Settle-Back Guarantees
When a NorthStar session closes (explicit close or TTL expiry), every delegated account commits its final ER-side state back to L1 in one atomic step. This page explains the formal guarantees and the failure modes.
The core guarantee
After CloseSession returns successfully, every delegated account's L1 state matches its final ER state. Either:
All delegated accounts settle, in one atomic operation, OR
Nothing settles, and the session reverts to its pre-close state for retry.
There is no intermediate state where some accounts settled and others didn't.
Why it's atomic
The Portal program treats settle-back as a single multi-account write. The ER's final state is committed to L1 by the sequencer; any partial failure unwinds. This is enforced at the Portal level, not at the runtime level.
For the cryptographic / dispute-game guarantees that back this — checkpoint bonds, fraud proofs, ZK verification — see the security model.
Failure modes
Owner explicitly closes (happy path)
All accounts settle atomically. Owner regains control.
Session TTL expires without close
Portal allows forced undelegation by the owner. State is whatever the ER had at expiry; same atomicity.
Sequencer goes offline mid-session
Session pauses; owner can force-undelegate after TTL expiry.
Sequencer publishes a bad checkpoint
Fraud proof from any uncensored validator triggers slashing + state correction.
Network partition
Unaffected — the session's state is on L1 throughout.
What about in-flight transactions at close time?
When CloseSession is called, the ER stops accepting new transactions for that session. Any tx already submitted but not yet confirmed:
If it lands before close finalizes — included in the final settle-back.
If it doesn't land before close finalizes — dropped. Resubmit against a new session, or accept that it won't complete.
Practical guidance: if you have outstanding work that must complete, wait for confirmed on every in-flight tx before closing.
See also
Security model — the cryptographic guarantees behind atomicity.
Sessions — full lifecycle.
Account delegation — what's settled.
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