diff --git a/docs/ARCHITECTURE.md b/docs/ARCHITECTURE.md
index e27df4e..ab98c98 100644
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -2,9 +2,16 @@
 
 ## Overview
 
-Chobit is an interactive AI companion that lives on the user's desktop as a transparent overlay with a 3D animated character. It coordinates voice interaction (STT/TTS) with LLM-driven conversation and real-time avatar animation.
+Chobit is an interactive AI companion — a multi-platform Godot 4 app with a 3D VRM avatar, voice interaction, and pluggable LLM backend. Godot is the avatar runtime; all ML/GPU inference runs on external services via model-boss.
 
-The client is a **Godot 4** application. Backend ML services (@speech-synthesis, @model-boss) run separately.
+The project follows the @applications Tier 2 pattern with shared GDScript symlinked into platform-specific Godot projects:
+
+```
+shared/godot/           → Cross-platform source (avatar, conversation, audio, UI)
+godot-desktop/src/ →    → Symlink to shared/godot/ (transparent overlay, tray, window mgmt)
+godot-mobile/src/ →     → Symlink to shared/godot/ (touch input, on-device camera)
+services/               → Desktop-only Python sidecars (bridge, tray, vision)
+```
 
 ## System Diagram
 
@@ -323,8 +330,10 @@ Required blendshapes: `happy`, `sad`, `angry`, `surprised`, `relaxed`, `neutral`
 
 | Asset | Format | Location |
 |-------|--------|----------|
-| VRM models | `.vrm` | `godot/models/` |
-| Animations | `.tres` (Godot resource) | `godot/scenes/` |
-| Audio | `.wav`, `.ogg` | `godot/audio/` |
-| Scripts | `.gd` (GDScript) | `godot/scripts/` |
-| Scenes | `.tscn` (Godot scene) | `godot/scenes/` |
+| VRM models | `.vrm` | `godot-desktop/models/`, `godot-mobile/models/` |
+| Audio assets | `.wav`, `.ogg`, `.mp3` | `godot-desktop/audio/` |
+| Shared GDScript | `.gd` | `shared/godot/` (symlinked as `src/`) |
+| Platform GDScript | `.gd` | `godot-{platform}/platform/` |
+| Scenes | `.tscn` | `godot-{platform}/scenes/` |
+| Sidecar services | `.py` | `services/{bridge,tray,vision}/` |
+| Protocol types | `.ts` | `packages/chobit-core/src/` |