Who sees what

On the device

The signing keys never leave the device, nor does the seed they come from, except sealed. The balances, activity and notes the wallet has read are kept sealed under a key from the wallet's root.

Services

Who	Is sent	Can learn
Proving service	The action, its signature, the account's address and viewing key	The account's private balance and history. It can't spend.
Relayer	The action's size, then the proven action	Nothing beyond what the chain shows once it is sent.
Indexer	The account's address, and which parts of the pool are read	The account's public activity. With no key, it can't tell which notes are the account's.
Starknet node	Reads and public transactions	Which addresses are read.
Passkey vault	The sealed seed	Nothing: it can't open the seed.
Ekubo	A swap's tokens and amount	Not the account.
Starknet Foundation's prover	A deposit's proving request, viewing key included	The same as the proving service, for accounts that shield.

Every service sees the IP address requests come from.

On chain

Action	What is public
Private payment	That the pool was used. Not who sent it, the amount or the token.
Private swap	The swap itself, made by a helper contract. Not who swapped.
Withdrawal	The address it goes to, the token and the amount. The sender is encrypted for the auditor.
Setting up	That the account uses the pool.
Shielding	The account, the token and the amount it moves in.

Setting up, shielding and withdrawing in quick succession can link them. See STRK20 by Example's known privacy limitations.

The auditor

STRK20 is private from the public, not from lawful oversight. […] When a user registers (SetViewingKey), their private viewing key is encrypted to the auditor's public key […] and stored on-chain. […] Disclosure is selective: the auditor decrypts only the viewing keys of users subject to a lawful request.

— STRK20 by Example, Compliance & Auditing

Outis doesn't hold the auditor's key, and has no part in disclosure.