Your first session
Start a session, pick a project folder, choose an agent and model, and send your first message.
A session is a chat plus the folder it works in. Start one, tell Mach Studio where to work and what to run, and send a message.
Start a session
Click New session at the top of the sidebar, or press Cmd+T. A fresh chat opens with the composer at the bottom and the picker controls underneath it.
Pick a folder
The folder control under the composer reads Work in a Project until you choose one.
- Click Work in a Project.
- Pick a folder from the list, or click New Project to choose a folder on your computer.
- To work without a folder, hover the folder icon and click the X to remove the project.
The agent reads and edits files inside the folder you choose. Set the folder new chats start in under Settings → General → Default working directory. See Projects.
Choose an agent
The Harness control picks what runs your chat. The built-in agent appears under Mach Studio. Each harness you have set up, such as Claude Code, Codex CLI, or OpenCode, appears with its signed-in accounts, so you can pick which account a chat runs as.
The harness is fixed once you send the first message, so choose before you start. Click Manage harnesses at the bottom of the list to add or sign in to one. See Harnesses.
Choose a model
Click the model control to open the model list. Type to search, or scroll the sections: Local holds the models on your computer, and the rest come from your providers, your harness, or your Syzygy account. Where the model supports it, the same menu offers Speed (Standard or Fast) and an Effort slider from Faster to Smarter. Click Manage providers to add a key or download a model.
You can change the model at any time, even mid-chat. See Switching models.
Send a message
Type in the composer and press Enter. Shift+Enter adds a new line.
- Type @ to add files and other context, or / to run a command.
- Choose a mode from the mode menu: Chat for plain conversation, Plan to research and write a plan first, or Agent to take actions and use tools.
- While the agent works, the send button becomes Stop generating. Type another message and queue it to run next.
When the agent wants to do something that needs your say-so, an approval card appears in the chat. See Permissions and The composer.