Your Mac or their cloud: moving a session between computers

Somebody else's computer.

In October 2025 Anthropic introduced Claude Code on the web: “you can assign multiple coding tasks to Claude that run on Anthropic-managed cloud infrastructure”. You connect a GitHub repository, describe the task, and “Each session runs in its own isolated environment”. The page now notes that these cloud sessions became generally available on 23 September 2026.

Simon Willison, who had early access, summed up the trade: “The benefit of Claude Code for web is entirely in its convenience as a way of running these tasks in a hosted container managed by Anthropic”. He also noted a “teleport” feature that copies the transcript and edited files down to your local command-line tool.

Cursor went further in August 2026. Its changelog describes “always-on agents” that “can automatically pick up work in response to events”, and subagents that “run on their own virtual machines”.

This is a good design for a lot of work. A container is clean, parallel and awake at 3 a.m. It also sees only what you cloned into it. Your local database, your simulator, your signed-in command-line tools and the half-finished branch you have not pushed stay on your desk.

A live window, not a copy.

The rule is written at the top of the commit that added the computer-to-computer lane on 15 September 2026: “A session runs on the computer that holds its files; every other computer is a live window into it, like the phone. No take-over exists.”

So if a session lives on the Mac mini under your desk and you open it on your MacBook, you are looking through a window. Its header shows a chip with the home computer's name; hover it and it says “Runs on” that computer, or that the computer is asleep. When you send a prompt, the MacBook does not run it. It sends it to the home, which runs the turn with its own files and logins and streams the answer back. Stop works the same way, as a stop request sent to the home.

Two switches on the home computer decide how much it trusts its windows. Accept work from other devices is on by default; turned off, the computer is private and refuses prompts from every other device with a clear note, while your own typing there is never affected. Protected Mode for turns from other devices is off by default; turned on, turns that arrive from elsewhere run inside the folder fence whatever the session's own setting, “so a lost phone or laptop cannot reach the rest of this Mac.” The first time a remote turn runs unfenced, the app says so and names the switch.

Pack it, prove it, archive the old one.

Sometimes the home is wrong. The session started on your laptop and now needs to run all night on the desktop. So the same day, a second change added Transfer to to the row menu of every local session and folder, listing your other computers that are online. The send itself is refused if that computer does not accept work. A window row gets the opposite: Transfer to this computer, which asks the home to send it over.

The confirmation spells out the deal: the session “moves to” the other computer “and runs there from now on. This computer keeps a live window and an archived copy of the transcript.” The other computer must have the same folder.

A transfer moves the session's transcript files and its Journal notes through your account room, in checked parts. The sender first builds a manifest listing every file with its size and a SHA-256 checksum. The receiver validates the manifest, accepts, and then takes the files in parts of 384 KB, at most three in flight, each acknowledged. When a file's last part arrives, its size and checksum must match the manifest exactly. Only then does the receiver adopt it, and only then does the sender move its own copy into a .transferred- folder with a timestamp and remember the new home.

One detail makes it work across real machines: your home folder is rarely the same path on two Macs. The receiver rewrites the sender's home path into its own before it looks for the folder, so a session in your project folder on one Mac lands in the same project folder on the other.

The harder case, not shipped yet.

Moving a session between your own computers is safe because both ends are you. Handing one to a teammate is harder: two accounts, two computers, and a crash at the wrong moment could leave two runnable copies.

The groundwork for that landed on 15 September as a durable transfer journal with checked transitions. Each handoff is a record that can only move forward through fixed states, each step allowed only for the right participant on the right computer:

The tests cover the cases that matter: a different computer cannot accept for a teammate, a sender cannot manufacture an acceptance, a crash after the commit starts stays frozen rather than rolling back into a second copy, and a manifest cannot smuggle in another session's transcript.

The cloud as a fallback.

Keeping agents at home has one obvious cost: if the home is asleep, nothing runs. For the phone, Luminair covers that gap with Cloud Mode. Connect your own Anthropic API key as the Claude Cloud connector, and the phone can answer whole turns on the server while your computer is off.

The first version had a quiet flaw, written up in the source on 30 July 2026. A cloud answer lived only in the phone's live view, one turn deep, overwritten by the next. When the Mac woke, the source notes, it had no memory of anything done while it slept, and the next prompt there resumed a session that had never heard the conversation.

Now each cloud turn is stored as its own record. When the Mac wakes, and then every ten seconds while the relay runs, it folds any waiting cloud turns into the session's real transcript, oldest first, and clears each one only after it has been written. Turns older than seven days are dropped, and a turn for a folder the Mac cannot find yet is left for a later sweep. The next time you type on the Mac, the session knows what you said to it on the train.

Three moves, no terminal.

1. 1Open a session that lives on another computer. The chip in its header names the home; hover it to see whether that computer is awake.
2. 2Open the ⋯ menu on a session or folder row and choose Transfer to another computer, or Transfer to this computer on a window row.
3. 3On each computer, open Settings › Mobile relay › This computer to make it private or to fence turns from other devices.

Checked, and not claimed.

Sources

• Anthropic · 20 October 2025Claude Code on the web
• Simon Willison · 20 October 2025Claude Code for web: a new asynchronous coding agent from Anthropic
• Cursor Changelog · 19 August 2026Cloud Agents and Cursor Harness Improvements