The frame pipe

Atlas.app's viewer window, the terminal viewer and the screen view agent apps draw from show_screen show the hidden helper through one shared stream of pictures, the frame pipe. The menu bar runs it beside its viewer service, so it lives as long as the menu bar does.

What it does

• One source. Only the frame service reads the helper's live stream, one picture at a time, on demand. Every window and terminal shares it, so opening a second viewer never starts a second capture. With no viewer asking for two seconds, the helper's stream is given back.
• Raw pictures. Pictures travel as packed RGB over two private Unix sockets, never as PNG. A picture is read while the previous one travels, so a viewer receives about as many pictures as the helper can capture (about 27 a second at 1600 pixels wide on a 2560 × 1440 helper, against one picture every two seconds before).
• Verified pictures only. Every picture is bracketed by the helper's session proofs, as before, and is refused once it is older than half a second.
• Committed pictures name input. A viewer acknowledges each picture it shows. Only those can be named by Take Control and input, which go through the menu bar viewer's guarded routes with the same leases, frame keys and session checks as before.

When the frame service is unavailable, the app reads pictures over the viewer's address as before, and tries the pipe again after a pause. Agents' screenshots and the menu bar panel keep their own reads.

The agent apps' screen view

The view the Claude and Codex apps draw from show_screen runs inside the app and reaches Atlas only through tool calls, so it can't hold the pipe itself. Its atlas mcp server does: each screen_frame call takes the newest picture from the frame service and sends it as a JPEG, and the view asks again as soon as it has drawn one (about 7 fresh pictures a second while an agent works or you have control, and one a second otherwise, against one a second at most before). The server lets go of the service ten seconds after the view stops asking. Without the menu bar's frame service, the view reads the viewer's pictures as before.

Private by construction

The service listens only in a folder /private/tmp/atlas-fp.<uid>.<key>/ that belongs to the controller account, with mode 0700 and no access control list. Each socket is mode 0600. Atlas refuses an unsafe folder or socket rather than repairing it, and removes only the sockets it bound.

A client must hold the observer capability from the viewer's private address to pair. The kernel must name the same process on both sockets, and the client checks that the service's own process answers. Every packet has a fixed 32-byte prefix and strict JSON metadata: duplicate keys, unknown keys and lengths past their bounds end the connection before anything is reserved.

Diagnostics

atlas monitor --terminal shares the frame service when the menu bar runs for the same helper. Otherwise it uses its own private viewer and the helper's stream directly, as it did before, and --max-dimension or --capture-backend sck select that private path explicitly.