secure_store_unavailable

Sign-in couldn't save the session token, so it throws instead of returning a session that would be lost on the next launch. All three of the SDK's stores raise it:

• BrowserTokenStore (@gemmein/sdk): the browser refused the localStorage write (private mode past its quota, site data blocked, a sandboxed iframe).
• @gemmein/sdk/expo: expo-secure-store is not installed, or the device refused the write.
• Swift KeychainTokenStore: the Keychain refused, and the OSStatus is in the message. -34018 is an unsigned build with no keychain access group, so sign the app (ad-hoc is enough).

The store's own error is on err.cause (in Swift, in the message). Reads and clears stay lenient on all three: an unreadable store means signed out, never a crash. The session itself is valid, so an app that should keep running catches this one code and rebuilds its client with a MemoryTokenStore. See Mobile