diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index ef90cb9..0141be0 100644
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,3 +1,21 @@
+2020-01-14  Commit Queue  <commit-queue@webkit.org>
+
+        Unreviewed, rolling out r254533 and r254535.
+        https://bugs.webkit.org/show_bug.cgi?id=206263
+
+        Breaks iOS and macOS builds (Requested by ryanhaddad on
+        #webkit).
+
+        Reverted changesets:
+
+        "[WebAuthn] Implement SPI to tell UI clients to select
+        assertion responses"
+        https://bugs.webkit.org/show_bug.cgi?id=206112
+        https://trac.webkit.org/changeset/254533
+
+        "Unreviewed, a build fix after r254533"
+        https://trac.webkit.org/changeset/254535
+
 2020-01-14  Myles C. Maxfield  <mmaxfield@apple.com>
 
         [Cocoa] Glyph lookup should be language-sensitive (specifically between Yiddish and Hebrew)
diff --git a/Source/WebCore/Modules/webauthn/AuthenticatorAssertionResponse.h b/Source/WebCore/Modules/webauthn/AuthenticatorAssertionResponse.h
index d70a9cc..dc4c803 100644
--- a/Source/WebCore/Modules/webauthn/AuthenticatorAssertionResponse.h
+++ b/Source/WebCore/Modules/webauthn/AuthenticatorAssertionResponse.h
@@ -42,9 +42,9 @@
     ArrayBuffer* userHandle() const { return m_userHandle.get(); }
 
     void setName(const String& name) { m_name = name; }
-    const String& name() const { return m_name; }
+    String name() const { return m_name; }
     void setDisplayName(const String& displayName) { m_displayName = displayName; }
-    const String& displayName() const { return m_displayName; }
+    String displayName() const { return m_displayName; }
     void setNumberOfCredentials(size_t numberOfCredentials) { m_numberOfCredentials = numberOfCredentials; }
     size_t numberOfCredentials() const { return m_numberOfCredentials; }
 
diff --git a/Source/WebKit/ChangeLog b/Source/WebKit/ChangeLog
index 44d8361..cc71c37 100644
--- a/Source/WebKit/ChangeLog
+++ b/Source/WebKit/ChangeLog
@@ -1,3 +1,21 @@
+2020-01-14  Commit Queue  <commit-queue@webkit.org>
+
+        Unreviewed, rolling out r254533 and r254535.
+        https://bugs.webkit.org/show_bug.cgi?id=206263
+
+        Breaks iOS and macOS builds (Requested by ryanhaddad on
+        #webkit).
+
+        Reverted changesets:
+
+        "[WebAuthn] Implement SPI to tell UI clients to select
+        assertion responses"
+        https://bugs.webkit.org/show_bug.cgi?id=206112
+        https://trac.webkit.org/changeset/254533
+
+        "Unreviewed, a build fix after r254533"
+        https://trac.webkit.org/changeset/254535
+
 2020-01-14  Wenson Hsieh  <wenson_hsieh@apple.com>
 
         [iOS] Keyboard input is severely delayed after switching away from unresponsive tab
diff --git a/Source/WebKit/Shared/API/APIObject.h b/Source/WebKit/Shared/API/APIObject.h
index 8da13c4..fdb81f4 100644
--- a/Source/WebKit/Shared/API/APIObject.h
+++ b/Source/WebKit/Shared/API/APIObject.h
@@ -183,7 +183,6 @@
 #endif
 
 #if ENABLE(WEB_AUTHN)
-        WebAuthenticationAssertionResponse,
         WebAuthenticationPanel,
 #endif
 
diff --git a/Source/WebKit/Shared/Cocoa/APIObject.mm b/Source/WebKit/Shared/Cocoa/APIObject.mm
index bf24db6..642f6ef 100644
--- a/Source/WebKit/Shared/Cocoa/APIObject.mm
+++ b/Source/WebKit/Shared/Cocoa/APIObject.mm
@@ -88,7 +88,6 @@
 #import "_WKUserInitiatedActionInternal.h"
 #import "_WKUserStyleSheetInternal.h"
 #import "_WKVisitedLinkStoreInternal.h"
-#import "_WKWebAuthenticationAssertionResponseInternal.h"
 #import "_WKWebAuthenticationPanelInternal.h"
 #import "_WKWebsiteDataStoreConfigurationInternal.h"
 
@@ -390,9 +389,6 @@
     case Type::WebAuthenticationPanel:
         wrapper = [_WKWebAuthenticationPanel alloc];
         break;
-    case Type::WebAuthenticationAssertionResponse:
-        wrapper = [_WKWebAuthenticationAssertionResponse alloc];
-        break;
 #endif
 
     case Type::BundleFrame:
diff --git a/Source/WebKit/Sources.txt b/Source/WebKit/Sources.txt
index 8f8a562..606f039 100644
--- a/Source/WebKit/Sources.txt
+++ b/Source/WebKit/Sources.txt
@@ -341,7 +341,6 @@
 UIProcess/API/APIUserContentWorld.cpp
 UIProcess/API/APIUserScript.cpp
 UIProcess/API/APIUserStyleSheet.cpp
-UIProcess/API/APIWebAuthenticationAssertionResponse.cpp
 UIProcess/API/APIWebAuthenticationPanel.cpp
 UIProcess/API/APIWebsitePolicies.cpp
 UIProcess/API/APIWindowFeatures.cpp
diff --git a/Source/WebKit/SourcesCocoa.txt b/Source/WebKit/SourcesCocoa.txt
index b73dd81..394c670 100644
--- a/Source/WebKit/SourcesCocoa.txt
+++ b/Source/WebKit/SourcesCocoa.txt
@@ -278,7 +278,6 @@
 UIProcess/API/Cocoa/_WKUserInitiatedAction.mm
 UIProcess/API/Cocoa/_WKUserStyleSheet.mm
 UIProcess/API/Cocoa/_WKVisitedLinkStore.mm
-UIProcess/API/Cocoa/_WKWebAuthenticationAssertionResponse.mm
 UIProcess/API/Cocoa/_WKWebAuthenticationPanel.mm
 UIProcess/API/Cocoa/_WKWebsiteDataSize.mm
 UIProcess/API/Cocoa/_WKWebsiteDataStore.mm
diff --git a/Source/WebKit/UIProcess/API/APIResourceLoadClient.h b/Source/WebKit/UIProcess/API/APIResourceLoadClient.h
index a30dd95..2181d8d 100644
--- a/Source/WebKit/UIProcess/API/APIResourceLoadClient.h
+++ b/Source/WebKit/UIProcess/API/APIResourceLoadClient.h
@@ -25,10 +25,6 @@
 
 #pragma once
 
-#include <WebCore/ResourceError.h>
-#include <WebCore/ResourceRequest.h>
-#include <WebCore/ResourceResponse.h>
-
 namespace WebKit {
 class AuthenticationChallengeProxy;
 struct ResourceLoadInfo;
diff --git a/Source/WebKit/UIProcess/API/APIWebAuthenticationAssertionResponse.cpp b/Source/WebKit/UIProcess/API/APIWebAuthenticationAssertionResponse.cpp
deleted file mode 100644
index c7976ff..0000000
--- a/Source/WebKit/UIProcess/API/APIWebAuthenticationAssertionResponse.cpp
+++ /dev/null
@@ -1,62 +0,0 @@
-/*
- * Copyright (C) 2020 Apple Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
- * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
- * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
- * THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#include "config.h"
-#include "APIWebAuthenticationAssertionResponse.h"
-
-#if ENABLE(WEB_AUTHN)
-
-#include "APIData.h"
-
-namespace API {
-using namespace WebCore;
-
-Ref<WebAuthenticationAssertionResponse> WebAuthenticationAssertionResponse::create(Ref<WebCore::AuthenticatorAssertionResponse>&& response)
-{
-    return adoptRef(*new WebAuthenticationAssertionResponse(WTFMove(response)));
-}
-
-WebAuthenticationAssertionResponse::WebAuthenticationAssertionResponse(Ref<WebCore::AuthenticatorAssertionResponse>&& response)
-    : m_response(WTFMove(response))
-{
-}
-
-WebAuthenticationAssertionResponse::~WebAuthenticationAssertionResponse() = default;
-
-RefPtr<Data> WebAuthenticationAssertionResponse::userHandle() const
-{
-    RefPtr<API::Data> data;
-    if (auto* userHandle = m_response->userHandle()) {
-        userHandle->ref();
-        data = API::Data::createWithoutCopying(reinterpret_cast<unsigned char*>(userHandle->data()), userHandle->byteLength(), [] (unsigned char*, const void* data) {
-            static_cast<ArrayBuffer*>(const_cast<void*>(data))->deref();
-        }, userHandle);
-    }
-    return data;
-}
-
-} // namespace API
-
-#endif // ENABLE(WEB_AUTHN)
diff --git a/Source/WebKit/UIProcess/API/APIWebAuthenticationAssertionResponse.h b/Source/WebKit/UIProcess/API/APIWebAuthenticationAssertionResponse.h
deleted file mode 100644
index 4176208..0000000
--- a/Source/WebKit/UIProcess/API/APIWebAuthenticationAssertionResponse.h
+++ /dev/null
@@ -1,56 +0,0 @@
-/*
- * Copyright (C) 2020 Apple Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
- * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
- * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
- * THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#pragma once
-
-#if ENABLE(WEB_AUTHN)
-
-#include "APIObject.h"
-#include <WebCore/AuthenticatorAssertionResponse.h>
-
-namespace API {
-
-class Data;
-
-class WebAuthenticationAssertionResponse final : public ObjectImpl<Object::Type::WebAuthenticationAssertionResponse> {
-public:
-    static Ref<WebAuthenticationAssertionResponse> create(Ref<WebCore::AuthenticatorAssertionResponse>&&);
-    ~WebAuthenticationAssertionResponse();
-
-    const WTF::String& name() const { return m_response->name(); }
-    const WTF::String& displayName() const { return m_response->displayName(); }
-    RefPtr<Data> userHandle() const;
-
-    const WebCore::AuthenticatorAssertionResponse& response() { return m_response.get(); }
-
-private:
-    WebAuthenticationAssertionResponse(Ref<WebCore::AuthenticatorAssertionResponse>&&);
-
-    Ref<WebCore::AuthenticatorAssertionResponse> m_response;
-};
-
-} // namespace API
-
-#endif // ENABLE(WEB_AUTHN)
diff --git a/Source/WebKit/UIProcess/API/APIWebAuthenticationPanelClient.h b/Source/WebKit/UIProcess/API/APIWebAuthenticationPanelClient.h
index 7010d78..0062f9a 100644
--- a/Source/WebKit/UIProcess/API/APIWebAuthenticationPanelClient.h
+++ b/Source/WebKit/UIProcess/API/APIWebAuthenticationPanelClient.h
@@ -50,8 +50,8 @@
 
     virtual void updatePanel(WebKit::WebAuthenticationStatus) const { }
     virtual void dismissPanel(WebKit::WebAuthenticationResult) const { }
+    virtual void selectAssertionResponses(const HashSet<Ref<WebCore::AuthenticatorAssertionResponse>>& responses, CompletionHandler<void(const Ref<WebCore::AuthenticatorAssertionResponse>&)>&& completionHandler) const { completionHandler(*responses.begin()); }
     virtual void requestPin(uint64_t, CompletionHandler<void(const WTF::String&)>&& completionHandler) const { completionHandler(emptyString()); }
-    virtual void selectAssertionResponse(const HashSet<Ref<WebCore::AuthenticatorAssertionResponse>>& responses, CompletionHandler<void(const WebCore::AuthenticatorAssertionResponse&)>&& completionHandler) const { ASSERT(!responses.isEmpty()); completionHandler(*responses.begin()); }
 };
 
 } // namespace API
diff --git a/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationAssertionResponse.h b/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationAssertionResponse.h
deleted file mode 100644
index 412f5af..0000000
--- a/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationAssertionResponse.h
+++ /dev/null
@@ -1,43 +0,0 @@
-/*
- * Copyright (C) 2020 Apple Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
- * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
- * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
- * THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#pragma once
-
-#import <WebKit/WKFoundation.h>
-
-#import <Foundation/Foundation.h>
-
-NS_ASSUME_NONNULL_BEGIN
-
-WK_CLASS_AVAILABLE(macos(WK_MAC_TBA), ios(WK_IOS_TBA))
-@interface _WKWebAuthenticationAssertionResponse : NSObject
-
-@property (nonatomic, readonly, copy) NSString *name;
-@property (nonatomic, readonly, copy) NSString *displayName;
-@property (nonatomic, readonly, copy) NSData *userHandle;
-
-@end
-
-NS_ASSUME_NONNULL_END
diff --git a/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationAssertionResponse.mm b/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationAssertionResponse.mm
deleted file mode 100644
index 971f236..0000000
--- a/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationAssertionResponse.mm
+++ /dev/null
@@ -1,65 +0,0 @@
-/*
- * Copyright (C) 2020 Apple Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
- * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
- * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
- * THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#import "config.h"
-#import "_WKWebAuthenticationAssertionResponseInternal.h"
-
-#import "WKNSData.h"
-
-@implementation _WKWebAuthenticationAssertionResponse
-
-#if ENABLE(WEB_AUTHN)
-
-- (void)dealloc
-{
-    _response->~WebAuthenticationAssertionResponse();
-
-    [super dealloc];
-}
-
-- (NSString *)name
-{
-    return _response->name();
-}
-
-- (NSString *)displayName
-{
-    return _response->displayName();
-}
-
-- (NSData *)userHandle
-{
-    return wrapper(_response->userHandle());
-}
-
-#pragma mark WKObject protocol implementation
-
-- (API::Object&)_apiObject
-{
-    return *_response;
-}
-#endif
-
-@end
diff --git a/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationAssertionResponseInternal.h b/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationAssertionResponseInternal.h
deleted file mode 100644
index ef3600f..0000000
--- a/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationAssertionResponseInternal.h
+++ /dev/null
@@ -1,49 +0,0 @@
-/*
- * Copyright (C) 2020 Apple Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
- * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
- * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
- * THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#pragma once
-
-#import "_WKWebAuthenticationAssertionResponse.h"
-
-#if ENABLE(WEB_AUTHN)
-
-#import "APIWebAuthenticationAssertionResponse.h"
-#import "WKObject.h"
-
-namespace WebKit {
-
-template<> struct WrapperTraits<API::WebAuthenticationAssertionResponse> {
-    using WrapperClass = _WKWebAuthenticationAssertionResponse;
-};
-
-}
-
-@interface _WKWebAuthenticationAssertionResponse () <WKObject> {
-@package
-    API::ObjectStorage<API::WebAuthenticationAssertionResponse> _response;
-}
-@end
-
-#endif // ENABLE(WEB_AUTHN)
diff --git a/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationPanel.h b/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationPanel.h
index 431c633b..8680623 100644
--- a/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationPanel.h
+++ b/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationPanel.h
@@ -31,7 +31,6 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-@class _WKWebAuthenticationAssertionResponse;
 @class _WKWebAuthenticationPanel;
 
 typedef NS_ENUM(NSInteger, _WKWebAuthenticationPanelResult) {
@@ -70,7 +69,6 @@
 - (void)panel:(_WKWebAuthenticationPanel *)panel updateWebAuthenticationPanel:(_WKWebAuthenticationPanelUpdate)update WK_API_AVAILABLE(macos(WK_MAC_TBA), ios(WK_IOS_TBA));
 - (void)panel:(_WKWebAuthenticationPanel *)panel dismissWebAuthenticationPanelWithResult:(_WKWebAuthenticationResult)result WK_API_AVAILABLE(macos(WK_MAC_TBA), ios(WK_IOS_TBA));
 - (void)panel:(_WKWebAuthenticationPanel *)panel requestPINWithRemainingRetries:(NSUInteger)retries completionHandler:(void (^)(NSString *))completionHandler WK_API_AVAILABLE(macos(WK_MAC_TBA), ios(WK_IOS_TBA));
-- (void)panel:(_WKWebAuthenticationPanel *)panel selectAssertionResponse:(NSArray < _WKWebAuthenticationAssertionResponse *> *)responses completionHandler:(void (^)(_WKWebAuthenticationAssertionResponse *))completionHandler WK_API_AVAILABLE(macos(WK_MAC_TBA), ios(WK_IOS_TBA));
 
 @end
 
diff --git a/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationPanel.mm b/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationPanel.mm
index 2eb31e8..4474bac 100644
--- a/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationPanel.mm
+++ b/Source/WebKit/UIProcess/API/Cocoa/_WKWebAuthenticationPanel.mm
@@ -24,10 +24,10 @@
  */
 
 #import "config.h"
-#import "_WKWebAuthenticationPanelInternal.h"
-
 #import "WebAuthenticationPanelClient.h"
+#import "_WKWebAuthenticationPanelInternal.h"
 #import <WebCore/WebAuthenticationConstants.h>
+
 #import <wtf/RetainPtr.h>
 
 @implementation _WKWebAuthenticationPanel {
diff --git a/Source/WebKit/UIProcess/Cocoa/ResourceLoadDelegate.h b/Source/WebKit/UIProcess/Cocoa/ResourceLoadDelegate.h
index a47b292..e835304 100644
--- a/Source/WebKit/UIProcess/Cocoa/ResourceLoadDelegate.h
+++ b/Source/WebKit/UIProcess/Cocoa/ResourceLoadDelegate.h
@@ -29,8 +29,6 @@
 #import "WKFoundation.h"
 #import <wtf/WeakObjCPtr.h>
 
-@class WKWebView;
-
 @protocol _WKResourceLoadDelegate;
 
 namespace API {
diff --git a/Source/WebKit/UIProcess/Cocoa/ResourceLoadDelegate.mm b/Source/WebKit/UIProcess/Cocoa/ResourceLoadDelegate.mm
index d426285..6b7800b 100644
--- a/Source/WebKit/UIProcess/Cocoa/ResourceLoadDelegate.mm
+++ b/Source/WebKit/UIProcess/Cocoa/ResourceLoadDelegate.mm
@@ -26,8 +26,6 @@
 #import "config.h"
 #import "ResourceLoadDelegate.h"
 
-#import "AuthenticationChallengeProxy.h"
-#import "WKNSURLAuthenticationChallenge.h"
 #import "_WKResourceLoadDelegate.h"
 #import "_WKResourceLoadInfoInternal.h"
 
@@ -82,7 +80,7 @@
     if (!delegate)
         return;
 
-    [delegate webView:m_resourceLoadDelegate.m_webView.get().get() resourceLoad:wrapper(API::ResourceLoadInfo::create(WTFMove(loadInfo)).get()) didSendRequest:request.nsURLRequest(WebCore::HTTPBodyUpdatePolicy::DoNotUpdateHTTPBody)];
+    [delegate webView:m_resourceLoadDelegate.m_webView.get().get() resourceLoad:wrapper(API::ResourceLoadInfo::create(WTFMove(loadInfo)).get()) didSendRequest:request.nsURLRequest(HTTPBodyUpdatePolicy::DoNotUpdateHTTPBody)];
 }
 
 void ResourceLoadDelegate::ResourceLoadClient::didPerformHTTPRedirection(WebKit::ResourceLoadInfo&& loadInfo, WebCore::ResourceResponse&& response, WebCore::ResourceRequest&& request) const
@@ -94,7 +92,7 @@
     if (!delegate)
         return;
 
-    [delegate webView:m_resourceLoadDelegate.m_webView.get().get() resourceLoad:wrapper(API::ResourceLoadInfo::create(WTFMove(loadInfo)).get()) didPerformHTTPRedirection:response.nsURLResponse() newRequest:request.nsURLRequest(WebCore::HTTPBodyUpdatePolicy::DoNotUpdateHTTPBody)];
+    [delegate webView:m_resourceLoadDelegate.m_webView.get().get() resourceLoad:wrapper(API::ResourceLoadInfo::create(WTFMove(loadInfo)).get()) didPerformHTTPRedirection:response.nsURLResponse() newRequest:request.nsURLRequest(HTTPBodyUpdatePolicy::DoNotUpdateHTTPBody)];
 }
 
 void ResourceLoadDelegate::ResourceLoadClient::didReceiveChallenge(WebKit::ResourceLoadInfo&& loadInfo, WebKit::AuthenticationChallengeProxy& challenge) const
diff --git a/Source/WebKit/UIProcess/WebAuthentication/Authenticator.h b/Source/WebKit/UIProcess/WebAuthentication/Authenticator.h
index d16b17d..32fc7d2 100644
--- a/Source/WebKit/UIProcess/WebAuthentication/Authenticator.h
+++ b/Source/WebKit/UIProcess/WebAuthentication/Authenticator.h
@@ -51,8 +51,8 @@
         virtual void respondReceived(Respond&&) = 0;
         virtual void downgrade(Authenticator* id, Ref<Authenticator>&& downgradedAuthenticator) = 0;
         virtual void authenticatorStatusUpdated(WebAuthenticationStatus) = 0;
+        virtual void selectAssertionResponses(const HashSet<Ref<WebCore::AuthenticatorAssertionResponse>>&, CompletionHandler<void(const Ref<WebCore::AuthenticatorAssertionResponse>&)>&&) = 0;
         virtual void requestPin(uint64_t retries, CompletionHandler<void(const WTF::String&)>&&) = 0;
-        virtual void selectAssertionResponse(const HashSet<Ref<WebCore::AuthenticatorAssertionResponse>>&, CompletionHandler<void(const WebCore::AuthenticatorAssertionResponse&)>&&) = 0;
     };
 
     virtual ~Authenticator() = default;
diff --git a/Source/WebKit/UIProcess/WebAuthentication/AuthenticatorManager.cpp b/Source/WebKit/UIProcess/WebAuthentication/AuthenticatorManager.cpp
index 3db63ef..9cd4547 100644
--- a/Source/WebKit/UIProcess/WebAuthentication/AuthenticatorManager.cpp
+++ b/Source/WebKit/UIProcess/WebAuthentication/AuthenticatorManager.cpp
@@ -273,18 +273,18 @@
         panel->client().updatePanel(status);
 }
 
+void AuthenticatorManager::selectAssertionResponses(const HashSet<Ref<WebCore::AuthenticatorAssertionResponse>>& responses, CompletionHandler<void(const Ref<WebCore::AuthenticatorAssertionResponse>&)>&& completionHandler)
+{
+    if (auto* panel = m_pendingRequestData.panel.get())
+        panel->client().selectAssertionResponses(responses, WTFMove(completionHandler));
+}
+
 void AuthenticatorManager::requestPin(uint64_t retries, CompletionHandler<void(const WTF::String&)>&& completionHandler)
 {
     if (auto* panel = m_pendingRequestData.panel.get())
         panel->client().requestPin(retries, WTFMove(completionHandler));
 }
 
-void AuthenticatorManager::selectAssertionResponse(const HashSet<Ref<WebCore::AuthenticatorAssertionResponse>>& responses, CompletionHandler<void(const WebCore::AuthenticatorAssertionResponse&)>&& completionHandler)
-{
-    if (auto* panel = m_pendingRequestData.panel.get())
-        panel->client().selectAssertionResponse(responses, WTFMove(completionHandler));
-}
-
 UniqueRef<AuthenticatorTransportService> AuthenticatorManager::createService(AuthenticatorTransport transport, AuthenticatorTransportService::Observer& observer) const
 {
     return AuthenticatorTransportService::create(transport, observer);
diff --git a/Source/WebKit/UIProcess/WebAuthentication/AuthenticatorManager.h b/Source/WebKit/UIProcess/WebAuthentication/AuthenticatorManager.h
index a9b6293..9fd523d 100644
--- a/Source/WebKit/UIProcess/WebAuthentication/AuthenticatorManager.h
+++ b/Source/WebKit/UIProcess/WebAuthentication/AuthenticatorManager.h
@@ -81,8 +81,8 @@
     void respondReceived(Respond&&) final;
     void downgrade(Authenticator* id, Ref<Authenticator>&& downgradedAuthenticator) final;
     void authenticatorStatusUpdated(WebAuthenticationStatus) final;
+    void selectAssertionResponses(const HashSet<Ref<WebCore::AuthenticatorAssertionResponse>>&, CompletionHandler<void(const Ref<WebCore::AuthenticatorAssertionResponse>&)>&&) final;
     void requestPin(uint64_t retries, CompletionHandler<void(const WTF::String&)>&&) final;
-    void selectAssertionResponse(const HashSet<Ref<WebCore::AuthenticatorAssertionResponse>>&, CompletionHandler<void(const WebCore::AuthenticatorAssertionResponse&)>&&) final;
 
     // Overriden by MockAuthenticatorManager.
     virtual UniqueRef<AuthenticatorTransportService> createService(WebCore::AuthenticatorTransport, AuthenticatorTransportService::Observer&) const;
diff --git a/Source/WebKit/UIProcess/WebAuthentication/Cocoa/WebAuthenticationPanelClient.h b/Source/WebKit/UIProcess/WebAuthentication/Cocoa/WebAuthenticationPanelClient.h
index fafaa81..1499466 100644
--- a/Source/WebKit/UIProcess/WebAuthentication/Cocoa/WebAuthenticationPanelClient.h
+++ b/Source/WebKit/UIProcess/WebAuthentication/Cocoa/WebAuthenticationPanelClient.h
@@ -50,7 +50,6 @@
     void updatePanel(WebAuthenticationStatus) const final;
     void dismissPanel(WebAuthenticationResult) const final;
     void requestPin(uint64_t, CompletionHandler<void(const WTF::String&)>&&) const final;
-    void selectAssertionResponse(const HashSet<Ref<WebCore::AuthenticatorAssertionResponse>>&, CompletionHandler<void(const WebCore::AuthenticatorAssertionResponse&)>&&) const final;
 
     _WKWebAuthenticationPanel *m_panel;
     WeakObjCPtr<id <_WKWebAuthenticationPanelDelegate> > m_delegate;
@@ -59,7 +58,6 @@
         bool panelUpdateWebAuthenticationPanel : 1;
         bool panelDismissWebAuthenticationPanelWithResult : 1;
         bool panelRequestPinWithRemainingRetriesCompletionHandler : 1;
-        bool panelselectAssertionResponseCompletionHandler : 1;
     } m_delegateMethods;
 };
 
diff --git a/Source/WebKit/UIProcess/WebAuthentication/Cocoa/WebAuthenticationPanelClient.mm b/Source/WebKit/UIProcess/WebAuthentication/Cocoa/WebAuthenticationPanelClient.mm
index 0c1bd4f..7f157bd 100644
--- a/Source/WebKit/UIProcess/WebAuthentication/Cocoa/WebAuthenticationPanelClient.mm
+++ b/Source/WebKit/UIProcess/WebAuthentication/Cocoa/WebAuthenticationPanelClient.mm
@@ -28,10 +28,8 @@
 
 #if ENABLE(WEB_AUTHN)
 
-#import "APIWebAuthenticationAssertionResponse.h"
 #import "CompletionHandlerCallChecker.h"
 #import "WebAuthenticationFlags.h"
-#import "_WKWebAuthenticationAssertionResponseInternal.h"
 #import "_WKWebAuthenticationPanel.h"
 #import <wtf/BlockPtr.h>
 #import <wtf/RunLoop.h>
@@ -45,7 +43,6 @@
     m_delegateMethods.panelUpdateWebAuthenticationPanel = [delegate respondsToSelector:@selector(panel:updateWebAuthenticationPanel:)];
     m_delegateMethods.panelDismissWebAuthenticationPanelWithResult = [delegate respondsToSelector:@selector(panel:dismissWebAuthenticationPanelWithResult:)];
     m_delegateMethods.panelRequestPinWithRemainingRetriesCompletionHandler = [delegate respondsToSelector:@selector(panel:requestPINWithRemainingRetries:completionHandler:)];
-    m_delegateMethods.panelselectAssertionResponseCompletionHandler = [delegate respondsToSelector:@selector(panel:selectAssertionResponse:completionHandler:)];
 }
 
 RetainPtr<id <_WKWebAuthenticationPanelDelegate> > WebAuthenticationPanelClient::delegate()
@@ -65,7 +62,6 @@
 
 void WebAuthenticationPanelClient::updatePanel(WebAuthenticationStatus status) const
 {
-    // FIXME(206248)
     // Call delegates in the next run loop to prevent clients' reentrance that would potentially modify the state
     // of the current run loop in unexpected ways.
     RunLoop::main().dispatch([weakThis = makeWeakPtr(*this), this, status] {
@@ -97,7 +93,6 @@
 
 void WebAuthenticationPanelClient::dismissPanel(WebAuthenticationResult result) const
 {
-    // FIXME(206248)
     // Call delegates in the next run loop to prevent clients' reentrance that would potentially modify the state
     // of the current run loop in unexpected ways.
     RunLoop::main().dispatch([weakThis = makeWeakPtr(*this), this, result] {
@@ -117,7 +112,6 @@
 
 void WebAuthenticationPanelClient::requestPin(uint64_t retries, CompletionHandler<void(const WTF::String&)>&& completionHandler) const
 {
-    // FIXME(206248)
     // Call delegates in the next run loop to prevent clients' reentrance that would potentially modify the state
     // of the current run loop in unexpected ways.
     RunLoop::main().dispatch([weakThis = makeWeakPtr(*this), this, retries, completionHandler = WTFMove(completionHandler)] () mutable {
@@ -147,43 +141,6 @@
     });
 }
 
-void WebAuthenticationPanelClient::selectAssertionResponse(const HashSet<Ref<WebCore::AuthenticatorAssertionResponse>>& responses, CompletionHandler<void(const WebCore::AuthenticatorAssertionResponse&)>&& completionHandler) const
-{
-    ASSERT(!responses.isEmpty());
-    auto nsResponses = adoptNS([[NSMutableArray alloc] initWithCapacity:responses.size()]);
-    for (auto& response : responses)
-        [nsResponses addObject:wrapper(API::WebAuthenticationAssertionResponse::create(response.copyRef()))];
-
-    // FIXME(206248)
-    // Call delegates in the next run loop to prevent clients' reentrance that would potentially modify the state
-    // of the current run loop in unexpected ways.
-    RunLoop::main().dispatch([weakThis = makeWeakPtr(*this), this, nsResponses = WTFMove(nsResponses), completionHandler = WTFMove(completionHandler)] () mutable {
-        if (!weakThis) {
-            completionHandler(static_cast<API::WebAuthenticationAssertionResponse&>([[nsResponses firstObject] _apiObject]).response());
-            return;
-        }
-
-        if (!m_delegateMethods.panelselectAssertionResponseCompletionHandler) {
-            completionHandler(static_cast<API::WebAuthenticationAssertionResponse&>([[nsResponses firstObject] _apiObject]).response());
-            return;
-        }
-
-        auto delegate = m_delegate.get();
-        if (!delegate) {
-            completionHandler(static_cast<API::WebAuthenticationAssertionResponse&>([[nsResponses firstObject] _apiObject]).response());
-            return;
-        }
-
-        auto checker = CompletionHandlerCallChecker::create(delegate.get(), @selector(panel:selectAssertionResponse:completionHandler:));
-        [delegate panel:m_panel selectAssertionResponse:nsResponses.get() completionHandler:makeBlockPtr([completionHandler = WTFMove(completionHandler), checker = WTFMove(checker)](_WKWebAuthenticationAssertionResponse *response) mutable {
-            if (checker->completionHandlerHasBeenCalled())
-                return;
-            checker->didCallCompletionHandler();
-            completionHandler(static_cast<API::WebAuthenticationAssertionResponse&>([response _apiObject]).response());
-        }).get()];
-    });
-}
-
 } // namespace WebKit
 
 #endif // ENABLE(WEB_AUTHN)
diff --git a/Source/WebKit/UIProcess/WebAuthentication/fido/CtapAuthenticator.cpp b/Source/WebKit/UIProcess/WebAuthentication/fido/CtapAuthenticator.cpp
index 9a0a8db..3c3f96218a 100644
--- a/Source/WebKit/UIProcess/WebAuthentication/fido/CtapAuthenticator.cpp
+++ b/Source/WebKit/UIProcess/WebAuthentication/fido/CtapAuthenticator.cpp
@@ -151,11 +151,11 @@
 
     if (!m_remainingAssertionResponses) {
         if (auto* observer = this->observer()) {
-            observer->selectAssertionResponse(m_assertionResponses, [this, weakThis = makeWeakPtr(*this)] (const AuthenticatorAssertionResponse& response) {
+            observer->selectAssertionResponses(m_assertionResponses, [this, weakThis = makeWeakPtr(*this)] (const Ref<AuthenticatorAssertionResponse>& response) {
                 ASSERT(RunLoop::isMain());
                 if (!weakThis)
                     return;
-                auto returnResponse = m_assertionResponses.take(const_cast<AuthenticatorAssertionResponse*>(&response));
+                auto returnResponse = m_assertionResponses.take(response);
                 if (!returnResponse)
                     return;
                 receiveRespond(WTFMove(*returnResponse));
diff --git a/Source/WebKit/UIProcess/WebAuthentication/fido/FidoAuthenticator.cpp b/Source/WebKit/UIProcess/WebAuthentication/fido/FidoAuthenticator.cpp
index 6b51bf9..6f7fb53 100644
--- a/Source/WebKit/UIProcess/WebAuthentication/fido/FidoAuthenticator.cpp
+++ b/Source/WebKit/UIProcess/WebAuthentication/fido/FidoAuthenticator.cpp
@@ -28,8 +28,6 @@
 
 #if ENABLE(WEB_AUTHN)
 
-#include "CtapDriver.h"
-
 namespace WebKit {
 
 FidoAuthenticator::FidoAuthenticator(std::unique_ptr<CtapDriver>&& driver)
diff --git a/Source/WebKit/WebKit.xcodeproj/project.pbxproj b/Source/WebKit/WebKit.xcodeproj/project.pbxproj
index 370a9b5..b19433a 100644
--- a/Source/WebKit/WebKit.xcodeproj/project.pbxproj
+++ b/Source/WebKit/WebKit.xcodeproj/project.pbxproj
@@ -1098,9 +1098,6 @@
 		577FF7822346E81C004EDFB9 /* APIWebAuthenticationPanelClient.h in Headers */ = {isa = PBXBuildFile; fileRef = 577FF7812346E81C004EDFB9 /* APIWebAuthenticationPanelClient.h */; };
 		577FF7852346ECAA004EDFB9 /* WebAuthenticationPanelClient.h in Headers */ = {isa = PBXBuildFile; fileRef = 577FF7832346ECAA004EDFB9 /* WebAuthenticationPanelClient.h */; };
 		578DC2982155A0020074E815 /* LocalAuthenticationSoftLink.h in Headers */ = {isa = PBXBuildFile; fileRef = 578DC2972155A0010074E815 /* LocalAuthenticationSoftLink.h */; };
-		579F1BF623C80DB600C7D4B4 /* _WKWebAuthenticationAssertionResponse.h in Headers */ = {isa = PBXBuildFile; fileRef = 579F1BF423C80DB600C7D4B4 /* _WKWebAuthenticationAssertionResponse.h */; settings = {ATTRIBUTES = (Private, ); }; };
-		579F1BF923C80EC600C7D4B4 /* _WKWebAuthenticationAssertionResponseInternal.h in Headers */ = {isa = PBXBuildFile; fileRef = 579F1BF823C80EC600C7D4B4 /* _WKWebAuthenticationAssertionResponseInternal.h */; };
-		579F1BFC23C811CF00C7D4B4 /* APIWebAuthenticationAssertionResponse.h in Headers */ = {isa = PBXBuildFile; fileRef = 579F1BFA23C811CF00C7D4B4 /* APIWebAuthenticationAssertionResponse.h */; };
 		57AC8F50217FEED90055438C /* HidConnection.h in Headers */ = {isa = PBXBuildFile; fileRef = 57AC8F4E217FEED90055438C /* HidConnection.h */; };
 		57B4B46020B504AC00D4AD79 /* ClientCertificateAuthenticationXPCConstants.h in Headers */ = {isa = PBXBuildFile; fileRef = 57B4B45E20B504AB00D4AD79 /* ClientCertificateAuthenticationXPCConstants.h */; };
 		57B826412304EB3E00B72EB0 /* NearFieldSPI.h in Headers */ = {isa = PBXBuildFile; fileRef = 57B826402304EB3E00B72EB0 /* NearFieldSPI.h */; };
@@ -3776,11 +3773,6 @@
 		577FF7832346ECAA004EDFB9 /* WebAuthenticationPanelClient.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = WebAuthenticationPanelClient.h; sourceTree = "<group>"; };
 		577FF7842346ECAA004EDFB9 /* WebAuthenticationPanelClient.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = WebAuthenticationPanelClient.mm; sourceTree = "<group>"; };
 		578DC2972155A0010074E815 /* LocalAuthenticationSoftLink.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = LocalAuthenticationSoftLink.h; sourceTree = "<group>"; };
-		579F1BF423C80DB600C7D4B4 /* _WKWebAuthenticationAssertionResponse.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = _WKWebAuthenticationAssertionResponse.h; sourceTree = "<group>"; };
-		579F1BF523C80DB600C7D4B4 /* _WKWebAuthenticationAssertionResponse.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = _WKWebAuthenticationAssertionResponse.mm; sourceTree = "<group>"; };
-		579F1BF823C80EC600C7D4B4 /* _WKWebAuthenticationAssertionResponseInternal.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = _WKWebAuthenticationAssertionResponseInternal.h; sourceTree = "<group>"; };
-		579F1BFA23C811CF00C7D4B4 /* APIWebAuthenticationAssertionResponse.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = APIWebAuthenticationAssertionResponse.h; sourceTree = "<group>"; };
-		579F1BFB23C811CF00C7D4B4 /* APIWebAuthenticationAssertionResponse.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = APIWebAuthenticationAssertionResponse.cpp; sourceTree = "<group>"; };
 		57AC8F4E217FEED90055438C /* HidConnection.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = HidConnection.h; sourceTree = "<group>"; };
 		57AC8F4F217FEED90055438C /* HidConnection.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = HidConnection.mm; sourceTree = "<group>"; };
 		57B4B45D20B504AB00D4AD79 /* AuthenticationManagerCocoa.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = AuthenticationManagerCocoa.mm; sourceTree = "<group>"; };
@@ -6883,9 +6875,6 @@
 				1A81B37F18BD66AD0007FDAC /* _WKVisitedLinkStore.h */,
 				1A81B37E18BD66AD0007FDAC /* _WKVisitedLinkStore.mm */,
 				1A81B38418BD673A0007FDAC /* _WKVisitedLinkStoreInternal.h */,
-				579F1BF423C80DB600C7D4B4 /* _WKWebAuthenticationAssertionResponse.h */,
-				579F1BF523C80DB600C7D4B4 /* _WKWebAuthenticationAssertionResponse.mm */,
-				579F1BF823C80EC600C7D4B4 /* _WKWebAuthenticationAssertionResponseInternal.h */,
 				574728CF23456E98001700AF /* _WKWebAuthenticationPanel.h */,
 				574728D023456E98001700AF /* _WKWebAuthenticationPanel.mm */,
 				574728D3234570AE001700AF /* _WKWebAuthenticationPanelInternal.h */,
@@ -8568,8 +8557,6 @@
 				7C89D2921A67122F003A5FDE /* APIUserScript.h */,
 				2D8786211BDB58FF00D02ABB /* APIUserStyleSheet.cpp */,
 				2D8786221BDB58FF00D02ABB /* APIUserStyleSheet.h */,
-				579F1BFB23C811CF00C7D4B4 /* APIWebAuthenticationAssertionResponse.cpp */,
-				579F1BFA23C811CF00C7D4B4 /* APIWebAuthenticationAssertionResponse.h */,
 				57EBE269234676C5008D8AF9 /* APIWebAuthenticationPanel.cpp */,
 				57EBE268234676C5008D8AF9 /* APIWebAuthenticationPanel.h */,
 				577FF7812346E81C004EDFB9 /* APIWebAuthenticationPanelClient.h */,
@@ -9942,8 +9929,6 @@
 				2D8786201BDB57F500D02ABB /* _WKUserStyleSheetInternal.h in Headers */,
 				1A81B38118BD66AD0007FDAC /* _WKVisitedLinkStore.h in Headers */,
 				1A81B38518BD673A0007FDAC /* _WKVisitedLinkStoreInternal.h in Headers */,
-				579F1BF623C80DB600C7D4B4 /* _WKWebAuthenticationAssertionResponse.h in Headers */,
-				579F1BF923C80EC600C7D4B4 /* _WKWebAuthenticationAssertionResponseInternal.h in Headers */,
 				574728D123456E98001700AF /* _WKWebAuthenticationPanel.h in Headers */,
 				574728D4234570AE001700AF /* _WKWebAuthenticationPanelInternal.h in Headers */,
 				1AE286781C7E76510069AC4F /* _WKWebsiteDataSize.h in Headers */,
@@ -10026,7 +10011,6 @@
 				2D8786241BDB58FF00D02ABB /* APIUserStyleSheet.h in Headers */,
 				C5E1AFED16B21017006CC1F2 /* APIWebArchive.h in Headers */,
 				C5E1AFEF16B21029006CC1F2 /* APIWebArchiveResource.h in Headers */,
-				579F1BFC23C811CF00C7D4B4 /* APIWebAuthenticationAssertionResponse.h in Headers */,
 				57EBE26A234676C5008D8AF9 /* APIWebAuthenticationPanel.h in Headers */,
 				577FF7822346E81C004EDFB9 /* APIWebAuthenticationPanelClient.h in Headers */,
 				1AE286841C7F93860069AC4F /* APIWebsiteDataRecord.h in Headers */,
diff --git a/Tools/ChangeLog b/Tools/ChangeLog
index ef5c12b..4f9d750 100644
--- a/Tools/ChangeLog
+++ b/Tools/ChangeLog
@@ -1,3 +1,21 @@
+2020-01-14  Commit Queue  <commit-queue@webkit.org>
+
+        Unreviewed, rolling out r254533 and r254535.
+        https://bugs.webkit.org/show_bug.cgi?id=206263
+
+        Breaks iOS and macOS builds (Requested by ryanhaddad on
+        #webkit).
+
+        Reverted changesets:
+
+        "[WebAuthn] Implement SPI to tell UI clients to select
+        assertion responses"
+        https://bugs.webkit.org/show_bug.cgi?id=206112
+        https://trac.webkit.org/changeset/254533
+
+        "Unreviewed, a build fix after r254533"
+        https://trac.webkit.org/changeset/254535
+
 2020-01-14  Wenson Hsieh  <wenson_hsieh@apple.com>
 
         [iOS] Keyboard input is severely delayed after switching away from unresponsive tab
diff --git a/Tools/TestWebKitAPI/TestWebKitAPI.xcodeproj/project.pbxproj b/Tools/TestWebKitAPI/TestWebKitAPI.xcodeproj/project.pbxproj
index de31b1e..a2d41e6 100644
--- a/Tools/TestWebKitAPI/TestWebKitAPI.xcodeproj/project.pbxproj
+++ b/Tools/TestWebKitAPI/TestWebKitAPI.xcodeproj/project.pbxproj
@@ -368,7 +368,6 @@
 		5797FE331EB15AB100B2F4A0 /* navigation-client-default-crypto.html in Copy Resources */ = {isa = PBXBuildFile; fileRef = 5797FE321EB15A8900B2F4A0 /* navigation-client-default-crypto.html */; };
 		5798337E236019A4008E5547 /* web-authentication-make-credential-hid.html in Copy Resources */ = {isa = PBXBuildFile; fileRef = 5798337D2360196D008E5547 /* web-authentication-make-credential-hid.html */; };
 		579833922368FA37008E5547 /* web-authentication-get-assertion-nfc-multiple-tags.html in Copy Resources */ = {isa = PBXBuildFile; fileRef = 5798337B235EB65C008E5547 /* web-authentication-get-assertion-nfc-multiple-tags.html */; };
-		579F1C0123C93AF500C7D4B4 /* web-authentication-get-assertion-hid-multiple-accounts.html in Copy Resources */ = {isa = PBXBuildFile; fileRef = 579F1BFF23C92FD300C7D4B4 /* web-authentication-get-assertion-hid-multiple-accounts.html */; };
 		57A79857224AB34E00A7F6F1 /* WebCryptoMasterKey.mm in Sources */ = {isa = PBXBuildFile; fileRef = 57A79856224AB34E00A7F6F1 /* WebCryptoMasterKey.mm */; };
 		57C3FA661F7C248F009D4B80 /* WeakPtr.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CB9BC371A67482300FE5678 /* WeakPtr.cpp */; };
 		57C6244E2346BCFA00383FE7 /* _WKWebAuthenticationPanel.mm in Sources */ = {isa = PBXBuildFile; fileRef = 57C6244D2346BCFA00383FE7 /* _WKWebAuthenticationPanel.mm */; };
@@ -1485,7 +1484,6 @@
 				2EBD9D0A2134730D002DA758 /* video.html in Copy Resources */,
 				CD577799211CE0E4001B371E /* web-audio-only.html in Copy Resources */,
 				57663DF32357E48900E85E09 /* web-authentication-get-assertion-hid-cancel.html in Copy Resources */,
-				579F1C0123C93AF500C7D4B4 /* web-authentication-get-assertion-hid-multiple-accounts.html in Copy Resources */,
 				577454D02359B378008E1ED7 /* web-authentication-get-assertion-hid-no-credentials.html in Copy Resources */,
 				570D26FC23C3F87000D5CF67 /* web-authentication-get-assertion-hid-pin.html in Copy Resources */,
 				57663DEC234F1F9300E85E09 /* web-authentication-get-assertion-hid.html in Copy Resources */,
@@ -1951,7 +1949,6 @@
 		5798337B235EB65C008E5547 /* web-authentication-get-assertion-nfc-multiple-tags.html */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.html; path = "web-authentication-get-assertion-nfc-multiple-tags.html"; sourceTree = "<group>"; };
 		5798337D2360196D008E5547 /* web-authentication-make-credential-hid.html */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.html; path = "web-authentication-make-credential-hid.html"; sourceTree = "<group>"; };
 		5798E2AF1CAF5C2800C5CBA0 /* ProvisionalURLNotChange.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ProvisionalURLNotChange.mm; sourceTree = "<group>"; };
-		579F1BFF23C92FD300C7D4B4 /* web-authentication-get-assertion-hid-multiple-accounts.html */ = {isa = PBXFileReference; lastKnownFileType = text.html; path = "web-authentication-get-assertion-hid-multiple-accounts.html"; sourceTree = "<group>"; };
 		57A79856224AB34E00A7F6F1 /* WebCryptoMasterKey.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = WebCryptoMasterKey.mm; sourceTree = "<group>"; };
 		57C6244D2346BCFA00383FE7 /* _WKWebAuthenticationPanel.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = _WKWebAuthenticationPanel.mm; sourceTree = "<group>"; };
 		57C6244F2346C1EC00383FE7 /* web-authentication-get-assertion.html */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.html; path = "web-authentication-get-assertion.html"; sourceTree = "<group>"; };
@@ -3504,7 +3501,6 @@
 				CD57779B211CE6CE001B371E /* video-with-audio-and-web-audio.html */,
 				CD577798211CDE8F001B371E /* web-audio-only.html */,
 				57663DF22357E45D00E85E09 /* web-authentication-get-assertion-hid-cancel.html */,
-				579F1BFF23C92FD300C7D4B4 /* web-authentication-get-assertion-hid-multiple-accounts.html */,
 				577454CF2359B338008E1ED7 /* web-authentication-get-assertion-hid-no-credentials.html */,
 				570D26FB23C3F86500D5CF67 /* web-authentication-get-assertion-hid-pin.html */,
 				57663DEB234F1F8000E85E09 /* web-authentication-get-assertion-hid.html */,
diff --git a/Tools/TestWebKitAPI/Tests/WebKitCocoa/_WKWebAuthenticationPanel.mm b/Tools/TestWebKitAPI/Tests/WebKitCocoa/_WKWebAuthenticationPanel.mm
index a975833..0cb2478 100644
--- a/Tools/TestWebKitAPI/Tests/WebKitCocoa/_WKWebAuthenticationPanel.mm
+++ b/Tools/TestWebKitAPI/Tests/WebKitCocoa/_WKWebAuthenticationPanel.mm
@@ -35,10 +35,8 @@
 #import <WebKit/WKPreferencesPrivate.h>
 #import <WebKit/WKUIDelegatePrivate.h>
 #import <WebKit/_WKExperimentalFeature.h>
-#import <WebKit/_WKWebAuthenticationAssertionResponse.h>
 #import <WebKit/_WKWebAuthenticationPanel.h>
 #import <wtf/BlockPtr.h>
-#import <wtf/RandomNumber.h>
 #import <wtf/text/StringConcatenateNumbers.h>
 
 static bool webAuthenticationPanelRan = false;
@@ -48,7 +46,6 @@
 static bool webAuthenticationPanelUpdateNoCredentialsFound = false;
 static bool webAuthenticationPanelCancelImmediately = false;
 static String webAuthenticationPanelPin;
-static BOOL webAuthenticationPanelNullUserHandle = NO;
 
 @interface TestWebAuthenticationPanelDelegate : NSObject <_WKWebAuthenticationPanelDelegate>
 @end
@@ -94,20 +91,6 @@
     completionHandler(webAuthenticationPanelPin);
 }
 
-- (void)panel:(_WKWebAuthenticationPanel *)panel selectAssertionResponse:(NSArray < _WKWebAuthenticationAssertionResponse *> *)responses completionHandler:(void (^)(_WKWebAuthenticationAssertionResponse *))completionHandler
-{
-    EXPECT_EQ(responses.count, 2ul);
-    for (_WKWebAuthenticationAssertionResponse *response in responses) {
-        EXPECT_TRUE([response.name isEqual:@"johnpsmith@example.com"] || [response.name isEqual:@""]);
-        EXPECT_TRUE([response.displayName isEqual:@"John P. Smith"] || [response.displayName isEqual:@""]);
-        EXPECT_TRUE([[response.userHandle base64EncodedStringWithOptions:0] isEqual:@"MIIBkzCCATigAwIBAjCCAZMwggE4oAMCAQIwggGTMII="] || !response.userHandle);
-    }
-
-    auto index = weakRandomUint32() % 2;
-    webAuthenticationPanelNullUserHandle = responses[index].userHandle ? NO : YES;
-    completionHandler(responses[index]);
-}
-
 @end
 
 @interface TestWebAuthenticationPanelFakeDelegate : NSObject <_WKWebAuthenticationPanelDelegate>
@@ -889,40 +872,6 @@
     [webView waitForMessage:@"Succeeded!"];
 }
 
-TEST(WebAuthenticationPanel, MultipleAccountsNullDelegate)
-{
-    reset();
-    RetainPtr<NSURL> testURL = [[NSBundle mainBundle] URLForResource:@"web-authentication-get-assertion-hid-multiple-accounts" withExtension:@"html" subdirectory:@"TestWebKitAPI.resources"];
-
-    auto *configuration = [WKWebViewConfiguration _test_configurationWithTestPlugInClassName:@"WebProcessPlugInWithInternals" configureJSCForTesting:YES];
-    [[configuration preferences] _setEnabled:YES forExperimentalFeature:webAuthenticationExperimentalFeature()];
-
-    auto webView = adoptNS([[TestWKWebView alloc] initWithFrame:NSZeroRect configuration:configuration]);
-    auto delegate = adoptNS([[TestWebAuthenticationPanelUIDelegate alloc] init]);
-    [delegate setIsNull:true];
-    [webView setUIDelegate:delegate.get()];
-
-    [webView loadRequest:[NSURLRequest requestWithURL:testURL.get()]];
-    [webView waitForMessage:@"Succeeded!"];
-}
-
-TEST(WebAuthenticationPanel, MultipleAccounts)
-{
-    reset();
-    RetainPtr<NSURL> testURL = [[NSBundle mainBundle] URLForResource:@"web-authentication-get-assertion-hid-multiple-accounts" withExtension:@"html" subdirectory:@"TestWebKitAPI.resources"];
-
-    auto *configuration = [WKWebViewConfiguration _test_configurationWithTestPlugInClassName:@"WebProcessPlugInWithInternals" configureJSCForTesting:YES];
-    [[configuration preferences] _setEnabled:YES forExperimentalFeature:webAuthenticationExperimentalFeature()];
-
-    auto webView = adoptNS([[TestWKWebView alloc] initWithFrame:NSZeroRect configuration:configuration]);
-    auto delegate = adoptNS([[TestWebAuthenticationPanelUIDelegate alloc] init]);
-    [webView setUIDelegate:delegate.get()];
-
-    [webView loadRequest:[NSURLRequest requestWithURL:testURL.get()]];
-    [webView waitForMessage:@"Succeeded!"];
-    EXPECT_EQ([[webView stringByEvaluatingJavaScript:@"userHandle"] isEqualToString:@"<null>"], webAuthenticationPanelNullUserHandle);
-}
-
 } // namespace TestWebKitAPI
 
 #endif // ENABLE(WEB_AUTHN)
diff --git a/Tools/TestWebKitAPI/Tests/WebKitCocoa/web-authentication-get-assertion-hid-multiple-accounts.html b/Tools/TestWebKitAPI/Tests/WebKitCocoa/web-authentication-get-assertion-hid-multiple-accounts.html
deleted file mode 100644
index d637e42..0000000
--- a/Tools/TestWebKitAPI/Tests/WebKitCocoa/web-authentication-get-assertion-hid-multiple-accounts.html
+++ /dev/null
@@ -1,56 +0,0 @@
-<input type="text" id="input">
-<script>
-    const testAssertionMessageLongBase64 =
-        "AKUBomJpZFhAKAitzuj+Tslzelf3/vZwIGtDQNgoKeFd5oEieYzhyzA65saf0tK2" +
-        "w/mooa7tQtGgDdwZIjOhjcuZ0pQ1ajoE4GR0eXBlanB1YmxpYy1rZXkCWCVGzH+5" +
-        "Z51VstuQkuHI2eXh0Ct1gPC0gSx3CWLh5I9a2AEAAABQA1hHMEUCIQCSFTuuBWgB" +
-        "4/F0VB7DlUVM09IHPmxe1MzHUwRoCRZbCAIgGKov6xoAx2MEf6/6qNs8OutzhP2C" +
-        "QoJ1L7Fe64G9uBcEpGJpZFggMIIBkzCCATigAwIBAjCCAZMwggE4oAMCAQIwggGT" +
-        "MIJkaWNvbngoaHR0cHM6Ly9waWNzLmFjbWUuY29tLzAwL3AvYUJqampwcVBiLnBu" +
-        "Z2RuYW1ldmpvaG5wc21pdGhAZXhhbXBsZS5jb21rZGlzcGxheU5hbWVtSm9obiBQ" +
-        "LiBTbWl0aAUC";
-    const testAssertionMessageBase64 =
-        "AKMBomJpZFhAKAitzuj+Tslzelf3/vZwIGtDQNgoKeFd5oEieYzhyzA65saf0tK2" +
-        "w/mooa7tQtGgDdwZIjOhjcuZ0pQ1ajoE4GR0eXBlanB1YmxpYy1rZXkCWCVGzH+5" +
-        "Z51VstuQkuHI2eXh0Ct1gPC0gSx3CWLh5I9a2AEAAABQA1hHMEUCIQCSFTuuBWgB" +
-        "4/F0VB7DlUVM09IHPmxe1MzHUwRoCRZbCAIgGKov6xoAx2MEf6/6qNs8OutzhP2C" +
-        "QoJ1L7Fe64G9uBc=";
-    if (window.internals) {
-        internals.setMockWebAuthenticationConfiguration({ silentFailure: true, hid: { payloadBase64: [testAssertionMessageLongBase64, testAssertionMessageBase64] } });
-        internals.withUserGesture(() => { input.focus(); });
-    }
-
-    function bytesToHexString(bytes)
-    {
-        if (!bytes)
-            return null;
-
-        bytes = new Uint8Array(bytes);
-        var hexBytes = [];
-
-        for (var i = 0; i < bytes.length; ++i) {
-            var byteString = bytes[i].toString(16);
-            if (byteString.length < 2)
-                byteString = "0" + byteString;
-            hexBytes.push(byteString);
-        }
-
-        return hexBytes.join("");
-    }
-
-    const options = {
-        publicKey: {
-            challenge: new Uint8Array(16),
-            timeout: 1000
-        }
-    };
-
-    navigator.credentials.get(options).then(credential => {
-        userHandle = bytesToHexString(credential.response.userHandle);
-        // console.log("Succeeded!");
-        window.webkit.messageHandlers.testHandler.postMessage("Succeeded!");
-    }, error => {
-        // console.log(error.message);
-        window.webkit.messageHandlers.testHandler.postMessage(error.message);
-    });
-</script>
diff --git a/Tools/TestWebKitAPI/Tests/WebKitCocoa/web-authentication-make-credential-hid.html b/Tools/TestWebKitAPI/Tests/WebKitCocoa/web-authentication-make-credential-hid.html
index e981a70..5b6aebe 100644
--- a/Tools/TestWebKitAPI/Tests/WebKitCocoa/web-authentication-make-credential-hid.html
+++ b/Tools/TestWebKitAPI/Tests/WebKitCocoa/web-authentication-make-credential-hid.html
@@ -39,7 +39,7 @@
             },
             challenge: new Uint8Array(16),
             pubKeyCredParams: [{ type: "public-key", alg: -7 }],
-            timeout: 100,
+            timeout: 100
         }
     };