Results & Errors

Passkeys KMP is Result-first. Ceremonies don’t throw for control flow — they return a sealed PasskeyResult you exhaustively when over.

when (val result = passkeys.create(optionsJson)) {
    is PasskeyResult.Success -> {
        val rawJson = result.value.rawJson   // send to your backend to verify
    }
    is PasskeyResult.Failure -> {
        val code = result.error.code         // stable, switchable code
        val message = result.error.message   // human-readable detail
    }
}

Success

PasskeyResult.Success wraps the ceremony output. The field you care about is value.rawJson — the full WebAuthn response (attestation for create, assertion for authenticate) carrying every field a server library expects: challenge, origin, RP ID, signature, sign-count, and any clientExtensionResults.

Failure

PasskeyResult.Failure carries a typed error with a stable code and a message. Handle the cases you care about explicitly — common ones include user cancellation, timeouts, no matching credential, and unsupported platform/OS.

Because the result type is sealed, the compiler forces you to handle both arms — there’s no silent path where a cancelled or failed ceremony looks like a success.