Launch Composer Studio

Start the app

Make sure the PDK server is running, activate the virtual environment from Install Composer Studio, then run from the root of the Composer Studio checkout:

cd app
./run_app.sh

The script:

Builds the editor into app/frontend/dist (npm run build).
Starts the backend on port 8011.
Opens http://localhost:8011 in your default browser. If no browser opens, browse to that address yourself.

Stop it with Ctrl+C in the terminal. The port is fixed at 8011 in run_app.sh; to use another, start the backend yourself:

python3 backend/web_server.py 8012 --directory frontend/dist

Choose the PDK server

The backend connects to localhost:50052 by default. To use a server on another port of this computer, set NEBULA_TARGET before starting:

NEBULA_TARGET=localhost:50053 ./run_app.sh

There is no setting for this in the editor. A server on another computer is not supported (Environment Compatibility).

Set the PDK Release Folder

The PDK Release Folder is the folder that holds the server’s workcell/ directory, where workcell files such as meshes and URDFs are kept. The backend reads and writes those files directly, so it must know where the folder is, both on your computer and as the server sees it.

Environment variables
Variable	Default	Meaning
`NEBULA_TARGET`	`localhost:50052`	Address of the PDK server on this computer.
`WORKCELL_ROOT`	See below	The PDK Release Folder on this computer.
`NEBULA_ROOT`	`/home/flexiv`	The same folder as the server sees it. For a PDK server running in a container, this is the path inside the container.

When WORKCELL_ROOT is not set, the backend uses the path written in /tmp/flexiv_nebula_sdk_server_path.txt if that file exists, and otherwise the folder that contains the Composer Studio checkout.

You can also change the folder while the app is running: type a path into PDK Release Folder: in the header bar and press Enter, or click the folder button to browse (Workcells). The setting lasts until the backend restarts. If the folder does not exist, the field turns red. Composer Studio shows Directory not found: <path> when you enter it, and this message when the page loads or you click Workcell Setup:

The path "<path>" does not exist. Please specify a valid Nebula release folder to continue.

Develop the editor with hot reload

To change the editor’s code and see the result without rebuilding, run the backend and the Vite development server separately:

python3 backend/web_server.py 8011 --directory frontend/dist   # terminal 1
cd frontend && npm run dev                                     # terminal 2

The editor calls the backend on the same address it was loaded from (paths starting /api), and the Vite configuration has no proxy for them. Add a server.proxy entry for /api to frontend/vite.config.ts that points at http://localhost:8011 (with ws: true, for live scene events) before using the development server.

Network access

Important

The backend listens on all network interfaces (0.0.0.0:8011) and has no login. Anyone who can reach port 8011 can edit your workcells and read files on this computer through the backend. Run Composer Studio only on a trusted network, or block port 8011 with a firewall.