Add new getClientCapabilities method

index.bs

@@ -2779,25 +2779,34 @@ Note: Invoking this method from a [=browsing context=] where the [=Web Authentic
 
 </div>
 
-### Availability of a [=passkey platform authenticator=] - PublicKeyCredential's `isPasskeyPlatformAuthenticatorAvailable()` Method ### {#sctn-isPasskeyPlatformAuthenticatorAvailable}
+### Availability of [=client=] capabilities - PublicKeyCredential's `getClientCapabilities()` Method ### {#sctn-getClientCapabilities}
 
-<div link-for-hint="WebAuthentication/isPasskeyPlatformAuthenticatorAvailable">
+<div link-for-hint="WebAuthentication/getClientCapabilities">
 
-[=[WRPS]=] use this method to determine whether they can create a new [=passkey=] using a [=user-verifying platform authenticator=] or a {{AuthenticatorTransport/hybrid}} authenticator.
-Upon invocation, the [=client=] employs a [=client platform=]-specific procedure to discover available [=user-verifying platform authenticators=] and the 
-availability of {{AuthenticatorTransport/hybrid}} transport.
-If one or both are discovered, the promise is resolved with the value of [TRUE].
-If neither is discovered, the promise is resolved with the value of [FALSE].
-Based on the result, the [=[RP]=] can take further actions to guide the user to create a [=passkey=].
+[=[WRPS]=] use this method to determine the availability of a limited set of [=WebAuthn Client|client=] capabilities to offer certain workflows and experiences to users. For example, an RP may offer a sign in button on clients where only {{AuthenticatorTransport/hybrid}} transport is available or where {{CredentialMediationRequirement/conditional}} mediation is unavailable (instead of showing a username field).
 
-This method has no arguments and returns a Boolean value.
+Upon invocation, the [=client=] employs a [=client platform=]-specific procedure to discover availablity of these capabilities.
+
+This method has no arguments and returns a map of capability keys to Boolean values. 
 
 <xmp class="idl">
     partial interface PublicKeyCredential {
-        static Promise<boolean> isPasskeyPlatformAuthenticatorAvailable();
+        static Promise<PublicKeyCredentialClientCapabilities> getClientCapabilities();
+    };
+
+    [SecureContext, Exposed=Window]
+    interface PublicKeyCredentialClientCapabilities {
+        readonly maplike<DOMString, boolean>;
     };
 </xmp>
 
+[=map/Keys=] in {{PublicKeyCredentialClientCapabilities}} MUST be sorted in ascending lexicographical order.
+The set of [=map/keys=] SHOULD equal the set of [=enumeration values=] of {{ClientCapability}}.
+
+When the value for a given capability is [TRUE], the feature is known to be currently supported by the client.
+When the value for a given capability is [FALSE], the feature is known to be not currently supported by the client.
+When a capability does not [=map/exist=] as a key, the availability of the client feature is not known.
+
 Note: Invoking this method from a [=browsing context=] where the [=Web Authentication API=] is "disabled" according to the [=allowed to use=] algorithm&mdash;i.e., by a [=permissions policy=]&mdash;will result in the promise being rejected with a {{DOMException}} whose name is "{{NotAllowedError}}". See also [[#sctn-permissions-policy]].
 
 </div>
@@ -3967,6 +3976,38 @@ Note: The {{UserVerificationRequirement}} enumeration is deliberately not refere
         interest of minimizing disruption to the user interaction flow).
 </div>
 
+### Client Capability Enumeration (enum <dfn enum>ClientCapability</dfn>) ### {#enum-clientCapability}
+
+<xmp class="idl">
+    enum ClientCapability {
+        "user-verifying-platform-authenticator",
+        "hybrid-transport",
+        "passkey-platform-authenticator",
+        "conditional-mediation",
+        "conditional-create"
+    };
+</xmp>
+
+This enumeration defines a limited set of client capabilities which a [=[WRP]=] may evaluate to offer certain workflows and experiences to users.
+
+Note: The {{ClientCapability}} enumeration is deliberately not referenced, see [[#sct-domstring-backwards-compatibility]].
+
+<div dfn-type="enum-value" dfn-for="ClientCapability">
+    :   <dfn>user-verifying-platform-authenticator</dfn>
+    ::  The [=WebAuthn Client=] supports usage of a [=user-verifying platform authenticator=].
+
+    :   <dfn>hybrid-transport</dfn>
+    ::  The [=WebAuthn Client=] supports usage of the {{AuthenticatorTransport/hybrid}} transport.
+
+    :   <dfn>passkey-platform-authenticator</dfn>
+    ::  The [=WebAuthn Client=] supports usage of a [=passkey platform authenticator=], locally and/or via {{AuthenticatorTransport/hybrid}} transport.
+
+    :   <dfn>conditional-mediation</dfn>
+    ::  The [=WebAuthn Client=] is capable of {{CredentialMediationRequirement/conditional}} mediation.
+
+    :   <dfn>conditional-create</dfn>
+    ::  The [=WebAuthn Client=] is capable of a {{CredentialMediationRequirement/conditional}} credential creation operation.
+</div>
 
 ## Permissions Policy integration ## {#sctn-permissions-policy}