Templates and plugins

Starting a project from a template

Templates are curated starting points. You pick one, choose where to put it, and the Lead agent walks you through the codebase before you make any changes.

The template gallery is the Templates page in the app.

Browsing the gallery

The Templates page has:

• A search box that matches a template's name, tags, and description.
• A row of category chips to filter by: All, Web, Mobile, Backend, AI, Productivity, and E-commerce.
• A Featured row of three templates that come with a guided walkthrough. The Featured row is shown only when you are not actively searching, so a search narrows cleanly to results.
• A main gallery grid of every template that matches your search and category.

Each card shows the template name, who it is by, a short description, tags, and how many times it has been used. Official templates carry an Official badge.

Creating the project

1. Click a template card to open its detail view.
2. Click Start from this template.
3. Choose a folder on your computer for the new project. (Cancelling the folder picker simply backs out, nothing is created.)
4. Castforge copies the template into your chosen folder and creates the project.
5. A short guided walkthrough appears so the Lead agent can orient you in the new codebase before you start changing things.

If you want to replay the walkthrough later, you can re-trigger it from Settings, in the About section.

Plugins and the marketplace

The plugin marketplace is the Plugins page (its top heading reads Plugins, under a Marketplace label). Plugins extend what your agents can do.

What a plugin is

A plugin is a small add-on that gives your agents extra capability. In the marketplace, plugins are described as system prompts, MCP servers, and tool bundles, and each plugin shows which agents it works with. Under the hood, a plugin can be one or more of four kinds:

• Overlay (a system prompt overlay): injects extra system-prompt guidance for the agent. It does no file or network input/output on its own.
• Tools (a tool bundle): adds tool functions the agent can call.
• MCP (an MCP server): spawns an external MCP server process that the agent can call into.
• Modifier (a behavior modifier): intercepts the agent's events and transforms them.

A single plugin can combine several of these kinds, and the detail page shows a badge for each kind it includes.

Plugins versus MCP, in plain terms

MCP (the Model Context Protocol) is an open standard for connecting an AI agent to an external tool server. An MCP server is a separate process that exposes tools and data over that protocol.

A plugin is the Castforge package you install. One common kind of plugin is an MCP server plugin: installing it tells Castforge to spawn and wire up an external MCP server so your agent can use its tools. So MCP is the underlying protocol and process, and an MCP-server plugin is the marketplace-friendly way to add one. Not every plugin is an MCP server, though. The other plugin kinds (Overlay, Tools, Modifier) extend the agent without running a separate MCP process.

Bring your own MCP server

The marketplace is the curated path to MCP tools, but you are not limited to it. If you run (or want to point at) your own MCP server, you can register it directly in Settings, no marketplace listing required. This complements the marketplace plugins: install curated MCP-server plugins for the common cases, and register a custom server for anything you host yourself or that is not in the catalog.

Where to add one

There are two places, depending on how widely you want the server available:

• Global: open Settings and go to the MCP Servers section. Servers you add here are available to every project.
• Per project: open a project's Settings and use its MCP Servers tab to add a server scoped to that one project.

Each server you add shows a Scope of either Global (all projects) or This project only, so you can keep a personal server everywhere while pinning a project-specific one to a single codebase.

Adding a server

Click Add MCP Server and fill in the form:

• Transport: choose Stdio (Castforge launches a local command that speaks MCP over its standard input and output) or HTTP (Castforge connects to a server URL).
• Name: a label for the server.
• For a Stdio server: the Command to run (for example, npx), its Arguments, and any Environment variables (values are masked, so you can pass secrets without showing them on screen).
• For an HTTP server: the Server URL (it must start with http:// or https://).
• Applies to: pick which agents get the server (Claude, Codex, Gemini). At least one is required, so a server is always scoped to the agents you choose rather than forced on all of them.

Once saved, the server joins that agent's tools the same way an MCP-server plugin would. You can edit or remove it later from the same list.

Browsing and searching the marketplace

The marketplace has a header counter showing how many plugins you have installed and how many are available, plus a filter bar with three axes:

• Search: type to filter the catalog. Press / anywhere on the page to jump to the search box.
• Category (single-select): All, MCP Server, Custom Commands, or Skill Pack.
• Agent compatibility (multi-select): GitHub Copilot, Claude, Codex, Gemini, Cursor, and the other connected agents. By default the list favors plugins compatible with your active agent.
• Plugin kind (multi-select): Overlay, Tools, MCP, Modifier.

Click a plugin card to open its detail page.

A plugin's detail page

The detail page shows screenshots, the plugin name, who published it, its category, which agents it is compatible with, and badges for each kind it includes. If the publisher provided a source repository link, a Source link opens it in your browser. There are three tabs:

• README: a description of the plugin. (Rich markdown rendering is still being built out, so for now this is the plugin's description text.)
• Permissions: exactly what the plugin can do (see below).
• Versions: the plugin's version history.

Installing a plugin and choosing where it applies

The install panel sits on the right of the detail page. You choose the targets the plugin should apply to, and you can pick agents, roles, or both:

• Install for (per agent): under the Install for heading, pick which agents get the plugin. Compatible agents are selectable; incompatible ones are dimmed with a note about what the plugin requires. By default, all compatible agents are pre-selected.
• Per role: if the plugin declares compatible roles, a Per role section appears below with a checkbox per supported role (for example, Lead, Coder, Tester, Reviewer, Researcher, Designer). By default, all the plugin's compatible roles are pre-selected. If a plugin does not target roles, this section does not appear.

You need at least one agent or one role selected to install. Click Install. Castforge installs the plugin for the targets you chose and confirms how many it installed for. If one target could not be installed, it tells you which one.

After installing, the panel switches to an Installed for view that lists the agents the plugin is installed for, each with a small control to uninstall it for that agent, plus an option to install it for more agents if any compatible ones remain.

Viewing a plugin's permissions

Open the Permissions tab on a plugin's detail page before you install. Castforge shows everything the plugin is asking for, expanded by default with no hidden "show more", so you can see exactly what you are granting:

• For an Overlay, it shows the system-prompt text the plugin will inject.
• For a Tools bundle, it lists each tool with a plain-language side-effect pill: No I/O, Reads files, Writes files, Network, or Shell. The Shell pill is the highest-risk and is colored to stand out.
• For an MCP server, it lists the permissions the server needs (for example, file read or write, shell, or network access).
• For a Modifier, it lists the agent events the plugin hooks into.

Managing installed plugins

Open a project's Settings and go to the Plugins tab to see a rollup of plugins across your team:

• In use: plugins currently equipped on a role, each tagged with which role uses it (for example, Used by Coder).
• Available: other catalog plugins not currently in use.

Each plugin card shows its version, where it is installed from (Built-in, bundled with Castforge, or a marketplace install path), and what it actually does, with badges like Tool bundle: N tools, Slash commands: M, or Inert plugin when it has neither. A per-row menu lets you Inspect manifest (view the full plugin manifest as JSON) and, for marketplace plugins, Reveal in Explorer to open the install folder.

This tab is a read-only rollup. To add a plugin to a specific role, use the per-role plugin picker on the Agents and Roles tab, or install it from the marketplace as described above.

Publishing to the marketplace and to Discover

There are two different "publish" ideas in Castforge, and it helps to keep them straight.

Publishing your project to Discover

Discover is the Made with Castforge gallery of finished projects you can browse, remix free ones, or buy. From Discover you can Publish your project: Castforge runs an audit of your project, shows you the score and any recommended fixes, then collects your listing details (name, description, category) and publishes the listing. This publishes a project, not a plugin.

Publishing a plugin to the marketplace

Publishing your own plugin to the plugin marketplace is not a self-service flow in the app today. The plugin catalog is curated, so there is no in-app "submit my plugin" wizard yet. If you build a plugin and want it listed, that happens outside the app for now. (The audit, review, and listing flow described above is for Discover project listings, not for plugins.)

Common questions

Where do I find templates and where do I find plugins?

Templates live on the Templates page (Start from a template). Plugins live on the marketplace, the Plugins page under the Marketplace label. Discover is a separate gallery of finished projects you can remix or buy.

What is the difference between a plugin and an MCP server?

MCP is the protocol, and an MCP server is an external process that speaks it. A plugin is what you install from Castforge. One kind of plugin is an MCP-server plugin, which makes Castforge run an MCP server for your agent. Other plugin kinds (Overlay, Tools, Modifier) extend the agent without a separate MCP process.

Can one plugin go to more than one agent or role?

Yes. The install panel lets you select multiple agents, and if the plugin supports roles, multiple roles too. By default all compatible agents and roles are pre-selected.

Why is an agent greyed out in the install picker?

The plugin is not compatible with that agent. The picker dims incompatible agents and shows what the plugin requires.

How do I see what a plugin is allowed to do before installing?

Open the Permissions tab on the plugin's detail page. Everything the plugin requests is listed and expanded by default, including tool side effects (reads, writes, network, shell) and MCP server permissions.

Can I add my own MCP server instead of one from the marketplace?

Yes. Open Settings, MCP Servers, and click Add MCP Server. Pick Stdio (a local command) or HTTP (a server URL), name it, and choose which agents it applies to. Add it globally for every project, or from a project's own MCP Servers tab to scope it to that project. This runs alongside any MCP-server plugins you installed from the marketplace.

How do I remove a plugin?

On the plugin detail page, the Installed for view has a control to uninstall it for a given agent. You can also manage role assignments from the Agents and Roles tab.

A template will not start. What happened?

Make sure you completed the folder picker (cancelling it backs out without creating anything). If the copy fails, the template detail stays open so you can try again with a different destination folder.

Can I publish my own plugin to the marketplace?

Not from inside the app yet. The plugin marketplace catalog is curated, and there is no self-service plugin submission flow today. The in-app Publish flow (Discover) is for publishing your finished project as a listing, not for publishing plugins.