diff --git a/README_DEVELOPER.md b/README_DEVELOPER.md
index 5976fde..ad6f0fb 100644
--- a/README_DEVELOPER.md
+++ b/README_DEVELOPER.md
@@ -1,19 +1,102 @@
 # Bahmcloud Store – Developer Documentation
 
-This document is intended for developers and contributors.
+For contributors and maintainers.
 
 ## Architecture
 
-BCS consists of:
-- Installer Add-on
-- Core Integration
-- Store Index
+Repositories:
+1) Installer Add-on (HAOS/Supervised)
+2) Core Integration
+3) Store Index (`store.yaml`)
 
-## Code Structure
+### Integration Layout
 
-See custom_components/bahmcloud_store
+custom_components/bahmcloud_store/
+- __init__.py: setup, panel registration, schedule background after HA started
+- core.py: index merge, enrichment, install/update/uninstall, backups, restore, caching
+- providers.py: GitHub/GitLab/Gitea repo info + latest version helpers
+- metadata.py: read bcs.yaml / hacs.json / hacs.yaml
+- storage.py: persistent storage (installed, custom, repo cache, hacs cache)
+- views.py: HTTP API endpoints
+- update.py: UpdateEntity implementation
+- repairs.py: (optional) Repairs flow for restart
+- panel/: UI (panel.js, styles.css, etc.)
+- manifest.json
 
-## Rules
+## Runtime Model
 
-- Code in English
-- No breaking changes without version bump
+- RepoItem (merged)
+- Installed repos (storage)
+- Repo cache (persisted enrichment)
+- HACS meta cache (mapping owner/repo → name/description)
+
+## Background
+
+- Heavy work only after `homeassistant_started`
+- Refresh: if index unchanged → installed-only refresh + schedule enrichment
+- Opening a repo triggers `ensure_repo_details()` and persists to cache
+
+## Providers
+
+- GitHub: API/releases/tags/atom + raw readme
+- GitLab: API releases/tags + raw readme
+- Gitea: API releases/tags + raw readme
+
+## Metadata
+
+- Prefer `bcs.yaml`, fallback `hacs.json` / `hacs.yaml`
+- Populate name/description/category/author/maintainer
+
+## HTTP API (excerpt)
+
+Base: /api/bcs
+
+- GET  /api/bcs
+- POST /api/bcs?action=refresh
+- GET  /api/bcs/readme?repo_id=...
+- GET  /api/bcs/versions?repo_id=...
+- POST /api/bcs/install?repo_id=...&version=...
+- POST /api/bcs/update?repo_id=...&version=...
+- POST /api/bcs/uninstall?repo_id=...
+- GET  /api/bcs/backups?repo_id=...
+- POST /api/bcs/restore?repo_id=...&backup_id=...
+- (optional) POST/DELETE custom_repo
+
+## Update Entities
+
+- Unique id bcs:<repo_id>
+- Compare installed ref vs latest ref
+- Dispatcher signal on refresh/install/update
+
+## Storage
+
+- JSON in HA `.storage`
+- async read/write helpers
+- repo cache applied on startup
+
+## Contributing to **BCS Official**
+
+1) Fork index repo (with `store.yaml`)  
+2) Add entry:
+```yaml
+- name: Your Integration Name
+  url: https://github.com/your-org/your-repo
+  category: Category
+```
+3) (Recommended) Add `bcs.yaml` to your repo:
+```yaml
+name: Your Integration Name
+description: One-liner for the store
+category: Sensors
+author: Your Name
+maintainer: Your Handle
+```
+4) Open PR; validation checks: reachable, has `custom_components/<domain>/manifest.json`, sensible metadata
+5) Merge → appears in **BCS Official** after refresh
+
+## Coding Guidelines
+
+- Async I/O, no blocking event loop
+- Respect provider rate limits
+- Clean logging around refresh/install/update/restore
+- Keep UI responsive; throttle updates