Stack Builder

The Stack Builder uses the same schemas, compatibility rules, and template generator as the CLI. Every change updates the reproducible command and the shareable URL.

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Two modes

Solo mode exposes one ecosystem's full category surface. Multi-Ecosystem mode composes frontend, backend, database, and mobile parts from different languages, then attaches capabilities to their owners through repeated --part role:ecosystem:tool flags. See Multi-Ecosystem for how parts and ownership work.

Builder state lives in the URL. Share a link and the recipient gets your exact selection. Sharing does not upload project files or saved configuration bodies. Saved stacks stay in browser storage. When analytics is enabled, the builder records bounded anonymous usage and stack-selection metadata as described in Privacy.

Compatibility adjustments

The builder runs every selection through the same compatibility engine as the CLI. When a choice requires another option or conflicts with the current stack, it explains or applies the compatible state before generating files. Read the final command when you accept an adjustment, so you know what changed.

Edit & Run

Edit & Run creates a disposable generated project and executes it in a browser WebContainer. It never deploys anything and never sends your edits to a server.

Requirements: Solo mode, the TypeScript ecosystem, at least one web frontend, and a WebContainer-capable browser. Redwood is excluded because its layout hides the root dev script the runner needs. Native and multi-ecosystem projects can still use Preview and ZIP download, then run locally with their own toolchains.

The flow: generate from the selection, mount files in the WebContainer, install dependencies with npm (WebContainers provide Node and npm; this does not change the package manager recorded for downloads or CLI scaffolds), start dev:web or dev, and show the preview URL. First installs need network access and can take a while.

Editing

Pick a text file from the tree and edit it in the code pane. Save & rerun syncs changes into the running project; editing package.json triggers another dependency install. Discard restores the last contents that synced successfully, Stop terminates the dev server, and reloading the page destroys the workspace along with unsaved edits. Copy out anything worth keeping before you leave.

When a stack or runtime reports as unsupported, download the ZIP and run it locally instead. If installation fails, check network access and console output; corporate proxies and content blockers commonly block WebContainer downloads. If the server stops responding, stop it and start again; a page reload is the final reset.

Download a ZIP

Download ZIP regenerates your selected stack with the shared template generator and builds an archive entirely in the browser:

• One sanitized top-level project directory; scripts keep executable metadata.
• The selected package manager is preserved.
• bts.jsonc holds the schema-validated configuration and bts.lock.json v2 records generator provenance plus byte hashes of template-comparable files, which later add, update, and check workflows rely on.
• No server-side workspace is ever created, and dependencies are not installed.

After extraction, follow the generated README and run the matching ecosystem install command.

Move to the CLI

For reproducible automation, copy the generated command rather than treating the ZIP as the only record. Browser ZIPs and CLI scaffolds both include the BTS files, so either path can continue with add, update, and check.

Privacy

Better Fullstack records bounded anonymous run outcomes such as started, ready, failed stage, duration, ecosystem, and capability IDs. It never records edited source, filenames, logs, URLs, env values, or raw errors. One browser-local preference gates all analytics and Do Not Track disables everything. See Anonymous Telemetry.