extension-devlisted

# Cross-Browser Extension Development This skill covers the full lifecycle of a browser extension built on the [extension.dev](https://extension.dev) platform (powered by the open-source [Extension.js](https://extension.js.org) framework): scaffold from a template, develop with hot reload, verify against a live browser, build per browser, and publish. Two companions do the heavy lifting. Prefer them over guessing: - **`@extension.dev/mcp`** (MCP server): 28 tools for scaffolding, building, live DOM inspection, log streaming, storage access, publishing, and headless release promotion. If its `extension_*` tools are available in the session, use them. - **`extension` CLI**: nearly every MCP capability has a CLI equivalent (`npx extension@latest <command>`). Use it when the MCP server is not connected. The exceptions are `extension_release_promote` (also reachable as `extension-mcp release promote`, but not via the `extension` CLI) and the session tools `extension_stop`/`extension_list_extensions`. ## Workflow 1. **Start from a template, not a blank file.** The catalog has 50+ working examples (React, Vue, Svelte, Preact, vanilla; every surface). Match the user's surface + framework, then scaffold: `npx extension@latest create my-ext --template=<slug>` (MCP: `extension_templates`, `extension_create`). See [references/templates.md](references/templates.md) before recommending one. 2. **manifest.json is the source of truth.** Only the manifest is