# continuity

With an iPhone and an iPad on the same Apple Account, a live session can
follow you between them. Tessera hands off **a pointer to the session — never
a password or a private key**; each device authenticates with its own
credentials.

## Handing off a session

With **settings → sync & continuity → hand off sessions** enabled (it is by
default), your focused connected session appears on your other device — in
the App Switcher on iPhone, in the Dock on iPad. Tap it and the other device
opens the same saved host.

For tmux-backed sessions that means *the same screen*: both devices attach to
the same tmux session, so the handoff continues exactly where you were. A
plain SSH or mosh session can't be shared mid-stream, so the other device
reconnects fresh instead — Tessera labels the two cases honestly.

Handoff is Apple's mechanism, so its requirements apply: the same Apple
Account on both devices, Bluetooth and Wi-Fi on, and Handoff enabled in the
iOS Settings app. While a device is locked it stops broadcasting, and an
incoming session waits for Face ID.

## First time on a new device

Credentials never travel, so the first continuation to a device that hasn't
connected to that host before shows a credential card: authenticate with a
password or [pick a key](https://bambouville.com/docs/keys/) on *this* device, stored only in this
device's keychain. After that, continuing is one tap. A host the device has
never seen arrives as a prefilled editor — nothing is saved silently, and
[host key verification](https://bambouville.com/docs/host-keys/#first-connection) still applies. When
the host's key matches what your other device already trusts, the sheet says
so — but the decision to trust stays yours, per device.

## Authorize this device

Instead of typing a password on the new device, the credential card can ask
your other device to vouch for it: **authorize this device from your other
device** installs the new device's *public* key on the host, over the session
your other device already has open. The other device shows exactly what will
be installed — device, host, key fingerprint — and asks for Face ID. No
password or private key crosses between devices; the host simply learns one
more public key.

Enrolled devices are listed under **device access** on the
[keys page](https://bambouville.com/docs/keys/#device-access), where the grant can be revoked — Tessera
removes the key from the host over your own access, the same way it was
installed.

## Take back control

When another device continues a tmux session you're attached to, your screen
doesn't silently reflow: the terminal blurs behind a card that names where
the session went, and **take back control** — a tap, or any key — brings it
home (that keystroke is consumed, not typed into the shell). Either device
can yield and reclaim; the arrangement is symmetric.

![A Tessera session blurred behind a frosted card reading 'This session is being controlled from another device', with a take back control button.](https://bambouville.com/docs/assets/img/takeover-overlay.png)

*The device that lost the grid says so, and offers it back in one tap.*

Take-back detection works through the tmux server itself, so it needs
**tmux 3.2 or later** on the host, and only applies to tmux launch modes — a
custom-command session reconnects a fresh shell, so there is nothing to take
back.

## What never syncs

Continuity moves session pointers and, with your explicit approval, installs
public keys. It never transfers passwords, private keys, or host-key trust —
each device keeps its own keychain and its own
[known hosts](https://bambouville.com/docs/host-keys/). To move your actual setup to a new device, use
[nearby setup](https://bambouville.com/docs/nearby-setup/).