diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 0000000..3a9c1e4
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1,429 @@
+# WooCommerce Tier and Package Prices - AI Context Document
+
+**Last Updated:** 2025-12-23
+**Current Version:** 1.1.20
+**Author:** Marco Graetsch
+**Project Status:** Production-ready WordPress plugin
+
+## Project Overview
+
+This is a WooCommerce plugin that adds flexible pricing capabilities to products through two distinct pricing models:
+
+1. **Tier Pricing (Volume Discounts)**: Progressive discounts based on quantity ranges (e.g., 1-9 items @ $12, 10-24 @ $10, 25+ @ $8)
+2. **Package Pricing (Fixed Bundles)**: Exact quantity packages at fixed prices (e.g., exactly 10 items for $95, exactly 25 for $200)
+
+### Key Fact: 100% AI-Generated
+This project is proudly **"vibe-coded"** using Claude.AI - the entire codebase was created through AI assistance.
+
+## Technical Stack
+
+- **Language:** PHP 7.4+
+- **Framework:** WordPress Plugin API
+- **E-commerce:** WooCommerce 8.0+ (tested up to 10.x)
+- **Template Engine:** Twig 3.0 (via Composer)
+- **Frontend:** Vanilla JavaScript + jQuery
+- **Styling:** Custom CSS
+- **Dependency Management:** Composer
+- **Internationalization:** WordPress i18n (.pot/.po/.mo files)
+
+### Dependencies
+```json
+{
+  "twig/twig": "^3.0",
+  "symfony/polyfill-ctype": "^1.x",
+  "symfony/polyfill-mbstring": "^1.x"
+}
+```
+
+## Architecture
+
+### Directory Structure
+```
+wc-tier-and-package-prices/
+├── wc-tier-and-package-prices.php    # Main plugin file (entry point)
+├── includes/                         # PHP classes
+│   ├── class-wc-tpp-admin.php        # Admin settings integration
+│   ├── class-wc-tpp-settings.php     # WooCommerce settings page
+│   ├── class-wc-tpp-product-meta.php # Product edit page meta boxes
+│   ├── class-wc-tpp-frontend.php     # Product page display logic
+│   ├── class-wc-tpp-cart.php         # Cart price calculations
+│   └── class-wc-tpp-template-loader.php # Twig template loader
+├── templates/                        # Twig templates
+│   ├── admin/                       # Admin interface templates
+│   │   ├── tier-row.twig           # Single tier input row
+│   │   └── package-row.twig        # Single package input row
+│   └── frontend/                    # Customer-facing templates
+│       ├── pricing-table.twig       # Main pricing display wrapper
+│       ├── tier-pricing-table.twig  # Tier pricing display
+│       └── package-pricing-display.twig # Package buttons/cards
+├── assets/
+│   ├── css/
+│   │   ├── admin.css               # Backend styling
+│   │   └── frontend.css            # Product page & cart styling
+│   └── js/
+│       ├── admin.js                # Meta box interaction (add/remove rows)
+│       └── frontend.js             # Dynamic price updates, package selection
+├── languages/                       # Translation files
+│   ├── *.pot                       # Translation template
+│   ├── *.po                        # Translation sources
+│   └── *.mo                        # Compiled translations
+├── vendor/                          # Composer dependencies (included in releases)
+├── releases/                        # Release packages (not in git)
+└── *.md                            # Documentation files
+
+```
+
+### Class Responsibilities
+
+#### 1. `WC_Tier_Package_Prices` (Main Plugin Class)
+- **Location:** `wc-tier-and-package-prices.php`
+- **Pattern:** Singleton
+- **Responsibilities:**
+  - Plugin initialization and bootstrapping
+  - Loading all component classes via `includes()`
+  - HPOS (High-Performance Order Storage) compatibility declaration
+  - Text domain loading for internationalization
+  - Activation/deactivation hooks
+
+#### 2. `WC_TPP_Admin`
+- **Location:** `includes/class-wc-tpp-admin.php`
+- **Pattern:** Singleton
+- **Responsibilities:**
+  - Enqueues admin CSS/JS
+  - Registers WooCommerce settings page via filter
+  - Manages settings page instance (cached to prevent duplicates)
+  - Product meta box asset loading
+
+#### 3. `WC_TPP_Settings`
+- **Location:** `includes/class-wc-tpp-settings.php`
+- **Extends:** `WC_Settings_Page` (WooCommerce core)
+- **Responsibilities:**
+  - Creates "Tier & Package Prices" tab in WooCommerce settings
+  - Defines global plugin settings (enable/disable features, display position, etc.)
+  - Setting persistence through WooCommerce options API
+
+**Global Settings:**
+- `wc_tpp_enable_tier_pricing` (yes/no)
+- `wc_tpp_enable_package_pricing` (yes/no)
+- `wc_tpp_display_table` (yes/no) - Show pricing tables on product pages
+- `wc_tpp_display_position` (before_add_to_cart / after_add_to_cart / after_price)
+- `wc_tpp_restrict_package_quantities` (yes/no) - Global quantity restrictions
+
+#### 4. `WC_TPP_Product_Meta`
+- **Location:** `includes/class-wc-tpp-product-meta.php`
+- **Responsibilities:**
+  - Adds tier/package pricing fields to product edit page
+  - Renders Twig templates for meta box rows
+  - Saves tier/package data to post meta
+  - Nonce verification and capability checks for security
+  - Prevents autosave from corrupting data
+
+**Product Meta Keys:**
+- `_wc_tpp_tiers` - Array of tier objects `[{min_qty, price, label}]`
+- `_wc_tpp_packages` - Array of package objects `[{qty, price, label}]`
+- `_wc_tpp_restrict_to_packages` - Per-product quantity restriction (yes/no)
+
+#### 5. `WC_TPP_Frontend`
+- **Location:** `includes/class-wc-tpp-frontend.php`
+- **Responsibilities:**
+  - Enqueues frontend CSS/JS on product pages
+  - Displays pricing tables via Twig templates
+  - Localizes currency settings to JavaScript
+  - Hides quantity inputs for restricted products
+  - Modifies catalog "Add to Cart" buttons to "View Options" for restricted products
+  - Static methods for price lookups (`get_tier_price()`, `get_package_price()`)
+
+#### 6. `WC_TPP_Cart`
+- **Location:** `includes/class-wc-tpp-cart.php`
+- **Responsibilities:**
+  - **MOST CRITICAL CLASS** - Handles all cart price calculations
+  - Applies tier/package pricing during cart totals calculation
+  - Stores pricing metadata in cart items for display
+  - Customizes cart item display (price labels, quantity indicators)
+  - Validates package quantities on add-to-cart
+  - Hides/disables quantity inputs for restricted products (classic cart + blocks)
+  - **WooCommerce Blocks support** via `woocommerce_store_api_product_quantity_editable` filter
+
+**Price Calculation Priority (in `apply_tier_package_pricing()`):**
+1. Check for exact package match → Use package price if found
+2. Check for tier match → Use tier price if found
+3. Fall back to regular product price
+
+#### 7. `WC_TPP_Template_Loader`
+- **Location:** `includes/class-wc-tpp-template-loader.php`
+- **Pattern:** Singleton
+- **Responsibilities:**
+  - Initializes Twig environment with proper paths
+  - Renders Twig templates from both admin and frontend directories
+  - Handles template caching and error handling
+
+## Important Implementation Details
+
+### Price Calculation Logic
+
+**Package Pricing** (exact match):
+```php
+// In cart: if quantity == 10 and package exists for 10, use package price
+if ($quantity == $package['qty']) {
+    $unit_price = $package['price'] / $quantity;  // Total price divided by quantity
+    $product->set_price($unit_price);  // WooCommerce expects unit price
+}
+```
+
+**Tier Pricing** (range-based):
+```php
+// In cart: if quantity >= 10, use tier price for quantities 10+
+foreach ($tiers as $tier) {
+    if ($quantity >= $tier['min_qty']) {
+        $applicable_price = $tier['price'];  // This is already unit price
+    }
+}
+$product->set_price($applicable_price);
+```
+
+### Quantity Restriction Feature
+
+Products can be configured to ONLY allow purchase in package quantities:
+
+- **Global setting:** `wc_tpp_restrict_package_quantities`
+- **Per-product setting:** `_wc_tpp_restrict_to_packages`
+- **When enabled:**
+  - Quantity inputs are hidden on product page, cart, and mini-cart
+  - Customers must use package selection buttons
+  - Validation prevents arbitrary quantities from being added
+  - Catalog buttons change to "View Options" instead of "Add to Cart"
+
+### WooCommerce Blocks Compatibility
+
+**CRITICAL BUG FIXED in v1.1.20:**
+- Filter `woocommerce_store_api_product_quantity_editable` passes `WC_Product` object, NOT cart item array
+- Previous code tried to use product object as array → fatal error
+- Fixed by accepting product object and using `$product->get_id()`
+
+### Cart Item Metadata
+
+The plugin stores additional data in cart items for display purposes:
+
+```php
+WC()->cart->cart_contents[$cart_item_key]['wc_tpp_pricing_type'] = 'package' | 'tier';
+WC()->cart->cart_contents[$cart_item_key]['wc_tpp_total_price'] = 99.99;  // For packages
+WC()->cart->cart_contents[$cart_item_key]['wc_tpp_unit_price'] = 9.99;   // For tiers
+```
+
+This metadata is used by display filters to show "(Package price)" or "(Volume discount)" labels.
+
+## Common Patterns & Conventions
+
+### Class Instantiation Pattern
+All classes auto-instantiate at the end of their file:
+```php
+if (!class_exists('WC_TPP_Frontend')) {
+    class WC_TPP_Frontend {
+        // class code
+    }
+}
+new WC_TPP_Frontend();  // Auto-instantiate
+```
+
+**Exception:** Admin and Settings classes use singleton pattern to prevent duplicates.
+
+### Security Best Practices
+- All user inputs are sanitized (integers for quantities/prices)
+- Nonce verification on form submissions
+- Capability checks (`edit_products`) before saving
+- Output escaping in templates (`esc_attr`, `esc_html`, `esc_js`)
+- Direct file access prevention via `ABSPATH` check
+
+### Translation Ready
+All user-facing strings use:
+```php
+__('Text to translate', 'wc-tier-package-prices')
+_e('Text to translate', 'wc-tier-package-prices')
+```
+
+Text domain: `wc-tier-package-prices`
+
+## Known Issues & Historical Context
+
+### Settings Page Duplication Saga (v1.1.15-1.1.19)
+Multiple versions attempted to fix settings page appearing twice:
+- **Root cause:** Settings file auto-instantiation + Composer autoloader
+- **Solution:** Removed auto-instantiation from settings file, explicit instantiation in admin class
+- **Prevention:** Singleton pattern + duplicate detection in array
+
+### Class Redeclaration Issues (v1.1.8-1.1.14)
+Plugin was completely non-functional:
+- **Cause:** Incorrect initialization pattern without `class_exists()` guards
+- **Solution:** Added guards and restored direct instantiation pattern
+- **Lesson:** Always wrap class declarations in `class_exists()` checks
+
+### WooCommerce Blocks Fatal Error (v1.1.19 → v1.1.20)
+```
+Fatal error: Cannot use object of type WC_Product_Simple as array
+Location: includes/class-wc-tpp-cart.php:233
+```
+- **Cause:** Filter signature mismatch - expected array, received product object
+- **Fix:** Changed method signature to accept `WC_Product $product` instead of `$cart_item` array
+- **Status:** FIXED in v1.1.20
+
+## Release Process
+
+### Version Bumping
+Update version in 3 places:
+1. `wc-tier-and-package-prices.php` - Plugin header comment (line 7)
+2. `wc-tier-and-package-prices.php` - `WC_TPP_VERSION` constant (line 26)
+3. `composer.json` - version field (optional, not critical)
+
+### Creating Release Package
+```bash
+# From project root
+cd releases
+
+# Create zip excluding dev files
+zip -r wc-tier-and-package-prices-X.X.X.zip .. \
+  -x '*.git*' '*.log' '.claude/*' 'releases/*' 'node_modules/*' \
+  '.DS_Store' 'Thumbs.db' '.vscode/*' '.idea/*' '*.sublime-*' \
+  'notes.*' 'logs/*' 'templates/cache/*' 'composer.lock'
+
+# Generate checksums
+md5sum wc-tier-and-package-prices-X.X.X.zip > wc-tier-and-package-prices-X.X.X.zip.md5
+sha256sum wc-tier-and-package-prices-X.X.X.zip > wc-tier-and-package-prices-X.X.X.zip.sha256
+```
+
+**IMPORTANT:** The `vendor/` directory MUST be included in releases (Twig dependency required for runtime).
+
+### What Gets Released
+- All plugin source files
+- Compiled vendor dependencies
+- Translation files (.mo compiled from .po)
+- Assets (CSS, JS)
+- Documentation (README, CHANGELOG, etc.)
+
+### What's Excluded
+- Git metadata (`.git/`)
+- Development files (`.vscode/`, `.idea/`)
+- Logs and cache files
+- Previous releases
+- `composer.lock` (but `vendor/` is included)
+
+## Testing Checklist
+
+When making changes, test these critical paths:
+
+### Admin
+- [ ] Settings page appears once under WooCommerce > Tier & Package Prices
+- [ ] Settings save correctly
+- [ ] Product edit page shows tier/package meta boxes
+- [ ] Adding/removing tiers works
+- [ ] Adding/removing packages works
+- [ ] Data saves when clicking "Update" on product
+
+### Frontend (Product Page)
+- [ ] Pricing tables display when configured
+- [ ] Package buttons update quantity selector
+- [ ] Price updates dynamically when quantity changes
+- [ ] Restricted products hide quantity input
+- [ ] "View Options" appears on catalog for restricted products
+
+### Cart & Checkout
+- [ ] Correct prices applied for tier pricing
+- [ ] Correct prices applied for package pricing
+- [ ] Cart displays pricing type labels
+- [ ] Package quantities can't be edited if restricted
+- [ ] Prices recalculate if quantity changed (non-restricted products)
+- [ ] Checkout totals are correct
+
+### WooCommerce Blocks (Critical!)
+- [ ] Mini cart block doesn't throw fatal errors
+- [ ] Cart block works correctly
+- [ ] Checkout block processes orders
+- [ ] Quantity editable flag works for blocks
+
+## Development Tips for Future AI Assistants
+
+### When Debugging Cart Issues
+1. Check `includes/class-wc-tpp-cart.php` first
+2. The `apply_tier_package_pricing()` method runs on `woocommerce_before_calculate_totals`
+3. Always validate product objects with `is_a($product, 'WC_Product')`
+4. Remember: WooCommerce expects UNIT prices, not total prices (except for internal calculations)
+
+### When Working with WooCommerce Hooks
+- WooCommerce has both classic and block-based systems
+- Classic cart uses different hooks than Store API (blocks)
+- Always check filter/action documentation for parameter types
+- Don't assume cart item arrays everywhere - sometimes it's product objects!
+
+### When Adding Features
+- Follow the existing pattern: add setting → add UI → add logic → add template
+- Use Twig for all new templates (consistency)
+- Add translations for all user-facing strings
+- Test with both simple products and variable products (if applicable)
+- Consider both classic and block-based cart/checkout
+
+### When Fixing Bugs
+1. Check `CHANGELOG.md` for historical context
+2. Look for similar issues in past versions
+3. Always add detailed changelog entry explaining root cause
+4. Consider edge cases (guest checkout, logged-in users, AJAX add-to-cart, etc.)
+
+## File Locations Quick Reference
+
+| Task | File(s) |
+|------|---------|
+| Change version | `wc-tier-and-package-prices.php` (2 places) |
+| Add global setting | `includes/class-wc-tpp-settings.php` |
+| Modify product meta box | `includes/class-wc-tpp-product-meta.php` + `templates/admin/*.twig` |
+| Change product page display | `includes/class-wc-tpp-frontend.php` + `templates/frontend/*.twig` |
+| Fix cart pricing | `includes/class-wc-tpp-cart.php` |
+| Update styles | `assets/css/frontend.css` or `assets/css/admin.css` |
+| Fix JavaScript bugs | `assets/js/frontend.js` or `assets/js/admin.js` |
+| Add translations | `languages/*.po` then compile to `.mo` |
+| Document changes | `CHANGELOG.md` |
+
+## Compatibility Notes
+
+### WordPress
+- Minimum: 6.0
+- Tested up to: 6.9.x
+- Uses standard plugin API, no deprecated functions
+
+### WooCommerce
+- Minimum: 8.0
+- Tested up to: 10.x
+- HPOS compatible (declared via `FeaturesUtil::declare_compatibility`)
+- Blocks compatible (with proper filter handling)
+
+### PHP
+- Minimum: 7.4
+- Uses modern PHP features (type hints acceptable in new code)
+- Composer autoloader handles namespacing
+
+### Browsers
+- Modern browsers (ES6+ JavaScript)
+- Responsive CSS (mobile-friendly)
+- jQuery dependency (WooCommerce provides)
+
+## Support & Resources
+
+- **Repository:** https://src.bundespruefstelle.ch/magdev/wc-tier-package-prices
+- **Documentation:** See `README.md`, `QUICKSTART.md`, `USAGE_EXAMPLES.md`, `INSTALLATION.md`
+- **Changelog:** `CHANGELOG.md` (detailed version history)
+- **Issue Tracking:** Check fatal-errors-*.log files for production errors
+
+## Final Notes
+
+This is a production-quality plugin with real-world usage. Any changes should:
+1. Maintain backward compatibility with existing tier/package configurations
+2. Not break WooCommerce core functionality
+3. Work with both classic and block-based themes
+4. Be thoroughly tested before release
+5. Include proper error handling and validation
+6. Update CHANGELOG.md with detailed explanations
+
+The plugin architecture is solid and well-tested. Most bugs arise from:
+- WooCommerce API changes (especially blocks)
+- Filter/action signature changes
+- Edge cases in cart calculations
+- Settings persistence issues
+
+Always refer to this document when starting work on this project. Good luck!
diff --git a/includes/class-wc-tpp-cart.php b/includes/class-wc-tpp-cart.php
index 0a98966..96487fc 100644
--- a/includes/class-wc-tpp-cart.php
+++ b/includes/class-wc-tpp-cart.php
@@ -226,11 +226,16 @@ if (!class_exists('WC_TPP_Cart')) {
      * Make quantity non-editable for restricted products in WooCommerce blocks
      *
      * @param bool $editable Whether the quantity is editable
-     * @param array $cart_item Cart item data
+     * @param WC_Product $product Product object
      * @return bool
      */
-    public function block_quantity_editable($editable, $cart_item) {
-        $product_id = $cart_item['id'] ?? ($cart_item['product_id'] ?? 0);
+    public function block_quantity_editable($editable, $product) {
+        // Validate product object
+        if (!$product || !is_a($product, 'WC_Product')) {
+            return $editable;
+        }
+
+        $product_id = $product->get_id();
 
         if (!$product_id) {
             return $editable;
diff --git a/releases/wc-tier-and-package-prices-1.1.20.zip b/releases/wc-tier-and-package-prices-1.1.20.zip
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diff --git a/releases/wc-tier-and-package-prices-1.1.20.zip.md5 b/releases/wc-tier-and-package-prices-1.1.20.zip.md5
new file mode 100644
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+++ b/releases/wc-tier-and-package-prices-1.1.20.zip.md5
@@ -0,0 +1 @@
+bfdeee75bfe3795c9ab9abfe47f12a41  wc-tier-and-package-prices-1.1.20.zip
diff --git a/releases/wc-tier-and-package-prices-1.1.20.zip.sha256 b/releases/wc-tier-and-package-prices-1.1.20.zip.sha256
new file mode 100644
index 0000000..152b6be
--- /dev/null
+++ b/releases/wc-tier-and-package-prices-1.1.20.zip.sha256
@@ -0,0 +1 @@
+953859241d15d76ec4783c72bac851ddd69e5a1f7b119ee4f9ebd30c7fabed17  wc-tier-and-package-prices-1.1.20.zip
diff --git a/wc-tier-and-package-prices.php b/wc-tier-and-package-prices.php
index 69ea88b..7efe470 100644
--- a/wc-tier-and-package-prices.php
+++ b/wc-tier-and-package-prices.php
@@ -4,7 +4,7 @@
  * Plugin Name: WooCommerce Tier and Package Prices
  * Plugin URI: https://src.bundespruefstelle.ch/magdev/wc-tier-package-prices
  * Description: Add tier pricing and package prices to WooCommerce products with configurable quantities at fixed prices
- * Version: 1.1.19
+ * Version: 1.1.20
  * Author: Marco Graetsch
  * Author URI: https://src.bundespruefstelle.ch/magdev
  * Text Domain: wc-tier-package-prices
@@ -23,7 +23,7 @@ if (!defined('ABSPATH')) {
 
 // Define plugin constants
 if (!defined('WC_TPP_VERSION')) {
-    define('WC_TPP_VERSION', '1.1.19');
+    define('WC_TPP_VERSION', '1.1.20');
 }
 if (!defined('WC_TPP_PLUGIN_DIR')) {
     define('WC_TPP_PLUGIN_DIR', plugin_dir_path(__FILE__));