Megastructure Arc 2.1.3

• Add agent now offers Behaviours every new agent starts with. Tick presets such as handling a #tag or following an agent, and the receipt lists what each new agent got, including a flow behaviour a Safe room saved paused or one Arc did not add.
• arc_spawn_agents takes workspace_path, an absolute folder the new seats work in instead of the room's. A read-only reviewer can read a folder the room does not have, and keeps it when the room's folder changes. Rooms that give every seat its own worktree refuse it.
• When a model request has waited more than a minute, the working strip names the provider and how many minutes it has waited, and the agent records one model_step_slow event for that step. A stalled provider no longer looks like a step counter that has stopped moving.
• Claude Desktop's Arc entry in claude_desktop_config.json is now mcpServers.arc-cowork instead of arc. The Claude desktop app loads that entry into every Code-tab conversation, where it replaced Claude Code's own arc entry, so a join in one conversation changed the identity of all of them. Installing or repairing the Claude Cowork adapter, and Arc Desktop at launch by default, move an existing Arc entry and leave a server of your own named arc alone. Restart Claude after the move; in the Code tab, the arc tools give each conversation its own identity.
• A join that switches a shared Arc connection to another identity says which identity it replaced, and the next few results say so too. Joining your own invite again gives back your earlier handle instead of the next number.
• POST /v1/invites accepts an acl of readable_rooms and writable_rooms from the invite's project, and refuses an invalid one. The field used to be dropped without a word.

• save_notes over 4,000 characters keeps the first 4,000 and says what was dropped, instead of refusing and leaving the agent with no notes at its next checkpoint.
• When three checkpoints in a row save no new notes, write no file and make no Arc write, Arc ends the turn with the reason and tells the room, instead of letting the agent repeat itself for hours.
• Joining through an invite can no longer widen what a session may do. Arc alone records which invite admitted a session and whether it is a verified operator, and claiming the operator role needs the operator key.
• Stopping the local hub no longer waits about 15 seconds for each Arc-managed agent, so it no longer keeps running for minutes after you stop it, update Arc, or quit with the hub set to stop.
• On Windows, agents keep the folder capitalisation you chose after a room's folder changes.
• The file relay retries a request file that an antivirus scanner or search indexer still holds open, instead of answering with an error.
• Coordination completion summaries keep up to 1,500 characters, the limit the tool already advertised; longer summaries had been cut at 1,000.

Windows 10/11 (64-bit), or macOS 11+ on Apple Silicon. Bundled Local AI requires macOS 26+. Computer use requires macOS 14+.