@ashley-shrok/viewmodel-shell

A server-driven UI framework built around one promise: an agent can build, test, and operate a complete app end-to-end — with no human in the loop and no browser anywhere in sight. That falls out of a single idea: the interface is structured data, not code.

The server is a pure transformer — current UI state + an action → next state + a fresh view tree (a JSON tree of typed nodes). A thin adapter renders it to the DOM (or, with the same wire, a terminal) with zero app-specific code; the browser never owns application state. Because the whole interface is data, three things come for free:

• Build it blind — there's nothing to look at to get it right; the view description is the truth.
• Test it without a browser — every interaction is a plain function from input → output, so the entire UI is exercised with ordinary in-process unit tests (no headless browser, no Playwright, no flake) on every CI run. The quiet giant: the full-coverage, test-everything-through-the-UI regime that's usually aspirational is the default here.
• Use it like an API — a finished app is already a clean, self-describing wire protocol, so a different agent can drive it (read the screen → act → read the next) as if it were an API, because it is one.

The frontend is backend-agnostic: it speaks a small JSON contract over a single POST endpoint that takes multipart/form-data (with _action and _state fields). A .NET reference backend ships in the repo, but any language can produce the same contract.

Install

npm install @ashley-shrok/viewmodel-shell

Use

import "@ashley-shrok/viewmodel-shell/styles.css";
import { ViewModelShell } from "@ashley-shrok/viewmodel-shell";
import { BrowserAdapter } from "@ashley-shrok/viewmodel-shell/browser";

const container = document.getElementById("app")!;
const shell = new ViewModelShell({
  endpoint:       "/api/tasks",
  actionEndpoint: "/api/tasks/action",
  adapter:        new BrowserAdapter(container),
});

shell.load();

If your backend is .NET: install the AshleyShrok.ViewModelShell NuGet package (dotnet add package AshleyShrok.ViewModelShell). It ships the full backend record set under the ViewModelShell namespace (ViewNode, PageNode, FormNode, ShellResponse<TState>, ActionPayload<TState>, etc.) — version-aligned with this npm package on major.minor.

For other backends, implement the same JSON shape: a GET returning { vm, state }, and a POST that takes multipart/form-data with _action and _state form fields and returns the next { vm, state }. See AGENTS.md for the full wire format.

Authenticated downloads

When a header-authenticated consumer (e.g. Authorization: Bearer <jwt> via ShellOptions.getRequestHeaders()) needs to offer a file download, return a "download" side-effect from your action handler — the shell fetches the URL with the same headers merged in, parses Content-Disposition + Content-Type, and triggers a browser "Save As":

return new ShellResponse<MyState>(BuildVm(state), state)
    .WithEffect(ShellSideEffect.Download("/api/invoices/42/pdf", "invoice-42.pdf"));

return { vm: buildVm(state), state,
  sideEffects: [shellSideEffect.download("/api/invoices/42/pdf", "invoice-42.pdf")] };

The download endpoint stays auth-gated and the server authorizes in the action handler — no signed-URL machinery. See AGENTS.md for the wire format and pattern.

Terminal (TUI)

⚠️ Experimental. The terminal adapter (@ashley-shrok/viewmodel-shell/tui + vms-tui) is incomplete and under active design — scrolling, keyboard/focus ergonomics, and layout coverage all need more work. Its API and behavior may change or be removed without a major-version bump; don't build production workflows on it yet. The browser/server/core packages are stable and unaffected. Constructing a TuiAdapter prints a one-time notice — silence it with VMS_TUI_SILENCE_EXPERIMENTAL=1.

The same backend renders in a terminal — same wire, no backend change, with a real lazygit-style UX: mouse clicks, wheel scroll, per-pane focus cycle, and a context-aware status bar. Point the CLI at any ViewModel Shell endpoint:

bunx vms-tui https://your-app.example/api/tasks

The action endpoint is derived by convention (<endpoint>/action). The TUI requires the Bun runtime — install once via curl -fsSL https://bun.sh/install | bash (or any installer on bun.sh). Browser and server consumers are unaffected; only /tui + vms-tui need Bun.

Wire it programmatically, exactly like BrowserAdapter:

import { ViewModelShell } from "@ashley-shrok/viewmodel-shell";
import { TuiAdapter } from "@ashley-shrok/viewmodel-shell/tui";

const shell = new ViewModelShell({
  endpoint:       "/api/tasks",
  actionEndpoint: "/api/tasks/action",
  adapter:        new TuiAdapter(),
});

shell.load();

Interaction model. Every section, top-level list, and top-level table is its own scrollable focus pane with a border. Tab/Shift-Tab cycles focus across panes; ↑↓ PgUp/PgDn scroll inside the focused pane; click any button, checkbox, link, copy-button, table header, or table row to act on it. Enter activates the focused pane's primary actionable (first button → dispatch, first link → navigate, first copy-button → OSC-52 copy). Space toggles the focused pane's first checkbox-with-action. When the pane has a text field, Enter submits the enclosing form (Field's <input onSubmit>) and Space is a normal character.

On an interactive terminal the app fills the screen via the alternate-screen buffer — a vim/htop-style takeover that re-flows on resize and restores your prior terminal verbatim on exit (every exit path: quit, Ctrl-C, SIGTERM, crash). Opt out with new TuiAdapter({ viewport: "content" }) for intrinsic content size and no screen takeover. Non-interactive runs (pipe / CI / agent / </dev/null) are unaffected.

The TUI is built on OpenTUI, declared as optional dependencies (@opentui/core, @opentui/react, react@19) so web and server consumers are unaffected — they are never imported by the browser, server, or core entrypoints. bunx vms-tui installs them automatically. Project consumers using TuiAdapter programmatically must add all three explicitly — optional dependencies are not pulled transitively:

bun add @ashley-shrok/viewmodel-shell @opentui/core @opentui/react react

See AGENTS.md for what the terminal renders.

Themes

The base stylesheet ships a light default (purple accent). To use a different look — including the prior dark-purple default — import a theme file on top:

import "@ashley-shrok/viewmodel-shell/styles.css";
import "@ashley-shrok/viewmodel-shell/themes/dark-blue.css";

The prior (pre-0.4.0) dark default is preserved byte-exact as themes/dark-purple.css. The current, authoritative theme set is the files under styles/themes/ — not listed here, so this README can't go stale as themes are added or renamed.

Docs

Full framework docs, architecture details, demo apps, and the C# backend pattern are in the GitHub repository's AGENTS.md.