[PM-40235] `mysignins.microsoft.com/security-info` refuses to register a CTAP key-pair that VC 21686 accepts.

### Origin

Web (Browser)

### Web URL or App name

[`mysignins.microsoft.com/security-info`](https://mysignins.microsoft.com/security-info)

### Passkey Action

- [x] Creating new passkey (Registration)
- [ ] Signing in (Authentication)

### Build Information

~~~YAML
© Bitwarden Inc. 2015-2026

Version: 2026.6.0 (21686)
📱 Fairphone FP5 🤖 15@35 📦 prod
🧱 commit: bitwarden/android/release/2026.6-rc56@cc9b7d3edf77f523433f6a8cda5577e56ae1a4e2
💻 build source: bitwarden/android/actions/runs/27437870956/attempts/1
🦀 SDK: 3.0.0-7338-5bdc976f
🌩 Server: 2026.6.1 @ US
~~~

### Additional Information

As in [`clients/issues/21792`](https://github.com/bitwarden/clients/issues/21792#issue-4856749621), the problem is that it fails to register, on Microsoft's side:

However, unlike where [`clients/issues/21201`](https://github.com/bitwarden/clients/issues/21201#issue-4641017352) applies, `bitwarden_flight_recorder4094515514079284772.zip/flight_recorder_2026-07-10_17-29-10.txt` contained:

~~~MA
Bitwarden Android - Password Manager
Log Start Time: 2026-07-10 17:29:10:601
Log Duration: 1h
App Version: 2026.6.0 (21686)
Build: release/standard
SDK Version: 🦀 3.0.0-7338-5bdc976f
CI Build Info: 🧱 commit: bitwarden/android/release/2026.6-rc56@cc9b7d3edf77f523433f6a8cda5577e56ae1a4e2
💻 build source: bitwarden/android/actions/runs/27437870956/attempts/1
Device: 📱 Fairphone FP5 🤖 15@35 📦 prod
🌩 Server: Bitwarden Cloud 2026.6.1 @ US
Fingerprint: Fairphone/FP5/FP5:15/AQ3A.240912.001/VT2X:user/release-keys
2026-07-10 17:29:10:609 – DEBUG – m38 – RootNavScreen destination changed: com.x8bit.bitwarden.ui.platform.feature.vaultunlockednavbar.VaultUnlockedNavbarRoute in com.x8bit.bitwarden.ui.platform.feature.vaultunlocked.VaultUnlockedGraphRoute
2026-07-10 17:29:10:655 – DEBUG – m38 – VaultUnlockedNavBarScreen destination changed: com.x8bit.bitwarden.ui.platform.feature.settings.about.SettingsAboutRoute.Standard in com.x8bit.bitwarden.ui.platform.feature.settings.SettingsGraphRoute
2026-07-10 17:29:13:901 – DEBUG – AppStateManagerImpl$AppForegroundObserver – App is backgrounded
2026-07-10 17:29:43:596 – DEBUG – BitwardenCredentialProviderService – Create credential request received.
2026-07-10 17:29:48:895 – DEBUG – AppStateManagerImpl$AppForegroundObserver – App is foregrounded
2026-07-10 17:29:49:015 – DEBUG – m38 – MainActivity destination changed: com.x8bit.bitwarden.ui.platform.feature.overlaynav.OverlayNavRoute
2026-07-10 17:29:49:024 – DEBUG – m38 – OverlayNavScreen destination changed: com.x8bit.bitwarden.ui.platform.feature.rootnav.RootNavigationRoute
2026-07-10 17:29:49:088 – DEBUG – m38 – RootNavScreen destination changed: com.x8bit.bitwarden.ui.platform.feature.splash.SplashRoute
2026-07-10 17:29:49:139 – DEBUG – m38 – RootNavScreen destination changed: com.x8bit.bitwarden.ui.platform.feature.vaultunlockednavbar.VaultUnlockedNavbarRoute in com.x8bit.bitwarden.ui.platform.feature.vaultunlocked.VaultUnlockedGraphRoute
2026-07-10 17:29:49:150 – DEBUG – m38 – RootNavScreen destination changed: pab/{encodedData} in com.x8bit.bitwarden.ui.platform.feature.vaultunlocked.VaultUnlockedGraphRoute
2026-07-10 17:29:49:367 – DEBUG – wn6 – resolveHostname(icons.bitwarden.net): no stored config found, using original
2026-07-10 17:29:49:368 – DEBUG – wn6 – getCookies(icons.bitwarden.net): resolved=icons.bitwarden.net, count=0
2026-07-10 17:29:49:372 – DEBUG – wn6 – resolveHostname(icons.bitwarden.net): no stored config found, using original
2026-07-10 17:29:49:374 – DEBUG – wn6 – getCookies(icons.bitwarden.net): resolved=icons.bitwarden.net, count=0
2026-07-10 17:29:49:726 – DEBUG – wn6 – getCookies(icons.bitwarden.net): resolved=icons.bitwarden.net, count=0
2026-07-10 17:29:49:726 – DEBUG – wn6 – resolveHostname(icons.bitwarden.net): no stored config found, using original
2026-07-10 17:29:53:822 – DEBUG – wn6 – resolveHostname(icons.bitwarden.net): no stored config found, using original
2026-07-10 17:29:53:823 – DEBUG – wn6 – getCookies(icons.bitwarden.net): resolved=icons.bitwarden.net, count=0
2026-07-10 17:29:59:222 – DEBUG – BitwardenNetworkClient – --> PUT https://api.bitwarden.com/ciphers/ebff0d3f-aa06-4235-9bb1-b48301083c14 (6302-byte body)
2026-07-10 17:29:59:224 – DEBUG – wn6 – resolveHostname(api.bitwarden.com): no stored config found, using original
2026-07-10 17:29:59:225 – DEBUG – wn6 – needsBootstrap(api.bitwarden.com): false (cookieDomain=null)
2026-07-10 17:29:59:227 – DEBUG – wn6 – getCookies(api.bitwarden.com): resolved=api.bitwarden.com, count=0
2026-07-10 17:29:59:994 – DEBUG – BitwardenNetworkClient – <-- 200 https://api.bitwarden.com/ciphers/ebff0d3f-aa06-4235-9bb1-b48301083c14 (771ms, unknown-length body)
2026-07-10 17:30:00:882 – DEBUG – AppStateManagerImpl$AppForegroundObserver – App is backgrounded
2026-07-10 17:30:20:478 – DEBUG – AppStateManagerImpl$AppForegroundObserver – App is foregrounded
2026-07-10 17:30:20:506 – DEBUG – m38 – MainActivity destination changed: com.x8bit.bitwarden.ui.platform.feature.overlaynav.OverlayNavRoute
2026-07-10 17:30:20:512 – DEBUG – m38 – OverlayNavScreen destination changed: com.x8bit.bitwarden.ui.platform.feature.rootnav.RootNavigationRoute
2026-07-10 17:30:20:540 – DEBUG – m38 – RootNavScreen destination changed: com.x8bit.bitwarden.ui.platform.feature.vaultunlockednavbar.VaultUnlockedNavbarRoute in com.x8bit.bitwarden.ui.platform.feature.vaultunlocked.VaultUnlockedGraphRoute
2026-07-10 17:30:20:579 – DEBUG – m38 – VaultUnlockedNavBarScreen destination changed: com.x8bit.bitwarden.ui.platform.feature.settings.about.SettingsAboutRoute.Standard in com.x8bit.bitwarden.ui.platform.feature.settings.SettingsGraphRoute
~~~

### Issue Tracking Info

- [x] I understand that work is tracked outside of Github. A PR will be linked to this issue should one be opened to address it, but Bitwarden doesn't use fields like "assigned", "milestone", or "project" to track progress.

Start by reproducing passkey registration at mysignins.microsoft.com/security-info and inspect the BitwardenCredentialProviderService entries in the supplied flight recorder. Compare the behavior with clients/issues/21792 and clients/issues/21201; done means identifying an actionable Android-side mismatch with a regression test, or documenting that Microsoft's rejection is external.

Written by the indexing model from the issue text.