diff --git a/.github/instructions/ui.instructions.md b/.github/instructions/ui.instructions.md
index 709ad03..c72749d 100644
--- a/.github/instructions/ui.instructions.md
+++ b/.github/instructions/ui.instructions.md
@@ -1,6 +1,53 @@
 ---
-description: Copilot rules for modifying the UI
+description: "Use when modifying the NiceGUI application under src/transcription/ui. Defines ownership and dependency boundaries for UI registration, pages, components, services, persistence, state, and static assets."
 applyTo: 'src/transcription/ui/**/*.py'
 ---
 
-The UI is forbidden from directly touching the database. All interactions should be done using the [services](../../src/transcription/services/)
+# UI Conceptual Boundaries
+
+Keep dependencies flowing in this direction:
+
+`ui/__init__.py` -> `pages` -> `components`
+
+Pages may depend on application services and framework-provided dependencies. Components may depend on smaller components and shared presentation helpers. Services and domain modules must never depend on the UI.
+
+## Package Root
+
+- Keep `ui/__init__.py` as the UI composition root: register global assets, register pages, and mount NiceGUI on FastAPI.
+- Do not put feature rendering, service calls, persistence, or route-specific state in the package root.
+
+## Pages
+
+- Pages own route registration and route-level orchestration.
+- Resolve request or application dependencies, call [services](../../src/transcription/services/), adapt returned data for presentation when needed, and coordinate refresh, navigation, and notifications here.
+- Do not query, mutate, commit, or roll back the database from a page. Do not import database engines, sessions, operations, or query-building APIs. Persistence belongs to services or workflow functions.
+- Framework dependency types may cross into page handlers only to construct or invoke services; do not pass sessions or session factories into components.
+- Keep business rules, lifecycle transitions, transaction boundaries, and cross-service workflows out of page callbacks.
+
+## Components
+
+- Components own reusable rendering, widget-local state, input normalization, and presentation-only formatting.
+- Expose user actions through typed callback parameters. The calling page decides which service or workflow runs and what refresh or navigation follows.
+- Do not register routes, resolve request/app state, instantiate services, or access persistence from components.
+- Components may accept ORM models returned by services as read-only snapshots. Only use fields and relationships that the service loaded eagerly; never mutate models, trigger lazy loading, or expose session behavior.
+- A component may compose lower-level components, but it must not import from `pages`.
+
+## Shared UI Infrastructure
+
+- Keep app-wide navigation and layout primitives in `components/app_shell.py`.
+- Keep generic table/event adaptation in `components/table/common.py`; feature-specific columns, row read models, and formatting belong in the feature table module.
+- Keep exception normalization and user-facing error display in `components/error_presenter.py`; preserve `AppError` details and operation identifiers at page/component boundaries.
+
+## CSS Assets
+
+- Keep CSS under `ui/static` and split it into manageable, feature-oriented files. Do not grow a monolithic stylesheet or embed substantial style blocks in Python components.
+- Load each stylesheet from the page, component, or composition root that needs it with `ui.add_css(...)`. Use shared registration only for genuinely application-wide styles.
+- Read stylesheet text through `importlib.resources.files(...)` so loading works from installed packages and is independent of the working directory.
+- Centralize CSS reading in one typed helper cached by relative resource path with `functools.cache` or an equivalent unbounded `lru_cache`. Cache the immutable stylesheet text to avoid repeated resource I/O during component renders; keep NiceGUI registration decisions at the caller.
+- Do not encode application behavior in CSS or other static assets.
+
+## State and Side Effects
+
+- Limit component state to ephemeral interaction state such as loading flags, form values, dialogs, and expansion state.
+- Application and worker state must be resolved at the page or application boundary and passed through narrow interfaces such as callbacks or notifier protocols.
+- Keep filesystem, network, provider, and worker orchestration behind application services or dedicated adapters. UI code may trigger those operations but must not implement them.