Re: [webauthn] Update Virtual Authenticator API to better emulate synced passkey behavior (#2382)

I'm trying to write this PR to also achieve Martin's desired end state of the Virtual Authenticator API defaulting into a "synced passkey" mode instead of the API's current "security key" mode.

@kreichgauer and @nsatragno, can you take a look at this PR with an eye on if these proposed changes would move us to that end state **if** a subsequent PR were to update **Add Virtual Authenticator** endpoint's `defaultBackupEligibility` argument to instead default to `true`? Right now it defaults to `false`:

<img width="763" height="80" alt="Screenshot 2026-02-19 at 10 13 44 AM" src="https://github.com/user-attachments/assets/94957d4a-4097-487d-a9b1-074c641b71e4" />

I'm thinking of a migration path for RPs with existing tests built around current Virtual Authenticator API behavior. I _think_ we can make it as simple as updating their calls to the **Add Virtual Authenticator** endpoint to add `defaultBackupEligibility: false` to get their tests passing again 🤔 

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Received on Thursday, 19 February 2026 18:17:53 UTC