diff --git a/CLAUDE.md b/CLAUDE.md
index b7ecfac..fde3a08 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -1,4 +1,76 @@
-# CLAUDE.md — 12-rule template
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+---
+
+## Build
+
+**Prerequisites:** MSVC 2022, CMake ≥ 3.20, Python 3.12 at `%LOCALAPPDATA%\Programs\Python\Python312`.  
+OpenUSD 25.05 is expected at `third_party/OpenUSD-v25.05` (set via `CMAKE_PREFIX_PATH` in the preset).
+
+```powershell
+# Configure (one-time; downloads ACES 1.2 OCIO config ~124 MB on first run)
+cmake --preset default
+
+# Build Release (copies all USD/DLL dependencies to build/Release/)
+cmake --build build --config Release
+
+# Install to install/bin/
+cmake --build build --config Release --target install
+```
+
+The `default` preset (in `CMakePresets.json`) enables `WITH_CYCLES=ON`, `HDARNOLD_ROOT`, and `HDEMBREE_USD_ROOT` for the maintainer's machine. For a minimal build without optional render delegates, configure manually:
+
+```powershell
+cmake -B build -G "Visual Studio 17 2022" `
+  -DCMAKE_PREFIX_PATH="third_party/OpenUSD-v25.05" `
+  -DIMGUI_DIR="third_party/imgui-1.92.7" `
+  -DWITH_CYCLES=OFF
+```
+
+**No test runner** — `BUILD_TESTS=OFF` by default. Tests (`ViewportDisplayTest`, `RendererDiagnosticTest`) have stale USD include paths; do not enable without fixing them first.
+
+---
+
+## Architecture
+
+**Entry point:** `src/main.cpp` — sets `PXR_PLUGINPATH_NAME`, pre-flight loads each plugin DLL via `LoadLibraryA` (skips missing deps gracefully), then hands off to `Application`.
+
+**Application** (`src/ui/Application.h/.cpp`) — owns all top-level managers and ImGui panels. Drives the main loop: `Update()` → `RenderUI()`. Persists viewport settings to `%APPDATA%\UsdLayerManager\viewport_settings.ini`.
+
+**Core managers** (all in `src/core/`):
+- `UsdStageManager` — opens/closes/saves USD stages; single source of truth for the active `UsdStageRefPtr`.
+- `LayerManager` — enumerates and manipulates SdfLayer stack (mute, set edit target, add/remove sublayers).
+- `PropertyManager` — reads/writes prim attributes; drives `PropertyPanel`.
+- `CommandHistory` — undo/redo stack; all mutating operations go through commands in `src/core/commands/`.
+
+**Viewport rendering pipeline** (the most complex subsystem):
+- `ViewportPanel` (`src/ui/`) — container for 1–4 `ViewportTile` instances, handles split layout and shared selection.
+- `ViewportTile` — owns one `ViewportCamera` + one `UsdSceneRenderer`. Renders into an ImGui child window by passing the scene texture as an ImGui image.
+- `UsdSceneRenderer` (`src/core/`) — wraps `UsdImagingGLEngine` (Hydra/Storm). Renders into a `GlfDrawTarget` (offscreen RGBA16F FBO). All GL overlay drawing (grid, axis, bbox, camera/light wireframes) happens here while the draw-target FBO is bound.
+- `ViewportColorCorrector` — **file-local class inside `UsdSceneRenderer.cpp`** (pimpl). Applies sRGB or OCIO color correction as a fullscreen GL pass *after* Hydra renders linear. Hydra's own `HdxColorCorrectionTask` is bypassed (`colorCorrectionMode = "disabled"` always passed to Hydra). See `docs/adr/0001-viewport-color-correction.md`.
+
+**OCIO config:** `$OCIO` is set at startup (in `Application.cpp`) to `resources/OpenColorIO-Configs/aces_1.2/config.ocio` (downloaded at CMake configure time). The `OcioConfigParser` utility (`src/utils/`) wraps the OCIO C++ API to enumerate displays/views/colorspaces for the UI.
+
+**UI panels** (all `src/ui/`):
+- `StageEditorPanel` — edit target, dirty state, drag-drop sublayer ordering.
+- `SceneHierarchyPanel` — prim tree with type icons.
+- `PropertyPanel` — attribute inspector/editor.
+- `TimelinePanel` — transport controls, loop/bounce, frame scrub.
+- `CurveEditorPanel` — Maya-style F-curve editor with Bezier round-trip to USD time samples.
+
+**GL loader:** `glad` (generated loader in `src/utils/GLExt.h`). Do not call GL functions before `gladLoadGL`.
+
+**Logging:** `LOG_INFO / LOG_WARNING / LOG_ERROR` macros (`src/utils/Logger.h`). USD diagnostics (`TF_WARN`, `TF_ERROR`) are routed to the same logger via a `TfDiagnosticMgr::Delegate` installed in `UsdSceneRenderer::InitRenderer()`.
+
+**DLL layout (Windows):**
+- Exe + all USD/OCIO/FFmpeg DLLs live in `build/Release/`.
+- Hydra plugin DLLs live in `build/Release/usd/` (so `plugInfo.json`'s `LibraryPath "../<name>.dll"` resolves correctly).
+
+---
+
+# 12-rule template
 
 These rules apply to every task in this project unless explicitly overridden.
 Bias: caution over speed on non-trivial work. Use judgment on trivial tasks.