Ask iOS not to suspend the app while a shell is open (#46)

[m96-chan]

Locking the screen or leaving the app drops the SSH session.

The app is not the one hanging up

enterBackground() keeps the shell, the parser state and the credentials, and on return checkRetainedConnection reuses the same PTY when the transport answers. The session dies because iOS suspends the process, and a suspended process cannot service its socket.

The app was not asking for any time before that happened. There is no beginBackgroundTask anywhere in it, so the system is free to suspend the moment the scene goes to the background.

What this buys

An assertion worth about thirty seconds, which covers the cases most likely to be behind the report:

• glancing at another app and coming straight back
• pressing the power button and unlocking a few seconds later
• pulling down a notification

Those survive today only by luck. With the assertion held, the probe on return finds a live transport rather than a dead one.

Taken only when a session is connected or checking. Asking the system to stay awake with nothing to keep alive is wasted battery and the kind of thing that gets noticed.

What this is not

This does not keep the app connected in the background, and is not meant to. No entitlement iOS grants an SSH client holds a TCP session open indefinitely — the categories are audio, location, VoIP, external accessory and NEAppPushProvider, and a terminal is none of them. README.md already points at a remote multiplexer for continuity across a real disconnection, and #39 tracks the one legitimate route to not being suspended at all.

Thirty seconds is a real improvement to the common case and nothing more. It is worth being plain about which one the report was about.

Tests

The assertion is injectable because the failure worth testing is not taking one — it is failing to give one back, which is how iOS kills an app.

test	covers
nothingIsAskedForWhenNoSessionIsConnected	no assertion with nothing to keep alive
theAssertionIsGivenBackWhenTheAppReturns	ended on foreground
theAssertionIsGivenBackWhenTheTimeRunsOut	ended from the expiry handler, and not ended twice afterwards
goingToTheBackgroundTwiceHoldsOneAssertion	no leak on a repeated transition

All four pass. Simulators shut down after the run.

🤖 Generated with Claude Code