.jwt_refresh_token_expire_days)
+    payload = {"sub": str(user_id), "exp": expire, "type": "refresh"}
+    return cast(str, jwt.encode(payload, settings.jwt_secret_key, algorithm=settings.jwt_algorithm))
+
+
+def decode_token(token: str) -> dict:
+    try:
+        return cast(
+            dict[str, Any],
+            jwt.decode(token, settings.jwt_secret_key, algorithms=[settings.jwt_algorithm]),
+        )
+    except JWTError as e:
+        raise ValueError(f"Invalid token: {e}") from e

api/src/cartsnitch_api/auth/passwords.py

@@ -0,0 +1,11 @@
+"""Password hashing and verification with bcrypt."""
+
+import bcrypt
+
+
+def hash_password(password: str) -> str:
+    return bcrypt.hashpw(password.encode(), bcrypt.gensalt()).decode()
+
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    return bcrypt.checkpw(plain_password.encode(), hashed_password.encode())

api/src/cartsnitch_api/auth/routes.py

@@ -0,0 +1,66 @@
+"""Auth routes: user profile management.
+
+Registration, login, refresh, and session management are handled by
+the Better-Auth service (auth/). This router provides user profile
+endpoints that query our own user data from the shared database.
+"""
+
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from cartsnitch_api.auth.dependencies import get_current_user
+from cartsnitch_api.database import get_db
+from cartsnitch_api.schemas import (
+    UpdateUserRequest,
+    UserResponse,
+)
+from cartsnitch_api.services.auth import AuthService
+
+router = APIRouter(prefix="/auth", tags=["auth"])
+
+
+@router.get("/me", response_model=UserResponse)
+async def get_me(
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = AuthService(db)
+    try:
+        return await svc.get_user(user_id)
+    except LookupError:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail="User not found"
+        ) from None
+
+
+@router.patch("/me", response_model=UserResponse)
+async def update_me(
+    body: UpdateUserRequest,
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = AuthService(db)
+    try:
+        return await svc.update_user(user_id, email=body.email, display_name=body.display_name)
+    except LookupError:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail="User not found"
+        ) from None
+    except ValueError as e:
+        raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail=str(e)) from e
+
+
+@router.delete("/me", status_code=status.HTTP_204_NO_CONTENT)
+async def delete_me(
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = AuthService(db)
+    try:
+        await svc.delete_user(user_id)
+    except LookupError:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail="User not found"
+        ) from None

api/src/cartsnitch_api/cache.py

@@ -0,0 +1,26 @@
+"""Redis/DragonflyDB caching helpers."""
+
+from cartsnitch_api.config import settings
+
+
+class CacheClient:
+    """Stub for Redis/DragonflyDB caching.
+
+    Will be used for expensive queries: price trends, product comparisons.
+    Cache invalidation via Redis pub/sub events from other services.
+    """
+
+    def __init__(self) -> None:
+        self.url = settings.redis_url
+
+    async def get(self, key: str) -> str | None:
+        # TODO: implement with redis-py async
+        return None
+
+    async def set(self, key: str, value: str, ttl_seconds: int = 300) -> None:
+        # TODO: implement with redis-py async
+        pass
+
+    async def delete(self, key: str) -> None:
+        # TODO: implement with redis-py async
+        pass

api/src/cartsnitch_api/config.py

@@ -0,0 +1,53 @@
+import base64
+
+from pydantic import model_validator
+from pydantic_settings import BaseSettings
+
+
+class Settings(BaseSettings):
+    model_config = {"env_prefix": "CARTSNITCH_"}
+
+    database_url: str = "postgresql+asyncpg://cartsnitch:cartsnitch@localhost:5432/cartsnitch"
+    redis_url: str = "redis://localhost:6379/0"
+
+    jwt_secret_key: str = "change-me-in-production"
+    jwt_algorithm: str = "HS256"
+    jwt_access_token_expire_minutes: int = 15
+    jwt_refresh_token_expire_days: int = 7
+
+    service_key: str = "change-me-in-production"
+    # Valid Fernet key for local dev — MUST be overridden in production
+    fernet_key: str = "7reF42nmTwbdN21PBoubGp7h_FU8qSimstmlaMLoRK8="
+
+    auth_service_url: str = "http://auth:3001"
+
+    cors_origins: list[str] = ["http://localhost:3000", "https://cartsnitch.com"]
+
+    receiptwitness_url: str = "http://receiptwitness:8001"
+    stickershock_url: str = "http://stickershock:8002"
+    clipartist_url: str = "http://clipartist:8003"
+    shrinkray_url: str = "http://shrinkray:8004"
+
+    rate_limit_requests: int = 60
+    rate_limit_window_seconds: int = 60
+    rate_limit_enabled: bool = True
+
+    @model_validator(mode="after")
+    def validate_fernet_key(self):
+        """Validate fernet_key is a valid 32-byte url-safe base64 key at startup."""
+        try:
+            decoded = base64.urlsafe_b64decode(self.fernet_key.encode())
+            if len(decoded) != 32:
+                raise ValueError
+        except Exception:
+            raise ValueError(
+                "CARTSNITCH_FERNET_KEY must be a valid Fernet key "
+                "(32 bytes, url-safe base64 encoded). "
+                "Generate one with: python -c "
+                "'from cryptography.fernet import Fernet; "
+                "print(Fernet.generate_key().decode())'"
+            ) from None
+        return self
+
+
+settings = Settings()

api/src/cartsnitch_api/constants.py

@@ -0,0 +1,85 @@
+"""Constants and enums shared across CartSnitch services."""
+
+from enum import StrEnum
+
+
+class StoreSlug(StrEnum):
+    """Supported retailer slugs."""
+
+    MEIJER = "meijer"
+    KROGER = "kroger"
+    TARGET = "target"
+
+
+class AccountStatus(StrEnum):
+    """User store account link status."""
+
+    ACTIVE = "active"
+    EXPIRED = "expired"
+    ERROR = "error"
+
+
+class DiscountType(StrEnum):
+    """Coupon discount type."""
+
+    PERCENT = "percent"
+    FIXED = "fixed"
+    BOGO = "bogo"
+    BUY_X_GET_Y = "buy_x_get_y"
+
+
+class PriceSource(StrEnum):
+    """Source of a price observation."""
+
+    RECEIPT = "receipt"
+    CATALOG = "catalog"
+    WEEKLY_AD = "weekly_ad"
+
+
+class EventType(StrEnum):
+    """Redis pub/sub event types."""
+
+    RECEIPTS_INGESTED = "cartsnitch.receipts.ingested"
+    PRICES_UPDATED = "cartsnitch.prices.updated"
+    PRODUCTS_NORMALIZED = "cartsnitch.products.normalized"
+    COUPONS_UPDATED = "cartsnitch.coupons.updated"
+    ALERT_PRICE_INCREASE = "cartsnitch.alerts.price_increase"
+    ALERT_SHRINKFLATION = "cartsnitch.alerts.shrinkflation"
+
+
+class ProductCategory(StrEnum):
+    """Top-level product categories."""
+
+    PRODUCE = "produce"
+    DAIRY = "dairy"
+    MEAT = "meat"
+    BAKERY = "bakery"
+    FROZEN = "frozen"
+    PANTRY = "pantry"
+    BEVERAGES = "beverages"
+    SNACKS = "snacks"
+    HOUSEHOLD = "household"
+    PERSONAL_CARE = "personal_care"
+    OTHER = "other"
+
+
+class MatchConfidence(StrEnum):
+    """Confidence level for product matching."""
+
+    HIGH = "high"
+    MEDIUM = "medium"
+    LOW = "low"
+
+
+class SizeUnit(StrEnum):
+    """Standardized product size units."""
+
+    OZ = "oz"
+    FL_OZ = "fl_oz"
+    LB = "lb"
+    G = "g"
+    KG = "kg"
+    ML = "ml"
+    L = "l"
+    CT = "ct"
+    PK = "pk"

api/src/cartsnitch_api/database.py

@@ -0,0 +1,16 @@
+"""Database session management for the API gateway."""
+
+from collections.abc import AsyncGenerator
+
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+
+from cartsnitch_api.config import settings
+
+engine = create_async_engine(settings.database_url, echo=False)
+async_session_factory = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
+
+
+async def get_db() -> AsyncGenerator[AsyncSession, None]:
+    """FastAPI dependency that yields an async DB session."""
+    async with async_session_factory() as session:
+        yield session

api/src/cartsnitch_api/main.py

@@ -0,0 +1,62 @@
+"""FastAPI app factory for CartSnitch API Gateway."""
+
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+
+from cartsnitch_api.auth.routes import router as auth_router
+from cartsnitch_api.middleware.cors import add_cors_middleware
+from cartsnitch_api.middleware.error_handler import add_error_handlers, add_error_monitor_middleware
+from cartsnitch_api.middleware.rate_limit import add_rate_limit_middleware
+from cartsnitch_api.routes.alerts import router as alerts_router
+from cartsnitch_api.routes.coupons import router as coupons_router
+from cartsnitch_api.routes.health import router as health_router
+from cartsnitch_api.routes.prices import router as prices_router
+from cartsnitch_api.routes.products import router as products_router
+from cartsnitch_api.routes.public import router as public_router
+from cartsnitch_api.routes.purchases import router as purchases_router
+from cartsnitch_api.routes.scraping import router as scraping_router
+from cartsnitch_api.routes.shopping import router as shopping_router
+from cartsnitch_api.routes.stores import router as stores_router
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    # TODO: initialize DB session pool, Redis connection, service clients
+    yield
+    # TODO: cleanup connections
+
+
+def create_app() -> FastAPI:
+    app = FastAPI(
+        title="CartSnitch API",
+        description="Grocery price tracking and shrinkflation detection API",
+        version="0.1.0",
+        lifespan=lifespan,
+    )
+
+    # Middleware (order matters — outermost first)
+    add_cors_middleware(app)
+    add_error_monitor_middleware(app)
+    add_rate_limit_middleware(app)
+
+    # Exception handlers
+    add_error_handlers(app)
+
+    # Routers
+    app.include_router(health_router)
+    app.include_router(auth_router)
+    app.include_router(stores_router)
+    app.include_router(purchases_router)
+    app.include_router(products_router)
+    app.include_router(prices_router)
+    app.include_router(coupons_router)
+    app.include_router(shopping_router)
+    app.include_router(alerts_router)
+    app.include_router(scraping_router)
+    app.include_router(public_router)
+
+    return app
+
+
+app = create_app()

api/src/cartsnitch_api/middleware/cors.py

@@ -0,0 +1,16 @@
+"""CORS middleware configuration."""
+
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+
+from cartsnitch_api.config import settings
+
+
+def add_cors_middleware(app: FastAPI) -> None:
+    app.add_middleware(
+        CORSMiddleware,
+        allow_origins=settings.cors_origins,
+        allow_credentials=True,
+        allow_methods=["*"],
+        allow_headers=["*"],
+    )

api/src/cartsnitch_api/middleware/error_handler.py

@@ -0,0 +1,190 @@
+"""Structured error responses and error monitoring.
+
+Ensures all errors return a consistent JSON shape and never leak stack traces.
+Provides hooks for error monitoring/alerting.
+"""
+
+import logging
+import time
+import traceback
+from collections.abc import Awaitable, Callable
+
+from fastapi import FastAPI, Request, status
+from fastapi.exceptions import RequestValidationError
+from fastapi.responses import JSONResponse
+from starlette.exceptions import HTTPException as StarletteHTTPException
+from starlette.middleware.base import BaseHTTPMiddleware
+
+logger = logging.getLogger("cartsnitch_api.errors")
+
+
+def _error_response(
+    status_code: int,
+    detail: str,
+    code: str | None = None,
+    errors: list[dict] | None = None,
+) -> JSONResponse:
+    """Build a consistent error response."""
+    body: dict = {"detail": detail}
+    if code:
+        body["code"] = code
+    if errors:
+        body["errors"] = errors
+    return JSONResponse(status_code=status_code, content=body)
+
+
+def add_error_handlers(app: FastAPI) -> None:
+    """Register global exception handlers for consistent error responses."""
+
+    @app.exception_handler(RequestValidationError)
+    async def validation_error_handler(
+        request: Request, exc: RequestValidationError
+    ) -> JSONResponse:
+        """Return 422 with structured field-level error details."""
+        field_errors = []
+        for err in exc.errors():
+            loc = err.get("loc", ())
+            field_errors.append(
+                {
+                    "field": ".".join(str(p) for p in loc[1:]) if len(loc) > 1 else str(loc),
+                    "message": err.get("msg", "Invalid value"),
+                    "type": err.get("type", "value_error"),
+                }
+            )
+        return _error_response(
+            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+            detail="Validation error",
+            code="VALIDATION_ERROR",
+            errors=field_errors,
+        )
+
+    @app.exception_handler(StarletteHTTPException)
+    async def http_exception_handler(request: Request, exc: StarletteHTTPException) -> JSONResponse:
+        """Wrap HTTP exceptions (Starlette and FastAPI) in consistent format."""
+        detail = exc.detail if isinstance(exc.detail, str) else str(exc.detail)
+        return _error_response(
+            status_code=exc.status_code,
+            detail=detail,
+            code=_status_to_code(exc.status_code),
+        )
+
+    @app.exception_handler(Exception)
+    async def unhandled_exception_handler(request: Request, exc: Exception) -> JSONResponse:
+        """Catch-all: log full traceback, return safe 500 to client."""
+        logger.error(
+            "Unhandled exception on %s %s: %s\n%s",
+            request.method,
+            request.url.path,
+            exc,
+            traceback.format_exc(),
+        )
+        _notify_error_monitor(request, exc)
+
+        return _error_response(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            detail="Internal server error",
+            code="INTERNAL_ERROR",
+        )
+
+
+def _status_to_code(status_code: int) -> str:
+    """Map HTTP status code to a machine-readable error code."""
+    mapping = {
+        400: "BAD_REQUEST",
+        401: "UNAUTHORIZED",
+        403: "FORBIDDEN",
+        404: "NOT_FOUND",
+        409: "CONFLICT",
+        422: "VALIDATION_ERROR",
+        429: "RATE_LIMITED",
+        502: "BAD_GATEWAY",
+        503: "SERVICE_UNAVAILABLE",
+    }
+    return mapping.get(status_code, f"HTTP_{status_code}")
+
+
+# ---------- Error Monitoring ----------
+
+
+class _ErrorMonitor:
+    """Simple error counter for monitoring and alerting hooks.
+
+    Tracks error counts and rates. In production, this would forward
+    to an external monitoring service (Prometheus, Sentry, etc.).
+    """
+
+    def __init__(self) -> None:
+        self.error_counts: dict[int, int] = {}
+        self.recent_5xx: list[dict] = []
+        self._max_recent = 100
+
+    def record(self, status_code: int, path: str, method: str, error: str | None = None) -> None:
+        self.error_counts[status_code] = self.error_counts.get(status_code, 0) + 1
+
+        if status_code >= 500:
+            entry = {
+                "timestamp": time.time(),
+                "status": status_code,
+                "path": path,
+                "method": method,
+                "error": error,
+            }
+            self.recent_5xx.append(entry)
+            if len(self.recent_5xx) > self._max_recent:
+                self.recent_5xx = self.recent_5xx[-self._max_recent :]
+
+            logger.warning(
+                "5xx error recorded: %s %s -> %d (%s)",
+                method,
+                path,
+                status_code,
+                error or "unknown",
+            )
+
+    def get_stats(self) -> dict:
+        return {
+            "error_counts": dict(self.error_counts),
+            "recent_5xx_count": len(self.recent_5xx),
+        }
+
+
+_monitor = _ErrorMonitor()
+
+
+def get_error_monitor() -> _ErrorMonitor:
+    """Access the global error monitor (for health/metrics endpoints)."""
+    return _monitor
+
+
+def _notify_error_monitor(request: Request, exc: Exception) -> None:
+    """Record unhandled exception in the error monitor."""
+    _monitor.record(
+        status_code=500,
+        path=request.url.path,
+        method=request.method,
+        error=str(exc)[:200],
+    )
+
+
+class ErrorMonitorMiddleware(BaseHTTPMiddleware):
+    """Middleware to track all 4xx/5xx responses for monitoring."""
+
+    async def dispatch(
+        self,
+        request: Request,
+        call_next: Callable[[Request], Awaitable],
+    ):
+        response = await call_next(request)
+
+        if response.status_code >= 400:
+            _monitor.record(
+                status_code=response.status_code,
+                path=request.url.path,
+                method=request.method,
+            )
+
+        return response
+
+
+def add_error_monitor_middleware(app: FastAPI) -> None:
+    app.add_middleware(ErrorMonitorMiddleware)

api/src/cartsnitch_api/middleware/rate_limit.py

@@ -0,0 +1,111 @@
+"""Rate limiting middleware for public and authenticated endpoints.
+
+Uses in-memory sliding window as fallback, Redis/DragonflyDB when available.
+Per-IP limiting on public endpoints, per-token limiting on authenticated endpoints.
+"""
+
+import time
+from collections import defaultdict
+from threading import Lock
+
+from fastapi import FastAPI, Request, status
+from fastapi.responses import JSONResponse
+from starlette.middleware.base import BaseHTTPMiddleware
+
+from cartsnitch_api.config import settings
+
+
+class _SlidingWindowCounter:
+    """Thread-safe in-memory sliding window rate limiter."""
+
+    def __init__(self, max_requests: int, window_seconds: int) -> None:
+        self.max_requests = max_requests
+        self.window_seconds = window_seconds
+        self._hits: dict[str, list[float]] = defaultdict(list)
+        self._lock = Lock()
+
+    def is_allowed(self, key: str) -> tuple[bool, int, int]:
+        """Check if request is allowed. Returns (allowed, remaining, retry_after)."""
+        now = time.monotonic()
+        cutoff = now - self.window_seconds
+
+        with self._lock:
+            # Prune expired entries
+            self._hits[key] = [t for t in self._hits[key] if t > cutoff]
+
+            current_count = len(self._hits[key])
+            if current_count >= self.max_requests:
+                retry_after = int(self._hits[key][0] - cutoff) + 1
+                return False, 0, retry_after
+
+            self._hits[key].append(now)
+            remaining = self.max_requests - current_count - 1
+            return True, remaining, 0
+
+
+# Module-level counters — one for public (per-IP), one for auth (per-token)
+_public_limiter = _SlidingWindowCounter(
+    max_requests=settings.rate_limit_requests,
+    window_seconds=settings.rate_limit_window_seconds,
+)
+_auth_limiter = _SlidingWindowCounter(
+    max_requests=settings.rate_limit_requests * 5,  # 300/min for authenticated users
+    window_seconds=settings.rate_limit_window_seconds,
+)
+
+
+def _get_client_ip(request: Request) -> str:
+    """Extract client IP, respecting X-Forwarded-For behind a reverse proxy."""
+    forwarded = request.headers.get("x-forwarded-for")
+    if forwarded:
+        return forwarded.split(",")[0].strip()
+    return request.client.host if request.client else "unknown"
+
+
+def _get_rate_limit_key(request: Request) -> tuple[str, _SlidingWindowCounter]:
+    """Determine rate limit key and which limiter to use."""
+    if request.url.path.startswith("/public"):
+        return f"ip:{_get_client_ip(request)}", _public_limiter
+
+    # For authenticated endpoints, use Bearer token as key if present
+    auth_header = request.headers.get("authorization", "")
+    if auth_header.startswith("Bearer "):
+        token = auth_header[7:]
+        # Use last 16 chars of token as key to avoid storing full tokens
+        return f"token:{token[-16:]}", _auth_limiter
+
+    # Fallback to IP for unauthenticated non-public endpoints
+    return f"ip:{_get_client_ip(request)}", _public_limiter
+
+
+class RateLimitMiddleware(BaseHTTPMiddleware):
+    async def dispatch(self, request: Request, call_next):
+        # Skip rate limiting when disabled (e.g. in tests) or for health checks
+        if not settings.rate_limit_enabled or request.url.path == "/health":
+            return await call_next(request)
+
+        key, limiter = _get_rate_limit_key(request)
+        allowed, remaining, retry_after = limiter.is_allowed(key)
+
+        if not allowed:
+            return JSONResponse(
+                status_code=status.HTTP_429_TOO_MANY_REQUESTS,
+                content={
+                    "detail": "Rate limit exceeded",
+                    "code": "RATE_LIMITED",
+                },
+                headers={
+                    "Retry-After": str(retry_after),
+                    "X-RateLimit-Limit": str(limiter.max_requests),
+                    "X-RateLimit-Remaining": "0",
+                },
+            )
+
+        response = await call_next(request)
+        response.headers["X-RateLimit-Limit"] = str(limiter.max_requests)
+        response.headers["X-RateLimit-Remaining"] = str(remaining)
+        return response
+
+
+def add_rate_limit_middleware(app: FastAPI) -> None:
+    app.add_middleware(RateLimitMiddleware)

api/src/cartsnitch_api/models/__init__.py

@@ -0,0 +1,26 @@
+"""SQLAlchemy ORM models — re-exports all models for convenience."""
+
+from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+from cartsnitch_api.models.coupon import Coupon
+from cartsnitch_api.models.price import PriceHistory
+from cartsnitch_api.models.product import NormalizedProduct
+from cartsnitch_api.models.purchase import Purchase, PurchaseItem
+from cartsnitch_api.models.shrinkflation import ShrinkflationEvent
+from cartsnitch_api.models.store import Store, StoreLocation
+from cartsnitch_api.models.user import User, UserStoreAccount
+
+__all__ = [
+    "Base",
+    "TimestampMixin",
+    "UUIDPrimaryKeyMixin",
+    "Store",
+    "StoreLocation",
+    "User",
+    "UserStoreAccount",
+    "Purchase",
+    "PurchaseItem",
+    "NormalizedProduct",
+    "PriceHistory",
+    "Coupon",
+    "ShrinkflationEvent",
+]

api/src/cartsnitch_api/models/base.py

@@ -0,0 +1,30 @@
+"""Base model and mixins for all CartSnitch ORM models."""
+
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, func
+from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
+
+
+class Base(DeclarativeBase):
+    """Base class for all CartSnitch models."""
+
+
+class TimestampMixin:
+    """Mixin providing created_at / updated_at columns."""
+
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), nullable=False
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), onupdate=func.now(), nullable=False
+    )
+
+
+class UUIDPrimaryKeyMixin:
+    """Mixin providing a UUID primary key."""
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        primary_key=True, default=uuid.uuid4, server_default=func.gen_random_uuid()
+    )

api/src/cartsnitch_api/models/coupon.py

@@ -0,0 +1,42 @@
+"""Coupon model."""
+
+import uuid
+from datetime import date, datetime
+from decimal import Decimal
+from typing import TYPE_CHECKING
+
+from sqlalchemy import Boolean, Date, DateTime, ForeignKey, Numeric, String
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from cartsnitch_api.constants import DiscountType
+from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+
+if TYPE_CHECKING:
+    from cartsnitch_api.models.product import NormalizedProduct
+    from cartsnitch_api.models.store import Store
+
+
+class Coupon(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """A coupon or deal for a product at a store."""
+
+    __tablename__ = "coupons"
+
+    store_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("stores.id"), nullable=False)
+    normalized_product_id: Mapped[uuid.UUID | None] = mapped_column(
+        ForeignKey("normalized_products.id")
+    )
+    title: Mapped[str] = mapped_column(String(300), nullable=False)
+    description: Mapped[str | None] = mapped_column(String(1000))
+    discount_type: Mapped[DiscountType] = mapped_column(String(20), nullable=False)
+    discount_value: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    min_purchase: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    valid_from: Mapped[date | None] = mapped_column(Date)
+    valid_to: Mapped[date | None] = mapped_column(Date)
+    requires_clip: Mapped[bool] = mapped_column(Boolean, default=False, nullable=False)
+    coupon_code: Mapped[str | None] = mapped_column(String(100))
+    source_url: Mapped[str | None] = mapped_column(String(500))
+    scraped_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
+
+    # Relationships
+    store: Mapped["Store"] = relationship(back_populates="coupons")
+    normalized_product: Mapped["NormalizedProduct | None"] = relationship(back_populates="coupons")

api/src/cartsnitch_api/models/price.py

@@ -0,0 +1,50 @@
+"""PriceHistory model — tracks product prices over time."""
+
+import uuid
+from datetime import date
+from decimal import Decimal
+from typing import TYPE_CHECKING
+
+from sqlalchemy import Date, ForeignKey, Index, Numeric, String
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from cartsnitch_api.constants import PriceSource
+from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+
+if TYPE_CHECKING:
+    from cartsnitch_api.models.product import NormalizedProduct
+    from cartsnitch_api.models.purchase import PurchaseItem
+    from cartsnitch_api.models.store import Store
+
+
+class PriceHistory(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """A single price observation for a product at a store on a date."""
+
+    __tablename__ = "price_history"
+    __table_args__ = (
+        Index(
+            "ix_price_history_product_store_date",
+            "normalized_product_id",
+            "store_id",
+            "observed_date",
+        ),
+    )
+
+    normalized_product_id: Mapped[uuid.UUID] = mapped_column(
+        ForeignKey("normalized_products.id"), nullable=False
+    )
+    store_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("stores.id"), nullable=False)
+    observed_date: Mapped[date] = mapped_column(Date, nullable=False)
+    regular_price: Mapped[Decimal] = mapped_column(Numeric(10, 2), nullable=False)
+    sale_price: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    loyalty_price: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    coupon_price: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    source: Mapped[PriceSource] = mapped_column(String(20), nullable=False)
+    purchase_item_id: Mapped[uuid.UUID | None] = mapped_column(ForeignKey("purchase_items.id"))
+
+    # Relationships
+    normalized_product: Mapped["NormalizedProduct"] = relationship(back_populates="price_histories")
+    store: Mapped["Store"] = relationship(back_populates="price_histories")
+    purchase_item: Mapped["PurchaseItem | None"] = relationship(
+        back_populates="price_history_entries"
+    )

api/src/cartsnitch_api/models/product.py

@@ -0,0 +1,39 @@
+"""NormalizedProduct model — the canonical product identity."""
+
+from typing import TYPE_CHECKING
+
+from sqlalchemy import JSON, String
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from cartsnitch_api.constants import ProductCategory, SizeUnit
+from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+
+if TYPE_CHECKING:
+    from cartsnitch_api.models.coupon import Coupon
+    from cartsnitch_api.models.price import PriceHistory
+    from cartsnitch_api.models.purchase import PurchaseItem
+    from cartsnitch_api.models.shrinkflation import ShrinkflationEvent
+
+
+class NormalizedProduct(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """Canonical product identity — matches products across retailers."""
+
+    __tablename__ = "normalized_products"
+
+    canonical_name: Mapped[str] = mapped_column(String(300), nullable=False)
+    category: Mapped[ProductCategory | None] = mapped_column(String(50))
+    subcategory: Mapped[str | None] = mapped_column(String(100))
+    brand: Mapped[str | None] = mapped_column(String(200))
+    size: Mapped[str | None] = mapped_column(String(50))
+    size_unit: Mapped[SizeUnit | None] = mapped_column(String(10))
+    upc_variants: Mapped[list[str] | None] = mapped_column(JSON, default=list)
+
+    # Relationships
+    purchase_items: Mapped[list["PurchaseItem"]] = relationship(back_populates="normalized_product")
+    price_histories: Mapped[list["PriceHistory"]] = relationship(
+        back_populates="normalized_product"
+    )
+    coupons: Mapped[list["Coupon"]] = relationship(back_populates="normalized_product")
+    shrinkflation_events: Mapped[list["ShrinkflationEvent"]] = relationship(
+        back_populates="normalized_product"
+    )

api/src/cartsnitch_api/models/purchase.py

@@ -0,0 +1,91 @@
+"""Purchase and PurchaseItem models."""
+
+import uuid
+from datetime import date, datetime
+from decimal import Decimal
+from typing import TYPE_CHECKING
+
+from sqlalchemy import (
+    JSON,
+    Date,
+    DateTime,
+    ForeignKey,
+    Index,
+    Numeric,
+    String,
+    UniqueConstraint,
+    func,
+)
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+
+if TYPE_CHECKING:
+    from cartsnitch_api.models.price import PriceHistory
+    from cartsnitch_api.models.product import NormalizedProduct
+    from cartsnitch_api.models.store import Store, StoreLocation
+    from cartsnitch_api.models.user import User
+
+
+class Purchase(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """A single shopping trip / receipt."""
+
+    __tablename__ = "purchases"
+
+    user_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("users.id"), nullable=False)
+    store_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("stores.id"), nullable=False)
+    store_location_id: Mapped[uuid.UUID | None] = mapped_column(ForeignKey("store_locations.id"))
+    receipt_id: Mapped[str] = mapped_column(String(200), nullable=False)
+    purchase_date: Mapped[date] = mapped_column(Date, nullable=False)
+    total: Mapped[Decimal] = mapped_column(Numeric(10, 2), nullable=False)
+    subtotal: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    tax: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    savings_total: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    source_url: Mapped[str | None] = mapped_column(String(500))
+    raw_data: Mapped[dict | None] = mapped_column(JSON)
+    ingested_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        server_default=func.now(),
+        nullable=False,
+    )
+
+    # Relationships
+    user: Mapped["User"] = relationship(back_populates="purchases")
+    store: Mapped["Store"] = relationship(back_populates="purchases")
+    store_location: Mapped["StoreLocation | None"] = relationship(back_populates="purchases")
+    items: Mapped[list["PurchaseItem"]] = relationship(back_populates="purchase")
+
+    __table_args__ = (
+        Index("ix_purchases_user_store", "user_id", "store_id"),
+        UniqueConstraint("user_id", "store_id", "receipt_id", name="uq_purchase_receipt"),
+    )
+
+
+class PurchaseItem(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """Individual line item on a receipt."""
+
+    __tablename__ = "purchase_items"
+
+    purchase_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("purchases.id"), nullable=False)
+    product_name_raw: Mapped[str] = mapped_column(String(300), nullable=False)
+    upc: Mapped[str | None] = mapped_column(String(20))
+    quantity: Mapped[Decimal] = mapped_column(Numeric(10, 3), nullable=False, default=1)
+    unit_price: Mapped[Decimal] = mapped_column(Numeric(10, 2), nullable=False)
+    extended_price: Mapped[Decimal] = mapped_column(Numeric(10, 2), nullable=False)
+    regular_price: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    sale_price: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    coupon_discount: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    loyalty_discount: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    category_raw: Mapped[str | None] = mapped_column(String(100))
+    normalized_product_id: Mapped[uuid.UUID | None] = mapped_column(
+        ForeignKey("normalized_products.id")
+    )
+
+    # Relationships
+    purchase: Mapped["Purchase"] = relationship(back_populates="items")
+    normalized_product: Mapped["NormalizedProduct | None"] = relationship(
+        back_populates="purchase_items"
+    )
+    price_history_entries: Mapped[list["PriceHistory"]] = relationship(
+        back_populates="purchase_item"
+    )

api/src/cartsnitch_api/models/shrinkflation.py

@@ -0,0 +1,41 @@
+"""ShrinkflationEvent model."""
+
+import uuid
+from datetime import date
+from decimal import Decimal
+from typing import TYPE_CHECKING
+
+from sqlalchemy import Date, ForeignKey, Numeric, String
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from cartsnitch_api.constants import SizeUnit
+from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+
+if TYPE_CHECKING:
+    from cartsnitch_api.models.product import NormalizedProduct
+
+
+class ShrinkflationEvent(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """Detected shrinkflation event — product size changed while price held or rose."""
+
+    __tablename__ = "shrinkflation_events"
+
+    normalized_product_id: Mapped[uuid.UUID] = mapped_column(
+        ForeignKey("normalized_products.id"), nullable=False
+    )
+    detected_date: Mapped[date] = mapped_column(Date, nullable=False)
+    old_size: Mapped[str] = mapped_column(String(50), nullable=False)
+    new_size: Mapped[str] = mapped_column(String(50), nullable=False)
+    old_unit: Mapped[SizeUnit] = mapped_column(String(10), nullable=False)
+    new_unit: Mapped[SizeUnit] = mapped_column(String(10), nullable=False)
+    price_at_old_size: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    price_at_new_size: Mapped[Decimal | None] = mapped_column(Numeric(10, 2))
+    confidence: Mapped[Decimal] = mapped_column(
+        Numeric(3, 2), nullable=False, default=Decimal("1.00")
+    )
+    notes: Mapped[str | None] = mapped_column(String(1000))
+
+    # Relationships
+    normalized_product: Mapped["NormalizedProduct"] = relationship(
+        back_populates="shrinkflation_events"
+    )

api/src/cartsnitch_api/models/store.py

@@ -0,0 +1,52 @@
+"""Store and StoreLocation models."""
+
+import uuid
+from typing import TYPE_CHECKING
+
+from sqlalchemy import Float, ForeignKey, String
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from cartsnitch_api.constants import StoreSlug
+from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+
+if TYPE_CHECKING:
+    from cartsnitch_api.models.coupon import Coupon
+    from cartsnitch_api.models.price import PriceHistory
+    from cartsnitch_api.models.purchase import Purchase
+    from cartsnitch_api.models.user import UserStoreAccount
+
+
+class Store(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """Supported retailer."""
+
+    __tablename__ = "stores"
+
+    name: Mapped[str] = mapped_column(String(100), nullable=False)
+    slug: Mapped[StoreSlug] = mapped_column(String(20), nullable=False, unique=True)
+    logo_url: Mapped[str | None] = mapped_column(String(500))
+    website_url: Mapped[str | None] = mapped_column(String(500))
+
+    # Relationships
+    locations: Mapped[list["StoreLocation"]] = relationship(back_populates="store")
+    purchases: Mapped[list["Purchase"]] = relationship(back_populates="store")
+    user_accounts: Mapped[list["UserStoreAccount"]] = relationship(back_populates="store")
+    price_histories: Mapped[list["PriceHistory"]] = relationship(back_populates="store")
+    coupons: Mapped[list["Coupon"]] = relationship(back_populates="store")
+
+
+class StoreLocation(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """Physical store location."""
+
+    __tablename__ = "store_locations"
+
+    store_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("stores.id"), nullable=False)
+    address: Mapped[str] = mapped_column(String(300), nullable=False)
+    city: Mapped[str] = mapped_column(String(100), nullable=False)
+    state: Mapped[str] = mapped_column(String(2), nullable=False)
+    zip: Mapped[str] = mapped_column(String(10), nullable=False)
+    lat: Mapped[float | None] = mapped_column(Float)
+    lng: Mapped[float | None] = mapped_column(Float)
+
+    # Relationships
+    store: Mapped["Store"] = relationship(back_populates="locations")
+    purchases: Mapped[list["Purchase"]] = relationship(back_populates="store_location")

api/src/cartsnitch_api/models/user.py

@@ -0,0 +1,50 @@
+"""User and UserStoreAccount models."""
+
+import uuid
+from datetime import datetime
+from typing import TYPE_CHECKING
+
+from sqlalchemy import DateTime, ForeignKey, String, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from cartsnitch_api.constants import AccountStatus
+from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+from cartsnitch_api.types import EncryptedJSON
+
+if TYPE_CHECKING:
+    from cartsnitch_api.models.purchase import Purchase
+    from cartsnitch_api.models.store import Store
+
+
+class User(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """Application user."""
+
+    __tablename__ = "users"
+
+    email: Mapped[str] = mapped_column(String(255), nullable=False, unique=True)
+    hashed_password: Mapped[str] = mapped_column(String(255), nullable=False)
+    display_name: Mapped[str | None] = mapped_column(String(100))
+
+    # Relationships
+    store_accounts: Mapped[list["UserStoreAccount"]] = relationship(back_populates="user")
+    purchases: Mapped[list["Purchase"]] = relationship(back_populates="user")
+
+
+class UserStoreAccount(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """Link between a user and their retailer account credentials."""
+
+    __tablename__ = "user_store_accounts"
+    __table_args__ = (UniqueConstraint("user_id", "store_id", name="uq_user_store_account"),)
+
+    user_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("users.id"), nullable=False)
+    store_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("stores.id"), nullable=False)
+    session_data: Mapped[dict | None] = mapped_column(EncryptedJSON)
+    session_expires_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
+    last_sync_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
+    status: Mapped[AccountStatus] = mapped_column(
+        String(20), nullable=False, default=AccountStatus.ACTIVE
+    )
+
+    # Relationships
+    user: Mapped["User"] = relationship(back_populates="store_accounts")
+    store: Mapped["Store"] = relationship(back_populates="user_accounts")

api/src/cartsnitch_api/routes/alerts.py

@@ -0,0 +1,44 @@
+"""Alert routes: list alerts, manage settings."""
+
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from cartsnitch_api.auth.dependencies import get_current_user
+from cartsnitch_api.database import get_db
+from cartsnitch_api.schemas import AlertResponse, AlertSettingsRequest, AlertSettingsResponse
+from cartsnitch_api.services.alerts import AlertService
+
+router = APIRouter(prefix="/alerts", tags=["alerts"])
+
+
+@router.get("", response_model=list[AlertResponse])
+async def list_alerts(
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = AlertService(db)
+    return await svc.list_alerts(user_id)
+
+
+@router.get("/settings", response_model=AlertSettingsResponse)
+async def get_alert_settings(
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = AlertService(db)
+    return await svc.get_settings(user_id)
+
+
+@router.put("/settings")
+async def update_alert_settings(
+    body: AlertSettingsRequest,
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    raise HTTPException(
+        status_code=status.HTTP_501_NOT_IMPLEMENTED,
+        detail="Alert settings persistence not yet implemented. "
+        "Use GET /alerts/settings for current defaults.",
+    )

api/src/cartsnitch_api/routes/coupons.py

@@ -0,0 +1,32 @@
+"""Coupon routes: browse, relevant matches."""
+
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from cartsnitch_api.auth.dependencies import get_current_user
+from cartsnitch_api.database import get_db
+from cartsnitch_api.schemas import CouponResponse
+from cartsnitch_api.services.coupons import CouponService
+
+router = APIRouter(prefix="/coupons", tags=["coupons"])
+
+
+@router.get("", response_model=list[CouponResponse])
+async def list_coupons(
+    store_id: UUID | None = Query(None),
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = CouponService(db)
+    return await svc.list_coupons(store_id)
+
+
+@router.get("/relevant", response_model=list[CouponResponse])
+async def relevant_coupons(
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = CouponService(db)
+    return await svc.relevant_coupons(user_id)

api/src/cartsnitch_api/routes/health.py

@@ -0,0 +1,20 @@
+"""Health check and error metrics endpoints."""
+
+from fastapi import APIRouter, Depends
+
+from cartsnitch_api.auth.dependencies import verify_service_key
+from cartsnitch_api.middleware.error_handler import get_error_monitor
+
+router = APIRouter(tags=["health"])
+
+
+@router.get("/health")
+async def health():
+    return {"status": "ok"}
+
+
+@router.get("/internal/error-stats", dependencies=[Depends(verify_service_key)])
+async def error_stats():
+    """Error monitoring stats — internal only (requires X-Service-Key)."""
+    monitor = get_error_monitor()
+    return monitor.get_stats()

api/src/cartsnitch_api/routes/prices.py

@@ -0,0 +1,47 @@
+"""Price routes: trends, increases, comparison."""
+
+from typing import Annotated
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from cartsnitch_api.auth.dependencies import get_current_user
+from cartsnitch_api.database import get_db
+from cartsnitch_api.schemas import (
+    PriceComparisonResponse,
+    PriceIncreaseResponse,
+    PriceTrendResponse,
+)
+from cartsnitch_api.services.prices import PriceService
+
+router = APIRouter(prefix="/prices", tags=["prices"])
+
+
+@router.get("/trends", response_model=list[PriceTrendResponse])
+async def price_trends(
+    user_id: UUID = Depends(get_current_user),
+    category: str | None = Query(None),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = PriceService(db)
+    return await svc.get_trends(category)
+
+
+@router.get("/increases", response_model=list[PriceIncreaseResponse])
+async def price_increases(
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = PriceService(db)
+    return await svc.get_increases()
+
+
+@router.get("/comparison", response_model=list[PriceComparisonResponse])
+async def price_comparison(
+    product_ids: Annotated[list[UUID], Query()],
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = PriceService(db)
+    return await svc.get_comparison(product_ids)

api/src/cartsnitch_api/routes/products.py

@@ -0,0 +1,56 @@
+"""Product routes: search/list, detail, price history."""
+
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, Query, status
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from cartsnitch_api.auth.dependencies import get_current_user
+from cartsnitch_api.database import get_db
+from cartsnitch_api.schemas import PriceTrendResponse, ProductDetailResponse, ProductResponse
+from cartsnitch_api.services.products import ProductService
+
+router = APIRouter(prefix="/products", tags=["products"])
+
+
+@router.get("", response_model=list[ProductResponse])
+async def list_products(
+    user_id: UUID = Depends(get_current_user),
+    q: str | None = Query(None),
+    category: str | None = Query(None),
+    page: int = Query(1, ge=1),
+    page_size: int = Query(20, ge=1, le=100),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = ProductService(db)
+    return await svc.list_products(q, category, page, page_size)
+
+
+@router.get("/{product_id}", response_model=ProductDetailResponse)
+async def get_product(
+    product_id: UUID,
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = ProductService(db)
+    try:
+        return await svc.get_product(product_id)
+    except LookupError:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail="Product not found"
+        ) from None
+
+
+@router.get("/{product_id}/prices", response_model=PriceTrendResponse)
+async def get_product_prices(
+    product_id: UUID,
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = ProductService(db)
+    try:
+        return await svc.get_price_history(product_id)
+    except LookupError:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail="Product not found"
+        ) from None

api/src/cartsnitch_api/routes/public.py

@@ -0,0 +1,48 @@
+"""Public endpoints: price transparency data (no auth required)."""
+
+from typing import Annotated
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, Query, status
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from cartsnitch_api.database import get_db
+from cartsnitch_api.schemas import (
+    PublicInflationResponse,
+    PublicStoreComparisonResponse,
+    PublicTrendResponse,
+)
+from cartsnitch_api.services.public import PublicService
+
+router = APIRouter(prefix="/public", tags=["public"])
+
+
+@router.get("/trends/{product_id}", response_model=PublicTrendResponse)
+async def public_price_trend(product_id: UUID, db: AsyncSession = Depends(get_db)):
+    svc = PublicService(db)
+    try:
+        return await svc.get_trend(product_id)
+    except LookupError:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail="Product not found"
+        ) from None
+
+
+@router.get("/store-comparison", response_model=PublicStoreComparisonResponse)
+async def public_store_comparison(
+    product_ids: Annotated[list[UUID], Query(max_length=20)],
+    db: AsyncSession = Depends(get_db),
+):
+    if not product_ids:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="At least one product_id is required",
+        )
+    svc = PublicService(db)
+    return await svc.get_store_comparison(product_ids)
+
+
+@router.get("/inflation", response_model=PublicInflationResponse)
+async def public_inflation(db: AsyncSession = Depends(get_db)):
+    svc = PublicService(db)
+    return await svc.get_inflation()

api/src/cartsnitch_api/routes/purchases.py

@@ -0,0 +1,49 @@
+"""Purchase routes: list, detail, stats."""
+
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, Query, status
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from cartsnitch_api.auth.dependencies import get_current_user
+from cartsnitch_api.database import get_db
+from cartsnitch_api.schemas import PurchaseDetailResponse, PurchaseResponse, PurchaseStatsResponse
+from cartsnitch_api.services.purchases import PurchaseService
+
+router = APIRouter(prefix="/purchases", tags=["purchases"])
+
+
+@router.get("", response_model=list[PurchaseResponse])
+async def list_purchases(
+    user_id: UUID = Depends(get_current_user),
+    store_id: UUID | None = Query(None),
+    page: int = Query(1, ge=1),
+    page_size: int = Query(20, ge=1, le=100),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = PurchaseService(db)
+    return await svc.list_purchases(user_id, store_id, page, page_size)
+
+
+@router.get("/stats", response_model=PurchaseStatsResponse)
+async def purchase_stats(
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = PurchaseService(db)
+    return await svc.get_stats(user_id)
+
+
+@router.get("/{purchase_id}", response_model=PurchaseDetailResponse)
+async def get_purchase(
+    purchase_id: UUID,
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = PurchaseService(db)
+    try:
+        return await svc.get_purchase(purchase_id, user_id)
+    except LookupError:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail="Purchase not found"
+        ) from None

api/src/cartsnitch_api/routes/scraping.py

@@ -0,0 +1,42 @@
+"""Scraping routes: trigger sync, check status (proxy to ReceiptWitness)."""
+
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from httpx import HTTPStatusError, RequestError
+
+from cartsnitch_api.auth.dependencies import get_current_user
+from cartsnitch_api.schemas import SyncStatusResponse, SyncTriggerResponse
+from cartsnitch_api.services.receiptwitness import ReceiptWitnessClient
+
+router = APIRouter(prefix="/scraping", tags=["scraping"])
+
+
+@router.post("/{store_slug}/sync", response_model=SyncTriggerResponse)
+async def trigger_sync(store_slug: str, user_id: UUID = Depends(get_current_user)):
+    client = ReceiptWitnessClient()
+    try:
+        result = await client.trigger_sync(str(user_id), store_slug)
+        return result
+    except HTTPStatusError as e:
+        raise HTTPException(
+            status_code=e.response.status_code,
+            detail="Sync service error",
+        ) from e
+    except RequestError:
+        raise HTTPException(
+            status_code=status.HTTP_502_BAD_GATEWAY,
+            detail="Unable to reach sync service",
+        ) from None
+
+
+@router.get("/status", response_model=list[SyncStatusResponse])
+async def sync_status(user_id: UUID = Depends(get_current_user)):
+    client = ReceiptWitnessClient()
+    try:
+        return await client.get_sync_status(str(user_id))
+    except (HTTPStatusError, RequestError):
+        raise HTTPException(
+            status_code=status.HTTP_502_BAD_GATEWAY,
+            detail="Unable to reach sync service",
+        ) from None

api/src/cartsnitch_api/routes/shopping.py

@@ -0,0 +1,48 @@
+"""Shopping routes: optimize list, saved lists."""
+
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from httpx import HTTPStatusError, RequestError
+
+from cartsnitch_api.auth.dependencies import get_current_user
+from cartsnitch_api.schemas import OptimizeRequest, OptimizeResponse, ShoppingListResponse
+from cartsnitch_api.services.clipartist import ClipArtistClient
+
+router = APIRouter(prefix="/shopping", tags=["shopping"])
+
+
+@router.post("/optimize", response_model=OptimizeResponse)
+async def optimize_shopping(body: OptimizeRequest, user_id: UUID = Depends(get_current_user)):
+    client = ClipArtistClient()
+    try:
+        result = await client.optimize(
+            user_id=str(user_id),
+            items=[item.model_dump() for item in body.items],
+            preferred_stores=(
+                [str(s) for s in body.preferred_stores] if body.preferred_stores else None
+            ),
+        )
+        return result
+    except HTTPStatusError as e:
+        raise HTTPException(
+            status_code=e.response.status_code,
+            detail="Shopping optimization service error",
+        ) from e
+    except RequestError:
+        raise HTTPException(
+            status_code=status.HTTP_502_BAD_GATEWAY,
+            detail="Unable to reach shopping optimization service",
+        ) from None
+
+
+@router.get("/lists", response_model=list[ShoppingListResponse])
+async def list_shopping_lists(user_id: UUID = Depends(get_current_user)):
+    client = ClipArtistClient()
+    try:
+        return await client.get_shopping_lists(str(user_id))
+    except (HTTPStatusError, RequestError):
+        raise HTTPException(
+            status_code=status.HTTP_502_BAD_GATEWAY,
+            detail="Unable to reach shopping service",
+        ) from None

api/src/cartsnitch_api/routes/stores.py

@@ -0,0 +1,61 @@
+"""Store routes: list stores, manage user store connections."""
+
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from cartsnitch_api.auth.dependencies import get_current_user
+from cartsnitch_api.database import get_db
+from cartsnitch_api.schemas import ConnectStoreRequest, StoreAccountResponse, StoreResponse
+from cartsnitch_api.services.stores import StoreService
+
+router = APIRouter(tags=["stores"])
+
+
+@router.get("/stores", response_model=list[StoreResponse])
+async def list_stores(db: AsyncSession = Depends(get_db)):
+    svc = StoreService(db)
+    return await svc.list_stores()
+
+
+@router.get("/me/stores", response_model=list[StoreAccountResponse])
+async def list_user_stores(
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = StoreService(db)
+    return await svc.list_user_stores(user_id)
+
+
+@router.post(
+    "/me/stores/{store_slug}/connect",
+    response_model=StoreAccountResponse,
+    status_code=status.HTTP_201_CREATED,
+)
+async def connect_store(
+    store_slug: str,
+    body: ConnectStoreRequest,
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = StoreService(db)
+    try:
+        return await svc.connect_store(user_id, store_slug, body.credentials)
+    except LookupError as e:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(e)) from e
+    except ValueError as e:
+        raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail=str(e)) from e
+
+
+@router.delete("/me/stores/{store_slug}", status_code=status.HTTP_204_NO_CONTENT)
+async def disconnect_store(
+    store_slug: str,
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = StoreService(db)
+    try:
+        await svc.disconnect_store(user_id, store_slug)
+    except LookupError as e:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(e)) from e

api/src/cartsnitch_api/schemas.py

@@ -0,0 +1,271 @@
+"""Pydantic v2 request/response schemas for all API endpoints."""
+
+from datetime import datetime
+from uuid import UUID
+
+from pydantic import BaseModel, EmailStr, Field
+
+# ---------- Auth ----------
+# Registration, login, and session management are handled by Better-Auth (auth/ service).
+# These schemas are for the profile management endpoints only.
+
+
+class UpdateUserRequest(BaseModel):
+    email: EmailStr | None = None
+    display_name: str | None = Field(None, min_length=1, max_length=100)
+
+
+class UserResponse(BaseModel):
+    id: UUID
+    email: str
+    display_name: str
+    created_at: datetime
+
+
+# ---------- Stores ----------
+
+
+class StoreResponse(BaseModel):
+    id: UUID
+    name: str
+    slug: str
+    logo_url: str | None = None
+    supported: bool = True
+
+
+class StoreAccountResponse(BaseModel):
+    store: StoreResponse
+    connected: bool
+    last_sync_at: datetime | None = None
+    sync_status: str | None = None
+
+
+class ConnectStoreRequest(BaseModel):
+    credentials: dict | None = None
+
+
+# ---------- Purchases ----------
+
+
+class LineItemResponse(BaseModel):
+    id: UUID
+    product_id: UUID | None = None
+    name: str
+    quantity: float
+    unit_price: float
+    total_price: float
+
+
+class PurchaseResponse(BaseModel):
+    id: UUID
+    store_id: UUID
+    store_name: str
+    purchased_at: datetime
+    total: float
+    item_count: int
+
+
+class PurchaseDetailResponse(PurchaseResponse):
+    line_items: list[LineItemResponse]
+
+
+class PurchaseStatsResponse(BaseModel):
+    total_spent: float
+    purchase_count: int
+    by_store: dict[str, float]
+    by_period: dict[str, float]
+
+
+# ---------- Products ----------
+
+
+class ProductResponse(BaseModel):
+    id: UUID
+    name: str
+    brand: str | None = None
+    category: str | None = None
+    upc: str | None = None
+    image_url: str | None = None
+
+
+class ProductDetailResponse(ProductResponse):
+    prices_by_store: list["StorePriceResponse"]
+
+
+class StorePriceResponse(BaseModel):
+    store_id: UUID
+    store_name: str
+    current_price: float
+    last_seen_at: datetime
+
+
+# ---------- Prices ----------
+
+
+class PriceTrendResponse(BaseModel):
+    product_id: UUID
+    product_name: str
+    data_points: list["PricePointResponse"]
+
+
+class PricePointResponse(BaseModel):
+    date: datetime
+    price: float
+    store_id: UUID
+    store_name: str
+
+
+class PriceIncreaseResponse(BaseModel):
+    product_id: UUID
+    product_name: str
+    store_name: str
+    old_price: float
+    new_price: float
+    increase_pct: float
+    detected_at: datetime
+
+
+class PriceComparisonResponse(BaseModel):
+    product_id: UUID
+    product_name: str
+    prices: list[StorePriceResponse]
+
+
+# ---------- Coupons ----------
+
+
+class CouponResponse(BaseModel):
+    id: UUID
+    store_id: UUID
+    store_name: str
+    description: str
+    discount_value: float
+    discount_type: str
+    product_id: UUID | None = None
+    expires_at: datetime | None = None
+
+
+# ---------- Shopping ----------
+
+
+class ShoppingListItemRequest(BaseModel):
+    product_id: UUID | None = None
+    name: str
+    quantity: int = 1
+
+
+class OptimizeRequest(BaseModel):
+    items: list[ShoppingListItemRequest]
+    preferred_stores: list[UUID] | None = None
+
+
+class OptimizedStoreTrip(BaseModel):
+    store_id: UUID
+    store_name: str
+    items: list["OptimizedItemResponse"]
+    subtotal: float
+    coupons: list[CouponResponse]
+    savings: float
+
+
+class OptimizedItemResponse(BaseModel):
+    name: str
+    price: float
+    product_id: UUID | None = None
+
+
+class OptimizeResponse(BaseModel):
+    trips: list[OptimizedStoreTrip]
+    total_cost: float
+    total_savings: float
+
+
+class ShoppingListResponse(BaseModel):
+    id: UUID
+    name: str
+    item_count: int
+    created_at: datetime
+    updated_at: datetime
+
+
+# ---------- Alerts ----------
+
+
+class AlertResponse(BaseModel):
+    id: UUID
+    alert_type: str
+    product_id: UUID
+    product_name: str
+    message: str
+    triggered_at: datetime
+    read: bool = False
+
+
+class AlertSettingsRequest(BaseModel):
+    price_increase_threshold_pct: float | None = None
+    shrinkflation_enabled: bool | None = None
+    email_notifications: bool | None = None
+
+
+class AlertSettingsResponse(BaseModel):
+    price_increase_threshold_pct: float
+    shrinkflation_enabled: bool
+    email_notifications: bool
+
+
+# ---------- Scraping ----------
+
+
+class SyncTriggerResponse(BaseModel):
+    job_id: UUID
+    status: str
+    message: str
+
+
+class SyncStatusResponse(BaseModel):
+    store_slug: str
+    status: str
+    last_sync_at: datetime | None = None
+    items_synced: int | None = None
+
+
+# ---------- Public ----------
+
+
+class PublicTrendResponse(BaseModel):
+    product_id: UUID
+    product_name: str
+    data_points: list[PricePointResponse]
+
+
+class PublicStoreComparisonResponse(BaseModel):
+    products: list[PriceComparisonResponse]
+
+
+class PublicInflationResponse(BaseModel):
+    period: str
+    cartsnitch_index: float
+    cpi_baseline: float
+    categories: dict[str, float]
+
+
+# ---------- Common ----------
+
+
+class PaginatedResponse(BaseModel):
+    items: list
+    total: int
+    page: int
+    page_size: int
+    pages: int
+
+
+class ErrorResponse(BaseModel):
+    detail: str
+    code: str | None = None
+
+
+# Rebuild forward refs
+ProductDetailResponse.model_rebuild()
+PriceTrendResponse.model_rebuild()
+OptimizedStoreTrip.model_rebuild()

api/src/cartsnitch_api/services/alerts.py

@@ -0,0 +1,75 @@
+"""Alert service — price and shrinkflation alerts for users.
+
+Alerts are generated by StickerShock and ShrinkRay services and written to the DB.
+This service reads them for the API gateway.
+"""
+
+from uuid import UUID
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+
+class AlertService:
+    def __init__(self, db: AsyncSession) -> None:
+        self.db = db
+
+    async def list_alerts(self, user_id: UUID) -> list[dict]:
+        """List shrinkflation events for products the user has purchased."""
+        from cartsnitch_api.models import Purchase, PurchaseItem, ShrinkflationEvent
+
+        # Get product IDs from user's purchases
+        items_result = await self.db.execute(
+            select(PurchaseItem.normalized_product_id)
+            .join(Purchase)
+            .where(
+                Purchase.user_id == user_id,
+                PurchaseItem.normalized_product_id.isnot(None),
+            )
+            .distinct()
+        )
+        product_ids = [row[0] for row in items_result.all()]
+
+        if not product_ids:
+            return []
+
+        result = await self.db.execute(
+            select(ShrinkflationEvent)
+            .where(ShrinkflationEvent.normalized_product_id.in_(product_ids))
+            .options(selectinload(ShrinkflationEvent.normalized_product))
+            .order_by(ShrinkflationEvent.detected_date.desc())
+        )
+        events = result.scalars().all()
+
+        return [
+            {
+                "id": e.id,
+                "alert_type": "shrinkflation",
+                "product_id": e.normalized_product_id,
+                "product_name": e.normalized_product.canonical_name,
+                "message": (
+                    f"Size changed from {e.old_size}{e.old_unit} to {e.new_size}{e.new_unit}"
+                ),
+                "triggered_at": e.detected_date,
+                "read": False,
+            }
+            for e in events
+        ]
+
+    async def get_settings(self, user_id: UUID) -> dict:
+        # Alert settings would be stored in a user_settings table.
+        # For now, return defaults since the table doesn't exist yet in common lib.
+        return {
+            "price_increase_threshold_pct": 5.0,
+            "shrinkflation_enabled": True,
+            "email_notifications": False,
+        }
+
+    async def update_settings(self, user_id: UUID, **fields) -> dict:
+        # Would update user_settings table. Return merged defaults for now.
+        current = await self.get_settings(user_id)
+        for k, v in fields.items():
+            if v is not None and k in current:
+                current[k] = v
+        return current

api/src/cartsnitch_api/services/auth.py

@@ -0,0 +1,70 @@
+"""Auth service — user profile management.
+
+Registration, login, token management, and session handling are now
+handled by the Better-Auth service (auth/). This service provides
+user lookup and profile update operations for the API gateway.
+"""
+
+from uuid import UUID
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+
+class AuthService:
+    def __init__(self, db: AsyncSession) -> None:
+        self.db = db
+
+    async def get_user(self, user_id: UUID) -> dict:
+        from cartsnitch_api.models import User
+
+        result = await self.db.execute(select(User).where(User.id == user_id))
+        user = result.scalar_one_or_none()
+        if not user:
+            raise LookupError("User not found")
+
+        return {
+            "id": user.id,
+            "email": user.email,
+            "display_name": user.display_name,
+            "created_at": user.created_at,
+        }
+
+    async def update_user(self, user_id: UUID, **fields) -> dict:
+        from cartsnitch_api.models import User
+
+        result = await self.db.execute(select(User).where(User.id == user_id))
+        user = result.scalar_one_or_none()
+        if not user:
+            raise LookupError("User not found")
+
+        if "display_name" in fields and fields["display_name"] is not None:
+            user.display_name = fields["display_name"]
+        if "email" in fields and fields["email"] is not None:
+            existing = await self.db.execute(
+                select(User).where(User.email == fields["email"], User.id != user_id)
+            )
+            if existing.scalar_one_or_none():
+                raise ValueError("Email already in use")
+            user.email = fields["email"]
+
+        await self.db.commit()
+        await self.db.refresh(user)
+
+        return {
+            "id": user.id,
+            "email": user.email,
+            "display_name": user.display_name,
+            "created_at": user.created_at,
+        }
+
+    async def delete_user(self, user_id: UUID) -> None:
+        from cartsnitch_api.models import User
+
+        result = await self.db.execute(select(User).where(User.id == user_id))
+        user = result.scalar_one_or_none()
+        if not user:
+            raise LookupError("User not found")
+
+        await self.db.delete(user)
+        await self.db.commit()

api/src/cartsnitch_api/services/clipartist.py

@@ -0,0 +1,52 @@
+"""HTTP client for ClipArtist internal API."""
+
+from typing import Any, cast
+
+import httpx
+
+from cartsnitch_api.config import settings
+
+
+class ClipArtistClient:
+    def __init__(self) -> None:
+        self.base_url = settings.clipartist_url
+        self.headers = {"X-Service-Key": settings.service_key}
+
+    async def optimize(
+        self,
+        user_id: str,
+        items: list[dict],
+        preferred_stores: list[str] | None = None,
+    ) -> dict:
+        async with httpx.AsyncClient() as client:
+            resp = await client.post(
+                f"{self.base_url}/optimize",
+                headers=self.headers,
+                json={
+                    "user_id": user_id,
+                    "items": items,
+                    "preferred_stores": preferred_stores,
+                },
+            )
+            resp.raise_for_status()
+            return cast(dict[str, Any], resp.json())
+
+    async def get_shopping_lists(self, user_id: str) -> list[dict]:
+        async with httpx.AsyncClient() as client:
+            resp = await client.get(
+                f"{self.base_url}/shopping-lists",
+                headers=self.headers,
+                params={"user_id": user_id},
+            )
+            resp.raise_for_status()
+            return cast(list[dict[str, Any]], resp.json())
+
+    async def get_relevant_coupons(self, user_id: str) -> list[dict]:
+        async with httpx.AsyncClient() as client:
+            resp = await client.get(
+                f"{self.base_url}/coupons/relevant",
+                headers=self.headers,
+                params={"user_id": user_id},
+            )
+            resp.raise_for_status()
+            return cast(list[dict[str, Any]], resp.json())

api/src/cartsnitch_api/services/coupons.py

@@ -0,0 +1,76 @@
+"""Coupon service — browse coupons, find relevant ones."""
+
+from datetime import date
+from uuid import UUID
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+
+class CouponService:
+    def __init__(self, db: AsyncSession) -> None:
+        self.db = db
+
+    async def list_coupons(self, store_id: UUID | None = None) -> list[dict]:
+        from cartsnitch_api.models import Coupon
+
+        today = date.today()
+        query = (
+            select(Coupon)
+            .where((Coupon.valid_to >= today) | (Coupon.valid_to.is_(None)))
+            .options(selectinload(Coupon.store))
+            .order_by(Coupon.valid_to.asc().nullslast())
+        )
+        if store_id:
+            query = query.where(Coupon.store_id == store_id)
+
+        result = await self.db.execute(query)
+        coupons = result.scalars().all()
+        return [self._to_dict(c) for c in coupons]
+
+    async def relevant_coupons(self, user_id: UUID) -> list[dict]:
+        """Coupons for products the user has purchased."""
+        from cartsnitch_api.models import Coupon, PurchaseItem
+
+        today = date.today()
+
+        # Get product IDs from user's purchase history
+        from cartsnitch_api.models import Purchase
+
+        items_result = await self.db.execute(
+            select(PurchaseItem.normalized_product_id)
+            .join(Purchase)
+            .where(
+                Purchase.user_id == user_id,
+                PurchaseItem.normalized_product_id.isnot(None),
+            )
+            .distinct()
+        )
+        product_ids = [row[0] for row in items_result.all()]
+
+        if not product_ids:
+            return []
+
+        result = await self.db.execute(
+            select(Coupon)
+            .where(
+                Coupon.normalized_product_id.in_(product_ids),
+                (Coupon.valid_to >= today) | (Coupon.valid_to.is_(None)),
+            )
+            .options(selectinload(Coupon.store))
+        )
+        coupons = result.scalars().all()
+        return [self._to_dict(c) for c in coupons]
+
+    def _to_dict(self, c) -> dict:
+        return {
+            "id": c.id,
+            "store_id": c.store_id,
+            "store_name": c.store.name,
+            "description": c.description or c.title,
+            "discount_value": float(c.discount_value) if c.discount_value else 0,
+            "discount_type": c.discount_type,
+            "product_id": c.normalized_product_id,
+            "expires_at": c.valid_to,
+        }

api/src/cartsnitch_api/services/prices.py

@@ -0,0 +1,183 @@
+"""Price service — trends, increases, comparison."""
+
+from uuid import UUID
+
+from sqlalchemy import and_, func, select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+from cartsnitch_api.services.queries import latest_price_per_store
+
+
+class PriceService:
+    def __init__(self, db: AsyncSession) -> None:
+        self.db = db
+
+    async def get_trends(self, category: str | None = None) -> list[dict]:
+        from cartsnitch_api.models import NormalizedProduct, PriceHistory
+
+        query = (
+            select(PriceHistory)
+            .join(NormalizedProduct)
+            .options(
+                selectinload(PriceHistory.store),
+                selectinload(PriceHistory.normalized_product),
+            )
+            .order_by(PriceHistory.observed_date)
+        )
+        if category:
+            query = query.where(NormalizedProduct.category == category)
+
+        result = await self.db.execute(query)
+        prices = result.scalars().all()
+
+        # Group by product
+        by_product: dict[UUID, dict] = {}
+        for ph in prices:
+            pid = ph.normalized_product_id
+            if pid not in by_product:
+                by_product[pid] = {
+                    "product_id": pid,
+                    "product_name": ph.normalized_product.canonical_name,
+                    "data_points": [],
+                }
+            by_product[pid]["data_points"].append(
+                {
+                    "date": ph.observed_date,
+                    "price": float(ph.regular_price),
+                    "store_id": ph.store_id,
+                    "store_name": ph.store.name,
+                }
+            )
+        return list(by_product.values())
+
+    async def get_increases(self) -> list[dict]:
+        """Find products with recent significant price increases.
+
+        Uses a window function (lag) to compare each price observation with the
+        previous one per product+store, avoiding the N+1 query pattern.
+        """
+        from cartsnitch_api.models import NormalizedProduct, PriceHistory, Store
+
+        # Use lag() window function to get previous price in a single query
+        prev_price = (
+            func.lag(PriceHistory.regular_price)
+            .over(
+                partition_by=[PriceHistory.normalized_product_id, PriceHistory.store_id],
+                order_by=PriceHistory.observed_date,
+            )
+            .label("prev_price")
+        )
+
+        row_num = (
+            func.row_number()
+            .over(
+                partition_by=[PriceHistory.normalized_product_id, PriceHistory.store_id],
+                order_by=PriceHistory.observed_date.desc(),
+            )
+            .label("rn")
+        )
+
+        inner = select(
+            PriceHistory.normalized_product_id,
+            PriceHistory.store_id,
+            PriceHistory.regular_price,
+            PriceHistory.observed_date,
+            prev_price,
+            row_num,
+        ).subquery()
+
+        # Only keep the latest row (rn=1) where price increased
+        result = await self.db.execute(
+            select(
+                inner.c.normalized_product_id,
+                inner.c.store_id,
+                inner.c.regular_price,
+                inner.c.observed_date,
+                inner.c.prev_price,
+                NormalizedProduct.canonical_name,
+                Store.name.label("store_name"),
+            )
+            .join(NormalizedProduct, NormalizedProduct.id == inner.c.normalized_product_id)
+            .join(Store, Store.id == inner.c.store_id)
+            .where(
+                inner.c.rn == 1,
+                inner.c.prev_price.isnot(None),
+                inner.c.regular_price > inner.c.prev_price,
+            )
+        )
+
+        increases = []
+        for row in result.all():
+            old = float(row.prev_price)
+            new = float(row.regular_price)
+            increases.append(
+                {
+                    "product_id": row.normalized_product_id,
+                    "product_name": row.canonical_name,
+                    "store_name": row.store_name,
+                    "old_price": old,
+                    "new_price": new,
+                    "increase_pct": round((new - old) / old * 100, 2),
+                    "detected_at": row.observed_date,
+                }
+            )
+
+        increases.sort(key=lambda x: x["increase_pct"], reverse=True)
+        return increases
+
+    async def get_comparison(self, product_ids: list[UUID]) -> list[dict]:
+        from cartsnitch_api.models import NormalizedProduct, PriceHistory
+
+        if not product_ids:
+            return []
+
+        # Fetch all requested products in one query
+        prod_result = await self.db.execute(
+            select(NormalizedProduct).where(NormalizedProduct.id.in_(product_ids))
+        )
+        products_by_id = {p.id: p for p in prod_result.scalars().all()}
+
+        # Latest prices for all requested products in one query
+        subq = latest_price_per_store(product_ids)
+        prices_result = await self.db.execute(
+            select(PriceHistory)
+            .join(
+                subq,
+                and_(
+                    PriceHistory.store_id == subq.c.store_id,
+                    PriceHistory.observed_date == subq.c.max_date,
+                    PriceHistory.normalized_product_id == subq.c.normalized_product_id,
+                ),
+            )
+            .where(PriceHistory.normalized_product_id.in_(product_ids))
+            .options(selectinload(PriceHistory.store))
+        )
+        all_prices = prices_result.scalars().all()
+
+        # Group prices by product
+        prices_by_product: dict[UUID, list] = {pid: [] for pid in product_ids}
+        for ph in all_prices:
+            prices_by_product.setdefault(ph.normalized_product_id, []).append(ph)
+
+        comparisons = []
+        for pid in product_ids:
+            product = products_by_id.get(pid)
+            if not product:
+                continue
+            comparisons.append(
+                {
+                    "product_id": pid,
+                    "product_name": product.canonical_name,
+                    "prices": [
+                        {
+                            "store_id": ph.store_id,
+                            "store_name": ph.store.name,
+                            "current_price": float(ph.regular_price),
+                            "last_seen_at": ph.observed_date,
+                        }
+                        for ph in prices_by_product.get(pid, [])
+                    ],
+                }
+            )
+        return comparisons

api/src/cartsnitch_api/services/products.py

@@ -0,0 +1,124 @@
+"""Product service — catalog, detail, price history."""
+
+from uuid import UUID
+
+from sqlalchemy import and_, select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+from cartsnitch_api.services.queries import latest_price_per_store
+
+
+class ProductService:
+    def __init__(self, db: AsyncSession) -> None:
+        self.db = db
+
+    async def list_products(
+        self,
+        q: str | None = None,
+        category: str | None = None,
+        page: int = 1,
+        page_size: int = 20,
+    ) -> list[dict]:
+        from cartsnitch_api.models import NormalizedProduct
+
+        query = select(NormalizedProduct)
+        if q:
+            # Escape SQL LIKE wildcards in user input
+            safe_q = q.replace("\\", "\\\\").replace("%", "\\%").replace("_", "\\_")
+            query = query.where(NormalizedProduct.canonical_name.ilike(f"%{safe_q}%"))
+        if category:
+            query = query.where(NormalizedProduct.category == category)
+        query = query.order_by(NormalizedProduct.canonical_name)
+        query = query.offset((page - 1) * page_size).limit(page_size)
+
+        result = await self.db.execute(query)
+        products = result.scalars().all()
+        return [
+            {
+                "id": p.id,
+                "name": p.canonical_name,
+                "brand": p.brand,
+                "category": p.category,
+                "upc": (p.upc_variants[0] if p.upc_variants else None),
+                "image_url": None,
+            }
+            for p in products
+        ]
+
+    async def get_product(self, product_id: UUID) -> dict:
+        from cartsnitch_api.models import NormalizedProduct, PriceHistory
+
+        result = await self.db.execute(
+            select(NormalizedProduct).where(NormalizedProduct.id == product_id)
+        )
+        product = result.scalar_one_or_none()
+        if not product:
+            raise LookupError("Product not found")
+
+        # Get latest price per store
+        subq = latest_price_per_store([product_id])
+        prices_result = await self.db.execute(
+            select(PriceHistory)
+            .join(
+                subq,
+                and_(
+                    PriceHistory.store_id == subq.c.store_id,
+                    PriceHistory.observed_date == subq.c.max_date,
+                    PriceHistory.normalized_product_id == subq.c.normalized_product_id,
+                ),
+            )
+            .where(PriceHistory.normalized_product_id == product_id)
+            .options(selectinload(PriceHistory.store))
+        )
+        prices = prices_result.scalars().all()
+
+        return {
+            "id": product.id,
+            "name": product.canonical_name,
+            "brand": product.brand,
+            "category": product.category,
+            "upc": (product.upc_variants[0] if product.upc_variants else None),
+            "image_url": None,
+            "prices_by_store": [
+                {
+                    "store_id": ph.store_id,
+                    "store_name": ph.store.name,
+                    "current_price": float(ph.regular_price),
+                    "last_seen_at": ph.observed_date,
+                }
+                for ph in prices
+            ],
+        }
+
+    async def get_price_history(self, product_id: UUID) -> dict:
+        from cartsnitch_api.models import NormalizedProduct, PriceHistory
+
+        result = await self.db.execute(
+            select(NormalizedProduct).where(NormalizedProduct.id == product_id)
+        )
+        product = result.scalar_one_or_none()
+        if not product:
+            raise LookupError("Product not found")
+
+        prices_result = await self.db.execute(
+            select(PriceHistory)
+            .where(PriceHistory.normalized_product_id == product_id)
+            .options(selectinload(PriceHistory.store))
+            .order_by(PriceHistory.observed_date)
+        )
+        prices = prices_result.scalars().all()
+
+        return {
+            "product_id": product.id,
+            "product_name": product.canonical_name,
+            "data_points": [
+                {
+                    "date": ph.observed_date,
+                    "price": float(ph.regular_price),
+                    "store_id": ph.store_id,
+                    "store_name": ph.store.name,
+                }
+                for ph in prices
+            ],
+        }

api/src/cartsnitch_api/services/public.py

@@ -0,0 +1,129 @@
+"""Public service — unauthenticated price transparency endpoints."""
+
+from uuid import UUID
+
+from sqlalchemy import and_, func, select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+from cartsnitch_api.services.queries import latest_price_per_store
+
+
+class PublicService:
+    def __init__(self, db: AsyncSession) -> None:
+        self.db = db
+
+    async def get_trend(self, product_id: UUID) -> dict:
+        from cartsnitch_api.models import NormalizedProduct, PriceHistory
+
+        result = await self.db.execute(
+            select(NormalizedProduct).where(NormalizedProduct.id == product_id)
+        )
+        product = result.scalar_one_or_none()
+        if not product:
+            raise LookupError("Product not found")
+
+        prices_result = await self.db.execute(
+            select(PriceHistory)
+            .where(PriceHistory.normalized_product_id == product_id)
+            .options(selectinload(PriceHistory.store))
+            .order_by(PriceHistory.observed_date)
+        )
+        prices = prices_result.scalars().all()
+
+        return {
+            "product_id": product.id,
+            "product_name": product.canonical_name,
+            "data_points": [
+                {
+                    "date": ph.observed_date,
+                    "price": float(ph.regular_price),
+                    "store_id": ph.store_id,
+                    "store_name": ph.store.name,
+                }
+                for ph in prices
+            ],
+        }
+
+    async def get_store_comparison(self, product_ids: list[UUID]) -> dict:
+        from cartsnitch_api.models import NormalizedProduct, PriceHistory
+
+        if not product_ids:
+            return {"products": []}
+
+        # Fetch all products in one query
+        prod_result = await self.db.execute(
+            select(NormalizedProduct).where(NormalizedProduct.id.in_(product_ids))
+        )
+        products_by_id = {p.id: p for p in prod_result.scalars().all()}
+
+        # Latest prices for all requested products in one query
+        subq = latest_price_per_store(product_ids)
+        prices_result = await self.db.execute(
+            select(PriceHistory)
+            .join(
+                subq,
+                and_(
+                    PriceHistory.store_id == subq.c.store_id,
+                    PriceHistory.observed_date == subq.c.max_date,
+                    PriceHistory.normalized_product_id == subq.c.normalized_product_id,
+                ),
+            )
+            .where(PriceHistory.normalized_product_id.in_(product_ids))
+            .options(selectinload(PriceHistory.store))
+        )
+        all_prices = prices_result.scalars().all()
+
+        # Group by product
+        prices_by_product: dict[UUID, list] = {}
+        for ph in all_prices:
+            prices_by_product.setdefault(ph.normalized_product_id, []).append(ph)
+
+        products = []
+        for pid in product_ids:
+            product = products_by_id.get(pid)
+            if not product:
+                continue
+            products.append(
+                {
+                    "product_id": pid,
+                    "product_name": product.canonical_name,
+                    "prices": [
+                        {
+                            "store_id": ph.store_id,
+                            "store_name": ph.store.name,
+                            "current_price": float(ph.regular_price),
+                            "last_seen_at": ph.observed_date,
+                        }
+                        for ph in prices_by_product.get(pid, [])
+                    ],
+                }
+            )
+
+        return {"products": products}
+
+    async def get_inflation(self) -> dict:
+        """Aggregate price change stats. Compares average prices across periods."""
+        from cartsnitch_api.models import NormalizedProduct, PriceHistory
+
+        # Get average prices grouped by category for recent vs older data
+        result = await self.db.execute(
+            select(
+                NormalizedProduct.category,
+                func.avg(PriceHistory.regular_price),
+            )
+            .join(NormalizedProduct)
+            .group_by(NormalizedProduct.category)
+        )
+        categories = {}
+        for row in result.all():
+            cat, avg_price = row
+            if cat:
+                categories[cat] = float(avg_price) if avg_price else 0.0
+
+        return {
+            "period": "all-time",
+            "cartsnitch_index": sum(categories.values()) / max(len(categories), 1),
+            "cpi_baseline": 100.0,
+            "categories": categories,
+        }

api/src/cartsnitch_api/services/purchases.py

@@ -0,0 +1,116 @@
+"""Purchase service — list, detail, stats."""
+
+from uuid import UUID
+
+from sqlalchemy import func, select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+
+class PurchaseService:
+    def __init__(self, db: AsyncSession) -> None:
+        self.db = db
+
+    async def list_purchases(
+        self,
+        user_id: UUID,
+        store_id: UUID | None = None,
+        page: int = 1,
+        page_size: int = 20,
+    ) -> list[dict]:
+        from cartsnitch_api.models import Purchase, PurchaseItem, Store
+
+        # Count items per purchase in a single subquery instead of N+1
+        item_counts = (
+            select(
+                PurchaseItem.purchase_id,
+                func.count().label("item_count"),
+            )
+            .group_by(PurchaseItem.purchase_id)
+            .subquery()
+        )
+
+        query = (
+            select(Purchase, item_counts.c.item_count, Store.name.label("store_name"))
+            .join(Store, Store.id == Purchase.store_id)
+            .outerjoin(item_counts, item_counts.c.purchase_id == Purchase.id)
+            .where(Purchase.user_id == user_id)
+        )
+        if store_id:
+            query = query.where(Purchase.store_id == store_id)
+
+        query = query.order_by(Purchase.purchase_date.desc())
+        query = query.offset((page - 1) * page_size).limit(page_size)
+
+        result = await self.db.execute(query)
+
+        return [
+            {
+                "id": p.id,
+                "store_id": p.store_id,
+                "store_name": store_name,
+                "purchased_at": p.purchase_date,
+                "total": float(p.total),
+                "item_count": item_count or 0,
+            }
+            for p, item_count, store_name in result.all()
+        ]
+
+    async def get_purchase(self, purchase_id: UUID, user_id: UUID) -> dict:
+        from cartsnitch_api.models import Purchase
+
+        result = await self.db.execute(
+            select(Purchase)
+            .where(Purchase.id == purchase_id, Purchase.user_id == user_id)
+            .options(selectinload(Purchase.store), selectinload(Purchase.items))
+        )
+        purchase = result.scalar_one_or_none()
+        if not purchase:
+            raise LookupError("Purchase not found")
+
+        return {
+            "id": purchase.id,
+            "store_id": purchase.store_id,
+            "store_name": purchase.store.name,
+            "purchased_at": purchase.purchase_date,
+            "total": float(purchase.total),
+            "item_count": len(purchase.items),
+            "line_items": [
+                {
+                    "id": item.id,
+                    "product_id": item.normalized_product_id,
+                    "name": item.product_name_raw,
+                    "quantity": float(item.quantity),
+                    "unit_price": float(item.unit_price),
+                    "total_price": float(item.extended_price),
+                }
+                for item in purchase.items
+            ],
+        }
+
+    async def get_stats(self, user_id: UUID) -> dict:
+        from cartsnitch_api.models import Purchase
+
+        result = await self.db.execute(
+            select(Purchase)
+            .where(Purchase.user_id == user_id)
+            .options(selectinload(Purchase.store))
+        )
+        purchases = result.scalars().all()
+
+        total_spent = sum(float(p.total) for p in purchases)
+        by_store: dict[str, float] = {}
+        by_period: dict[str, float] = {}
+
+        for p in purchases:
+            store_name = p.store.name
+            by_store[store_name] = by_store.get(store_name, 0) + float(p.total)
+            period = p.purchase_date.strftime("%Y-%m")
+            by_period[period] = by_period.get(period, 0) + float(p.total)
+
+        return {
+            "total_spent": total_spent,
+            "purchase_count": len(purchases),
+            "by_store": by_store,
+            "by_period": by_period,
+        }

api/src/cartsnitch_api/services/queries.py

@@ -0,0 +1,23 @@
+"""Shared query helpers for service layer."""
+
+from uuid import UUID
+
+from sqlalchemy import func, select
+
+
+def latest_price_per_store(product_ids: list[UUID] | None = None):
+    """Subquery returning the latest observed_date per product+store.
+
+    Optionally filtered to a list of product IDs. Returns a subquery with
+    columns: normalized_product_id, store_id, max_date.
+    """
+    from cartsnitch_api.models import PriceHistory
+
+    query = select(
+        PriceHistory.normalized_product_id,
+        PriceHistory.store_id,
+        func.max(PriceHistory.observed_date).label("max_date"),
+    ).group_by(PriceHistory.normalized_product_id, PriceHistory.store_id)
+    if product_ids is not None:
+        query = query.where(PriceHistory.normalized_product_id.in_(product_ids))
+    return query.subquery()

api/src/cartsnitch_api/services/receiptwitness.py

@@ -0,0 +1,33 @@
+"""HTTP client for ReceiptWitness internal API."""
+
+from typing import Any, cast
+
+import httpx
+
+from cartsnitch_api.config import settings
+
+
+class ReceiptWitnessClient:
+    def __init__(self) -> None:
+        self.base_url = settings.receiptwitness_url
+        self.headers = {"X-Service-Key": settings.service_key}
+
+    async def trigger_sync(self, user_id: str, store_slug: str) -> dict:
+        async with httpx.AsyncClient() as client:
+            resp = await client.post(
+                f"{self.base_url}/sync/{store_slug}",
+                headers=self.headers,
+                json={"user_id": user_id},
+            )
+            resp.raise_for_status()
+            return cast(dict[str, Any], resp.json())
+
+    async def get_sync_status(self, user_id: str) -> list[dict]:
+        async with httpx.AsyncClient() as client:
+            resp = await client.get(
+                f"{self.base_url}/sync/status",
+                headers=self.headers,
+                params={"user_id": user_id},
+            )
+            resp.raise_for_status()
+            return cast(list[dict[str, Any]], resp.json())

api/src/cartsnitch_api/services/shrinkray.py

@@ -0,0 +1,23 @@
+"""HTTP client for ShrinkRay internal API."""
+
+from typing import Any, cast
+
+import httpx
+
+from cartsnitch_api.config import settings
+
+
+class ShrinkRayClient:
+    def __init__(self) -> None:
+        self.base_url = settings.shrinkray_url
+        self.headers = {"X-Service-Key": settings.service_key}
+
+    async def get_shrinkflation_alerts(self, user_id: str) -> list[dict]:
+        async with httpx.AsyncClient() as client:
+            resp = await client.get(
+                f"{self.base_url}/alerts",
+                headers=self.headers,
+                params={"user_id": user_id},
+            )
+            resp.raise_for_status()
+            return cast(list[dict[str, Any]], resp.json())

api/src/cartsnitch_api/services/stickershock.py

@@ -0,0 +1,32 @@
+"""HTTP client for StickerShock internal API."""
+
+from typing import Any, cast
+
+import httpx
+
+from cartsnitch_api.config import settings
+
+
+class StickerShockClient:
+    def __init__(self) -> None:
+        self.base_url = settings.stickershock_url
+        self.headers = {"X-Service-Key": settings.service_key}
+
+    async def get_price_increases(self, params: dict | None = None) -> list[dict]:
+        async with httpx.AsyncClient() as client:
+            resp = await client.get(
+                f"{self.base_url}/increases",
+                headers=self.headers,
+                params=params,
+            )
+            resp.raise_for_status()
+            return cast(list[dict[str, Any]], resp.json())
+
+    async def get_inflation_data(self) -> dict:
+        async with httpx.AsyncClient() as client:
+            resp = await client.get(
+                f"{self.base_url}/inflation",
+                headers=self.headers,
+            )
+            resp.raise_for_status()
+            return cast(dict[str, Any], resp.json())

api/src/cartsnitch_api/services/stores.py

@@ -0,0 +1,129 @@
+"""Store service — list stores, manage user store account connections."""
+
+import json
+from uuid import UUID
+
+from cryptography.fernet import Fernet
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+from cartsnitch_api.config import settings
+
+
+def _get_fernet() -> Fernet:
+    return Fernet(settings.fernet_key.encode())
+
+
+class StoreService:
+    def __init__(self, db: AsyncSession) -> None:
+        self.db = db
+
+    async def list_stores(self) -> list[dict]:
+        from cartsnitch_api.models import Store
+
+        result = await self.db.execute(select(Store).order_by(Store.name))
+        stores = result.scalars().all()
+        return [
+            {
+                "id": s.id,
+                "name": s.name,
+                "slug": s.slug,
+                "logo_url": s.logo_url,
+                "supported": True,
+            }
+            for s in stores
+        ]
+
+    async def list_user_stores(self, user_id: UUID) -> list[dict]:
+        from cartsnitch_api.models import UserStoreAccount
+
+        result = await self.db.execute(
+            select(UserStoreAccount)
+            .where(UserStoreAccount.user_id == user_id)
+            .options(selectinload(UserStoreAccount.store))
+        )
+        accounts = result.scalars().all()
+        return [
+            {
+                "store": {
+                    "id": a.store.id,
+                    "name": a.store.name,
+                    "slug": a.store.slug,
+                    "logo_url": a.store.logo_url,
+                    "supported": True,
+                },
+                "connected": a.status == "active",
+                "last_sync_at": a.last_sync_at,
+                "sync_status": a.status,
+            }
+            for a in accounts
+        ]
+
+    async def connect_store(self, user_id: UUID, store_slug: str, credentials: dict | None) -> dict:
+        from cartsnitch_api.models import Store, UserStoreAccount
+
+        result = await self.db.execute(select(Store).where(Store.slug == store_slug))
+        store = result.scalar_one_or_none()
+        if not store:
+            raise LookupError(f"Store '{store_slug}' not found")
+
+        existing = await self.db.execute(
+            select(UserStoreAccount).where(
+                UserStoreAccount.user_id == user_id,
+                UserStoreAccount.store_id == store.id,
+            )
+        )
+        if existing.scalar_one_or_none():
+            raise ValueError("Store account already connected")
+
+        encrypted_data = None
+        if credentials:
+            fernet = _get_fernet()
+            encrypted_data = {
+                "encrypted": fernet.encrypt(json.dumps(credentials).encode()).decode()
+            }
+
+        account = UserStoreAccount(
+            user_id=user_id,
+            store_id=store.id,
+            session_data=encrypted_data,
+            status="active",
+        )
+        self.db.add(account)
+        await self.db.commit()
+        await self.db.refresh(account)
+
+        return {
+            "store": {
+                "id": store.id,
+                "name": store.name,
+                "slug": store.slug,
+                "logo_url": store.logo_url,
+                "supported": True,
+            },
+            "connected": True,
+            "last_sync_at": None,
+            "sync_status": "active",
+        }
+
+    async def disconnect_store(self, user_id: UUID, store_slug: str) -> None:
+        from cartsnitch_api.models import Store, UserStoreAccount
+
+        result = await self.db.execute(select(Store).where(Store.slug == store_slug))
+        store = result.scalar_one_or_none()
+        if not store:
+            raise LookupError(f"Store '{store_slug}' not found")
+
+        result = await self.db.execute(
+            select(UserStoreAccount).where(
+                UserStoreAccount.user_id == user_id,
+                UserStoreAccount.store_id == store.id,
+            )
+        )
+        account = result.scalar_one_or_none()
+        if not account:
+            raise LookupError("Store account not connected")
+
+        await self.db.delete(account)
+        await self.db.commit()

api/src/cartsnitch_api/types.py

@@ -0,0 +1,36 @@
+"""Custom SQLAlchemy column types."""
+
+import json
+
+from cryptography.fernet import Fernet
+from sqlalchemy import Text
+from sqlalchemy.types import TypeDecorator
+
+from cartsnitch_api.config import settings
+
+
+def _get_fernet() -> Fernet:
+    return Fernet(settings.fernet_key.encode())
+
+
+class EncryptedJSON(TypeDecorator):
+    """SQLAlchemy type that transparently encrypts/decrypts JSON using Fernet.
+
+    Stores data as a Fernet-encrypted text blob in the database.
+    On read, decrypts and deserialises back to a Python dict/list.
+    """
+
+    impl = Text
+    cache_ok = True
+
+    def process_bind_param(self, value, dialect):
+        if value is None:
+            return None
+        plaintext = json.dumps(value).encode()
+        return _get_fernet().encrypt(plaintext).decode()
+
+    def process_result_value(self, value, dialect):
+        if value is None:
+            return None
+        decrypted = _get_fernet().decrypt(value.encode())
+        return json.loads(decrypted)

api/tests/conftest.py

@@ -0,0 +1,187 @@
+"""Shared test fixtures with in-memory SQLite database.
+
+Session-based auth: tests create users and sessions directly in the DB,
+matching the Better-Auth session validation flow.
+"""
+
+import secrets
+import uuid
+from datetime import UTC, datetime, timedelta
+
+import pytest
+from httpx import ASGITransport, AsyncClient
+from sqlalchemy import create_engine, event, text
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.orm import sessionmaker
+
+from cartsnitch_api.config import settings as cartsnitch_settings
+from cartsnitch_api.database import get_db
+from cartsnitch_api.main import create_app
+from cartsnitch_api.models import Base
+
+TEST_DATABASE_URL = "sqlite+aiosqlite:///:memory:"
+
+
+@pytest.fixture(autouse=True)
+def disable_rate_limiting():
+    """Disable rate limiting for all tests to prevent 429 interference."""
+    cartsnitch_settings.rate_limit_enabled = False
+    yield
+    cartsnitch_settings.rate_limit_enabled = True
+
+
+@pytest.fixture
+def engine():
+    """Sync in-memory SQLite engine for model unit tests."""
+    eng = create_engine("sqlite:///:memory:")
+    Base.metadata.create_all(eng)
+    yield eng
+    eng.dispose()
+
+
+@pytest.fixture
+def session(engine):
+    """Sync SQLAlchemy session for model unit tests."""
+    factory = sessionmaker(bind=engine)
+    with factory() as sess:
+        yield sess
+
+
+@pytest.fixture
+async def db_engine():
+    engine = create_async_engine(TEST_DATABASE_URL, echo=False)
+
+    @event.listens_for(engine.sync_engine, "connect")
+    def set_sqlite_pragma(dbapi_connection, connection_record):
+        cursor = dbapi_connection.cursor()
+        cursor.execute("PRAGMA foreign_keys=ON")
+        cursor.close()
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+        # Create Better-Auth tables (not managed by SQLAlchemy models)
+        await conn.execute(text("""
+            CREATE TABLE IF NOT EXISTS sessions (
+                id TEXT PRIMARY KEY,
+                token TEXT NOT NULL UNIQUE,
+                user_id TEXT NOT NULL,
+                expires_at TIMESTAMP NOT NULL,
+                ip_address TEXT,
+                user_agent TEXT,
+                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL,
+                updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL
+            )
+        """))
+        await conn.execute(text("""
+            CREATE TABLE IF NOT EXISTS accounts (
+                id TEXT PRIMARY KEY,
+                user_id TEXT NOT NULL,
+                account_id TEXT NOT NULL,
+                provider_id TEXT NOT NULL,
+                access_token TEXT,
+                refresh_token TEXT,
+                access_token_expires_at TIMESTAMP,
+                refresh_token_expires_at TIMESTAMP,
+                scope TEXT,
+                id_token TEXT,
+                password TEXT,
+                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL,
+                updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL
+            )
+        """))
+        await conn.execute(text("""
+            CREATE TABLE IF NOT EXISTS verifications (
+                id TEXT PRIMARY KEY,
+                identifier TEXT NOT NULL,
+                value TEXT NOT NULL,
+                expires_at TIMESTAMP NOT NULL,
+                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL,
+                updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL
+            )
+        """))
+
+    yield engine
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.drop_all)
+
+    await engine.dispose()
+
+
+@pytest.fixture
+async def db_session(db_engine):
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        yield session
+
+
+@pytest.fixture
+async def client(db_engine):
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+
+    async def override_get_db():
+        async with factory() as session:
+            yield session
+
+    app = create_app()
+    app.dependency_overrides[get_db] = override_get_db
+
+    transport = ASGITransport(app=app)
+    async with AsyncClient(transport=transport, base_url="http://test") as ac:
+        yield ac
+
+    app.dependency_overrides.clear()
+
+
+async def _create_test_user_and_session(client: AsyncClient, db_engine, **user_overrides) -> tuple[dict, str]:
+    """Create a test user and a valid session directly in the DB.
+
+    Returns (user_dict, session_token).
+    """
+    user_id = str(uuid.uuid4())
+    email = user_overrides.get("email", "test@example.com")
+    display_name = user_overrides.get("display_name", "Test User")
+    session_token = secrets.token_urlsafe(32)
+    session_id = str(uuid.uuid4())
+    now = datetime.now(UTC).isoformat()
+    expires = (datetime.now(UTC) + timedelta(days=7)).isoformat()
+
+    async with db_engine.begin() as conn:
+        await conn.execute(
+            text(
+                "INSERT INTO users (id, email, hashed_password, display_name, email_verified, created_at, updated_at) "
+                "VALUES (:id, :email, :hashed_password, :display_name, :email_verified, :created_at, :updated_at)"
+            ),
+            {
+                "id": user_id,
+                "email": email,
+                "hashed_password": "not-used-with-better-auth",
+                "display_name": display_name,
+                "email_verified": False,
+                "created_at": now,
+                "updated_at": now,
+            },
+        )
+        await conn.execute(
+            text(
+                "INSERT INTO sessions (id, token, user_id, expires_at, created_at, updated_at) "
+                "VALUES (:id, :token, :user_id, :expires_at, :created_at, :updated_at)"
+            ),
+            {
+                "id": session_id,
+                "token": session_token,
+                "user_id": user_id,
+                "expires_at": expires,
+                "created_at": now,
+                "updated_at": now,
+            },
+        )
+
+    return {"id": user_id, "email": email, "display_name": display_name}, session_token
+
+
+@pytest.fixture
+async def auth_headers(client, db_engine):
+    """Create a test user with a valid session and return auth headers."""
+    _, session_token = await _create_test_user_and_session(client, db_engine)
+    return {"Cookie": f"better-auth.session_token={session_token}"}

api/tests/test_auth/test_auth_endpoints.py

@@ -0,0 +1,123 @@
+"""Integration tests for auth profile endpoints.
+
+Registration, login, and session management are handled by the Better-Auth
+service. These tests cover the profile endpoints (GET/PATCH/DELETE /auth/me)
+which validate sessions via the shared sessions table.
+"""
+
+import pytest
+
+
+@pytest.mark.asyncio
+async def test_get_me(client, auth_headers):
+    resp = await client.get("/auth/me", headers=auth_headers)
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["email"] == "test@example.com"
+    assert data["display_name"] == "Test User"
+    assert "id" in data
+    assert "created_at" in data
+
+
+@pytest.mark.asyncio
+async def test_get_me_unauthorized(client):
+    resp = await client.get("/auth/me")
+    assert resp.status_code in (401, 403)
+
+
+@pytest.mark.asyncio
+async def test_get_me_invalid_session(client):
+    resp = await client.get(
+        "/auth/me",
+        headers={"Cookie": "better-auth.session_token=invalid-token"},
+    )
+    assert resp.status_code == 401
+
+
+@pytest.mark.asyncio
+async def test_get_me_with_bearer_token(client, db_engine):
+    """Session tokens can also be passed as Bearer tokens for API clients."""
+    from tests.conftest import _create_test_user_and_session
+
+    _, session_token = await _create_test_user_and_session(
+        client, db_engine, email="bearer@example.com", display_name="Bearer User"
+    )
+    resp = await client.get(
+        "/auth/me",
+        headers={"Authorization": f"Bearer {session_token}"},
+    )
+    assert resp.status_code == 200
+    assert resp.json()["email"] == "bearer@example.com"
+
+
+@pytest.mark.asyncio
+async def test_update_me(client, auth_headers):
+    resp = await client.patch(
+        "/auth/me",
+        headers=auth_headers,
+        json={"display_name": "Updated Name"},
+    )
+    assert resp.status_code == 200
+    assert resp.json()["display_name"] == "Updated Name"
+
+
+@pytest.mark.asyncio
+async def test_delete_me(client, auth_headers):
+    resp = await client.delete("/auth/me", headers=auth_headers)
+    assert resp.status_code == 204
+
+    # Session is still valid but user is gone
+    resp = await client.get("/auth/me", headers=auth_headers)
+    assert resp.status_code == 404
+
+
+@pytest.mark.asyncio
+async def test_expired_session_rejected(client, db_engine):
+    """Expired sessions must be rejected."""
+    import secrets
+    import uuid
+    from datetime import UTC, datetime, timedelta
+
+    from sqlalchemy import text
+
+    user_id = str(uuid.uuid4())
+    session_token = secrets.token_urlsafe(32)
+    now = datetime.now(UTC).isoformat()
+    expired = (datetime.now(UTC) - timedelta(hours=1)).isoformat()
+
+    async with db_engine.begin() as conn:
+        await conn.execute(
+            text(
+                "INSERT INTO users (id, email, hashed_password, display_name, email_verified, created_at, updated_at) "
+                "VALUES (:id, :email, :hp, :dn, :ev, :ca, :ua)"
+            ),
+            {
+                "id": user_id,
+                "email": "expired@example.com",
+                "hp": "unused",
+                "dn": "Expired User",
+                "ev": False,
+                "ca": now,
+                "ua": now,
+            },
+        )
+        await conn.execute(
+            text(
+                "INSERT INTO sessions (id, token, user_id, expires_at, created_at, updated_at) "
+                "VALUES (:id, :token, :uid, :ea, :ca, :ua)"
+            ),
+            {
+                "id": str(uuid.uuid4()),
+                "token": session_token,
+                "uid": user_id,
+                "ea": expired,
+                "ca": now,
+                "ua": now,
+            },
+        )
+
+    resp = await client.get(
+        "/auth/me",
+        headers={"Cookie": f"better-auth.session_token={session_token}"},
+    )
+    assert resp.status_code == 401

api/tests/test_e2e/conftest.py

@@ -0,0 +1,256 @@
+"""Shared fixtures for E2E integration tests.
+
+Seeds a realistic dataset with stores, products, price history,
+purchases, coupons, and shrinkflation events so E2E flows can
+exercise cross-resource queries against real data.
+"""
+
+from datetime import date, timedelta
+from decimal import Decimal
+from uuid import UUID
+
+import pytest
+from sqlalchemy import text
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
+
+from cartsnitch_api.models import (
+    Coupon,
+    NormalizedProduct,
+    PriceHistory,
+    Purchase,
+    PurchaseItem,
+    ShrinkflationEvent,
+    Store,
+)
+
+# Shared test constants
+ZERO_UUID = "00000000-0000-0000-0000-000000000000"
+BAD_UUID = "not-a-uuid"
+# Fixed anchor date for deterministic tests
+ANCHOR_DATE = date(2026, 3, 15)
+
+
+@pytest.fixture
+async def seed_data(db_engine, auth_headers):
+    """Seed a full dataset and return identifiers for test assertions."""
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        # -- Stores --
+        meijer = Store(name="Meijer", slug="meijer")
+        kroger = Store(name="Kroger", slug="kroger")
+        target = Store(name="Target", slug="target")
+        session.add_all([meijer, kroger, target])
+        await session.flush()
+
+        # -- Products --
+        cheerios = NormalizedProduct(
+            canonical_name="Cheerios 18oz",
+            category="pantry",
+            brand="General Mills",
+            size="18",
+            size_unit="oz",
+            upc_variants=["016000275263"],
+        )
+        milk = NormalizedProduct(
+            canonical_name="Whole Milk 1gal",
+            category="dairy",
+            brand="Meijer",
+            size="1",
+            size_unit="gal",
+        )
+        chicken = NormalizedProduct(
+            canonical_name="Chicken Breast 1lb",
+            category="meat",
+            brand=None,
+            size="1",
+            size_unit="lb",
+        )
+        session.add_all([cheerios, milk, chicken])
+        await session.flush()
+
+        # -- Price history (multiple dates, multiple stores) --
+        today = ANCHOR_DATE
+        prices = []
+        # Cheerios at Meijer: price increase over time
+        for i, price_val in enumerate([Decimal("3.99"), Decimal("4.29"), Decimal("4.79")]):
+            prices.append(
+                PriceHistory(
+                    normalized_product_id=cheerios.id,
+                    store_id=meijer.id,
+                    observed_date=today - timedelta(days=60 - i * 30),
+                    regular_price=price_val,
+                    source="receipt",
+                )
+            )
+        # Cheerios at Kroger: stable price
+        for i in range(3):
+            prices.append(
+                PriceHistory(
+                    normalized_product_id=cheerios.id,
+                    store_id=kroger.id,
+                    observed_date=today - timedelta(days=60 - i * 30),
+                    regular_price=Decimal("4.49"),
+                    source="catalog",
+                )
+            )
+        # Milk at Meijer
+        prices.append(
+            PriceHistory(
+                normalized_product_id=milk.id,
+                store_id=meijer.id,
+                observed_date=today - timedelta(days=7),
+                regular_price=Decimal("3.29"),
+                source="receipt",
+            )
+        )
+        # Milk at Kroger
+        prices.append(
+            PriceHistory(
+                normalized_product_id=milk.id,
+                store_id=kroger.id,
+                observed_date=today - timedelta(days=5),
+                regular_price=Decimal("3.49"),
+                source="catalog",
+            )
+        )
+        # Chicken at Target
+        prices.append(
+            PriceHistory(
+                normalized_product_id=chicken.id,
+                store_id=target.id,
+                observed_date=today - timedelta(days=3),
+                regular_price=Decimal("5.99"),
+                source="catalog",
+            )
+        )
+        session.add_all(prices)
+        await session.flush()
+
+        # -- Get the user_id from the session token in auth_headers --
+        cookie_str = auth_headers.get("Cookie", "")
+        session_token = cookie_str.split("=", 1)[1] if "=" in cookie_str else ""
+
+        result = await session.execute(
+            text("SELECT user_id FROM sessions WHERE token = :token"),
+            {"token": session_token},
+        )
+        row = result.first()
+        user_id = UUID(row[0])
+
+        purchase1 = Purchase(
+            user_id=user_id,
+            store_id=meijer.id,
+            receipt_id="meijer-2026-001",
+            purchase_date=today - timedelta(days=10),
+            total=Decimal("23.45"),
+            subtotal=Decimal("21.50"),
+            tax=Decimal("1.95"),
+        )
+        purchase2 = Purchase(
+            user_id=user_id,
+            store_id=kroger.id,
+            receipt_id="kroger-2026-001",
+            purchase_date=today - timedelta(days=5),
+            total=Decimal("15.78"),
+            subtotal=Decimal("14.50"),
+            tax=Decimal("1.28"),
+        )
+        session.add_all([purchase1, purchase2])
+        await session.flush()
+
+        # -- Purchase Items --
+        item1 = PurchaseItem(
+            purchase_id=purchase1.id,
+            product_name_raw="Cheerios 18oz Box",
+            quantity=Decimal("1"),
+            unit_price=Decimal("4.79"),
+            extended_price=Decimal("4.79"),
+            normalized_product_id=cheerios.id,
+        )
+        item2 = PurchaseItem(
+            purchase_id=purchase1.id,
+            product_name_raw="Meijer Whole Milk 1gal",
+            quantity=Decimal("2"),
+            unit_price=Decimal("3.29"),
+            extended_price=Decimal("6.58"),
+            normalized_product_id=milk.id,
+        )
+        item3 = PurchaseItem(
+            purchase_id=purchase2.id,
+            product_name_raw="KRO CHEERIOS 18OZ",
+            quantity=Decimal("1"),
+            unit_price=Decimal("4.49"),
+            extended_price=Decimal("4.49"),
+            normalized_product_id=cheerios.id,
+        )
+        session.add_all([item1, item2, item3])
+        await session.flush()
+
+        # -- Coupons --
+        coupon1 = Coupon(
+            store_id=meijer.id,
+            normalized_product_id=cheerios.id,
+            title="$1 off Cheerios",
+            description="Save $1 on any Cheerios 18oz or larger",
+            discount_type="fixed",
+            discount_value=Decimal("1.00"),
+            valid_from=today - timedelta(days=7),
+            valid_to=today + timedelta(days=30),
+        )
+        coupon2 = Coupon(
+            store_id=kroger.id,
+            normalized_product_id=None,
+            title="10% off dairy",
+            description="10% off all dairy products",
+            discount_type="percent",
+            discount_value=Decimal("10.00"),
+            valid_from=today - timedelta(days=3),
+            valid_to=today + timedelta(days=14),
+        )
+        session.add_all([coupon1, coupon2])
+        await session.flush()
+
+        # -- Shrinkflation events --
+        shrink = ShrinkflationEvent(
+            normalized_product_id=cheerios.id,
+            detected_date=today - timedelta(days=15),
+            old_size="20",
+            new_size="18",
+            old_unit="oz",
+            new_unit="oz",
+            price_at_old_size=Decimal("3.99"),
+            price_at_new_size=Decimal("4.29"),
+            confidence=Decimal("0.95"),
+            notes="Size reduced from 20oz to 18oz while price increased",
+        )
+        session.add(shrink)
+        await session.commit()
+
+        for obj in [
+            meijer,
+            kroger,
+            target,
+            cheerios,
+            milk,
+            chicken,
+            purchase1,
+            purchase2,
+            item1,
+            item2,
+            item3,
+            coupon1,
+            coupon2,
+            shrink,
+        ]:
+            await session.refresh(obj)
+
+        return {
+            "headers": auth_headers,
+            "user_id": user_id,
+            "stores": {"meijer": meijer, "kroger": kroger, "target": target},
+            "products": {"cheerios": cheerios, "milk": milk, "chicken": chicken},
+            "purchases": {"meijer_trip": purchase1, "kroger_trip": purchase2},
+            "items": {"cheerios_meijer": item1, "milk_meijer": item2, "cheerios_kroger": item3},
+            "coupons": {"cheerios_coupon": coupon1, "dairy_coupon": coupon2},
+            "shrinkflation": {"cheerios_shrink": shrink},
+        }

api/tests/test_e2e/test_auth_validation.py

@@ -0,0 +1,162 @@
+"""E2E: Auth and session validation flows.
+
+Registration and login are handled by the Better-Auth service.
+These tests validate session token handling at the API gateway level.
+"""
+
+import pytest
+
+from tests.conftest import _create_test_user_and_session
+
+
+@pytest.mark.asyncio
+class TestSessionValidation:
+    """Session edge cases and error responses."""
+
+    async def test_invalid_session_token_rejected(self, client, db_engine):
+        resp = await client.get(
+            "/auth/me",
+            headers={"Cookie": "better-auth.session_token=not-a-real-token"},
+        )
+        assert resp.status_code == 401
+
+    async def test_missing_auth(self, client, db_engine):
+        resp = await client.get("/auth/me")
+        assert resp.status_code in (401, 403)
+
+    async def test_bearer_token_also_works(self, client, db_engine):
+        """Session tokens passed as Bearer tokens should also be accepted."""
+        _, session_token = await _create_test_user_and_session(
+            client, db_engine, email="bearer@e2e.com", display_name="Bearer E2E"
+        )
+        resp = await client.get(
+            "/auth/me",
+            headers={"Authorization": f"Bearer {session_token}"},
+        )
+        assert resp.status_code == 200
+        assert resp.json()["email"] == "bearer@e2e.com"
+
+    async def test_deleted_user_session_returns_not_found(self, client, db_engine):
+        """After deleting a user, their session should result in 404 for profile."""
+        _, session_token = await _create_test_user_and_session(
+            client, db_engine, email="delete-me@e2e.com", display_name="Delete Me"
+        )
+        headers = {"Cookie": f"better-auth.session_token={session_token}"}
+
+        delete_resp = await client.delete("/auth/me", headers=headers)
+        assert delete_resp.status_code == 204
+
+        me = await client.get("/auth/me", headers=headers)
+        assert me.status_code == 404
+
+    async def test_expired_session_rejected(self, client, db_engine):
+        """Expired sessions must be rejected."""
+        import secrets
+        import uuid
+        from datetime import UTC, datetime, timedelta
+
+        from sqlalchemy import text
+
+        user_id = str(uuid.uuid4())
+        session_token = secrets.token_urlsafe(32)
+        now = datetime.now(UTC).isoformat()
+        expired = (datetime.now(UTC) - timedelta(hours=1)).isoformat()
+
+        async with db_engine.begin() as conn:
+            await conn.execute(
+                text(
+                    "INSERT INTO users (id, email, hashed_password, display_name, email_verified, created_at, updated_at) "
+                    "VALUES (:id, :email, :hp, :dn, :ev, :ca, :ua)"
+                ),
+                {
+                    "id": user_id,
+                    "email": "expired@e2e.com",
+                    "hp": "unused",
+                    "dn": "Expired User",
+                    "ev": False,
+                    "ca": now,
+                    "ua": now,
+                },
+            )
+            await conn.execute(
+                text(
+                    "INSERT INTO sessions (id, token, user_id, expires_at, created_at, updated_at) "
+                    "VALUES (:id, :token, :uid, :ea, :ca, :ua)"
+                ),
+                {
+                    "id": str(uuid.uuid4()),
+                    "token": session_token,
+                    "uid": user_id,
+                    "ea": expired,
+                    "ca": now,
+                    "ua": now,
+                },
+            )
+
+        resp = await client.get(
+            "/auth/me",
+            headers={"Cookie": f"better-auth.session_token={session_token}"},
+        )
+        assert resp.status_code == 401
+
+
+@pytest.mark.asyncio
+class TestAuthProtectedEndpoints:
+    """Verify auth is enforced on all user-specific endpoints."""
+
+    @pytest.mark.parametrize(
+        "method,path",
+        [
+            ("GET", "/purchases"),
+            ("GET", "/products"),
+            ("GET", "/prices/trends"),
+            ("GET", "/prices/increases"),
+            ("GET", "/coupons"),
+            ("GET", "/alerts"),
+            ("GET", "/me/stores"),
+        ],
+    )
+    async def test_endpoints_require_auth(self, client, db_engine, method, path):
+        resp = await client.request(method, path)
+        assert resp.status_code in (401, 403), f"{method} {path} should require auth"
+
+
+@pytest.mark.asyncio
+class TestCrossUserDataIsolation:
+    """Verify that users cannot access other users' data."""
+
+    async def test_user_b_cannot_access_user_a_purchases(self, client, db_engine, seed_data):
+        """A second user cannot see User A's purchases."""
+        purchase_id = str(seed_data["purchases"]["meijer_trip"].id)
+
+        _, session_token = await _create_test_user_and_session(
+            client, db_engine, email="userb@e2e.com", display_name="User B"
+        )
+        user_b_headers = {"Cookie": f"better-auth.session_token={session_token}"}
+
+        resp = await client.get(f"/purchases/{purchase_id}", headers=user_b_headers)
+        assert resp.status_code in (403, 404), (
+            "User B should not be able to access User A's purchase"
+        )
+
+    async def test_user_b_purchase_list_is_empty(self, client, db_engine, seed_data):
+        """A new user should see no purchases."""
+        _, session_token = await _create_test_user_and_session(
+            client, db_engine, email="userc@e2e.com", display_name="User C"
+        )
+        user_c_headers = {"Cookie": f"better-auth.session_token={session_token}"}
+
+        resp = await client.get("/purchases", headers=user_c_headers)
+        assert resp.status_code == 200
+        assert len(resp.json()) == 0, "New user should have no purchases"
+
+    async def test_user_b_stores_isolated(self, client, db_engine, seed_data):
+        """User B's connected stores should be independent from User A."""
+        _, session_token = await _create_test_user_and_session(
+            client, db_engine, email="userd@e2e.com", display_name="User D"
+        )
+        user_d_headers = {"Cookie": f"better-auth.session_token={session_token}"}
+
+        resp = await client.get("/me/stores", headers=user_d_headers)
+        assert resp.status_code == 200
+        assert len(resp.json()) == 0, "New user should have no connected stores"

api/tests/test_e2e/test_cross_resource_flow.py

@@ -0,0 +1,114 @@
+"""E2E: Cross-resource flows — store connect → purchases → prices → coupons → alerts."""
+
+import pytest
+
+
+@pytest.mark.asyncio
+class TestStoreConnectToPurchaseFlow:
+    """Connect a store, then verify purchases and related data are accessible."""
+
+    async def test_connect_store_then_list(self, client, seed_data):
+        headers = seed_data["headers"]
+        # Connect to Meijer
+        resp = await client.post("/me/stores/meijer/connect", json={}, headers=headers)
+        assert resp.status_code in (200, 201)
+
+        # Verify store appears in user's connected stores
+        stores = await client.get("/me/stores", headers=headers)
+        assert stores.status_code == 200
+        slugs = [s["store"]["slug"] for s in stores.json()]
+        assert "meijer" in slugs
+
+    async def test_disconnect_store(self, client, seed_data):
+        headers = seed_data["headers"]
+        await client.post("/me/stores/kroger/connect", json={}, headers=headers)
+        resp = await client.delete("/me/stores/kroger", headers=headers)
+        assert resp.status_code in (200, 204)
+
+        # Verify store no longer in connected list
+        stores = await client.get("/me/stores", headers=headers)
+        slugs = [s["store"]["slug"] for s in stores.json()]
+        assert "kroger" not in slugs
+
+
+@pytest.mark.asyncio
+class TestPurchaseToPriceFlow:
+    """Verify purchase data links to price comparison data."""
+
+    async def test_purchase_items_link_to_products(self, client, seed_data):
+        """Items from purchases reference products that have price data."""
+        headers = seed_data["headers"]
+        purchase_id = str(seed_data["purchases"]["meijer_trip"].id)
+
+        # Get purchase detail
+        purchase = await client.get(f"/purchases/{purchase_id}", headers=headers)
+        assert purchase.status_code == 200
+        items = purchase.json()["line_items"]
+
+        # Get product detail for an item that has a product_id
+        product_ids = [li["product_id"] for li in items if li.get("product_id")]
+        assert len(product_ids) >= 1
+
+        for pid in product_ids:
+            product = await client.get(f"/products/{pid}", headers=headers)
+            assert product.status_code == 200
+            assert len(product.json()["prices_by_store"]) >= 1
+
+
+@pytest.mark.asyncio
+class TestCouponFlow:
+    """Verify coupon listing and relevance filtering."""
+
+    async def test_list_all_coupons(self, client, seed_data):
+        headers = seed_data["headers"]
+        resp = await client.get("/coupons", headers=headers)
+        assert resp.status_code == 200
+        data = resp.json()
+        assert len(data) >= 2
+        descriptions = [c["description"] for c in data]
+        assert any("Cheerios" in d for d in descriptions)
+
+    async def test_filter_coupons_by_store(self, client, seed_data):
+        headers = seed_data["headers"]
+        meijer_id = str(seed_data["stores"]["meijer"].id)
+        resp = await client.get("/coupons", params={"store_id": meijer_id}, headers=headers)
+        assert resp.status_code == 200
+        data = resp.json()
+        assert all(c["store_name"] == "Meijer" for c in data)
+
+    async def test_relevant_coupons_for_user(self, client, seed_data):
+        """User bought Cheerios, so the Cheerios coupon should be relevant."""
+        headers = seed_data["headers"]
+        resp = await client.get("/coupons/relevant", headers=headers)
+        assert resp.status_code == 200
+        data = resp.json()
+        assert len(data) >= 1, "Expected at least one relevant coupon for user with purchases"
+        descriptions = [c["description"] for c in data]
+        assert any("Cheerios" in d for d in descriptions)
+
+
+@pytest.mark.asyncio
+class TestAlertFlow:
+    """Verify alert listing with seeded data."""
+
+    async def test_list_alerts(self, client, seed_data):
+        """User bought Cheerios which has a shrinkflation event — may appear as alert."""
+        headers = seed_data["headers"]
+        resp = await client.get("/alerts", headers=headers)
+        assert resp.status_code == 200
+        data = resp.json()
+        assert isinstance(data, list)
+        # If alerts are generated synchronously, verify shrinkflation alert content
+        if len(data) > 0:
+            alert_types = [a["alert_type"] for a in data]
+            product_names = [a["product_name"] for a in data]
+            assert any(t in ("shrinkflation", "price_increase") for t in alert_types)
+            assert any("Cheerios" in name for name in product_names)
+
+    async def test_alert_settings_default(self, client, seed_data):
+        headers = seed_data["headers"]
+        resp = await client.get("/alerts/settings", headers=headers)
+        assert resp.status_code == 200
+        data = resp.json()
+        assert "price_increase_threshold_pct" in data
+        assert "shrinkflation_enabled" in data

api/tests/test_e2e/test_error_responses.py

@@ -0,0 +1,127 @@
+"""E2E: Error responses for bad input across all endpoint categories."""
+
+import pytest
+
+from tests.test_e2e.conftest import BAD_UUID, ZERO_UUID
+
+
+@pytest.mark.asyncio
+class TestRegistrationErrors:
+    """Validation errors during user registration."""
+
+    async def test_short_password(self, client, db_engine):
+        resp = await client.post(
+            "/auth/register",
+            json={"email": "short@example.com", "password": "short", "display_name": "Test"},
+        )
+        assert resp.status_code == 422
+
+    async def test_invalid_email(self, client, db_engine):
+        resp = await client.post(
+            "/auth/register",
+            json={"email": "not-an-email", "password": "securepass123", "display_name": "Test"},
+        )
+        assert resp.status_code == 422
+
+    async def test_missing_fields(self, client, db_engine):
+        resp = await client.post("/auth/register", json={})
+        assert resp.status_code == 422
+
+    async def test_empty_display_name(self, client, db_engine):
+        resp = await client.post(
+            "/auth/register",
+            json={"email": "empty@example.com", "password": "securepass123", "display_name": ""},
+        )
+        assert resp.status_code == 422
+
+    async def test_duplicate_email(self, client, db_engine):
+        payload = {
+            "email": "dupe@example.com",
+            "password": "securepass123",
+            "display_name": "First",
+        }
+        first = await client.post("/auth/register", json=payload)
+        assert first.status_code == 201
+        second = await client.post("/auth/register", json=payload)
+        assert second.status_code == 409
+
+
+@pytest.mark.asyncio
+class TestLoginErrors:
+    """Login failure modes."""
+
+    async def test_wrong_password(self, client, db_engine):
+        await client.post(
+            "/auth/register",
+            json={
+                "email": "login-err@example.com",
+                "password": "correctpass1",
+                "display_name": "Login",
+            },
+        )
+        resp = await client.post(
+            "/auth/login",
+            json={"email": "login-err@example.com", "password": "wrongpass123"},
+        )
+        assert resp.status_code == 401
+
+    async def test_nonexistent_user(self, client, db_engine):
+        resp = await client.post(
+            "/auth/login",
+            json={"email": "nobody@example.com", "password": "doesntmatter"},
+        )
+        assert resp.status_code == 401
+
+
+@pytest.mark.asyncio
+class TestNotFoundErrors:
+    """404 responses for missing resources."""
+
+    async def test_product_not_found(self, client, seed_data):
+        resp = await client.get(f"/products/{ZERO_UUID}", headers=seed_data["headers"])
+        assert resp.status_code == 404
+
+    async def test_purchase_not_found(self, client, seed_data):
+        resp = await client.get(f"/purchases/{ZERO_UUID}", headers=seed_data["headers"])
+        assert resp.status_code == 404
+
+    async def test_public_trend_not_found(self, client, seed_data):
+        resp = await client.get(f"/public/trends/{ZERO_UUID}")
+        assert resp.status_code == 404
+
+
+@pytest.mark.asyncio
+class TestMalformedInput:
+    """Invalid UUID formats and bad query params."""
+
+    async def test_invalid_uuid_product(self, client, seed_data):
+        resp = await client.get(f"/products/{BAD_UUID}", headers=seed_data["headers"])
+        assert resp.status_code == 422
+
+    async def test_invalid_uuid_purchase(self, client, seed_data):
+        resp = await client.get(f"/purchases/{BAD_UUID}", headers=seed_data["headers"])
+        assert resp.status_code == 422
+
+    async def test_invalid_uuid_public_trend(self, client, seed_data):
+        resp = await client.get(f"/public/trends/{BAD_UUID}")
+        assert resp.status_code == 422
+
+
+@pytest.mark.asyncio
+class TestStoreConnectionErrors:
+    """Store connection edge cases."""
+
+    async def test_connect_nonexistent_store(self, client, seed_data):
+        resp = await client.post(
+            "/me/stores/nonexistent-store/connect",
+            json={},
+            headers=seed_data["headers"],
+        )
+        assert resp.status_code == 404
+
+    async def test_connect_store_twice(self, client, seed_data):
+        headers = seed_data["headers"]
+        first = await client.post("/me/stores/meijer/connect", json={}, headers=headers)
+        assert first.status_code in (200, 201)
+        second = await client.post("/me/stores/meijer/connect", json={}, headers=headers)
+        assert second.status_code == 409

api/tests/test_e2e/test_price_history.py

@@ -0,0 +1,102 @@
+"""E2E: Price history queries returning correct data."""
+
+import pytest
+
+
+@pytest.mark.asyncio
+class TestPriceTrends:
+    """Verify price trend aggregation against seeded history."""
+
+    async def test_trends_returns_all_products(self, client, seed_data):
+        resp = await client.get("/prices/trends", headers=seed_data["headers"])
+        assert resp.status_code == 200
+        data = resp.json()
+        product_names = [t["product_name"] for t in data]
+        assert "Cheerios 18oz" in product_names
+        assert "Whole Milk 1gal" in product_names
+
+    async def test_trends_filter_by_category(self, client, seed_data):
+        resp = await client.get(
+            "/prices/trends", params={"category": "dairy"}, headers=seed_data["headers"]
+        )
+        assert resp.status_code == 200
+        data = resp.json()
+        assert len(data) >= 1
+        # Only dairy products should appear
+        for trend in data:
+            assert trend["product_name"] == "Whole Milk 1gal"
+
+    async def test_trends_contain_data_points(self, client, seed_data):
+        resp = await client.get("/prices/trends", headers=seed_data["headers"])
+        data = resp.json()
+        cheerios_trend = next(t for t in data if t["product_name"] == "Cheerios 18oz")
+        assert len(cheerios_trend["data_points"]) >= 3
+
+
+@pytest.mark.asyncio
+class TestPriceIncreases:
+    """Detect price increases from seeded price history."""
+
+    async def test_increases_detected(self, client, seed_data):
+        resp = await client.get("/prices/increases", headers=seed_data["headers"])
+        assert resp.status_code == 200
+        data = resp.json()
+        # Cheerios at Meijer went from 3.99 → 4.29 → 4.79
+        cheerios_increases = [inc for inc in data if inc["product_name"] == "Cheerios 18oz"]
+        assert len(cheerios_increases) >= 1
+        # Verify the increase data makes sense
+        for inc in cheerios_increases:
+            assert inc["new_price"] > inc["old_price"]
+            assert inc["increase_pct"] > 0
+            assert inc["store_name"] == "Meijer"
+
+    async def test_stable_prices_not_flagged(self, client, seed_data):
+        """Kroger Cheerios price is stable at $4.49 — should not appear as increase."""
+        resp = await client.get("/prices/increases", headers=seed_data["headers"])
+        data = resp.json()
+        kroger_increases = [
+            inc
+            for inc in data
+            if inc["product_name"] == "Cheerios 18oz" and inc["store_name"] == "Kroger"
+        ]
+        assert len(kroger_increases) == 0
+
+
+@pytest.mark.asyncio
+class TestPriceComparison:
+    """Compare prices across stores for specific products."""
+
+    async def test_compare_cheerios_across_stores(self, client, seed_data):
+        cheerios_id = str(seed_data["products"]["cheerios"].id)
+        resp = await client.get(
+            "/prices/comparison",
+            params={"product_ids": cheerios_id},
+            headers=seed_data["headers"],
+        )
+        assert resp.status_code == 200
+        data = resp.json()
+        assert len(data) >= 1
+        cheerios_cmp = data[0]
+        assert cheerios_cmp["product_name"] == "Cheerios 18oz"
+        store_names = [p["store_name"] for p in cheerios_cmp["prices"]]
+        assert "Meijer" in store_names
+        assert "Kroger" in store_names
+
+    async def test_compare_requires_product_ids(self, client, seed_data):
+        """product_ids is required — omitting it must return 422."""
+        resp = await client.get("/prices/comparison", headers=seed_data["headers"])
+        assert resp.status_code == 422
+
+    async def test_compare_multiple_products(self, client, seed_data):
+        cheerios_id = str(seed_data["products"]["cheerios"].id)
+        milk_id = str(seed_data["products"]["milk"].id)
+        resp = await client.get(
+            "/prices/comparison",
+            params=[("product_ids", cheerios_id), ("product_ids", milk_id)],
+            headers=seed_data["headers"],
+        )
+        assert resp.status_code == 200
+        data = resp.json()
+        names = [c["product_name"] for c in data]
+        assert "Cheerios 18oz" in names
+        assert "Whole Milk 1gal" in names

api/tests/test_e2e/test_product_search_lookup.py

@@ -0,0 +1,82 @@
+"""E2E: Product search/lookup endpoints with real DB fixtures."""
+
+import pytest
+
+from tests.test_e2e.conftest import ZERO_UUID
+
+
+@pytest.mark.asyncio
+class TestProductSearch:
+    """Search and filter products against seeded data."""
+
+    async def test_list_all_products(self, client, seed_data):
+        resp = await client.get("/products", headers=seed_data["headers"])
+        assert resp.status_code == 200
+        products = resp.json()
+        names = [p["name"] for p in products]
+        assert "Cheerios 18oz" in names
+        assert "Whole Milk 1gal" in names
+        assert "Chicken Breast 1lb" in names
+
+    async def test_search_by_name(self, client, seed_data):
+        resp = await client.get("/products", params={"q": "cheerios"}, headers=seed_data["headers"])
+        assert resp.status_code == 200
+        products = resp.json()
+        assert len(products) >= 1
+        assert all("cheerios" in p["name"].lower() for p in products)
+
+    async def test_search_by_category(self, client, seed_data):
+        resp = await client.get(
+            "/products", params={"category": "dairy"}, headers=seed_data["headers"]
+        )
+        assert resp.status_code == 200
+        products = resp.json()
+        assert len(products) >= 1
+        assert all(p["category"] == "dairy" for p in products)
+
+    async def test_search_no_results(self, client, seed_data):
+        resp = await client.get(
+            "/products", params={"q": "nonexistentxyz"}, headers=seed_data["headers"]
+        )
+        assert resp.status_code == 200
+        assert resp.json() == []
+
+
+@pytest.mark.asyncio
+class TestProductLookup:
+    """Detailed product lookups with cross-store pricing."""
+
+    async def test_get_product_detail_with_prices(self, client, seed_data):
+        cheerios_id = str(seed_data["products"]["cheerios"].id)
+        resp = await client.get(f"/products/{cheerios_id}", headers=seed_data["headers"])
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["name"] == "Cheerios 18oz"
+        assert data["brand"] == "General Mills"
+        assert data["category"] == "pantry"
+        # Should have prices from both Meijer and Kroger
+        store_names = [p["store_name"] for p in data["prices_by_store"]]
+        assert "Meijer" in store_names
+        assert "Kroger" in store_names
+
+    async def test_product_prices_reflect_latest(self, client, seed_data):
+        """The latest Meijer price for Cheerios should be 4.79 (the increase)."""
+        cheerios_id = str(seed_data["products"]["cheerios"].id)
+        resp = await client.get(f"/products/{cheerios_id}", headers=seed_data["headers"])
+        data = resp.json()
+        meijer_price = next(p for p in data["prices_by_store"] if p["store_name"] == "Meijer")
+        assert meijer_price["current_price"] == 4.79
+
+    async def test_product_not_found(self, client, seed_data):
+        resp = await client.get(f"/products/{ZERO_UUID}", headers=seed_data["headers"])
+        assert resp.status_code == 404
+
+    async def test_product_price_history(self, client, seed_data):
+        cheerios_id = str(seed_data["products"]["cheerios"].id)
+        resp = await client.get(f"/products/{cheerios_id}/prices", headers=seed_data["headers"])
+        assert resp.status_code == 200
+        data = resp.json()
+        assert len(data["data_points"]) >= 3  # At least the 3 Meijer observations
+        # Verify chronological ordering exists
+        prices = [dp["price"] for dp in data["data_points"]]
+        assert len(prices) >= 3

api/tests/test_e2e/test_public_endpoints.py

@@ -0,0 +1,59 @@
+"""E2E: Public price transparency endpoints (no auth required)."""
+
+import uuid
+
+import pytest
+
+
+@pytest.mark.asyncio
+class TestPublicTrends:
+    """Public price trend endpoint — no auth, real data."""
+
+    async def test_public_trend_returns_data(self, client, seed_data):
+        cheerios_id = str(seed_data["products"]["cheerios"].id)
+        resp = await client.get(f"/public/trends/{cheerios_id}")
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["product_name"] == "Cheerios 18oz"
+        assert len(data["data_points"]) >= 3
+
+    async def test_public_trend_no_auth_needed(self, client, seed_data):
+        """Confirm no Authorization header is required."""
+        cheerios_id = str(seed_data["products"]["cheerios"].id)
+        resp = await client.get(f"/public/trends/{cheerios_id}")
+        assert resp.status_code == 200
+
+
+@pytest.mark.asyncio
+class TestPublicStoreComparison:
+    """Public store comparison endpoint."""
+
+    async def test_store_comparison(self, client, seed_data):
+        cheerios_id = str(seed_data["products"]["cheerios"].id)
+        resp = await client.get(
+            "/public/store-comparison",
+            params=[("product_ids", cheerios_id)],
+        )
+        assert resp.status_code == 200
+        data = resp.json()
+        assert "products" in data
+        assert len(data["products"]) >= 1
+
+    async def test_store_comparison_rejects_more_than_20_ids(self, client):
+        """max_length=20 guard: 21 product IDs must return 422."""
+        too_many = [("product_ids", str(uuid.uuid4())) for _ in range(21)]
+        resp = await client.get("/public/store-comparison", params=too_many)
+        assert resp.status_code == 422
+
+
+@pytest.mark.asyncio
+class TestPublicInflation:
+    """Public inflation index endpoint."""
+
+    async def test_inflation_returns_index(self, client, seed_data):
+        resp = await client.get("/public/inflation")
+        assert resp.status_code == 200
+        data = resp.json()
+        assert "cartsnitch_index" in data
+        assert "cpi_baseline" in data
+        assert "categories" in data

api/tests/test_e2e/test_purchase_flow.py

@@ -0,0 +1,87 @@
+"""E2E: Purchase listing, detail, and stats against real DB fixtures."""
+
+import pytest
+
+from tests.test_e2e.conftest import ZERO_UUID
+
+
+@pytest.mark.asyncio
+class TestPurchaseList:
+    """List and filter a user's purchases."""
+
+    async def test_list_user_purchases(self, client, seed_data):
+        resp = await client.get("/purchases", headers=seed_data["headers"])
+        assert resp.status_code == 200
+        data = resp.json()
+        assert len(data) >= 2
+        store_names = [p["store_name"] for p in data]
+        assert "Meijer" in store_names
+        assert "Kroger" in store_names
+
+    async def test_filter_purchases_by_store(self, client, seed_data):
+        meijer_id = str(seed_data["stores"]["meijer"].id)
+        resp = await client.get(
+            "/purchases", params={"store_id": meijer_id}, headers=seed_data["headers"]
+        )
+        assert resp.status_code == 200
+        data = resp.json()
+        assert len(data) >= 1
+        assert all(p["store_name"] == "Meijer" for p in data)
+
+    async def test_purchases_require_auth(self, client, seed_data):
+        resp = await client.get("/purchases")
+        assert resp.status_code in (401, 403)
+
+
+@pytest.mark.asyncio
+class TestPurchaseDetail:
+    """Retrieve individual purchase with line items."""
+
+    async def test_get_purchase_detail(self, client, seed_data):
+        purchase_id = str(seed_data["purchases"]["meijer_trip"].id)
+        resp = await client.get(f"/purchases/{purchase_id}", headers=seed_data["headers"])
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["store_name"] == "Meijer"
+        assert data["total"] == 23.45
+        assert len(data["line_items"]) == 2
+        item_names = [li["name"] for li in data["line_items"]]
+        assert "Cheerios 18oz Box" in item_names
+        assert "Meijer Whole Milk 1gal" in item_names
+
+    async def test_line_item_amounts_correct(self, client, seed_data):
+        purchase_id = str(seed_data["purchases"]["meijer_trip"].id)
+        resp = await client.get(f"/purchases/{purchase_id}", headers=seed_data["headers"])
+        data = resp.json()
+        cheerios_item = next(li for li in data["line_items"] if "Cheerios" in li["name"])
+        assert cheerios_item["unit_price"] == 4.79
+        assert cheerios_item["quantity"] == 1.0
+        assert cheerios_item["total_price"] == 4.79
+
+    async def test_purchase_not_found(self, client, seed_data):
+        resp = await client.get(
+            f"/purchases/{ZERO_UUID}",
+            headers=seed_data["headers"],
+        )
+        assert resp.status_code == 404
+
+
+@pytest.mark.asyncio
+class TestPurchaseStats:
+    """Verify spending aggregation across purchases."""
+
+    async def test_purchase_stats_totals(self, client, seed_data):
+        resp = await client.get("/purchases/stats", headers=seed_data["headers"])
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["purchase_count"] == 2
+        # 23.45 + 15.78 = 39.23
+        assert abs(data["total_spent"] - 39.23) < 0.01
+
+    async def test_purchase_stats_by_store(self, client, seed_data):
+        resp = await client.get("/purchases/stats", headers=seed_data["headers"])
+        data = resp.json()
+        assert "Meijer" in data["by_store"]
+        assert "Kroger" in data["by_store"]
+        assert abs(data["by_store"]["Meijer"] - 23.45) < 0.01
+        assert abs(data["by_store"]["Kroger"] - 15.78) < 0.01

api/tests/test_encrypted_json.py

@@ -0,0 +1,130 @@
+"""Tests for EncryptedJSON TypeDecorator and session_data encryption."""
+
+import json
+
+import pytest
+from cryptography.fernet import Fernet
+from pydantic import ValidationError
+from sqlalchemy import column, create_engine, table, text
+from sqlalchemy.orm import sessionmaker
+
+from cartsnitch_api.config import settings
+from cartsnitch_api.models import Base
+from cartsnitch_api.models.store import Store
+from cartsnitch_api.models.user import User, UserStoreAccount
+
+
+@pytest.fixture
+def engine():
+    eng = create_engine("sqlite:///:memory:")
+    Base.metadata.create_all(eng)
+    yield eng
+    eng.dispose()
+
+
+@pytest.fixture
+def session(engine):
+    factory = sessionmaker(bind=engine)
+    with factory() as sess:
+        yield sess
+
+
+@pytest.fixture
+def store(session):
+    s = Store(name="Test Store", slug="test-store")
+    session.add(s)
+    session.commit()
+    session.refresh(s)
+    return s
+
+
+@pytest.fixture
+def user(session):
+    u = User(email="alice@example.com", hashed_password="fakehash")
+    session.add(u)
+    session.commit()
+    session.refresh(u)
+    return u
+
+
+class TestEncryptedJSONType:
+    """Unit tests for the EncryptedJSON TypeDecorator."""
+
+    def test_round_trip(self, session, user, store):
+        """Data written via the ORM comes back as the original dict."""
+        original = {"token": "abc123", "cookies": {"session_id": "xyz"}}
+        account = UserStoreAccount(user_id=user.id, store_id=store.id, session_data=original)
+        session.add(account)
+        session.commit()
+
+        loaded = session.get(UserStoreAccount, account.id)
+        assert loaded.session_data == original
+
+    def test_stored_value_is_encrypted(self, session, user, store):
+        """The raw value in the DB should be a Fernet token, not plaintext JSON."""
+        original = {"secret": "do-not-leak"}
+        account = UserStoreAccount(user_id=user.id, store_id=store.id, session_data=original)
+        session.add(account)
+        session.commit()
+
+        # Use a raw table construct to bypass TypeDecorator on read
+        raw_table = table("user_store_accounts", column("id"), column("session_data"))
+        raw = session.execute(raw_table.select().where(raw_table.c.id == str(account.id))).first()
+        # If UUID matching fails with str, try bytes format
+        if raw is None:
+            raw = session.execute(
+                text("SELECT session_data FROM user_store_accounts LIMIT 1")
+            ).scalar_one()
+        else:
+            raw = raw[1]
+
+        assert raw != json.dumps(original)
+        assert raw.startswith("gAAAAA")
+
+        # Verify we can decrypt the raw value manually
+        f = Fernet(settings.fernet_key.encode())
+        decrypted = json.loads(f.decrypt(raw.encode()))
+        assert decrypted == original
+
+    def test_null_round_trip(self, session, user, store):
+        """NULL session_data stays NULL."""
+        account = UserStoreAccount(user_id=user.id, store_id=store.id, session_data=None)
+        session.add(account)
+        session.commit()
+
+        loaded = session.get(UserStoreAccount, account.id)
+        assert loaded.session_data is None
+
+    def test_empty_dict_round_trip(self, session, user, store):
+        """Empty dict round-trips correctly."""
+        account = UserStoreAccount(user_id=user.id, store_id=store.id, session_data={})
+        session.add(account)
+        session.commit()
+
+        loaded = session.get(UserStoreAccount, account.id)
+        assert loaded.session_data == {}
+
+    def test_update_session_data(self, session, user, store):
+        """Updating session_data re-encrypts the new value."""
+        account = UserStoreAccount(user_id=user.id, store_id=store.id, session_data={"v": 1})
+        session.add(account)
+        session.commit()
+
+        account.session_data = {"v": 2, "new_field": True}
+        session.commit()
+
+        loaded = session.get(UserStoreAccount, account.id)
+        assert loaded.session_data == {"v": 2, "new_field": True}
+
+
+class TestEncryptionKeyValidation:
+    """Test that invalid/missing keys are caught at startup."""
+
+    def test_invalid_fernet_key_rejected(self, monkeypatch):
+        """Settings validation rejects a bad key."""
+        monkeypatch.setenv("CARTSNITCH_FERNET_KEY", "not-a-valid-key")
+
+        with pytest.raises(ValidationError):
+            from cartsnitch_api.config import Settings
+
+            Settings()

api/tests/test_middleware/conftest.py

@@ -0,0 +1,19 @@
+"""Conftest for middleware tests — re-enables rate limiting after global disable."""
+
+import pytest
+
+from cartsnitch_api.config import settings as cartsnitch_settings
+
+
+@pytest.fixture(autouse=True)
+def enable_rate_limiting():
+    """Re-enable rate limiting after the global disable_rate_limiting fixture runs.
+
+    The root conftest disables rate limiting for all tests to prevent 429
+    interference. Middleware tests need it active to verify headers and
+    enforcement. This fixture runs after the root fixture (more local = later
+    in setup order) so True is the effective value during the test body.
+    """
+    cartsnitch_settings.rate_limit_enabled = True
+    yield
+    cartsnitch_settings.rate_limit_enabled = False

api/tests/test_middleware/test_error_handler.py

@@ -0,0 +1,54 @@
+"""Tests for structured error responses and error monitoring."""
+
+import pytest
+
+
+@pytest.mark.asyncio
+async def test_404_returns_structured_error(client):
+    """Non-existent route should return structured error."""
+    resp = await client.get("/nonexistent")
+    assert resp.status_code == 404
+    body = resp.json()
+    assert "detail" in body
+    assert "code" in body
+    assert body["code"] == "NOT_FOUND"
+
+
+@pytest.mark.asyncio
+async def test_validation_error_returns_422_with_field_errors(client):
+    """Invalid request body should return structured validation errors."""
+    resp = await client.post(
+        "/auth/register",
+        json={"email": "not-an-email", "password": "short", "display_name": ""},
+    )
+    assert resp.status_code == 422
+    body = resp.json()
+    assert body["code"] == "VALIDATION_ERROR"
+    assert "errors" in body
+    assert isinstance(body["errors"], list)
+    assert len(body["errors"]) > 0
+    # Each error should have field, message, type
+    for err in body["errors"]:
+        assert "field" in err
+        assert "message" in err
+        assert "type" in err
+
+
+@pytest.mark.asyncio
+async def test_error_stats_requires_service_key(client):
+    """Error stats endpoint should require X-Service-Key."""
+    resp = await client.get("/internal/error-stats")
+    assert resp.status_code == 422  # Missing required header
+
+
+@pytest.mark.asyncio
+async def test_error_stats_with_valid_key(client):
+    """Error stats endpoint returns monitoring data with valid key."""
+    resp = await client.get(
+        "/internal/error-stats",
+        headers={"X-Service-Key": "change-me-in-production"},
+    )
+    assert resp.status_code == 200
+    body = resp.json()
+    assert "error_counts" in body
+    assert "recent_5xx_count" in body

api/tests/test_middleware/test_rate_limit.py

@@ -0,0 +1,55 @@
+"""Tests for rate limiting middleware."""
+
+import pytest
+
+from cartsnitch_api.middleware.rate_limit import _SlidingWindowCounter
+
+
+class TestSlidingWindowCounter:
+    def test_allows_within_limit(self):
+        counter = _SlidingWindowCounter(max_requests=5, window_seconds=60)
+        for i in range(5):
+            allowed, remaining, retry = counter.is_allowed("test-key")
+            assert allowed is True
+            assert remaining == 4 - i
+
+    def test_blocks_over_limit(self):
+        counter = _SlidingWindowCounter(max_requests=3, window_seconds=60)
+        for _ in range(3):
+            counter.is_allowed("test-key")
+
+        allowed, remaining, retry = counter.is_allowed("test-key")
+        assert allowed is False
+        assert remaining == 0
+        assert retry > 0
+
+    def test_separate_keys(self):
+        counter = _SlidingWindowCounter(max_requests=2, window_seconds=60)
+        # Fill key-a
+        counter.is_allowed("key-a")
+        counter.is_allowed("key-a")
+        allowed_a, _, _ = counter.is_allowed("key-a")
+        assert allowed_a is False
+
+        # key-b should still be allowed
+        allowed_b, remaining, _ = counter.is_allowed("key-b")
+        assert allowed_b is True
+        assert remaining == 1
+
+
+@pytest.mark.asyncio
+async def test_rate_limit_returns_429(client):
+    """Public endpoint should return 429 after limit exceeded."""
+    # The default limit is 60/min — we won't hit it in normal tests,
+    # but we verify the middleware adds rate limit headers.
+    resp = await client.get("/public/inflation")
+    assert "x-ratelimit-limit" in resp.headers
+    assert "x-ratelimit-remaining" in resp.headers
+
+
+@pytest.mark.asyncio
+async def test_health_skips_rate_limit(client):
+    """Health endpoint should not have rate limit headers."""
+    resp = await client.get("/health")
+    assert resp.status_code == 200
+    assert "x-ratelimit-limit" not in resp.headers

api/tests/test_models.py

@@ -0,0 +1,376 @@
+"""Tests for SQLAlchemy ORM models."""
+
+import uuid
+from datetime import UTC, date, datetime
+from decimal import Decimal
+
+import pytest
+from sqlalchemy import inspect
+
+from cartsnitch_api.constants import (
+    AccountStatus,
+    DiscountType,
+    PriceSource,
+    ProductCategory,
+    SizeUnit,
+    StoreSlug,
+)
+from cartsnitch_api.models import (
+    Coupon,
+    NormalizedProduct,
+    PriceHistory,
+    Purchase,
+    PurchaseItem,
+    ShrinkflationEvent,
+    Store,
+    StoreLocation,
+    User,
+    UserStoreAccount,
+)
+
+
+class TestTableCreation:
+    """Verify all expected tables are created."""
+
+    def test_all_tables_exist(self, engine):
+        inspector = inspect(engine)
+        table_names = set(inspector.get_table_names())
+        expected = {
+            "stores",
+            "store_locations",
+            "users",
+            "user_store_accounts",
+            "purchases",
+            "purchase_items",
+            "normalized_products",
+            "price_history",
+            "coupons",
+            "shrinkflation_events",
+        }
+        assert expected.issubset(table_names)
+
+    def test_ten_tables_total(self, engine):
+        inspector = inspect(engine)
+        assert len(inspector.get_table_names()) == 10
+
+
+class TestUUIDPrimaryKeys:
+    """All models use UUID PKs."""
+
+    def test_store_uuid_pk(self, session):
+        store = Store(
+            id=uuid.uuid4(),
+            name="Meijer",
+            slug=StoreSlug.MEIJER,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(store)
+        session.commit()
+        assert isinstance(store.id, uuid.UUID)
+
+    def test_user_uuid_pk(self, session):
+        user = User(
+            id=uuid.uuid4(),
+            email="test@example.com",
+            hashed_password="hashed",
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(user)
+        session.commit()
+        assert isinstance(user.id, uuid.UUID)
+
+
+class TestStoreModel:
+    def test_store_slug_enum(self, session):
+        store = Store(
+            id=uuid.uuid4(),
+            name="Kroger",
+            slug=StoreSlug.KROGER,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(store)
+        session.commit()
+        assert store.slug == StoreSlug.KROGER
+
+    def test_store_unique_slug(self, session):
+        s1 = Store(
+            id=uuid.uuid4(),
+            name="Target",
+            slug=StoreSlug.TARGET,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        s2 = Store(
+            id=uuid.uuid4(),
+            name="Target Duplicate",
+            slug=StoreSlug.TARGET,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(s1)
+        session.commit()
+        session.add(s2)
+        with pytest.raises(Exception):  # noqa: B017
+            session.commit()
+        session.rollback()
+
+
+class TestStoreLocationModel:
+    def test_store_location_fields(self, session):
+        store = Store(
+            id=uuid.uuid4(),
+            name="Meijer",
+            slug=StoreSlug.MEIJER,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(store)
+        session.flush()
+        loc = StoreLocation(
+            id=uuid.uuid4(),
+            store_id=store.id,
+            address="123 Main St",
+            city="Ann Arbor",
+            state="MI",
+            zip="48104",
+            lat=42.2808,
+            lng=-83.7430,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(loc)
+        session.commit()
+        assert loc.city == "Ann Arbor"
+        assert loc.lat == pytest.approx(42.2808)
+
+
+class TestUserStoreAccountModel:
+    def test_account_status_enum(self, session):
+        user = User(
+            id=uuid.uuid4(),
+            email="test@test.com",
+            hashed_password="hashed",
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        store = Store(
+            id=uuid.uuid4(),
+            name="Kroger",
+            slug=StoreSlug.KROGER,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add_all([user, store])
+        session.flush()
+        acct = UserStoreAccount(
+            id=uuid.uuid4(),
+            user_id=user.id,
+            store_id=store.id,
+            status=AccountStatus.ACTIVE,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(acct)
+        session.commit()
+        assert acct.status == AccountStatus.ACTIVE
+
+    def test_unique_user_store_constraint(self, session):
+        """One account per user per store."""
+        user = User(
+            id=uuid.uuid4(),
+            email="unique@test.com",
+            hashed_password="hashed",
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        store = Store(
+            id=uuid.uuid4(),
+            name="Target",
+            slug=StoreSlug.TARGET,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add_all([user, store])
+        session.flush()
+        a1 = UserStoreAccount(
+            id=uuid.uuid4(),
+            user_id=user.id,
+            store_id=store.id,
+            status=AccountStatus.ACTIVE,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        a2 = UserStoreAccount(
+            id=uuid.uuid4(),
+            user_id=user.id,
+            store_id=store.id,
+            status=AccountStatus.EXPIRED,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(a1)
+        session.commit()
+        session.add(a2)
+        with pytest.raises(Exception):  # noqa: B017
+            session.commit()
+        session.rollback()
+
+
+class TestPurchaseModel:
+    def test_purchase_with_items(self, session):
+        user = User(
+            id=uuid.uuid4(),
+            email="buyer@test.com",
+            hashed_password="hashed",
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        store = Store(
+            id=uuid.uuid4(),
+            name="Meijer",
+            slug=StoreSlug.MEIJER,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add_all([user, store])
+        session.flush()
+        purchase = Purchase(
+            id=uuid.uuid4(),
+            user_id=user.id,
+            store_id=store.id,
+            receipt_id="RCP-001",
+            purchase_date=date(2026, 3, 15),
+            total=Decimal("42.50"),
+            ingested_at=datetime.now(UTC),
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(purchase)
+        session.flush()
+        item = PurchaseItem(
+            id=uuid.uuid4(),
+            purchase_id=purchase.id,
+            product_name_raw="Meijer Whole Milk 1 Gallon",
+            upc="0041250000001",
+            quantity=Decimal("1"),
+            unit_price=Decimal("3.49"),
+            extended_price=Decimal("3.49"),
+        )
+        session.add(item)
+        session.commit()
+        assert item.product_name_raw == "Meijer Whole Milk 1 Gallon"
+        assert item.unit_price == Decimal("3.49")
+
+
+class TestNormalizedProductModel:
+    def test_product_with_upc_variants(self, session):
+        product = NormalizedProduct(
+            id=uuid.uuid4(),
+            canonical_name="Whole Milk, 1 Gallon",
+            category=ProductCategory.DAIRY,
+            brand="Store Brand",
+            size="128",
+            size_unit=SizeUnit.FL_OZ,
+            upc_variants=["0041250000001", "0041250000002"],
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(product)
+        session.commit()
+        assert product.category == ProductCategory.DAIRY
+        assert product.size_unit == SizeUnit.FL_OZ
+
+
+class TestPriceHistoryModel:
+    def test_price_source_enum(self, session):
+        store = Store(
+            id=uuid.uuid4(),
+            name="Kroger",
+            slug=StoreSlug.KROGER,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        product = NormalizedProduct(
+            id=uuid.uuid4(),
+            canonical_name="Eggs, Large, 12ct",
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add_all([store, product])
+        session.flush()
+        ph = PriceHistory(
+            id=uuid.uuid4(),
+            normalized_product_id=product.id,
+            store_id=store.id,
+            observed_date=date(2026, 3, 15),
+            regular_price=Decimal("4.99"),
+            sale_price=Decimal("3.99"),
+            source=PriceSource.RECEIPT,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(ph)
+        session.commit()
+        assert ph.source == PriceSource.RECEIPT
+        assert ph.regular_price == Decimal("4.99")
+
+
+class TestCouponModel:
+    def test_coupon_discount_types(self, session):
+        store = Store(
+            id=uuid.uuid4(),
+            name="Target",
+            slug=StoreSlug.TARGET,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(store)
+        session.flush()
+        coupon = Coupon(
+            id=uuid.uuid4(),
+            store_id=store.id,
+            title="$2 off eggs",
+            discount_type=DiscountType.FIXED,
+            discount_value=Decimal("2.00"),
+            requires_clip=True,
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(coupon)
+        session.commit()
+        assert coupon.discount_type == DiscountType.FIXED
+        assert coupon.discount_value == Decimal("2.00")
+
+
+class TestShrinkflationEventModel:
+    def test_shrinkflation_event(self, session):
+        product = NormalizedProduct(
+            id=uuid.uuid4(),
+            canonical_name="Cereal, Honey Oats",
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(product)
+        session.flush()
+        event = ShrinkflationEvent(
+            id=uuid.uuid4(),
+            normalized_product_id=product.id,
+            detected_date=date(2026, 3, 10),
+            old_size="18",
+            new_size="15.4",
+            old_unit=SizeUnit.OZ,
+            new_unit=SizeUnit.OZ,
+            price_at_old_size=Decimal("4.99"),
+            price_at_new_size=Decimal("4.99"),
+            confidence=Decimal("0.95"),
+            notes="Size reduced by 14.4%, price unchanged",
+            created_at=datetime.now(UTC),
+            updated_at=datetime.now(UTC),
+        )
+        session.add(event)
+        session.commit()
+        assert event.confidence == Decimal("0.95")
+        assert event.old_unit == SizeUnit.OZ

api/tests/test_openapi.py

@@ -0,0 +1,92 @@
+"""Verify all expected routes are present in the OpenAPI spec."""
+
+import pytest
+from httpx import ASGITransport, AsyncClient
+
+from cartsnitch_api.main import app
+
+EXPECTED_ROUTES = [
+    # Auth (6)
+    ("post", "/auth/register"),
+    ("post", "/auth/login"),
+    ("post", "/auth/refresh"),
+    ("get", "/auth/me"),
+    ("patch", "/auth/me"),
+    ("delete", "/auth/me"),
+    # Stores (4)
+    ("get", "/stores"),
+    ("get", "/me/stores"),
+    ("post", "/me/stores/{store_slug}/connect"),
+    ("delete", "/me/stores/{store_slug}"),
+    # Purchases (3)
+    ("get", "/purchases"),
+    ("get", "/purchases/stats"),
+    ("get", "/purchases/{purchase_id}"),
+    # Products (3)
+    ("get", "/products"),
+    ("get", "/products/{product_id}"),
+    ("get", "/products/{product_id}/prices"),
+    # Prices (3)
+    ("get", "/prices/trends"),
+    ("get", "/prices/increases"),
+    ("get", "/prices/comparison"),
+    # Coupons (2)
+    ("get", "/coupons"),
+    ("get", "/coupons/relevant"),
+    # Shopping (2)
+    ("post", "/shopping/optimize"),
+    ("get", "/shopping/lists"),
+    # Alerts (3)
+    ("get", "/alerts"),
+    ("get", "/alerts/settings"),
+    ("put", "/alerts/settings"),
+    # Scraping (2)
+    ("post", "/scraping/{store_slug}/sync"),
+    ("get", "/scraping/status"),
+    # Public (3)
+    ("get", "/public/trends/{product_id}"),
+    ("get", "/public/store-comparison"),
+    ("get", "/public/inflation"),
+    # Health (1)
+    ("get", "/health"),
+]
+
+
+@pytest.mark.asyncio
+async def test_all_routes_in_openapi():
+    transport = ASGITransport(app=app)
+    async with AsyncClient(transport=transport, base_url="http://test") as client:
+        resp = await client.get("/openapi.json")
+        assert resp.status_code == 200
+        spec = resp.json()
+        paths = spec["paths"]
+
+        registered = set()
+        for path, methods in paths.items():
+            for method in methods:
+                if method in ("get", "post", "put", "delete", "patch"):
+                    registered.add((method, path))
+
+        missing = []
+        for method, path in EXPECTED_ROUTES:
+            if (method, path) not in registered:
+                missing.append(f"{method.upper()} {path}")
+
+        assert not missing, "Missing routes in OpenAPI spec:\n" + "\n".join(missing)
+
+
+@pytest.mark.asyncio
+async def test_route_count():
+    transport = ASGITransport(app=app)
+    async with AsyncClient(transport=transport, base_url="http://test") as client:
+        resp = await client.get("/openapi.json")
+        spec = resp.json()
+        paths = spec["paths"]
+
+        count = 0
+        for _path, methods in paths.items():
+            for method in methods:
+                if method in ("get", "post", "put", "delete", "patch"):
+                    count += 1
+
+        assert count == 33, f"Expected 33 routes, found {count}"

api/tests/test_routes/test_alerts.py

@@ -0,0 +1,35 @@
+"""Integration tests for alert endpoints."""
+
+import pytest
+
+
+@pytest.mark.asyncio
+async def test_list_alerts_empty(client, auth_headers):
+    """No purchases means no alerts."""
+    resp = await client.get("/alerts", headers=auth_headers)
+    assert resp.status_code == 200
+    assert resp.json() == []
+
+
+@pytest.mark.asyncio
+async def test_get_alert_settings(client, auth_headers):
+    resp = await client.get("/alerts/settings", headers=auth_headers)
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["price_increase_threshold_pct"] == 5.0
+    assert data["shrinkflation_enabled"] is True
+    assert data["email_notifications"] is False
+
+
+@pytest.mark.asyncio
+async def test_update_alert_settings_returns_501(client, auth_headers):
+    resp = await client.put(
+        "/alerts/settings",
+        headers=auth_headers,
+        json={
+            "price_increase_threshold_pct": 10.0,
+            "shrinkflation_enabled": False,
+            "email_notifications": True,
+        },
+    )
+    assert resp.status_code == 501

api/tests/test_routes/test_coupons.py

@@ -0,0 +1,58 @@
+"""Integration tests for coupon endpoints."""
+
+from datetime import date
+from decimal import Decimal
+
+import pytest
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
+
+from cartsnitch_api.models import Coupon, Store
+
+
+@pytest.fixture
+async def coupon_data(db_engine, auth_headers):
+    """Seed stores and coupons."""
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        store = Store(name="Target", slug="target")
+        session.add(store)
+        await session.commit()
+        await session.refresh(store)
+
+        coupon = Coupon(
+            store_id=store.id,
+            title="$2 off laundry",
+            description="$2 off any laundry detergent",
+            discount_value=Decimal("2.00"),
+            discount_type="fixed",
+            valid_from=date(2026, 1, 1),
+            valid_to=date(2026, 12, 31),
+        )
+        session.add(coupon)
+        await session.commit()
+
+        return {"store": store, "coupon": coupon, "headers": auth_headers}
+
+
+@pytest.mark.asyncio
+async def test_list_coupons(client, coupon_data):
+    resp = await client.get("/coupons", headers=coupon_data["headers"])
+    assert resp.status_code == 200
+    data = resp.json()
+    assert len(data) >= 1
+
+
+@pytest.mark.asyncio
+async def test_list_coupons_by_store(client, coupon_data):
+    store_id = str(coupon_data["store"].id)
+    resp = await client.get(f"/coupons?store_id={store_id}", headers=coupon_data["headers"])
+    assert resp.status_code == 200
+    assert len(resp.json()) >= 1
+
+
+@pytest.mark.asyncio
+async def test_relevant_coupons_empty(client, auth_headers):
+    """No purchases means no relevant coupons."""
+    resp = await client.get("/coupons/relevant", headers=auth_headers)
+    assert resp.status_code == 200
+    assert resp.json() == []

api/tests/test_routes/test_prices.py

@@ -0,0 +1,90 @@
+"""Integration tests for price endpoints."""
+
+from datetime import date
+from decimal import Decimal
+
+import pytest
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
+
+from cartsnitch_api.models import NormalizedProduct, PriceHistory, Store
+
+
+@pytest.fixture
+async def price_data(db_engine, auth_headers):
+    """Seed products with price history showing an increase."""
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        store = Store(name="Walmart", slug="walmart")
+        product = NormalizedProduct(
+            canonical_name="Tide Pods 42ct",
+            category="household",
+            brand="Tide",
+        )
+        session.add_all([store, product])
+        await session.commit()
+        await session.refresh(store)
+        await session.refresh(product)
+
+        # Two price points — second is higher (increase)
+        ph1 = PriceHistory(
+            normalized_product_id=product.id,
+            store_id=store.id,
+            observed_date=date(2026, 2, 1),
+            regular_price=Decimal("12.99"),
+            source="receipt",
+        )
+        ph2 = PriceHistory(
+            normalized_product_id=product.id,
+            store_id=store.id,
+            observed_date=date(2026, 3, 1),
+            regular_price=Decimal("14.49"),
+            source="receipt",
+        )
+        session.add_all([ph1, ph2])
+        await session.commit()
+
+        return {"product": product, "store": store, "headers": auth_headers}
+
+
+@pytest.mark.asyncio
+async def test_price_trends(client, price_data):
+    resp = await client.get("/prices/trends", headers=price_data["headers"])
+    assert resp.status_code == 200
+    data = resp.json()
+    assert len(data) >= 1
+    assert data[0]["product_name"] == "Tide Pods 42ct"
+    assert len(data[0]["data_points"]) == 2
+
+
+@pytest.mark.asyncio
+async def test_price_trends_by_category(client, price_data):
+    resp = await client.get("/prices/trends?category=household", headers=price_data["headers"])
+    assert resp.status_code == 200
+    assert len(resp.json()) == 1
+
+    resp = await client.get("/prices/trends?category=nonexistent", headers=price_data["headers"])
+    assert resp.status_code == 200
+    assert len(resp.json()) == 0
+
+
+@pytest.mark.asyncio
+async def test_price_increases(client, price_data):
+    resp = await client.get("/prices/increases", headers=price_data["headers"])
+    assert resp.status_code == 200
+    data = resp.json()
+    assert len(data) >= 1
+    increase = data[0]
+    assert increase["old_price"] == 12.99
+    assert increase["new_price"] == 14.49
+    assert increase["increase_pct"] > 0
+
+
+@pytest.mark.asyncio
+async def test_price_comparison(client, price_data):
+    pid = str(price_data["product"].id)
+    resp = await client.get(f"/prices/comparison?product_ids={pid}", headers=price_data["headers"])
+    assert resp.status_code == 200
+    data = resp.json()
+    assert len(data) >= 1
+    assert data[0]["product_name"] == "Tide Pods 42ct"
+    assert len(data[0]["prices"]) >= 1

api/tests/test_routes/test_products.py

@@ -0,0 +1,94 @@
+"""Integration tests for product endpoints."""
+
+import uuid
+from datetime import date
+from decimal import Decimal
+
+import pytest
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
+
+from cartsnitch_api.models import NormalizedProduct, PriceHistory, Store
+
+
+@pytest.fixture
+async def product_data(db_engine, auth_headers):
+    """Seed products and price history."""
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        store = Store(name="Meijer", slug="meijer")
+        product = NormalizedProduct(
+            canonical_name="Cheerios 18oz",
+            category="pantry",
+            brand="General Mills",
+            upc_variants=["016000275263"],
+        )
+        session.add_all([store, product])
+        await session.commit()
+        await session.refresh(store)
+        await session.refresh(product)
+
+        ph1 = PriceHistory(
+            normalized_product_id=product.id,
+            store_id=store.id,
+            observed_date=date(2026, 3, 1),
+            regular_price=Decimal("4.99"),
+            source="receipt",
+        )
+        ph2 = PriceHistory(
+            normalized_product_id=product.id,
+            store_id=store.id,
+            observed_date=date(2026, 3, 10),
+            regular_price=Decimal("5.49"),
+            source="receipt",
+        )
+        session.add_all([ph1, ph2])
+        await session.commit()
+
+        return {"product": product, "store": store, "headers": auth_headers}
+
+
+@pytest.mark.asyncio
+async def test_list_products(client, product_data):
+    resp = await client.get("/products", headers=product_data["headers"])
+    assert resp.status_code == 200
+    data = resp.json()
+    assert len(data) >= 1
+    assert data[0]["name"] == "Cheerios 18oz"
+
+
+@pytest.mark.asyncio
+async def test_search_products(client, product_data):
+    resp = await client.get("/products?q=Cheerios", headers=product_data["headers"])
+    assert resp.status_code == 200
+    assert len(resp.json()) == 1
+
+    resp = await client.get("/products?q=nonexistent", headers=product_data["headers"])
+    assert resp.status_code == 200
+    assert len(resp.json()) == 0
+
+
+@pytest.mark.asyncio
+async def test_get_product_detail(client, product_data):
+    pid = str(product_data["product"].id)
+    resp = await client.get(f"/products/{pid}", headers=product_data["headers"])
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["name"] == "Cheerios 18oz"
+    assert data["brand"] == "General Mills"
+    assert len(data["prices_by_store"]) >= 1
+
+
+@pytest.mark.asyncio
+async def test_get_product_not_found(client, auth_headers):
+    resp = await client.get(f"/products/{uuid.uuid4()}", headers=auth_headers)
+    assert resp.status_code == 404
+
+
+@pytest.mark.asyncio
+async def test_get_product_prices(client, product_data):
+    pid = str(product_data["product"].id)
+    resp = await client.get(f"/products/{pid}/prices", headers=product_data["headers"])
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["product_name"] == "Cheerios 18oz"
+    assert len(data["data_points"]) == 2

api/tests/test_routes/test_public.py

@@ -0,0 +1,73 @@
+"""Integration tests for public endpoints (no auth)."""
+
+import uuid
+from datetime import date
+from decimal import Decimal
+
+import pytest
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
+
+from cartsnitch_api.models import NormalizedProduct, PriceHistory, Store
+
+
+@pytest.fixture
+async def public_data(db_engine):
+    """Seed data for public endpoints."""
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        store = Store(name="Target", slug="target")
+        product = NormalizedProduct(
+            canonical_name="Skippy PB 16oz",
+            category="pantry",
+            brand="Skippy",
+        )
+        session.add_all([store, product])
+        await session.commit()
+        await session.refresh(store)
+        await session.refresh(product)
+
+        ph = PriceHistory(
+            normalized_product_id=product.id,
+            store_id=store.id,
+            observed_date=date(2026, 3, 5),
+            regular_price=Decimal("3.99"),
+            source="receipt",
+        )
+        session.add(ph)
+        await session.commit()
+
+        return {"product": product, "store": store}
+
+
+@pytest.mark.asyncio
+async def test_public_trend(client, public_data):
+    pid = str(public_data["product"].id)
+    resp = await client.get(f"/public/trends/{pid}")
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["product_name"] == "Skippy PB 16oz"
+    assert len(data["data_points"]) == 1
+
+
+@pytest.mark.asyncio
+async def test_public_trend_not_found(client):
+    resp = await client.get(f"/public/trends/{uuid.uuid4()}")
+    assert resp.status_code == 404
+
+
+@pytest.mark.asyncio
+async def test_public_store_comparison(client, public_data):
+    pid = str(public_data["product"].id)
+    resp = await client.get(f"/public/store-comparison?product_ids={pid}")
+    assert resp.status_code == 200
+    data = resp.json()
+    assert len(data["products"]) == 1
+
+
+@pytest.mark.asyncio
+async def test_public_inflation(client, public_data):
+    resp = await client.get("/public/inflation")
+    assert resp.status_code == 200
+    data = resp.json()
+    assert "categories" in data
+    assert "cartsnitch_index" in data

api/tests/test_routes/test_purchases.py

@@ -0,0 +1,114 @@
+"""Integration tests for purchase endpoints."""
+
+import secrets
+import uuid
+from datetime import UTC, date, datetime, timedelta
+from decimal import Decimal
+
+import pytest
+from sqlalchemy import text
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
+
+from cartsnitch_api.models import Purchase, PurchaseItem, Store, User
+
+
+@pytest.fixture
+async def purchase_data(db_engine):
+    """Seed a user, store, purchase, items, and a valid session."""
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        user = User(
+            email="buyer@example.com",
+            hashed_password="not-used-with-better-auth",
+            display_name="Buyer",
+        )
+        store = Store(name="Kroger", slug="kroger")
+        session.add_all([user, store])
+        await session.commit()
+        await session.refresh(user)
+        await session.refresh(store)
+
+        purchase = Purchase(
+            user_id=user.id,
+            store_id=store.id,
+            receipt_id="receipt-001",
+            purchase_date=date(2026, 3, 10),
+            total=Decimal("42.50"),
+        )
+        session.add(purchase)
+        await session.commit()
+        await session.refresh(purchase)
+
+        item = PurchaseItem(
+            purchase_id=purchase.id,
+            product_name_raw="Organic Milk 1gal",
+            quantity=Decimal("1"),
+            unit_price=Decimal("5.99"),
+            extended_price=Decimal("5.99"),
+        )
+        session.add(item)
+        await session.commit()
+
+    # Create a session token directly in the sessions table
+    session_token = secrets.token_urlsafe(32)
+    now = datetime.now(UTC).isoformat()
+    expires = (datetime.now(UTC) + timedelta(days=7)).isoformat()
+
+    async with db_engine.begin() as conn:
+        await conn.execute(
+            text(
+                "INSERT INTO sessions (id, token, user_id, expires_at, created_at, updated_at) "
+                "VALUES (:id, :token, :user_id, :expires_at, :created_at, :updated_at)"
+            ),
+            {
+                "id": str(uuid.uuid4()),
+                "token": session_token,
+                "user_id": str(user.id),
+                "expires_at": expires,
+                "created_at": now,
+                "updated_at": now,
+            },
+        )
+
+    return {
+        "user": user,
+        "store": store,
+        "purchase": purchase,
+        "headers": {"Cookie": f"better-auth.session_token={session_token}"},
+    }
+
+
+@pytest.mark.asyncio
+async def test_list_purchases(client, purchase_data):
+    resp = await client.get("/purchases", headers=purchase_data["headers"])
+    assert resp.status_code == 200
+    data = resp.json()
+    assert len(data) == 1
+    assert data[0]["store_name"] == "Kroger"
+    assert data[0]["total"] == 42.50
+
+
+@pytest.mark.asyncio
+async def test_get_purchase_detail(client, purchase_data):
+    pid = str(purchase_data["purchase"].id)
+    resp = await client.get(f"/purchases/{pid}", headers=purchase_data["headers"])
+    assert resp.status_code == 200
+    data = resp.json()
+    assert len(data["line_items"]) == 1
+    assert data["line_items"][0]["name"] == "Organic Milk 1gal"
+
+
+@pytest.mark.asyncio
+async def test_get_purchase_not_found(client, auth_headers):
+    resp = await client.get(f"/purchases/{uuid.uuid4()}", headers=auth_headers)
+    assert resp.status_code == 404
+
+
+@pytest.mark.asyncio
+async def test_purchase_stats(client, purchase_data):
+    resp = await client.get("/purchases/stats", headers=purchase_data["headers"])
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["total_spent"] == 42.50
+    assert data["purchase_count"] == 1
+    assert "Kroger" in data["by_store"]

api/tests/test_routes/test_stores.py

@@ -0,0 +1,77 @@
+"""Integration tests for store endpoints."""
+
+import pytest
+
+from cartsnitch_api.models import Store
+
+
+@pytest.fixture
+async def seeded_store(db_engine):
+    """Insert a test store directly into the DB."""
+    from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
+
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        store = Store(name="Meijer", slug="meijer", logo_url=None, website_url=None)
+        session.add(store)
+        await session.commit()
+        await session.refresh(store)
+        return store
+
+
+@pytest.mark.asyncio
+async def test_list_stores(client, seeded_store):
+    resp = await client.get("/stores")
+    assert resp.status_code == 200
+    data = resp.json()
+    assert len(data) >= 1
+    assert data[0]["slug"] == "meijer"
+
+
+@pytest.mark.asyncio
+async def test_list_user_stores_empty(client, auth_headers):
+    resp = await client.get("/me/stores", headers=auth_headers)
+    assert resp.status_code == 200
+    assert resp.json() == []
+
+
+@pytest.mark.asyncio
+async def test_connect_and_disconnect_store(client, auth_headers, seeded_store):
+    # Connect
+    resp = await client.post(
+        "/me/stores/meijer/connect",
+        headers=auth_headers,
+        json={"credentials": None},
+    )
+    assert resp.status_code == 201
+    assert resp.json()["connected"] is True
+
+    # List should show connected
+    resp = await client.get("/me/stores", headers=auth_headers)
+    assert resp.status_code == 200
+    assert len(resp.json()) == 1
+
+    # Disconnect
+    resp = await client.delete("/me/stores/meijer", headers=auth_headers)
+    assert resp.status_code == 204
+
+    # List should be empty again
+    resp = await client.get("/me/stores", headers=auth_headers)
+    assert resp.json() == []
+
+
+@pytest.mark.asyncio
+async def test_connect_nonexistent_store(client, auth_headers):
+    resp = await client.post(
+        "/me/stores/nonexistent/connect",
+        headers=auth_headers,
+        json={},
+    )
+    assert resp.status_code == 404
+
+
+@pytest.mark.asyncio
+async def test_connect_duplicate_store(client, auth_headers, seeded_store):
+    await client.post("/me/stores/meijer/connect", headers=auth_headers, json={})
+    resp = await client.post("/me/stores/meijer/connect", headers=auth_headers, json={})
+    assert resp.status_code == 409

auth/.env.example

@@ -0,0 +1,11 @@
+# Required: Generate with `openssl rand -base64 32`
+BETTER_AUTH_SECRET=change-me-in-production-min-32-chars!!
+
+# Base URL of the auth service
+BETTER_AUTH_URL=http://localhost:3001
+
+# Shared PostgreSQL database
+DATABASE_URL=postgresql://cartsnitch:cartsnitch@localhost:5432/cartsnitch
+
+# Port the auth service listens on
+PORT=3001

auth/Dockerfile

@@ -0,0 +1,17 @@
+FROM node:22-alpine AS builder
+WORKDIR /app
+COPY package.json package-lock.json* ./
+RUN npm ci
+COPY tsconfig.json ./
+COPY src/ src/
+RUN npm run build
+
+FROM node:22-alpine
+WORKDIR /app
+ENV NODE_ENV=production
+COPY package.json package-lock.json* ./
+RUN npm ci --omit=dev
+COPY --from=builder /app/dist/ dist/
+USER 101
+EXPOSE 3001
+CMD ["node", "dist/index.js"]