textual

# Textual Write current, compiling Textual code (pinned to **8.2.7**, Python **≥3.9**, Rich **15.0.0**) and refuse the pre-1.0 / 0.x patterns the model remembers from training — the 1.0 (Dec 2024) and 2.0 (Feb 2025) releases were hard breaks. The body is the load-bearing 20%: one mental model and one **run-verified** example per concept. Everything enumerable — the full widget catalog, every TCSS rule, the streaming model, testing, deploy, migration — lives in `references/`. Open the matching reference before writing nontrivial code in that area. ## Mental model Textual is a **retained, reactive, DOM-like** framework — the opposite of Ratatui's immediate mode and Bubble Tea's MVU. You build a tree of widget objects **once**, then mutate their state; Textual re-renders only the affected parts, like a web framework. It is **async-native** (asyncio) and styled with **Textual CSS (TCSS)**, not layout math. Four nouns carry everything: - **App** — the application and event loop; `App().run()` (or `await run_async()`). Holds screens, handles input, owns the `@work` workers. - **Screen** — a full-window container you push/pop; the default screen hosts your `compose()`. Modals/dialogs are screens. - **Widget** — a node in the DOM tree. **Leaf** widgets draw themselves (`render()`); **compound** widgets yield children (`compose()`). - **DOM + TCSS** — widgets form a tree you query with `query_one`/`query` (CSS selectors) and style with TCSS. Mutating a widget's `reactive` state s...