Nuvyn CLI 1.2.0: Spec-Driven .NET MAUI, From a New App or One You Already Have

Nuvyntra Labs released Nuvyn CLI 1.2.0, a standalone .NET 10 global tool that scaffolds spec-driven .NET MAUI applications through `nuvyn init` for new projects and `nuvyn adopt` for existing ones. The tool writes a constitution, specification, plan, tasks, and analysis into the repository so coding agents build against a checked-in spec rather than a chat thread, and it locks the MAUI and Lumina stack while leaving individual plugins and NuvyntraLabs.UIKit independently installable. It is MIT licensed and distributed on nuget.org as NuvyntraLabs.Nuvyn.Cli.

A coding agent will happily build a .NET MAUI app from a chat thread. The next session often builds a different one. Nuvyn is the CLI that keeps that work on one stack and one written spec. Version 1.2.0 is on nuget.org as the global tool NuvyntraLabs.Nuvyn.Cli . The command is nuvyn . This post is the walkthrough: what the tool is, how to install it, how to start a new app, how to attach it to an app you already have, and the slash commands the agent runs after that. Nuvyn is a standalone PackAsTool CLI for .NET 10 . It depends on System.CommandLine and Spectre.Console . It is MIT licensed. It does two jobs: nuvyn init nuvyn adopt The product domain is yours: clinic, field, bank, civic, retail, or anything else. The skills stay domain-agnostic. On a new host they lock only the MAUI and Lumina stack. Individual plugins and NuvyntraLabs.UIKit stay installable on their own. You do not need Nuvyn to use one package. | Package | NuvyntraLabs.Nuvyn.Cli https://www.nuget.org/packages/NuvyntraLabs.Nuvyn.Cli 1.2.0 | | Command | nuvyn | | Source | github.com/nuvyntralabs/Nuvyn https://github.com/nuvyntralabs/Nuvyn | | Docs | nuvyntralabs.github.io/toolkits/nuvyn/ https://nuvyntralabs.github.io/toolkits/nuvyn/ | | Guide | Install, init, adopt, slash workflow https://nuvyntralabs.github.io/toolkits/nuvyn/guide/ | Install it as a global dotnet tool . Do not add NuvyntraLabs.Nuvyn.Cli as a PackageReference in an app. Spec-driven development treats a checked-in specification as the source of truth. Code follows that spec. A chat thread is a prompt log: it disappears, it contradicts itself, and a teammate cannot review it. Nuvyn writes the artifacts into the repo: | Artifact | Role | |---|---| | Constitution | Standing principles: stack, platforms, privacy | | Specification | This increment: users, journeys, edge cases | | Plan | Smallest package set and one screen recipe per screen | | Tasks | Dependency-ordered work T001 P US1 | | Analysis | Consistency check before production code | That matters more once an agent writes the code. The same prompt can pick a different MVVM library on a different day. Long chats drop acceptance rules that were never written down. Agents add a login page, a second UI kit, or persistence nobody asked for, because a finished-looking app is an easy completion. Nuvyn narrows that search space. Constitution locks the stack. Specify writes the product. Plan names packages and screens. Analysis fails the loop before implement invents a second architecture. GitHub Spec Kit specify init remains the usual choice when the stack is open. Nuvyn is the door when the host should be Nuvyntra, or when an existing MAUI app should grow through the same slash chain. | Requirement | Why | |---|---| | .NET 10 SDK | The CLI is net10.0 . Hosts target net10.0-android , net10.0-ios , net10.0-maccatalyst , and net10.0-windows10.0.19041.0 | | MAUI workload | So the host can build and run | | A coding agent | Cursor, GitHub Copilot, Claude Code, Gemini CLI, Codex, Windsurf, or any other Spec Kit agent | | nuget.org | init adds the default Nuvyntra packages at the latest stable versions | Nuvyn targets those four platforms. It is the wrong tool for Tizen, Flutter, React Native, WPF, WinUI, Avalonia, or Uno. dotnet tool install -g NuvyntraLabs.Nuvyn.Cli --source https://api.nuget.org/v3/index.json nuvyn version nuvyn version prints NuvyntraLabs.Nuvyn.Cli 1.2.0 . Already installed? Update the tool only. Existing apps keep the packages they already reference: dotnet tool update -g NuvyntraLabs.Nuvyn.Cli --source https://api.nuget.org/v3/index.json nuvyn version On an interactive terminal, nuvyn asks every four hours whether to update from nuget.org y/N , default no . Skip that prompt with --no-update-check or NUVYNTRA NO UPDATE CHECK=1 . The cache file is ~/.nuvyntra/cli-updates.json , shared with maui-dev and maui-perf . The CLIs do not phone home. nuvyn init <folder name always creates a new folder . If that name already exists, init prints an error and exits 1 . The existing tree is left untouched. nuvyn init HarborDesk --agent cursor Omit --agent and the CLI shows a searchable picker cursor Cursor , agy Antigravity , and the rest of the Spec Kit set . Non-interactive runs default to Cursor. What init does: .nuvyn/ constitution, templates, reference, init-options.json . The tree looks like this: HarborDesk/ ├── HarborDesk.sln ├── HarborDesk/ MAUI app │ ├── MauiProgram.cs │ ├── Pages/MainPage.xaml │ └── Resources/Images/nuvyntra.png ├── HarborDesk.Core/ ViewModels ├── HarborDesk.Tests/ ├── .nuvyn/ │ ├── constitution.md │ ├── init-options.json │ ├── templates/ │ └── reference/ ├── specs/ empty until /nuvyn.specify ├── .cursor/skills/nuvyn- / when --agent cursor └── README.md MainPage is a Lumina screen: the Nuvyntra mark, an NVHeading counter, and Increase / Decrease NVButton controls. There is no stock Entry / Button / Label starter, and no seeded Login / Items / Edit pages. Screens come from the spec. Build it the usual way: cd HarborDesk dotnet restore dotnet build dotnet build HarborDesk/HarborDesk.csproj -f net10.0-android init adds these, and nothing else from the catalog, until the spec asks: | Package | Role | |---|---| | Plugin.Maui.MVVMExpress https://nuvyntralabs.github.io/packages/plugin-maui-mvvmexpress/ | App shell, ViewModels, navigation | | NuvyntraLabs.UIKit https://nuvyntralabs.github.io/uikit/ | Lumina NV controls and page recipes | | Plugin.Maui.HttpForge https://nuvyntralabs.github.io/packages/plugin-maui-httpforge/ | Typed REST client | | Plugin.Maui.FormValidation https://nuvyntralabs.github.io/packages/plugin-maui-form-validation/ | Form rules on the host | | Plugin.Maui.KeyboardManager https://nuvyntralabs.github.io/packages/plugin-maui-keyboard-manager/ | Soft keyboard hide, show, and resize | The MAUI app gets MVVMExpress plus Dialogs and Navigation, UIKit, HttpForge, FormValidation, and KeyboardManager. Core gets Plugin.Maui.MVVMExpress.Core and the source generators. Tests get Plugin.Maui.MVVMExpress.Testing . Versions are never pinned: dotnet add package runs without --version . The host wires up like this: js builder .UseMauiApp<App .UseMvvmExpress o = o .UseNavigationPage nav, = nav .Map<MainPageViewModel, MainPage "main" .UseDialogs .UseNuvyntraUIKit .UseHttpForge .UseMauiFormValidation .UseKeyboardManager ; builder.Services.AddTransient<MainPageViewModel ; builder.Services.AddTransient<MainPage ; Register both the page and the view-model in MauiProgram . RegisterViewModel is a map for the generator, and it is not the DI registration. Chrome is NavigationPage unless the spec names Shell. LocalStore, NuvexaDB, AppLock, and the rest of the catalog wait until you ask. /nuvyn.plan then picks the smallest fit. An outside library needs a Catalog gap row in plan.md . 1.2.0 adds nuvyn adopt . This is the door for a tree that already exists. cd FieldApp nuvyn adopt --agent cursor Or point at another folder: nuvyn adopt --path ../FieldApp --agent copilot Adopt: UseMaui in a csproj , or when specs/ folder, and .nuvyn/adopt-report.md . "mode": "adopt" in maui-dev doctor when MauiDev is on PATH . It does not add MVVMExpress, Lumina UIKit, or HttpForge. It does not edit MauiProgram , pages, or HttpClient call sites. New work keeps the stack the app already uses. Lumina NV is allowed on new screens only when UIKit is already referenced. /nuvyn.plan and /nuvyn.implement read adopt-report.md first. Open the project folder in the agent you selected. Run the commands in order. Extra text after a command is the prompt. An empty /nuvyn.specify asks you to describe the product. /nuvyn.constitution → /nuvyn.specify → /nuvyn.clarify → /nuvyn.plan → /nuvyn.checklist → /nuvyn.task → /nuvyn.analysis → /nuvyn.implement → /nuvyn.converge In Cursor the skill folders are named nuvyn-constitution a folder name cannot contain . . Type /nuvyn-constitution in Cursor. Type /nuvyn.constitution in Copilot, Claude, Gemini, and the other command-file agents. | Step | You do | The agent writes | |---|---|---| | /nuvyn.constitution | Optional product rules PII, lock, offline | Updates .nuvyn/constitution.md . The stack stays locked on a new host. | | /nuvyn.specify | Required: what the app is for | specs/NNN-short-name/spec.md , .nuvyn/feature.json , checklists/requirements.md | | /nuvyn.clarify | Answer at most five questions | Updates spec.md | | /nuvyn.plan | Extra constraints, if any | plan.md + research.md — packages and one Lumina recipe per screen | | /nuvyn.checklist | Optional quality review | checklists/<domain .md | | /nuvyn.task | — | tasks.md T001 P US1 … | | /nuvyn.analysis | — | A report only: spec, plan, and tasks agree | | /nuvyn.implement | Optional scope, such as Foundation only | Host code | | /nuvyn.converge | — | Appends remaining work to tasks.md | A specify prompt can carry the product in one line: /nuvyn.specify Resident 311 desk: sign in, report a bin miss, see live bus times. /nuvyn.implement Implement only Foundation Standing law lives in .nuvyn/reference/constraints.md . Each slash command stays short and points at that file, so the agent spends the window on the domain instead of restating the catalog every turn. UI on a new host is Lumina first. One recipe per screen. Bound fields go inside the recipe so they replace the demo seed. Prefer NVInputField , NVPasswordField , and NVButton when an NV control exists. Control reference: UIKit MAUI docs https://nuvyntralabs.github.io/uikit/docs/ . nuvyn init and nuvyn adopt write into the folder that agent already reads. The set matches Spec Kit, including more than thirty additional agents. | Agent | --agent | On disk | |---|---|---| | Cursor | cursor | .cursor/skills/nuvyn- / | | GitHub Copilot | copilot | .github/skills/ | | Claude Code | claude | .claude/commands/ | | Gemini CLI | gemini | .gemini/commands/ | | Codex CLI | codex | .agents/skills/ | | Goose | goose | .goose/recipes/ | | Windsurf | windsurf | .windsurf/workflows/ | | Generic | generic | .agents/commands/ | Pass --agent cursor-agent when that Spec Kit key is the one you already use. Do not re-run nuvyn init on a tree that already exists. After the global tool updates, refresh slash files from inside the app: cd HarborDesk nuvyn update nuvyn update --agent cursor nuvyn update overwrites .nuvyn/templates/ , .nuvyn/reference/ , and the agent command files. It leaves host code, specs/ , .nuvyn/constitution.md , and .nuvyn/adopt-report.md alone. It does not change PackageReference versions. nuvyn check confirms dotnet and the payload. Inside a greenfield app it also proves the host still uses MVVMExpress, UIKit, HttpForge, FormValidation, and KeyboardManager. Inside an adopted app it prints the inventory and skips that proof. When MauiDev https://nuvyntralabs.github.io/toolkits/maui-dev/ is on PATH , init , adopt , and check run maui-dev doctor --path . A missing doctor is a warning. Nuvyn still succeeds. Install it when you want the environment report: dotnet tool install -g Plugin.Maui.MauiDev.Cli --source https://api.nuget.org/v3/index.json maui-dev doctor | What you see | What to do | |---|---| | HarborDesk already exists | init is for a new folder. Pick another name, or delete a leftover failed scaffold and retry. For an existing MAUI app, cd in and run nuvyn adopt . | | is already a Nuvyn project | Adopt or init already ran. Use nuvyn update . | | is not a MAUI app | adopt needs a UseMaui csproj in that folder. | | Not a Nuvyn project | update and check need a .nuvyn/ folder from init or adopt . | | Unable to resolve MainPageViewModel | Add builder.Services.AddTransient<MainPageViewModel . | | AddGeneratedViewModels fails to build | Remove that call. Register the view-model with AddTransient . | | The agent added LocalStore, Syncfusion, or Refit | You did not ask. Revert. Catalog first, UIKit first. | | MAUI workload or TFM errors | Read the printed maui-dev doctor report. Do not re-run nuvyn init . | | Update prompt every few hours | Expected. Answer n , or pass --no-update-check . | | Need | Tool | |---|---| | New Nuvyntra MAUI host and the spec chain | Nuvyn — nuvyn init , then nuvyn update | | Existing MAUI app, same spec chain, keep its stack | Nuvyn — nuvyn adopt | | Diagnose an existing MAUI tree | MauiDev https://nuvyntralabs.github.io/toolkits/maui-dev/ — maui-dev doctor | | Sibling .resx localization | NuvLoc https://nuvyntralabs.github.io/toolkits/nuvloc/ | | Any stack, spec only | GitHub Spec Kit https://github.com/github/spec-kit | | One runtime plugin | The matching Plugin.Maui. https://nuvyntralabs.github.io/packages/ package | dotnet tool install -g NuvyntraLabs.Nuvyn.Cli --source https://api.nuget.org/v3/index.json nuvyn init HarborDesk --agent cursor cd HarborDesk Open that folder in your agent and run /nuvyn.constitution , then /nuvyn.specify with the product in one sentence. If the app already exists: cd YourMauiApp nuvyn adopt --agent cursor Then read .nuvyn/adopt-report.md before /nuvyn.plan .