Dominus 2

Dominus 2 is a secure, MCP-native engineering bridge for Roblox Studio. It gives an MCP host direct, typed access to Studio instances, scripts, UI, reflection, output, and tests without embedding a second chat model or exposing arbitrary Luau execution.

What changed

• MCP-only product: the old Ink chat CLI is no longer published.
• 17 focused tools with input/output schemas, structured results, and risk hints.
• MCP-native parallel coordination uses the host's model through Sampling, with proposal-only workers and coordinator-owned Studio writes.
• Stable instance refs survive dots in names, renames, reparenting, and duplicate sibling names for the life of the Studio session.
• Script writes require a revision from studio_read_script.
• Mutation batches and UI replacement are undoable and roll back on failure.
• The installer provisions a local bridge credential automatically; users never copy connection IDs or pairing codes.
• A single background bridge keeps Studio connected while MCP hosts and agents start, stop, or run in parallel.
• Multiple Studio windows are selected by unique connection ID, not place ID.
• Roblox Creator Docs API lookup is built in.

Requirements

• Node.js 20 or newer
• Roblox Studio with HTTP requests enabled for Studio/plugin use
• An MCP client such as Codex, Claude Desktop, Cursor, or VS Code

Dominus does not require its own AI API key. Your MCP host supplies the model.

Install

Install the npm package globally:

npm install -g dominus-cli@latest

Install or update the Studio plugin:

dominus-install-plugin

Roblox Studio normally reloads the local plugin automatically. Restart Studio only if the Dominus 2 toolbar button does not appear or reconnect.

MCP configuration

Add Dominus to your MCP client's server configuration:

{
  "mcpServers": {
    "dominus": {
      "command": "dominus-mcp"
    }
  }
}

For a version-pinned configuration that does not require a global install:

{
  "mcpServers": {
    "dominus": {
      "command": "npx",
      "args": ["-y", "-p", "[email protected]", "dominus-mcp"]
    }
  }
}

Restart the MCP client after changing its configuration.

First connection

1. Run dominus-install-plugin; it installs the personalized plugin and starts the local Studio bridge in the background.
2. Open Roblox Studio and start the MCP client. Dominus authenticates automatically with no connection ID or pairing code.

If the local credential is replaced or lost, run dominus-install-plugin again. Studio normally reloads it without a restart.

If several Studio windows are open, call dominus_select_studio with the exact connection ID before editing. Two windows on the same place ID remain distinct.

Agent workflow

Dominus instructs MCP hosts to use this loop:

1. Inspect the target tree, selection, instances, scripts, and API references.
2. Plan the smallest coherent change and define acceptance checks.
3. Apply a transactional mutation or revision-checked script update.
4. Read the changed state back.
5. Run a Studio test when behavior changed.

For UI fidelity work, use studio_snapshot_ui after studio_build_ui and compare fonts, UDim2 values, colors, strokes, and hierarchy rather than relying on a successful write response alone.

For broad tasks with independent branches, use run_parallel_task. Dominus partitions immediate child scopes, supplies each worker with hierarchy and typed property evidence, runs up to five Sampling workers concurrently, validates their proposals, and applies only the coordinator-approved atomic plan. Workers never receive direct write access. Clients without Sampling continue to use the normal single-agent workflow.

Tool catalog

Connection tools:

• dominus_status
• dominus_select_studio

Parallel coordination:

• run_parallel_task

Studio inspection:

• studio_get_tree
• studio_inspect
• studio_get_selection
• studio_read_script
• studio_snapshot_ui
• studio_get_output
• studio_get_reflection

Studio changes and verification:

• studio_update_script
• studio_apply
• studio_delete_instances
• studio_build_ui
• studio_run_test

Roblox documentation:

• roblox_search_api
• roblox_get_api

Security model

The MCP transport is stdio. A single background Studio WebSocket bridge binds only to 127.0.0.1, limits messages to one MiB, rate-limits sockets, times out incomplete handshakes, and authenticates both Studio plugins and MCP controllers. The distributed plugin contains only a credential placeholder; dominus-install-plugin writes the user-specific token into the local copy. The plugin only accepts an explicit command allowlist and contains no loadstring executor.

The bridge token protects against accidental or opportunistic access by unrelated local processes. Like other user-level credentials, it cannot protect against a process that already has permission to read all files in the same user account.

Development

pnpm install
pnpm typecheck
pnpm test
pnpm build
pnpm build:plugin
npm pack --dry-run

Run the MCP server in development:

pnpm dev:mcp

The design and research notes are in docs/DOMINUS_2_PLAN.md.

License

MIT