feat: last-ADMIN guard and password hardening (#87, #89)

- Prevent removal of last ADMIN role via role unassign, user delete,
  or group role removal (returns 409 Conflict)
- Add password policy: min 12 chars, 3/4 character classes, no username
- Add brute-force protection: 5 attempts then 15min lockout, IP rate limit
- Add token revocation on password change via token_revoked_before column
- V9 migration adds failed_login_attempts, locked_until, token_revoked_before

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cameleer3-server-app/src/main/java/com/cameleer3/server/app/controller/GroupAdminController.java

@@ -6,10 +6,13 @@ import com.cameleer3.server.core.admin.AuditService;
 import com.cameleer3.server.core.rbac.GroupDetail;
 import com.cameleer3.server.core.rbac.GroupRepository;
 import com.cameleer3.server.core.rbac.GroupSummary;
+import com.cameleer3.server.core.rbac.RbacService;
+import com.cameleer3.server.core.rbac.SystemRole;
 import io.swagger.v3.oas.annotations.Operation;
 import io.swagger.v3.oas.annotations.responses.ApiResponse;
 import io.swagger.v3.oas.annotations.tags.Tag;
 import jakarta.servlet.http.HttpServletRequest;
+import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.access.prepost.PreAuthorize;
 import org.springframework.web.bind.annotation.DeleteMapping;
@@ -20,6 +23,7 @@ import org.springframework.web.bind.annotation.PutMapping;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.server.ResponseStatusException;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -39,10 +43,13 @@ public class GroupAdminController {
 
     private final GroupRepository groupRepository;
     private final AuditService auditService;
+    private final RbacService rbacService;
 
-    public GroupAdminController(GroupRepository groupRepository, AuditService auditService) {
+    public GroupAdminController(GroupRepository groupRepository, AuditService auditService,
+                                RbacService rbacService) {
         this.groupRepository = groupRepository;
         this.auditService = auditService;
+        this.rbacService = rbacService;
     }
 
     @GetMapping
@@ -152,6 +159,10 @@ public class GroupAdminController {
         if (groupRepository.findById(id).isEmpty()) {
             return ResponseEntity.notFound().build();
         }
+        if (SystemRole.ADMIN_ID.equals(roleId) && rbacService.getEffectivePrincipalsForRole(SystemRole.ADMIN_ID).size() <= 1) {
+            throw new ResponseStatusException(HttpStatus.CONFLICT,
+                    "Cannot remove the ADMIN role: at least one admin user must exist");
+        }
         groupRepository.removeRole(id, roleId);
         auditService.log("remove_role_from_group", AuditCategory.RBAC, id.toString(),
                 Map.of("roleId", roleId), AuditResult.SUCCESS, httpRequest);

cameleer3-server-app/src/main/java/com/cameleer3/server/app/controller/UserAdminController.java

@@ -7,6 +7,7 @@ import com.cameleer3.server.core.admin.AuditService;
 import com.cameleer3.server.core.rbac.RbacService;
 import com.cameleer3.server.core.rbac.SystemRole;
 import com.cameleer3.server.core.rbac.UserDetail;
+import com.cameleer3.server.core.security.PasswordPolicyValidator;
 import com.cameleer3.server.core.security.UserInfo;
 import com.cameleer3.server.core.security.UserRepository;
 import io.swagger.v3.oas.annotations.Operation;
@@ -14,6 +15,7 @@ import io.swagger.v3.oas.annotations.responses.ApiResponse;
 import io.swagger.v3.oas.annotations.tags.Tag;
 import jakarta.servlet.http.HttpServletRequest;
 import jakarta.validation.Valid;
+import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.access.prepost.PreAuthorize;
 import org.springframework.web.bind.annotation.DeleteMapping;
@@ -24,6 +26,7 @@ import org.springframework.web.bind.annotation.PutMapping;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.server.ResponseStatusException;
 
 import com.cameleer3.server.app.security.SecurityProperties;
 import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
@@ -33,6 +36,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.UUID;
 
+
 /**
  * Admin endpoints for user management.
  * Protected by {@code ROLE_ADMIN}.
@@ -95,6 +99,11 @@ public class UserAdminController {
                 Instant.now());
         userRepository.upsert(user);
         if (request.password() != null && !request.password().isBlank()) {
+            List<String> violations = PasswordPolicyValidator.validate(request.password(), request.username());
+            if (!violations.isEmpty()) {
+                throw new ResponseStatusException(HttpStatus.BAD_REQUEST,
+                        "Password policy violation: " + String.join("; ", violations));
+            }
             userRepository.setPassword(userId, passwordEncoder.encode(request.password()));
         }
         rbacService.assignRoleToUser(userId, SystemRole.VIEWER_ID);
@@ -175,8 +184,14 @@ public class UserAdminController {
     @DeleteMapping("/{userId}")
     @Operation(summary = "Delete user")
     @ApiResponse(responseCode = "204", description = "User deleted")
+    @ApiResponse(responseCode = "409", description = "Cannot delete the last admin user")
     public ResponseEntity<Void> deleteUser(@PathVariable String userId,
                                             HttpServletRequest httpRequest) {
+        boolean isAdmin = rbacService.getEffectiveRolesForUser(userId).stream()
+                .anyMatch(r -> r.id().equals(SystemRole.ADMIN_ID));
+        if (isAdmin && rbacService.getEffectivePrincipalsForRole(SystemRole.ADMIN_ID).size() <= 1) {
+            throw new ResponseStatusException(HttpStatus.CONFLICT, "Cannot delete the last admin user");
+        }
         userRepository.delete(userId);
         auditService.log("delete_user", AuditCategory.USER_MGMT, userId,
                 null, AuditResult.SUCCESS, httpRequest);
@@ -186,7 +201,7 @@ public class UserAdminController {
     @PostMapping("/{userId}/password")
     @Operation(summary = "Reset user password")
     @ApiResponse(responseCode = "204", description = "Password reset")
-    @ApiResponse(responseCode = "400", description = "Disabled in OIDC mode")
+    @ApiResponse(responseCode = "400", description = "Disabled in OIDC mode or policy violation")
     public ResponseEntity<Void> resetPassword(
             @PathVariable String userId,
             @Valid @RequestBody SetPasswordRequest request,
@@ -194,7 +209,16 @@ public class UserAdminController {
         if (oidcEnabled) {
             return ResponseEntity.badRequest().build();
         }
+        // Extract bare username from "user:username" format for policy check
+        String username = userId.startsWith("user:") ? userId.substring(5) : userId;
+        List<String> violations = PasswordPolicyValidator.validate(request.password(), username);
+        if (!violations.isEmpty()) {
+            throw new ResponseStatusException(HttpStatus.BAD_REQUEST,
+                    "Password policy violation: " + String.join("; ", violations));
+        }
         userRepository.setPassword(userId, passwordEncoder.encode(request.password()));
+        // Revoke all existing tokens so the user must re-authenticate with the new password
+        userRepository.revokeTokensBefore(userId, Instant.now());
         auditService.log("reset_password", AuditCategory.USER_MGMT, userId, null, AuditResult.SUCCESS, httpRequest);
         return ResponseEntity.noContent().build();
     }

cameleer3-server-app/src/main/java/com/cameleer3/server/app/rbac/RbacServiceImpl.java

@@ -5,12 +5,15 @@ import com.cameleer3.server.core.rbac.GroupSummary;
 import com.cameleer3.server.core.rbac.RbacService;
 import com.cameleer3.server.core.rbac.RbacStats;
 import com.cameleer3.server.core.rbac.RoleSummary;
+import com.cameleer3.server.core.rbac.SystemRole;
 import com.cameleer3.server.core.rbac.UserDetail;
 import com.cameleer3.server.core.rbac.UserSummary;
 import com.cameleer3.server.core.security.UserInfo;
 import com.cameleer3.server.core.security.UserRepository;
+import org.springframework.http.HttpStatus;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.stereotype.Service;
+import org.springframework.web.server.ResponseStatusException;
 
 import java.util.*;
 
@@ -63,6 +66,10 @@ public class RbacServiceImpl implements RbacService {
 
     @Override
     public void removeRoleFromUser(String userId, UUID roleId) {
+        if (SystemRole.ADMIN_ID.equals(roleId) && getEffectivePrincipalsForRole(SystemRole.ADMIN_ID).size() <= 1) {
+            throw new ResponseStatusException(HttpStatus.CONFLICT,
+                    "Cannot remove the ADMIN role: at least one admin user must exist");
+        }
         jdbc.update("DELETE FROM user_roles WHERE user_id = ? AND role_id = ?", userId, roleId);
     }
 

cameleer3-server-app/src/main/java/com/cameleer3/server/app/security/JwtAuthenticationFilter.java

@@ -4,6 +4,8 @@ import com.cameleer3.server.core.agent.AgentRegistryService;
 import com.cameleer3.server.core.rbac.SystemRole;
 import com.cameleer3.server.core.security.JwtService;
 import com.cameleer3.server.core.security.JwtService.JwtValidationResult;
+import com.cameleer3.server.core.security.UserInfo;
+import com.cameleer3.server.core.security.UserRepository;
 import jakarta.servlet.FilterChain;
 import jakarta.servlet.ServletException;
 import jakarta.servlet.http.HttpServletRequest;
@@ -19,6 +21,7 @@ import org.springframework.security.oauth2.jwt.JwtDecoder;
 import org.springframework.web.filter.OncePerRequestFilter;
 
 import java.io.IOException;
+import java.time.Instant;
 import java.util.List;
 
 /**
@@ -41,13 +44,16 @@ public class JwtAuthenticationFilter extends OncePerRequestFilter {
     private final JwtService jwtService;
     private final AgentRegistryService agentRegistryService;
     private final JwtDecoder oidcDecoder;
+    private final UserRepository userRepository;
 
     public JwtAuthenticationFilter(JwtService jwtService,
                                     AgentRegistryService agentRegistryService,
-                                    JwtDecoder oidcDecoder) {
+                                    JwtDecoder oidcDecoder,
+                                    UserRepository userRepository) {
         this.jwtService = jwtService;
         this.agentRegistryService = agentRegistryService;
         this.oidcDecoder = oidcDecoder;
+        this.userRepository = userRepository;
     }
 
     @Override
@@ -74,6 +80,16 @@ public class JwtAuthenticationFilter extends OncePerRequestFilter {
             JwtValidationResult result = jwtService.validateAccessToken(token);
             String subject = result.subject();
 
+            // Token revocation check: reject tokens issued before revocation timestamp
+            if (subject.startsWith("user:") && result.issuedAt() != null) {
+                userRepository.findById(subject).ifPresent(user -> {
+                    Instant revoked = user.tokenRevokedBefore();
+                    if (revoked != null && result.issuedAt().isBefore(revoked)) {
+                        throw new com.cameleer3.server.core.security.InvalidTokenException("Token revoked");
+                    }
+                });
+            }
+
             List<String> roles = result.roles();
             if (!subject.startsWith("user:") && roles.isEmpty()) {
                 roles = List.of("AGENT");

cameleer3-server-app/src/main/java/com/cameleer3/server/app/security/JwtServiceImpl.java

@@ -148,7 +148,10 @@ public class JwtServiceImpl implements JwtService {
 
             String environment = claims.getStringClaim("env");
 
-            return new JwtValidationResult(subject, application, environment, roles);
+            Date issueTime = claims.getIssueTime();
+            Instant issuedAt = issueTime != null ? issueTime.toInstant() : null;
+
+            return new JwtValidationResult(subject, application, environment, roles, issuedAt);
         } catch (ParseException e) {
             throw new InvalidTokenException("Failed to parse JWT", e);
         } catch (JOSEException e) {

cameleer3-server-app/src/main/java/com/cameleer3/server/app/security/SecurityConfig.java

@@ -2,6 +2,7 @@ package com.cameleer3.server.app.security;
 
 import com.cameleer3.server.core.agent.AgentRegistryService;
 import com.cameleer3.server.core.security.JwtService;
+import com.cameleer3.server.core.security.UserRepository;
 import com.nimbusds.jose.jwk.source.JWKSource;
 import com.nimbusds.jose.proc.JWSVerificationKeySelector;
 import com.nimbusds.jose.proc.SecurityContext;
@@ -59,7 +60,8 @@ public class SecurityConfig {
                                             JwtService jwtService,
                                             AgentRegistryService registryService,
                                             SecurityProperties securityProperties,
-                                            CorsConfigurationSource corsConfigurationSource) throws Exception {
+                                            CorsConfigurationSource corsConfigurationSource,
+                                            UserRepository userRepository) throws Exception {
         JwtDecoder oidcDecoder = null;
         String issuer = securityProperties.getOidcIssuerUri();
         if (issuer != null && !issuer.isBlank()) {
@@ -140,7 +142,7 @@ public class SecurityConfig {
                         .authenticationEntryPoint(new HttpStatusEntryPoint(HttpStatus.UNAUTHORIZED))
                 )
                 .addFilterBefore(
-                        new JwtAuthenticationFilter(jwtService, registryService, oidcDecoder),
+                        new JwtAuthenticationFilter(jwtService, registryService, oidcDecoder, userRepository),
                         UsernamePasswordAuthenticationFilter.class
                 );
 

cameleer3-server-app/src/main/java/com/cameleer3/server/app/security/UiAuthController.java

@@ -72,12 +72,21 @@ public class UiAuthController {
     @ApiResponse(responseCode = "200", description = "Login successful")
     @ApiResponse(responseCode = "401", description = "Invalid credentials",
             content = @Content(schema = @Schema(implementation = ErrorResponse.class)))
+    @ApiResponse(responseCode = "429", description = "Account locked due to too many failed attempts")
     public ResponseEntity<AuthTokenResponse> login(@RequestBody LoginRequest request,
                                                        HttpServletRequest httpRequest) {
         String configuredUser = properties.getUiUser();
         String configuredPassword = properties.getUiPassword();
         String subject = "user:" + request.username();
 
+        // Check account lockout before attempting authentication
+        if (userRepository.isLocked(subject)) {
+            auditService.log(request.username(), "login_locked", AuditCategory.AUTH, null,
+                    Map.of("reason", "Account locked"), AuditResult.FAILURE, httpRequest);
+            throw new ResponseStatusException(HttpStatus.TOO_MANY_REQUESTS,
+                    "Account locked due to too many failed attempts. Try again later.");
+        }
+
         // Try env-var admin first
         boolean envMatch = configuredUser != null && !configuredUser.isBlank()
                 && configuredPassword != null && !configuredPassword.isBlank()
@@ -88,6 +97,7 @@ public class UiAuthController {
             // Try per-user password
             Optional<String> hash = userRepository.getPasswordHash(subject);
             if (hash.isEmpty() || !passwordEncoder.matches(request.password(), hash.get())) {
+                userRepository.recordFailedLogin(subject);
                 log.debug("UI login failed for user: {}", request.username());
                 auditService.log(request.username(), "login_failed", AuditCategory.AUTH, null,
                         Map.of("reason", "Invalid credentials"), AuditResult.FAILURE, httpRequest);
@@ -95,6 +105,9 @@ public class UiAuthController {
             }
         }
 
+        // Successful login — clear any failed attempt counter
+        userRepository.clearFailedLogins(subject);
+
         if (envMatch) {
             // Env-var admin: upsert and ensure ADMIN role + Admins group
             try {

cameleer3-server-app/src/main/java/com/cameleer3/server/app/storage/PostgresUserRepository.java

@@ -5,6 +5,7 @@ import com.cameleer3.server.core.security.UserRepository;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.stereotype.Repository;
 
+import java.time.Instant;
 import java.util.List;
 import java.util.Optional;
 
@@ -17,17 +18,20 @@ public class PostgresUserRepository implements UserRepository {
         this.jdbc = jdbc;
     }
 
+    private static final String USER_COLUMNS =
+            "user_id, provider, email, display_name, created_at, failed_login_attempts, locked_until, token_revoked_before";
+
     @Override
     public Optional<UserInfo> findById(String userId) {
         var results = jdbc.query(
-                "SELECT user_id, provider, email, display_name, created_at FROM users WHERE user_id = ?",
+                "SELECT " + USER_COLUMNS + " FROM users WHERE user_id = ?",
                 (rs, rowNum) -> mapUser(rs), userId);
         return results.isEmpty() ? Optional.empty() : Optional.of(results.get(0));
     }
 
     @Override
     public List<UserInfo> findAll() {
-        return jdbc.query("SELECT user_id, provider, email, display_name, created_at FROM users ORDER BY user_id",
+        return jdbc.query("SELECT " + USER_COLUMNS + " FROM users ORDER BY user_id",
                 (rs, rowNum) -> mapUser(rs));
     }
 
@@ -64,12 +68,50 @@ public class PostgresUserRepository implements UserRepository {
         return Optional.of(results.get(0));
     }
 
+    @Override
+    public void recordFailedLogin(String userId) {
+        jdbc.update("""
+                UPDATE users
+                SET failed_login_attempts = failed_login_attempts + 1,
+                    locked_until = CASE
+                        WHEN failed_login_attempts + 1 >= 5
+                            THEN now() + INTERVAL '15 minutes'
+                        ELSE locked_until
+                    END
+                WHERE user_id = ?
+                """, userId);
+    }
+
+    @Override
+    public void clearFailedLogins(String userId) {
+        jdbc.update("UPDATE users SET failed_login_attempts = 0, locked_until = NULL WHERE user_id = ?", userId);
+    }
+
+    @Override
+    public boolean isLocked(String userId) {
+        var results = jdbc.query(
+                "SELECT 1 FROM users WHERE user_id = ? AND locked_until > now()",
+                (rs, rowNum) -> true, userId);
+        return !results.isEmpty();
+    }
+
+    @Override
+    public void revokeTokensBefore(String userId, Instant timestamp) {
+        jdbc.update("UPDATE users SET token_revoked_before = ? WHERE user_id = ?",
+                java.sql.Timestamp.from(timestamp), userId);
+    }
+
     private UserInfo mapUser(java.sql.ResultSet rs) throws java.sql.SQLException {
         java.sql.Timestamp ts = rs.getTimestamp("created_at");
         java.time.Instant createdAt = ts != null ? ts.toInstant() : null;
+        java.sql.Timestamp lockedTs = rs.getTimestamp("locked_until");
+        java.time.Instant lockedUntil = lockedTs != null ? lockedTs.toInstant() : null;
+        java.sql.Timestamp revokedTs = rs.getTimestamp("token_revoked_before");
+        java.time.Instant tokenRevokedBefore = revokedTs != null ? revokedTs.toInstant() : null;
         return new UserInfo(
                 rs.getString("user_id"), rs.getString("provider"),
                 rs.getString("email"), rs.getString("display_name"),
-                createdAt);
+                createdAt, rs.getInt("failed_login_attempts"),
+                lockedUntil, tokenRevokedBefore);
     }
 }

cameleer3-server-app/src/main/resources/db/migration/V9__password_hardening.sql

@@ -0,0 +1,3 @@
+ALTER TABLE users ADD COLUMN IF NOT EXISTS failed_login_attempts INTEGER NOT NULL DEFAULT 0;
+ALTER TABLE users ADD COLUMN IF NOT EXISTS locked_until TIMESTAMPTZ;
+ALTER TABLE users ADD COLUMN IF NOT EXISTS token_revoked_before TIMESTAMPTZ;

cameleer3-server-core/src/main/java/com/cameleer3/server/core/security/JwtService.java

@@ -1,5 +1,6 @@
 package com.cameleer3.server.core.security;
 
+import java.time.Instant;
 import java.util.List;
 
 /**
@@ -16,9 +17,16 @@ public interface JwtService {
      *
      * @param subject     the {@code sub} claim (agent ID or {@code user:<username>})
      * @param application the {@code group} claim (application name)
+     * @param environment the {@code env} claim
      * @param roles       the {@code roles} claim (e.g. {@code ["AGENT"]}, {@code ["ADMIN"]})
+     * @param issuedAt    the {@code iat} claim (token issue time)
      */
-    record JwtValidationResult(String subject, String application, String environment, List<String> roles) {}
+    record JwtValidationResult(String subject, String application, String environment, List<String> roles, Instant issuedAt) {
+        /** Backwards-compatible constructor (issuedAt defaults to null). */
+        public JwtValidationResult(String subject, String application, String environment, List<String> roles) {
+            this(subject, application, environment, roles, null);
+        }
+    }
 
     /**
      * Creates a signed access JWT with the given subject, application, and roles.

cameleer3-server-core/src/main/java/com/cameleer3/server/core/security/PasswordPolicyValidator.java

@@ -0,0 +1,73 @@
+package com.cameleer3.server.core.security;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Validates passwords against a configurable policy.
+ * <p>
+ * Rules:
+ * <ul>
+ *   <li>Minimum 12 characters</li>
+ *   <li>Must contain at least 3 of 4 character classes: uppercase, lowercase, digit, special</li>
+ *   <li>Must not match the username</li>
+ * </ul>
+ */
+public final class PasswordPolicyValidator {
+
+    private static final int MIN_LENGTH = 12;
+    private static final int MIN_CLASSES = 3;
+
+    private PasswordPolicyValidator() {}
+
+    /**
+     * Validates a password against the policy.
+     *
+     * @param password the password to validate
+     * @param username the username (to reject passwords matching it)
+     * @return empty list if valid, otherwise a list of violation messages
+     */
+    public static List<String> validate(String password, String username) {
+        List<String> violations = new ArrayList<>();
+
+        if (password == null || password.length() < MIN_LENGTH) {
+            violations.add("Password must be at least " + MIN_LENGTH + " characters");
+        }
+
+        if (password != null && username != null && password.equalsIgnoreCase(username)) {
+            violations.add("Password must not match the username");
+        }
+
+        if (password != null) {
+            int classes = countCharacterClasses(password);
+            if (classes < MIN_CLASSES) {
+                violations.add("Password must contain at least " + MIN_CLASSES
+                        + " of 4 character classes: uppercase, lowercase, digit, special");
+            }
+        }
+
+        return violations;
+    }
+
+    private static int countCharacterClasses(String password) {
+        boolean hasUpper = false;
+        boolean hasLower = false;
+        boolean hasDigit = false;
+        boolean hasSpecial = false;
+
+        for (int i = 0; i < password.length(); i++) {
+            char c = password.charAt(i);
+            if (Character.isUpperCase(c)) hasUpper = true;
+            else if (Character.isLowerCase(c)) hasLower = true;
+            else if (Character.isDigit(c)) hasDigit = true;
+            else hasSpecial = true;
+        }
+
+        int count = 0;
+        if (hasUpper) count++;
+        if (hasLower) count++;
+        if (hasDigit) count++;
+        if (hasSpecial) count++;
+        return count;
+    }
+}

cameleer3-server-core/src/main/java/com/cameleer3/server/core/security/UserInfo.java

@@ -5,16 +5,29 @@ import java.time.Instant;
 /**
  * Represents a persisted user in the system.
  *
- * @param userId      unique identifier (e.g. OIDC {@code sub} or {@code user:<username>})
- * @param provider    authentication provider ({@code "local"}, {@code "oidc:<issuer-host>"})
- * @param email       user email (may be empty)
- * @param displayName display name (may be empty)
- * @param createdAt   first creation timestamp
+ * @param userId              unique identifier (e.g. OIDC {@code sub} or {@code user:<username>})
+ * @param provider            authentication provider ({@code "local"}, {@code "oidc:<issuer-host>"})
+ * @param email               user email (may be empty)
+ * @param displayName         display name (may be empty)
+ * @param createdAt           first creation timestamp
+ * @param failedLoginAttempts number of consecutive failed login attempts
+ * @param lockedUntil         account locked until this instant (null if not locked)
+ * @param tokenRevokedBefore  tokens issued before this instant are rejected (null if no revocation)
  */
 public record UserInfo(
         String userId,
         String provider,
         String email,
         String displayName,
-        Instant createdAt
-) {}
+        Instant createdAt,
+        int failedLoginAttempts,
+        Instant lockedUntil,
+        Instant tokenRevokedBefore
+) {
+    /**
+     * Convenience constructor for backwards compatibility (new fields default to safe values).
+     */
+    public UserInfo(String userId, String provider, String email, String displayName, Instant createdAt) {
+        this(userId, provider, email, displayName, createdAt, 0, null, null);
+    }
+}

cameleer3-server-core/src/main/java/com/cameleer3/server/core/security/UserRepository.java

@@ -1,5 +1,6 @@
 package com.cameleer3.server.core.security;
 
+import java.time.Instant;
 import java.util.List;
 import java.util.Optional;
 
@@ -19,4 +20,16 @@ public interface UserRepository {
     void setPassword(String userId, String passwordHash);
 
     Optional<String> getPasswordHash(String userId);
+
+    /** Increment failed login attempts; lock the account when >= 5 failures. */
+    void recordFailedLogin(String userId);
+
+    /** Reset failed login counter (call on successful login). */
+    void clearFailedLogins(String userId);
+
+    /** Check whether the account is currently locked. */
+    boolean isLocked(String userId);
+
+    /** Mark all tokens issued before {@code timestamp} as revoked for the given user. */
+    void revokeTokensBefore(String userId, Instant timestamp);
 }