diff --git a/config/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcTests.java b/config/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcTests.java
index ec0322aa5af..06bcea879ea 100644
--- a/config/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcTests.java
+++ b/config/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcTests.java
@@ -79,6 +79,7 @@
 import org.springframework.security.oauth2.jwt.Jwt;
 import org.springframework.security.oauth2.jwt.JwtDecoder;
 import org.springframework.security.oauth2.jwt.NimbusJwtEncoder;
+import org.springframework.security.oauth2.server.authorization.InMemoryOAuth2AuthorizationService;
 import org.springframework.security.oauth2.server.authorization.JdbcOAuth2AuthorizationService;
 import org.springframework.security.oauth2.server.authorization.OAuth2Authorization;
 import org.springframework.security.oauth2.server.authorization.OAuth2AuthorizationCode;
@@ -99,6 +100,8 @@
 import org.springframework.security.oauth2.server.authorization.token.OAuth2TokenCustomizer;
 import org.springframework.security.oauth2.server.authorization.token.OAuth2TokenGenerator;
 import org.springframework.security.web.SecurityFilterChain;
+import org.springframework.security.web.webauthn.api.TestPublicKeyCredentialUserEntities;
+import org.springframework.security.web.webauthn.authentication.WebAuthnAuthentication;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.MvcResult;
 import org.springframework.util.LinkedMultiValueMap;
@@ -113,6 +116,7 @@
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
+import static org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.authentication;
 import static org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.user;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
@@ -324,6 +328,52 @@ public void requestWhenRefreshTokenRequestThenIdTokenContainsSidClaim() throws E
 		assertThat(idToken.<String>getClaim("sid")).isEqualTo(sidClaim);
 	}
 
+	// gh-19202
+	@Test
+	public void requestWhenWebAuthnAuthenticationThenIdTokenContainsSidAndAuthTimeClaims() throws Exception {
+		this.spring.register(AuthorizationServerConfigurationWithWebAuthn.class).autowire();
+
+		RegisteredClient registeredClient = TestRegisteredClients.registeredClient().scope(OidcScopes.OPENID).build();
+		this.registeredClientRepository.save(registeredClient);
+
+		WebAuthnAuthentication webAuthnAuthentication = new WebAuthnAuthentication(
+				TestPublicKeyCredentialUserEntities.userEntity().build(),
+				List.of(FactorGrantedAuthority.fromAuthority(FactorGrantedAuthority.WEBAUTHN_AUTHORITY)));
+
+		MultiValueMap<String, String> authorizationRequestParameters = getAuthorizationRequestParameters(
+				registeredClient);
+		MvcResult mvcResult = this.mvc
+			.perform(get(DEFAULT_AUTHORIZATION_ENDPOINT_URI).queryParams(authorizationRequestParameters)
+				.with(authentication(webAuthnAuthentication)))
+			.andExpect(status().is3xxRedirection())
+			.andReturn();
+		String redirectedUrl = mvcResult.getResponse().getRedirectedUrl();
+		assertThat(redirectedUrl).matches(".+\\?code=.{15,}&state=state");
+
+		String authorizationCode = extractParameterFromRedirectUri(redirectedUrl, "code");
+		OAuth2Authorization authorization = this.authorizationService.findByToken(authorizationCode,
+				AUTHORIZATION_CODE_TOKEN_TYPE);
+
+		mvcResult = this.mvc
+			.perform(post(DEFAULT_TOKEN_ENDPOINT_URI).params(getTokenRequestParameters(registeredClient, authorization))
+				.header(HttpHeaders.AUTHORIZATION,
+						"Basic " + encodeBasicAuth(registeredClient.getClientId(), registeredClient.getClientSecret())))
+			.andExpect(status().isOk())
+			.andReturn();
+
+		MockHttpServletResponse servletResponse = mvcResult.getResponse();
+		MockClientHttpResponse httpResponse = new MockClientHttpResponse(servletResponse.getContentAsByteArray(),
+				HttpStatus.valueOf(servletResponse.getStatus()));
+		OAuth2AccessTokenResponse accessTokenResponse = accessTokenHttpResponseConverter
+			.read(OAuth2AccessTokenResponse.class, httpResponse);
+
+		Jwt idToken = this.jwtDecoder
+			.decode((String) accessTokenResponse.getAdditionalParameters().get(OidcParameterNames.ID_TOKEN));
+
+		assertThat(idToken.<String>getClaim("sid")).isNotNull();
+		assertThat(idToken.<Object>getClaim("auth_time")).isNotNull();
+	}
+
 	@Test
 	public void requestWhenLogoutRequestThenLogout() throws Exception {
 		this.spring.register(AuthorizationServerConfiguration.class).autowire();
@@ -696,6 +746,23 @@ SessionRegistry sessionRegistry() {
 
 	}
 
+	// gh-19202
+	// Uses InMemoryOAuth2AuthorizationService to avoid Jackson serialization complexity
+	// when storing WebAuthnAuthentication (which requires both Jackson 2 and 3 WebAuthn
+	// modules to be registered in JdbcOAuth2AuthorizationService).
+	@EnableWebSecurity
+	@Configuration
+	static class AuthorizationServerConfigurationWithWebAuthn extends AuthorizationServerConfiguration {
+
+		@Bean
+		@Override
+		OAuth2AuthorizationService authorizationService(JdbcOperations jdbcOperations,
+				RegisteredClientRepository registeredClientRepository) {
+			return new InMemoryOAuth2AuthorizationService();
+		}
+
+	}
+
 	@EnableWebSecurity
 	@Configuration
 	static class AuthorizationServerConfigurationWithTokenGenerator extends AuthorizationServerConfiguration {
diff --git a/webauthn/src/main/java/org/springframework/security/web/webauthn/api/PublicKeyCredentialUserEntity.java b/webauthn/src/main/java/org/springframework/security/web/webauthn/api/PublicKeyCredentialUserEntity.java
index 269cc750e58..b0359bad33a 100644
--- a/webauthn/src/main/java/org/springframework/security/web/webauthn/api/PublicKeyCredentialUserEntity.java
+++ b/webauthn/src/main/java/org/springframework/security/web/webauthn/api/PublicKeyCredentialUserEntity.java
@@ -20,6 +20,7 @@
 
 import org.jspecify.annotations.Nullable;
 
+import org.springframework.security.core.AuthenticatedPrincipal;
 import org.springframework.security.web.webauthn.management.RelyingPartyAuthenticationRequest;
 import org.springframework.security.web.webauthn.management.WebAuthnRelyingPartyOperations;
 
@@ -34,7 +35,7 @@
  * @since 6.4
  * @see WebAuthnRelyingPartyOperations#authenticate(RelyingPartyAuthenticationRequest)
  */
-public interface PublicKeyCredentialUserEntity extends Serializable {
+public interface PublicKeyCredentialUserEntity extends Serializable, AuthenticatedPrincipal {
 
 	/**
 	 * The <a href=
@@ -42,6 +43,7 @@ public interface PublicKeyCredentialUserEntity extends Serializable {
 	 * property is a human-palatable identifier for a user account.
 	 * @return the name
 	 */
+	@Override
 	String getName();
 
 	/**
diff --git a/webauthn/src/test/java/org/springframework/security/web/webauthn/authentication/WebAuthnAuthenticationTests.java b/webauthn/src/test/java/org/springframework/security/web/webauthn/authentication/WebAuthnAuthenticationTests.java
index 409e05623e5..5051c1729ac 100644
--- a/webauthn/src/test/java/org/springframework/security/web/webauthn/authentication/WebAuthnAuthenticationTests.java
+++ b/webauthn/src/test/java/org/springframework/security/web/webauthn/authentication/WebAuthnAuthenticationTests.java
@@ -16,11 +16,14 @@
 
 package org.springframework.security.web.webauthn.authentication;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.security.authentication.AbstractAuthenticationToken;
+import org.springframework.security.core.AuthenticatedPrincipal;
 import org.springframework.security.core.GrantedAuthority;
 import org.springframework.security.core.authority.AuthorityUtils;
 import org.springframework.security.web.webauthn.api.PublicKeyCredentialUserEntity;
@@ -56,6 +59,43 @@ void setAuthenticationWhenFalseThenNotAuthenticated() {
 		assertThat(authentication.isAuthenticated()).isFalse();
 	}
 
+	@Test
+	void getNameReturnsUserEntityName() {
+		PublicKeyCredentialUserEntity userEntity = TestPublicKeyCredentialUserEntities.userEntity().build();
+		WebAuthnAuthentication authentication = new WebAuthnAuthentication(userEntity,
+				AuthorityUtils.createAuthorityList("ROLE_USER"));
+		assertThat(authentication.getName()).isEqualTo(userEntity.getName());
+	}
+
+	// gh-19202
+	@Test
+	void principalImplementsAuthenticatedPrincipal() {
+		PublicKeyCredentialUserEntity userEntity = TestPublicKeyCredentialUserEntities.userEntity().build();
+		assertThat(userEntity).isInstanceOf(AuthenticatedPrincipal.class);
+		assertThat(((AuthenticatedPrincipal) userEntity).getName()).isEqualTo(userEntity.getName());
+	}
+
+	// gh-19202
+	// Simulates the name-extraction logic used internally by SpringSessionBackedSessionRegistry.
+	// Before the fix, AbstractAuthenticationToken falls through to toString() because
+	// PublicKeyCredentialUserEntity did not implement AuthenticatedPrincipal.
+	@Test
+	void principalNameResolvableViaAbstractAuthenticationToken() {
+		PublicKeyCredentialUserEntity userEntity = TestPublicKeyCredentialUserEntities.userEntity().build();
+		AbstractAuthenticationToken wrapper = new AbstractAuthenticationToken(Collections.emptyList()) {
+			@Override
+			public Object getPrincipal() {
+				return userEntity;
+			}
+
+			@Override
+			public Object getCredentials() {
+				return null;
+			}
+		};
+		assertThat(wrapper.getName()).isEqualTo(userEntity.getName());
+	}
+
 	@Test
 	void toBuilderWhenApplyThenCopies() {
 		PublicKeyCredentialUserEntity alice = TestPublicKeyCredentialUserEntities.userEntity().build();