Tessera

Build terminal apps that feel like real products, not throwaway demos.

Tessera is a C#-first terminal UI framework for .NET 10. It gives you a small public app model, first-class controls and layouts, semantic theming, and enough structure to build serious terminal software without dragging you into a host-heavy framework story.

Tessera is in public alpha. It is ready for evaluation, experimentation, and contribution. Breaking changes are still allowed when they simplify the long-term public path.

Architecture Note

Tessera's app loop is inspired by The Elm Architecture (TEA):

• model/state lives in your app type
• Update(Message) handles transitions and decides effects
• Build(ScreenContext) renders the next UI tree from current state

It is not a direct Elm runtime clone. Tessera keeps .NET-first semantics, control events, and terminal/runtime seams that fit C# product apps.

Why Tessera

• explicit C# object model instead of a nested layout DSL
• no DI container or Generic Host required for the normal path
• built-in controls, layouts, themes, and runtime options
• state-driven app model with TesseraApp, Update(...), and Build(...)
• advanced hosting seams available when needed, but not forced on beginners
• public examples that aim to look like products, not widget dumps

What You Get

• a small startup story: TesseraApplication.RunAsync(...) or TesseraApplication.CreateBuilder()
• default authoring namespaces: Tessera, Tessera.Controls, Tessera.Layout, Tessera.Styles
• a broad built-in widget catalog for dashboards, forms, workflows, data surfaces, and overlays
• semantic theme tokens and override layers
• public examples that cover starter apps, dashboards, workbench shells, and command-heavy apps
• regression and integration coverage around the public contract

Start Here

1. Read docs/overview.md.
2. Follow docs/install-and-prerequisites.md.
3. Build the sample from docs/first-app.md.
4. Run the onboarding ladder from docs/examples.md: HelloWorld, CounterForm, WorkspaceApp.
5. Open docs/showcase.md for the flagship evaluation path.
6. Use docs/app-model.md, docs/layout-and-screen-composition.md, docs/runtime-and-screen-options.md, and docs/architectural-review.md when you need the deeper concepts.
7. If you want to contribute, read CONTRIBUTING.md and docs/architecture-overview.md.

Quick Start

using Tessera;
using Tessera.Controls;
using Tessera.Layout;

var app = TesseraApplication.CreateBuilder()
    .UseApp<CounterApp>()
    .ConfigureRuntime(static runtime =>
    {
        runtime.MaxFps = 60;
        runtime.Screen = new ScreenOptions
        {
            AltScreen = true,
            WindowTitle = "Counter",
        };
    })
    .Build();

await app.RunAsync();

internal sealed class CounterApp : TesseraApp
{
    private readonly CounterState _state = new();
    private readonly Button _increment = new()
    {
        Text = "Increment",
    };
    private readonly StatusBar _status = new();

    public CounterApp() => _increment.Activated += (_, _) => _state.Count++;

    public override TesseraEffect? Update(Message message)
        => message is KeyPressed key && key.IsCharacter('c', ModifierKeys.Ctrl)
            ? TesseraEffects.Quit
            : null;

    public override Screen Build(ScreenContext context)
    {
        _status.LeftText = $"Count: {_state.Count}";
        _status.RightText = "Enter increments   Ctrl+C quits";

        return Screen.Build(window =>
        {
            window.Padding(1);
            window.Footer(1, _status);
            window.Body(body => body.Center(_increment, width: 20, height: 3));
        });
    }
}

internal sealed class CounterState
{
    public int Count { get; set; }
}

Minimal path still exists:

await TesseraApplication.RunAsync(new MyApp());

Run Something Real

Starter ladder:

• dotnet run --project examples/HelloWorld/HelloWorld.csproj
• dotnet run --project examples/CounterForm/CounterForm.csproj
• dotnet run --project examples/WorkspaceApp/WorkspaceApp.csproj

Then tour the flagship examples:

• dotnet run --project examples/GitConsole/GitConsole.csproj
• dotnet run --project examples/OpsWatch/OpsWatch.csproj
• dotnet run --project examples/DataWorkbench/DataWorkbench.csproj

Supporting demos:

• dotnet run --project examples/DownloadCenter/DownloadCenter.csproj
• dotnet run --project examples/IncidentDesk/IncidentDesk.csproj
• dotnet run --project examples/MusicDeck/MusicDeck.csproj
• dotnet run --project examples/TransitBoard/TransitBoard.csproj

Example Lineup

Starter Ladder

• examples/HelloWorld
  • smallest centered starter
  • first contact with TesseraApp, layout centering, buttons, and status
• examples/CounterForm
  • interactive form-first starter
  • inputs, choice, progress, and message-driven state
• examples/WorkspaceApp
  • first multi-pane app
  • navigation, editing, preview, and action flow in one centered shell

Flagship

• examples/GitConsole
  • command-driven workflow surface
  • editing, navigation, diff review, action history
• examples/OpsWatch
  • dashboard-first operations surface
  • alerts, telemetry, health, action rails
• examples/DataWorkbench
  • multi-pane workbench shell
  • richer composition and pointer-ready runtime configuration

Supporting

• examples/DownloadCenter
• examples/IncidentDesk
• examples/MusicDeck
• examples/TransitBoard

The full guide lives in docs/examples.md.

Repo Layout

• src/Tessera: default public app-authoring API
• src/Tessera/Core: advanced low-level runtime internals (namespaced as Tessera.Core)
• tests/Tessera.Tests: unit, contract, and regression tests
• tests/Tessera.IntegrationTests: integration coverage
• examples: public examples and showcase apps
• docs: product, architecture, release, and contributor docs

Docs

• docs home: docs/index.mdx
• overview: docs/overview.md
• onboarding guide: docs/getting-started.md
• install and prerequisites: docs/install-and-prerequisites.md
• first app guide: docs/first-app.md
• example guide: docs/examples.md
• showcase guide: docs/showcase.md
• app model: docs/app-model.md
• screen and layout composition: docs/layout-and-screen-composition.md
• runtime and screen options: docs/runtime-and-screen-options.md
• architectural review: docs/architectural-review.md
• widgets overview: docs/controls-overview.md
• widgets: docs/widgets-inputs-and-forms.md, docs/widgets-navigation-and-workflow.md, docs/widgets-data-and-inspection.md, docs/widgets-dashboards-and-plots.md, docs/widgets-shells-and-overlays.md
• recipes: docs/recipes.md, docs/recipes-app-shells.md, docs/recipes-effects-and-refresh.md, docs/recipes-data-and-workspaces.md
• troubleshooting: docs/troubleshooting.md
• faq: docs/faq.md
• architecture overview: docs/architecture-overview.md
• design contract: docs/spec.md
• public API guidelines: docs/public-api-guidelines.md
• public API inventory: docs/public-api-inventory.md
• theme system: docs/theme-system.md
• custom controls: docs/custom-components.md
• changelog: CHANGELOG.md
• contributor guide: CONTRIBUTING.md
• support policy: SUPPORT.md
• code of conduct: CODE_OF_CONDUCT.md
• security policy: SECURITY.md

Build And Verify

Tessera uses .NET 10 from global.json (baseline 10.0.100 with feature-band roll-forward).

Primary repo verification commands:

dotnet build Tessera.slnx
dotnet build examples/Tessera.Examples.slnx
dotnet test Tessera.slnx
dotnet run --project examples/DataWorkbench/DataWorkbench.csproj --no-build
dotnet run --project examples/OpsWatch/OpsWatch.csproj --no-build
dotnet run --project examples/GitConsole/GitConsole.csproj --no-build

Contributing

Tessera is being shaped in public. If you want to contribute, start with CONTRIBUTING.md.