diff --git a/src/api/SIGCM2.Api/Controllers/UsuariosController.cs b/src/api/SIGCM2.Api/Controllers/UsuariosController.cs
index f9279b7..89184c6 100644
--- a/src/api/SIGCM2.Api/Controllers/UsuariosController.cs
+++ b/src/api/SIGCM2.Api/Controllers/UsuariosController.cs
@@ -3,26 +3,42 @@ using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
 using SIGCM2.Api.Authorization;
 using SIGCM2.Application.Abstractions;
+using SIGCM2.Application.Common;
 using SIGCM2.Application.Usuarios.Create;
+using SIGCM2.Application.Usuarios.Deactivate;
+using SIGCM2.Application.Usuarios.GetById;
+using SIGCM2.Application.Usuarios.List;
+using SIGCM2.Application.Usuarios.Reactivate;
+using SIGCM2.Application.Usuarios.Update;
+using SIGCM2.Application.Usuarios.ChangeMyPassword;
+using SIGCM2.Application.Usuarios.ResetPassword;
+using System.IdentityModel.Tokens.Jwt;
+using System.Security.Claims;
 
 namespace SIGCM2.Api.Controllers;
 
+/// <summary>
+/// UDT-001/UDT-008: Usuario management endpoints.
+/// RequirePermission moved to method level to allow /me/password with [Authorize] only.
+/// </summary>
 [ApiController]
 [Route("api/v1/users")]
-[RequirePermission("administracion:usuarios:gestionar")]
 public sealed class UsuariosController : ControllerBase
 {
     private readonly IDispatcher _dispatcher;
-    private readonly IValidator<CreateUsuarioCommand> _validator;
+    private readonly IValidator<CreateUsuarioCommand> _createValidator;
 
-    public UsuariosController(IDispatcher dispatcher, IValidator<CreateUsuarioCommand> validator)
+    public UsuariosController(
+        IDispatcher dispatcher,
+        IValidator<CreateUsuarioCommand> createValidator)
     {
         _dispatcher = dispatcher;
-        _validator = validator;
+        _createValidator = createValidator;
     }
 
-    /// <summary>Creates a new user. Requires admin role.</summary>
+    /// <summary>Creates a new user. Requires administracion:usuarios:gestionar.</summary>
     [HttpPost]
+    [RequirePermission("administracion:usuarios:gestionar")]
     [ProducesResponseType(typeof(UsuarioCreatedDto), StatusCodes.Status201Created)]
     [ProducesResponseType(StatusCodes.Status400BadRequest)]
     [ProducesResponseType(StatusCodes.Status401Unauthorized)]
@@ -38,7 +54,7 @@ public sealed class UsuariosController : ControllerBase
             Email: request.Email,
             Rol: request.Rol ?? string.Empty);
 
-        var validation = await _validator.ValidateAsync(command);
+        var validation = await _createValidator.ValidateAsync(command);
         if (!validation.IsValid)
         {
             var errors = validation.Errors
@@ -51,8 +67,144 @@ public sealed class UsuariosController : ControllerBase
 
         return CreatedAtAction(nameof(CreateUsuario), new { id = result.Id }, result);
     }
+
+    /// <summary>Lists usuarios with optional filters and pagination.</summary>
+    [HttpGet]
+    [RequirePermission("administracion:usuarios:gestionar")]
+    [ProducesResponseType(typeof(PagedResult<UsuarioListItemDto>), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status401Unauthorized)]
+    [ProducesResponseType(StatusCodes.Status403Forbidden)]
+    public async Task<IActionResult> ListUsuarios(
+        [FromQuery] int page = 1,
+        [FromQuery] int pageSize = 20,
+        [FromQuery] string? rol = null,
+        [FromQuery] bool? activo = null,
+        [FromQuery] string? search = null)
+    {
+        if (page < 1) return BadRequest(new { error = "page must be >= 1" });
+        if (pageSize < 1) return BadRequest(new { error = "pageSize must be >= 1" });
+
+        var query = new ListUsuariosQuery(page, pageSize, rol, activo, search);
+        var result = await _dispatcher.Send<ListUsuariosQuery, PagedResult<UsuarioListItemDto>>(query);
+        return Ok(result);
+    }
+
+    /// <summary>Gets a single usuario by id.</summary>
+    [HttpGet("{id:int}")]
+    [RequirePermission("administracion:usuarios:gestionar")]
+    [ProducesResponseType(typeof(UsuarioDetailDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status401Unauthorized)]
+    [ProducesResponseType(StatusCodes.Status403Forbidden)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> GetUsuarioById([FromRoute] int id)
+    {
+        var query = new GetUsuarioByIdQuery(id);
+        var result = await _dispatcher.Send<GetUsuarioByIdQuery, UsuarioDetailDto>(query);
+        return Ok(result);
+    }
+
+    /// <summary>Updates a usuario's editable fields.</summary>
+    [HttpPut("{id:int}")]
+    [RequirePermission("administracion:usuarios:gestionar")]
+    [ProducesResponseType(typeof(UsuarioDetailDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status401Unauthorized)]
+    [ProducesResponseType(StatusCodes.Status403Forbidden)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> UpdateUsuario([FromRoute] int id, [FromBody] UpdateUsuarioRequest request)
+    {
+        var command = new UpdateUsuarioCommand(
+            Id: id,
+            Nombre: request.Nombre ?? string.Empty,
+            Apellido: request.Apellido ?? string.Empty,
+            Email: request.Email,
+            Rol: request.Rol ?? string.Empty,
+            Activo: request.Activo ?? true);
+
+        var result = await _dispatcher.Send<UpdateUsuarioCommand, UsuarioDetailDto>(command);
+        return Ok(result);
+    }
+
+    /// <summary>Deactivates a usuario (idempotent).</summary>
+    [HttpPatch("{id:int}/deactivate")]
+    [RequirePermission("administracion:usuarios:gestionar")]
+    [ProducesResponseType(typeof(UsuarioDetailDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status401Unauthorized)]
+    [ProducesResponseType(StatusCodes.Status403Forbidden)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> DeactivateUsuario([FromRoute] int id)
+    {
+        var command = new DeactivateUsuarioCommand(id);
+        var result = await _dispatcher.Send<DeactivateUsuarioCommand, UsuarioDetailDto>(command);
+        return Ok(result);
+    }
+
+    /// <summary>Reactivates a usuario (idempotent).</summary>
+    [HttpPatch("{id:int}/reactivate")]
+    [RequirePermission("administracion:usuarios:gestionar")]
+    [ProducesResponseType(typeof(UsuarioDetailDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status401Unauthorized)]
+    [ProducesResponseType(StatusCodes.Status403Forbidden)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> ReactivateUsuario([FromRoute] int id)
+    {
+        var command = new ReactivateUsuarioCommand(id);
+        var result = await _dispatcher.Send<ReactivateUsuarioCommand, UsuarioDetailDto>(command);
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Changes the authenticated user's own password.
+    /// Declared BEFORE /{id:int} route to avoid routing ambiguity (though :int constraint handles it).
+    /// Requires only authentication (no specific permission).
+    /// </summary>
+    [HttpPut("me/password")]
+    [Authorize]
+    [ProducesResponseType(StatusCodes.Status204NoContent)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status401Unauthorized)]
+    public async Task<IActionResult> ChangeMyPassword([FromBody] ChangeMyPasswordRequest request)
+    {
+        var sub = User.FindFirstValue(JwtRegisteredClaimNames.Sub)
+            ?? User.FindFirstValue(ClaimTypes.NameIdentifier)
+            ?? throw new UnauthorizedAccessException();
+
+        var command = new ChangeMyPasswordCommand(
+            UsuarioId: int.Parse(sub),
+            OldPassword: request.OldPassword ?? string.Empty,
+            NewPassword: request.NewPassword ?? string.Empty);
+
+        await _dispatcher.Send<ChangeMyPasswordCommand, Unit>(command);
+        return NoContent();
+    }
+
+    /// <summary>Resets a usuario's password (admin only). Returns a one-time temp password.</summary>
+    [HttpPost("{id:int}/password/reset")]
+    [RequirePermission("administracion:usuarios:gestionar")]
+    [ProducesResponseType(typeof(ResetUsuarioPasswordResponse), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status401Unauthorized)]
+    [ProducesResponseType(StatusCodes.Status403Forbidden)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> ResetUsuarioPassword([FromRoute] int id)
+    {
+        var sub = User.FindFirstValue(JwtRegisteredClaimNames.Sub)
+            ?? User.FindFirstValue(ClaimTypes.NameIdentifier)
+            ?? throw new UnauthorizedAccessException();
+
+        var command = new ResetUsuarioPasswordCommand(
+            TargetId: id,
+            CallerId: int.Parse(sub));
+
+        var result = await _dispatcher.Send<ResetUsuarioPasswordCommand, ResetUsuarioPasswordResponse>(command);
+        return Ok(result);
+    }
 }
 
+// ── request body records ──────────────────────────────────────────────────────
+
 /// <summary>Create user request body — nullable to catch missing field scenarios.</summary>
 public sealed record CreateUsuarioRequest(
     string? Username,
@@ -61,3 +213,14 @@ public sealed record CreateUsuarioRequest(
     string? Apellido,
     string? Email,
     string? Rol);
+
+public sealed record UpdateUsuarioRequest(
+    string? Nombre,
+    string? Apellido,
+    string? Email,
+    string? Rol,
+    bool? Activo);
+
+public sealed record ChangeMyPasswordRequest(
+    string? OldPassword,
+    string? NewPassword);
diff --git a/src/api/SIGCM2.Api/Filters/ExceptionFilter.cs b/src/api/SIGCM2.Api/Filters/ExceptionFilter.cs
index e1911b8..f583aed 100644
--- a/src/api/SIGCM2.Api/Filters/ExceptionFilter.cs
+++ b/src/api/SIGCM2.Api/Filters/ExceptionFilter.cs
@@ -19,6 +19,56 @@ public sealed class ExceptionFilter : IExceptionFilter
     {
         switch (context.Exception)
         {
+            case UsuarioNotFoundException usuarioNotFoundEx:
+                context.Result = new ObjectResult(new
+                {
+                    error = "usuario_not_found",
+                    message = usuarioNotFoundEx.Message
+                })
+                {
+                    StatusCode = StatusCodes.Status404NotFound
+                };
+                context.ExceptionHandled = true;
+                break;
+
+            case LastAdminLockoutException:
+                context.Result = new ObjectResult(new Microsoft.AspNetCore.Mvc.ProblemDetails
+                {
+                    Type = "about:blank",
+                    Title = "last-admin-lockout",
+                    Status = 400,
+                    Detail = "No se puede desactivar o cambiar el rol del último administrador activo."
+                })
+                {
+                    StatusCode = StatusCodes.Status400BadRequest
+                };
+                context.ExceptionHandled = true;
+                break;
+
+            case CannotSelfResetException:
+                context.Result = new ObjectResult(new
+                {
+                    error = "cannot-self-reset",
+                    message = "Un administrador no puede resetear su propia contraseña. Use el endpoint de cambio de contraseña propio."
+                })
+                {
+                    StatusCode = StatusCodes.Status400BadRequest
+                };
+                context.ExceptionHandled = true;
+                break;
+
+            case InvalidOldPasswordException:
+                context.Result = new ObjectResult(new
+                {
+                    error = "invalid-old-password",
+                    message = "La contraseña actual es incorrecta."
+                })
+                {
+                    StatusCode = StatusCodes.Status400BadRequest
+                };
+                context.ExceptionHandled = true;
+                break;
+
             case UsernameAlreadyExistsException usernameEx:
                 context.Result = new ObjectResult(new
                 {
diff --git a/src/api/SIGCM2.Application/Common/TempPasswordGenerator.cs b/src/api/SIGCM2.Application/Common/TempPasswordGenerator.cs
new file mode 100644
index 0000000..2998f28
--- /dev/null
+++ b/src/api/SIGCM2.Application/Common/TempPasswordGenerator.cs
@@ -0,0 +1,43 @@
+using System.Security.Cryptography;
+using System.Text;
+
+namespace SIGCM2.Application.Common;
+
+/// <summary>
+/// Generates cryptographically secure temporary passwords.
+/// Excludes visually ambiguous characters (I, O, l, o, 0, 1).
+/// </summary>
+public static class TempPasswordGenerator
+{
+    private const string UpperChars = "ABCDEFGHJKLMNPQRSTUVWXYZ"; // no I, O
+    private const string LowerChars = "abcdefghijkmnpqrstuvwxyz"; // no l, o
+    private const string DigitChars = "23456789";                  // no 0, 1
+    private const string SymbolChars = "!@#$%&*+-=?";             // copy-paste safe
+
+    private const string Charset = UpperChars + LowerChars + DigitChars + SymbolChars;
+
+    public static string Generate(int length = 12)
+    {
+        if (length < 8)
+            throw new ArgumentOutOfRangeException(nameof(length), "Password length must be at least 8.");
+
+        // SECURITY: NEVER log the result of this method
+        Span<byte> bytes = stackalloc byte[length];
+        RandomNumberGenerator.Fill(bytes);
+
+        var sb = new StringBuilder(length);
+        for (int i = 0; i < length; i++)
+            sb.Append(Charset[bytes[i] % Charset.Length]);
+
+        var result = sb.ToString();
+
+        // Guarantee diversity: at least 1 upper, 1 lower, 1 digit, 1 symbol
+        return HasDiversity(result) ? result : Generate(length);
+    }
+
+    private static bool HasDiversity(string pwd)
+        => pwd.Any(c => UpperChars.Contains(c))
+        && pwd.Any(c => LowerChars.Contains(c))
+        && pwd.Any(c => DigitChars.Contains(c))
+        && pwd.Any(c => SymbolChars.Contains(c));
+}
diff --git a/src/api/SIGCM2.Application/Common/Unit.cs b/src/api/SIGCM2.Application/Common/Unit.cs
new file mode 100644
index 0000000..2ca3b64
--- /dev/null
+++ b/src/api/SIGCM2.Application/Common/Unit.cs
@@ -0,0 +1,7 @@
+namespace SIGCM2.Application.Common;
+
+/// <summary>Represents the absence of a meaningful return value.</summary>
+public readonly struct Unit
+{
+    public static readonly Unit Value = default;
+}
diff --git a/src/api/SIGCM2.Application/DependencyInjection.cs b/src/api/SIGCM2.Application/DependencyInjection.cs
index c864f1a..1476873 100644
--- a/src/api/SIGCM2.Application/DependencyInjection.cs
+++ b/src/api/SIGCM2.Application/DependencyInjection.cs
@@ -4,6 +4,7 @@ using SIGCM2.Application.Abstractions;
 using SIGCM2.Application.Auth.Login;
 using SIGCM2.Application.Auth.Logout;
 using SIGCM2.Application.Auth.Refresh;
+using SIGCM2.Application.Common;
 using SIGCM2.Application.Permisos.Assign;
 using SIGCM2.Application.Permisos.Dtos;
 using SIGCM2.Application.Permisos.GetByRol;
@@ -14,7 +15,14 @@ using SIGCM2.Application.Roles.Dtos;
 using SIGCM2.Application.Roles.Get;
 using SIGCM2.Application.Roles.List;
 using SIGCM2.Application.Roles.Update;
+using SIGCM2.Application.Usuarios.ChangeMyPassword;
 using SIGCM2.Application.Usuarios.Create;
+using SIGCM2.Application.Usuarios.Deactivate;
+using SIGCM2.Application.Usuarios.GetById;
+using SIGCM2.Application.Usuarios.List;
+using SIGCM2.Application.Usuarios.Reactivate;
+using SIGCM2.Application.Usuarios.ResetPassword;
+using SIGCM2.Application.Usuarios.Update;
 
 namespace SIGCM2.Application;
 
@@ -40,6 +48,15 @@ public static class DependencyInjection
         services.AddScoped<ICommandHandler<GetRolPermisosQuery, IReadOnlyList<PermisoDto>>, GetRolPermisosQueryHandler>();
         services.AddScoped<ICommandHandler<AssignPermisosToRolCommand, IReadOnlyList<PermisoDto>>, AssignPermisosToRolCommandHandler>();
 
+        // Usuarios (UDT-008)
+        services.AddScoped<ICommandHandler<ListUsuariosQuery, PagedResult<UsuarioListItemDto>>, ListUsuariosQueryHandler>();
+        services.AddScoped<ICommandHandler<GetUsuarioByIdQuery, UsuarioDetailDto>, GetUsuarioByIdQueryHandler>();
+        services.AddScoped<ICommandHandler<UpdateUsuarioCommand, UsuarioDetailDto>, UpdateUsuarioCommandHandler>();
+        services.AddScoped<ICommandHandler<DeactivateUsuarioCommand, UsuarioDetailDto>, DeactivateUsuarioCommandHandler>();
+        services.AddScoped<ICommandHandler<ReactivateUsuarioCommand, UsuarioDetailDto>, ReactivateUsuarioCommandHandler>();
+        services.AddScoped<ICommandHandler<ChangeMyPasswordCommand, Unit>, ChangeMyPasswordCommandHandler>();
+        services.AddScoped<ICommandHandler<ResetUsuarioPasswordCommand, ResetUsuarioPasswordResponse>, ResetUsuarioPasswordCommandHandler>();
+
         // FluentValidation validators (scans entire Application assembly)
         services.AddValidatorsFromAssemblyContaining<LoginCommandValidator>();
 
diff --git a/src/api/SIGCM2.Application/Usuarios/ChangeMyPassword/ChangeMyPasswordCommand.cs b/src/api/SIGCM2.Application/Usuarios/ChangeMyPassword/ChangeMyPasswordCommand.cs
new file mode 100644
index 0000000..9182179
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/ChangeMyPassword/ChangeMyPasswordCommand.cs
@@ -0,0 +1,7 @@
+namespace SIGCM2.Application.Usuarios.ChangeMyPassword;
+
+public sealed record ChangeMyPasswordCommand(
+    int UsuarioId,
+    string OldPassword,
+    string NewPassword
+);
diff --git a/src/api/SIGCM2.Application/Usuarios/ChangeMyPassword/ChangeMyPasswordCommandHandler.cs b/src/api/SIGCM2.Application/Usuarios/ChangeMyPassword/ChangeMyPasswordCommandHandler.cs
new file mode 100644
index 0000000..60df389
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/ChangeMyPassword/ChangeMyPasswordCommandHandler.cs
@@ -0,0 +1,37 @@
+using SIGCM2.Application.Abstractions;
+using SIGCM2.Application.Abstractions.Persistence;
+using SIGCM2.Application.Abstractions.Security;
+using SIGCM2.Application.Common;
+using SIGCM2.Domain.Exceptions;
+
+namespace SIGCM2.Application.Usuarios.ChangeMyPassword;
+
+public sealed class ChangeMyPasswordCommandHandler : ICommandHandler<ChangeMyPasswordCommand, Unit>
+{
+    private readonly IUsuarioRepository _repository;
+    private readonly IPasswordHasher _hasher;
+
+    public ChangeMyPasswordCommandHandler(
+        IUsuarioRepository repository,
+        IPasswordHasher hasher)
+    {
+        _repository = repository;
+        _hasher = hasher;
+    }
+
+    public async Task<Unit> Handle(ChangeMyPasswordCommand cmd)
+    {
+        var user = await _repository.GetByIdAsync(cmd.UsuarioId)
+            ?? throw new UsuarioNotFoundException(cmd.UsuarioId);
+
+        if (!_hasher.Verify(cmd.OldPassword, user.PasswordHash))
+            throw new InvalidOldPasswordException();
+
+        var newHash = _hasher.Hash(cmd.NewPassword);
+        await _repository.UpdatePasswordAsync(cmd.UsuarioId, newHash, mustChangePassword: false);
+
+        // TODO: audit — defer to ADM-004
+        // NOTE: intentionally does NOT revoke own refresh tokens (spec REQ-BCP-05)
+        return Unit.Value;
+    }
+}
diff --git a/src/api/SIGCM2.Application/Usuarios/ChangeMyPassword/ChangeMyPasswordCommandValidator.cs b/src/api/SIGCM2.Application/Usuarios/ChangeMyPassword/ChangeMyPasswordCommandValidator.cs
new file mode 100644
index 0000000..44c8c6e
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/ChangeMyPassword/ChangeMyPasswordCommandValidator.cs
@@ -0,0 +1,34 @@
+using FluentValidation;
+using SIGCM2.Application.Auth;
+
+namespace SIGCM2.Application.Usuarios.ChangeMyPassword;
+
+public sealed class ChangeMyPasswordCommandValidator : AbstractValidator<ChangeMyPasswordCommand>
+{
+    public ChangeMyPasswordCommandValidator(AuthOptions authOptions)
+    {
+        RuleFor(x => x.OldPassword)
+            .NotEmpty()
+            .WithMessage("La contraseña actual es requerida.");
+
+        RuleFor(x => x.NewPassword)
+            .NotEmpty()
+            .WithMessage("La nueva contraseña es requerida.")
+            .MinimumLength(authOptions.PasswordMinLength)
+            .WithMessage($"La contraseña debe tener al menos {authOptions.PasswordMinLength} caracteres.");
+
+        if (authOptions.PasswordRequireLetter)
+        {
+            RuleFor(x => x.NewPassword)
+                .Matches(@"[a-zA-Z]")
+                .WithMessage("La contraseña debe contener al menos una letra.");
+        }
+
+        if (authOptions.PasswordRequireDigit)
+        {
+            RuleFor(x => x.NewPassword)
+                .Matches(@"\d")
+                .WithMessage("La contraseña debe contener al menos un dígito.");
+        }
+    }
+}
diff --git a/src/api/SIGCM2.Application/Usuarios/Deactivate/DeactivateUsuarioCommand.cs b/src/api/SIGCM2.Application/Usuarios/Deactivate/DeactivateUsuarioCommand.cs
new file mode 100644
index 0000000..d48fd3e
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/Deactivate/DeactivateUsuarioCommand.cs
@@ -0,0 +1,3 @@
+namespace SIGCM2.Application.Usuarios.Deactivate;
+
+public sealed record DeactivateUsuarioCommand(int UsuarioId);
diff --git a/src/api/SIGCM2.Application/Usuarios/Deactivate/DeactivateUsuarioCommandHandler.cs b/src/api/SIGCM2.Application/Usuarios/Deactivate/DeactivateUsuarioCommandHandler.cs
new file mode 100644
index 0000000..48b1449
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/Deactivate/DeactivateUsuarioCommandHandler.cs
@@ -0,0 +1,54 @@
+using SIGCM2.Application.Abstractions;
+using SIGCM2.Application.Abstractions.Persistence;
+using SIGCM2.Application.Common;
+using SIGCM2.Application.Usuarios.GetById;
+using SIGCM2.Domain.Exceptions;
+
+namespace SIGCM2.Application.Usuarios.Deactivate;
+
+public sealed class DeactivateUsuarioCommandHandler : ICommandHandler<DeactivateUsuarioCommand, UsuarioDetailDto>
+{
+    private readonly IUsuarioRepository _repository;
+    private readonly IRefreshTokenRepository _refreshTokenRepository;
+
+    public DeactivateUsuarioCommandHandler(
+        IUsuarioRepository repository,
+        IRefreshTokenRepository refreshTokenRepository)
+    {
+        _repository = repository;
+        _refreshTokenRepository = refreshTokenRepository;
+    }
+
+    public async Task<UsuarioDetailDto> Handle(DeactivateUsuarioCommand cmd)
+    {
+        var target = await _repository.GetByIdAsync(cmd.UsuarioId)
+            ?? throw new UsuarioNotFoundException(cmd.UsuarioId);
+
+        // Idempotent: already inactive → return as-is without touching FechaModificacion
+        if (!target.Activo)
+        {
+            return new UsuarioDetailDto(
+                target.Id, target.Username, target.Nombre, target.Apellido,
+                target.Email, target.Rol, target.Activo, target.MustChangePassword,
+                target.UltimoLogin, target.FechaModificacion);
+        }
+
+        // Guard: anti-lockout
+        if (target.Rol == "admin" && await _repository.CountActiveAdminsAsync() <= 1)
+            throw new LastAdminLockoutException();
+
+        var fields = new UpdateUsuarioFields(target.Nombre, target.Apellido, target.Email, target.Rol, false);
+        var now = DateTime.UtcNow;
+        await _repository.UpdateAsync(cmd.UsuarioId, fields, now);
+        await _refreshTokenRepository.RevokeAllActiveForUserAsync(cmd.UsuarioId, now);
+
+        // TODO: audit — defer to ADM-004
+        var updated = await _repository.GetDetailAsync(cmd.UsuarioId)
+            ?? throw new UsuarioNotFoundException(cmd.UsuarioId);
+
+        return new UsuarioDetailDto(
+            updated.Id, updated.Username, updated.Nombre, updated.Apellido,
+            updated.Email, updated.Rol, updated.Activo, updated.MustChangePassword,
+            updated.UltimoLogin, updated.FechaModificacion);
+    }
+}
diff --git a/src/api/SIGCM2.Application/Usuarios/GetById/GetUsuarioByIdQuery.cs b/src/api/SIGCM2.Application/Usuarios/GetById/GetUsuarioByIdQuery.cs
new file mode 100644
index 0000000..7d2c1fa
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/GetById/GetUsuarioByIdQuery.cs
@@ -0,0 +1,3 @@
+namespace SIGCM2.Application.Usuarios.GetById;
+
+public sealed record GetUsuarioByIdQuery(int Id);
diff --git a/src/api/SIGCM2.Application/Usuarios/GetById/GetUsuarioByIdQueryHandler.cs b/src/api/SIGCM2.Application/Usuarios/GetById/GetUsuarioByIdQueryHandler.cs
new file mode 100644
index 0000000..01baf7d
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/GetById/GetUsuarioByIdQueryHandler.cs
@@ -0,0 +1,34 @@
+using SIGCM2.Application.Abstractions;
+using SIGCM2.Application.Abstractions.Persistence;
+using SIGCM2.Domain.Exceptions;
+
+namespace SIGCM2.Application.Usuarios.GetById;
+
+public sealed class GetUsuarioByIdQueryHandler : ICommandHandler<GetUsuarioByIdQuery, UsuarioDetailDto>
+{
+    private readonly IUsuarioRepository _repository;
+
+    public GetUsuarioByIdQueryHandler(IUsuarioRepository repository)
+    {
+        _repository = repository;
+    }
+
+    public async Task<UsuarioDetailDto> Handle(GetUsuarioByIdQuery query)
+    {
+        var usuario = await _repository.GetDetailAsync(query.Id)
+            ?? throw new UsuarioNotFoundException(query.Id);
+
+        return new UsuarioDetailDto(
+            Id: usuario.Id,
+            Username: usuario.Username,
+            Nombre: usuario.Nombre,
+            Apellido: usuario.Apellido,
+            Email: usuario.Email,
+            Rol: usuario.Rol,
+            Activo: usuario.Activo,
+            MustChangePassword: usuario.MustChangePassword,
+            UltimoLogin: usuario.UltimoLogin,
+            FechaModificacion: usuario.FechaModificacion
+        );
+    }
+}
diff --git a/src/api/SIGCM2.Application/Usuarios/GetById/UsuarioDetailDto.cs b/src/api/SIGCM2.Application/Usuarios/GetById/UsuarioDetailDto.cs
new file mode 100644
index 0000000..f6b1451
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/GetById/UsuarioDetailDto.cs
@@ -0,0 +1,17 @@
+namespace SIGCM2.Application.Usuarios.GetById;
+
+/// <summary>
+/// Full detail projection — excludes PasswordHash and PermisosJson (security).
+/// </summary>
+public sealed record UsuarioDetailDto(
+    int Id,
+    string Username,
+    string Nombre,
+    string Apellido,
+    string? Email,
+    string Rol,
+    bool Activo,
+    bool MustChangePassword,
+    DateTime? UltimoLogin,
+    DateTime? FechaModificacion
+);
diff --git a/src/api/SIGCM2.Application/Usuarios/List/ListUsuariosQuery.cs b/src/api/SIGCM2.Application/Usuarios/List/ListUsuariosQuery.cs
new file mode 100644
index 0000000..ec0cc09
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/List/ListUsuariosQuery.cs
@@ -0,0 +1,9 @@
+namespace SIGCM2.Application.Usuarios.List;
+
+public sealed record ListUsuariosQuery(
+    int Page,
+    int PageSize,
+    string? Rol,
+    bool? Activo,
+    string? Search
+);
diff --git a/src/api/SIGCM2.Application/Usuarios/List/ListUsuariosQueryHandler.cs b/src/api/SIGCM2.Application/Usuarios/List/ListUsuariosQueryHandler.cs
new file mode 100644
index 0000000..bbc6124
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/List/ListUsuariosQueryHandler.cs
@@ -0,0 +1,31 @@
+using SIGCM2.Application.Abstractions;
+using SIGCM2.Application.Abstractions.Persistence;
+using SIGCM2.Application.Common;
+
+namespace SIGCM2.Application.Usuarios.List;
+
+public sealed class ListUsuariosQueryHandler : ICommandHandler<ListUsuariosQuery, PagedResult<UsuarioListItemDto>>
+{
+    private readonly IUsuarioRepository _repository;
+
+    public ListUsuariosQueryHandler(IUsuarioRepository repository)
+    {
+        _repository = repository;
+    }
+
+    public async Task<PagedResult<UsuarioListItemDto>> Handle(ListUsuariosQuery query)
+    {
+        // Clamp paging params
+        var page = Math.Max(1, query.Page);
+        var pageSize = Math.Clamp(query.PageSize, 1, 100);
+
+        var repoQuery = new UsuariosQuery(page, pageSize, query.Rol, query.Activo, query.Search);
+        var paged = await _repository.GetPagedAsync(repoQuery);
+
+        var items = paged.Items
+            .Select(u => new UsuarioListItemDto(u.Id, u.Username, u.Nombre, u.Apellido, u.Email, u.Rol, u.Activo, u.UltimoLogin))
+            .ToList();
+
+        return new PagedResult<UsuarioListItemDto>(items, paged.Page, paged.PageSize, paged.Total);
+    }
+}
diff --git a/src/api/SIGCM2.Application/Usuarios/List/UsuarioListItemDto.cs b/src/api/SIGCM2.Application/Usuarios/List/UsuarioListItemDto.cs
new file mode 100644
index 0000000..56bb3ed
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/List/UsuarioListItemDto.cs
@@ -0,0 +1,12 @@
+namespace SIGCM2.Application.Usuarios.List;
+
+public sealed record UsuarioListItemDto(
+    int Id,
+    string Username,
+    string Nombre,
+    string Apellido,
+    string? Email,
+    string Rol,
+    bool Activo,
+    DateTime? UltimoLogin
+);
diff --git a/src/api/SIGCM2.Application/Usuarios/Reactivate/ReactivateUsuarioCommand.cs b/src/api/SIGCM2.Application/Usuarios/Reactivate/ReactivateUsuarioCommand.cs
new file mode 100644
index 0000000..5a9e503
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/Reactivate/ReactivateUsuarioCommand.cs
@@ -0,0 +1,3 @@
+namespace SIGCM2.Application.Usuarios.Reactivate;
+
+public sealed record ReactivateUsuarioCommand(int UsuarioId);
diff --git a/src/api/SIGCM2.Application/Usuarios/Reactivate/ReactivateUsuarioCommandHandler.cs b/src/api/SIGCM2.Application/Usuarios/Reactivate/ReactivateUsuarioCommandHandler.cs
new file mode 100644
index 0000000..3c56919
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/Reactivate/ReactivateUsuarioCommandHandler.cs
@@ -0,0 +1,45 @@
+using SIGCM2.Application.Abstractions;
+using SIGCM2.Application.Abstractions.Persistence;
+using SIGCM2.Application.Common;
+using SIGCM2.Application.Usuarios.GetById;
+using SIGCM2.Domain.Exceptions;
+
+namespace SIGCM2.Application.Usuarios.Reactivate;
+
+public sealed class ReactivateUsuarioCommandHandler : ICommandHandler<ReactivateUsuarioCommand, UsuarioDetailDto>
+{
+    private readonly IUsuarioRepository _repository;
+
+    public ReactivateUsuarioCommandHandler(IUsuarioRepository repository)
+    {
+        _repository = repository;
+    }
+
+    public async Task<UsuarioDetailDto> Handle(ReactivateUsuarioCommand cmd)
+    {
+        var target = await _repository.GetByIdAsync(cmd.UsuarioId)
+            ?? throw new UsuarioNotFoundException(cmd.UsuarioId);
+
+        // Idempotent: already active → return as-is without touching FechaModificacion
+        if (target.Activo)
+        {
+            return new UsuarioDetailDto(
+                target.Id, target.Username, target.Nombre, target.Apellido,
+                target.Email, target.Rol, target.Activo, target.MustChangePassword,
+                target.UltimoLogin, target.FechaModificacion);
+        }
+
+        var fields = new UpdateUsuarioFields(target.Nombre, target.Apellido, target.Email, target.Rol, true);
+        var now = DateTime.UtcNow;
+        await _repository.UpdateAsync(cmd.UsuarioId, fields, now);
+
+        // TODO: audit — defer to ADM-004
+        var updated = await _repository.GetDetailAsync(cmd.UsuarioId)
+            ?? throw new UsuarioNotFoundException(cmd.UsuarioId);
+
+        return new UsuarioDetailDto(
+            updated.Id, updated.Username, updated.Nombre, updated.Apellido,
+            updated.Email, updated.Rol, updated.Activo, updated.MustChangePassword,
+            updated.UltimoLogin, updated.FechaModificacion);
+    }
+}
diff --git a/src/api/SIGCM2.Application/Usuarios/ResetPassword/ResetUsuarioPasswordCommand.cs b/src/api/SIGCM2.Application/Usuarios/ResetPassword/ResetUsuarioPasswordCommand.cs
new file mode 100644
index 0000000..023deb2
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/ResetPassword/ResetUsuarioPasswordCommand.cs
@@ -0,0 +1,3 @@
+namespace SIGCM2.Application.Usuarios.ResetPassword;
+
+public sealed record ResetUsuarioPasswordCommand(int TargetId, int CallerId);
diff --git a/src/api/SIGCM2.Application/Usuarios/ResetPassword/ResetUsuarioPasswordCommandHandler.cs b/src/api/SIGCM2.Application/Usuarios/ResetPassword/ResetUsuarioPasswordCommandHandler.cs
new file mode 100644
index 0000000..502ef98
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/ResetPassword/ResetUsuarioPasswordCommandHandler.cs
@@ -0,0 +1,44 @@
+using SIGCM2.Application.Abstractions;
+using SIGCM2.Application.Abstractions.Persistence;
+using SIGCM2.Application.Abstractions.Security;
+using SIGCM2.Application.Common;
+using SIGCM2.Domain.Exceptions;
+
+namespace SIGCM2.Application.Usuarios.ResetPassword;
+
+public sealed class ResetUsuarioPasswordCommandHandler : ICommandHandler<ResetUsuarioPasswordCommand, ResetUsuarioPasswordResponse>
+{
+    private readonly IUsuarioRepository _repository;
+    private readonly IPasswordHasher _hasher;
+    private readonly IRefreshTokenRepository _refreshTokenRepository;
+
+    public ResetUsuarioPasswordCommandHandler(
+        IUsuarioRepository repository,
+        IPasswordHasher hasher,
+        IRefreshTokenRepository refreshTokenRepository)
+    {
+        _repository = repository;
+        _hasher = hasher;
+        _refreshTokenRepository = refreshTokenRepository;
+    }
+
+    public async Task<ResetUsuarioPasswordResponse> Handle(ResetUsuarioPasswordCommand cmd)
+    {
+        // Cannot self-reset: admin must use /me/password
+        if (cmd.CallerId == cmd.TargetId)
+            throw new CannotSelfResetException();
+
+        var target = await _repository.GetByIdAsync(cmd.TargetId)
+            ?? throw new UsuarioNotFoundException(cmd.TargetId);
+
+        var temp = TempPasswordGenerator.Generate(12);
+        // SECURITY: NEVER log tempPassword
+        var hash = _hasher.Hash(temp);
+
+        await _repository.UpdatePasswordAsync(cmd.TargetId, hash, mustChangePassword: true);
+        await _refreshTokenRepository.RevokeAllActiveForUserAsync(cmd.TargetId, DateTime.UtcNow);
+
+        // TODO: audit — defer to ADM-004
+        return new ResetUsuarioPasswordResponse(temp, MustChangeOnLogin: true);
+    }
+}
diff --git a/src/api/SIGCM2.Application/Usuarios/ResetPassword/ResetUsuarioPasswordResponse.cs b/src/api/SIGCM2.Application/Usuarios/ResetPassword/ResetUsuarioPasswordResponse.cs
new file mode 100644
index 0000000..83007a8
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/ResetPassword/ResetUsuarioPasswordResponse.cs
@@ -0,0 +1,6 @@
+namespace SIGCM2.Application.Usuarios.ResetPassword;
+
+public sealed record ResetUsuarioPasswordResponse(
+    string TempPassword,
+    bool MustChangeOnLogin
+);
diff --git a/src/api/SIGCM2.Application/Usuarios/Update/UpdateUsuarioCommand.cs b/src/api/SIGCM2.Application/Usuarios/Update/UpdateUsuarioCommand.cs
new file mode 100644
index 0000000..707c161
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/Update/UpdateUsuarioCommand.cs
@@ -0,0 +1,10 @@
+namespace SIGCM2.Application.Usuarios.Update;
+
+public sealed record UpdateUsuarioCommand(
+    int Id,
+    string Nombre,
+    string Apellido,
+    string? Email,
+    string Rol,
+    bool Activo
+);
diff --git a/src/api/SIGCM2.Application/Usuarios/Update/UpdateUsuarioCommandHandler.cs b/src/api/SIGCM2.Application/Usuarios/Update/UpdateUsuarioCommandHandler.cs
new file mode 100644
index 0000000..02c5370
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/Update/UpdateUsuarioCommandHandler.cs
@@ -0,0 +1,70 @@
+using SIGCM2.Application.Abstractions;
+using SIGCM2.Application.Abstractions.Persistence;
+using SIGCM2.Application.Common;
+using SIGCM2.Application.Usuarios.GetById;
+using SIGCM2.Domain.Exceptions;
+
+namespace SIGCM2.Application.Usuarios.Update;
+
+public sealed class UpdateUsuarioCommandHandler : ICommandHandler<UpdateUsuarioCommand, UsuarioDetailDto>
+{
+    private readonly IUsuarioRepository _repository;
+    private readonly IRolRepository _rolRepository;
+    private readonly IRefreshTokenRepository _refreshTokenRepository;
+
+    public UpdateUsuarioCommandHandler(
+        IUsuarioRepository repository,
+        IRolRepository rolRepository,
+        IRefreshTokenRepository refreshTokenRepository)
+    {
+        _repository = repository;
+        _rolRepository = rolRepository;
+        _refreshTokenRepository = refreshTokenRepository;
+    }
+
+    public async Task<UsuarioDetailDto> Handle(UpdateUsuarioCommand cmd)
+    {
+        var target = await _repository.GetByIdAsync(cmd.Id)
+            ?? throw new UsuarioNotFoundException(cmd.Id);
+
+        // Guard: validate rol exists and is active
+        var rolExists = await _rolRepository.ExistsActiveByCodigoAsync(cmd.Rol);
+        if (!rolExists)
+            throw new FluentValidation.ValidationException(
+                [new FluentValidation.Results.ValidationFailure("Rol", $"El rol '{cmd.Rol}' no existe o está inactivo.")]);
+
+        // Guard: anti-lockout — cannot remove last active admin
+        if (target.Rol == "admin" && target.Activo)
+        {
+            var isChangingRol = !string.Equals(cmd.Rol, "admin", StringComparison.Ordinal);
+            var isDeactivating = !cmd.Activo;
+
+            if ((isChangingRol || isDeactivating)
+                && await _repository.CountActiveAdminsAsync() <= 1)
+            {
+                throw new LastAdminLockoutException();
+            }
+        }
+
+        var fields = new UpdateUsuarioFields(cmd.Nombre, cmd.Apellido, cmd.Email, cmd.Rol, cmd.Activo);
+        var now = DateTime.UtcNow;
+        await _repository.UpdateAsync(cmd.Id, fields, now);
+
+        // Revoke refresh tokens if rol changed or user deactivated
+        var rolChanged = !string.Equals(target.Rol, cmd.Rol, StringComparison.Ordinal);
+        var justDeactivated = target.Activo && !cmd.Activo;
+        if (rolChanged || justDeactivated)
+        {
+            await _refreshTokenRepository.RevokeAllActiveForUserAsync(cmd.Id, now);
+        }
+
+        // TODO: audit — defer to ADM-004
+        var updated = await _repository.GetDetailAsync(cmd.Id)
+            ?? throw new UsuarioNotFoundException(cmd.Id);
+
+        return new UsuarioDetailDto(
+            updated.Id, updated.Username, updated.Nombre, updated.Apellido,
+            updated.Email, updated.Rol, updated.Activo, updated.MustChangePassword,
+            updated.UltimoLogin, updated.FechaModificacion);
+    }
+}
diff --git a/src/api/SIGCM2.Application/Usuarios/Update/UpdateUsuarioCommandValidator.cs b/src/api/SIGCM2.Application/Usuarios/Update/UpdateUsuarioCommandValidator.cs
new file mode 100644
index 0000000..40e315b
--- /dev/null
+++ b/src/api/SIGCM2.Application/Usuarios/Update/UpdateUsuarioCommandValidator.cs
@@ -0,0 +1,29 @@
+using FluentValidation;
+using SIGCM2.Application.Abstractions.Persistence;
+
+namespace SIGCM2.Application.Usuarios.Update;
+
+public sealed class UpdateUsuarioCommandValidator : AbstractValidator<UpdateUsuarioCommand>
+{
+    public UpdateUsuarioCommandValidator(IRolRepository rolRepository)
+    {
+        RuleFor(x => x.Email)
+            .EmailAddress()
+            .When(x => x.Email is not null)
+            .WithMessage("El formato del email es inválido.");
+
+        RuleFor(x => x.Nombre)
+            .NotEmpty()
+            .WithMessage("El nombre es requerido.");
+
+        RuleFor(x => x.Apellido)
+            .NotEmpty()
+            .WithMessage("El apellido es requerido.");
+
+        RuleFor(x => x.Rol)
+            .NotEmpty()
+            .WithMessage("El rol es requerido.")
+            .MustAsync(async (rol, ct) => await rolRepository.ExistsActiveByCodigoAsync(rol, ct))
+            .WithMessage(x => $"El rol '{x.Rol}' no existe o está inactivo.");
+    }
+}
diff --git a/src/api/SIGCM2.Domain/Exceptions/InvalidOldPasswordException.cs b/src/api/SIGCM2.Domain/Exceptions/InvalidOldPasswordException.cs
new file mode 100644
index 0000000..2a12a08
--- /dev/null
+++ b/src/api/SIGCM2.Domain/Exceptions/InvalidOldPasswordException.cs
@@ -0,0 +1,10 @@
+namespace SIGCM2.Domain.Exceptions;
+
+/// <summary>
+/// Thrown when a user provides an incorrect current password during password change.
+/// </summary>
+public sealed class InvalidOldPasswordException : DomainException
+{
+    public InvalidOldPasswordException()
+        : base("La contraseña actual es incorrecta.") { }
+}
diff --git a/tests/SIGCM2.Api.Tests/Usuarios/GetUsuarioByIdEndpointTests.cs b/tests/SIGCM2.Api.Tests/Usuarios/GetUsuarioByIdEndpointTests.cs
new file mode 100644
index 0000000..57088c6
--- /dev/null
+++ b/tests/SIGCM2.Api.Tests/Usuarios/GetUsuarioByIdEndpointTests.cs
@@ -0,0 +1,131 @@
+using System.Net;
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+using System.Text.Json;
+using Dapper;
+using Microsoft.Data.SqlClient;
+using SIGCM2.TestSupport;
+
+namespace SIGCM2.Api.Tests.Usuarios;
+
+/// <summary>
+/// Integration tests for GET /api/v1/users/{id} (UDT-008 B3).
+/// </summary>
+[Collection("ApiIntegration")]
+public sealed class GetUsuarioByIdEndpointTests : IAsyncLifetime
+{
+    private const string TestConnectionString =
+        "Server=TECNICA3;Database=SIGCM2_Test;User Id=desarrollo;Password=desarrollo2026;TrustServerCertificate=True;";
+
+    private readonly HttpClient _client;
+    private readonly SqlTestFixture _db;
+
+    public GetUsuarioByIdEndpointTests(TestWebAppFactory factory)
+    {
+        _client = factory.CreateClient();
+        _db = new SqlTestFixture(TestConnectionString);
+    }
+
+    public async Task InitializeAsync() => await _db.InitializeAsync();
+    public async Task DisposeAsync() => await _db.DisposeAsync();
+
+    private async Task<string> GetAdminTokenAsync()
+    {
+        var response = await _client.PostAsJsonAsync("/api/v1/auth/login",
+            new { username = "admin", password = "@Diego550@" });
+        response.EnsureSuccessStatusCode();
+        var json = await response.Content.ReadFromJsonAsync<JsonElement>();
+        return json.GetProperty("accessToken").GetString()!;
+    }
+
+    private async Task<int> GetAdminIdAsync()
+    {
+        await using var conn = new SqlConnection(TestConnectionString);
+        await conn.OpenAsync();
+        return await conn.ExecuteScalarAsync<int>("SELECT Id FROM dbo.Usuario WHERE Username = 'admin'");
+    }
+
+    private async Task<string> GetCajeroTokenAsync()
+    {
+        await using var conn = new SqlConnection(TestConnectionString);
+        await conn.OpenAsync();
+        await conn.ExecuteAsync("""
+            IF NOT EXISTS (SELECT 1 FROM dbo.Usuario WHERE Username = 'cajero_getbyid')
+            INSERT INTO dbo.Usuario (Username, PasswordHash, Nombre, Apellido, Rol, PermisosJson, Activo, MustChangePassword)
+            VALUES ('cajero_getbyid', '$2a$12$rmq6tlSAQ8WXhR2CwLCSeuwCJKz/.8Eab95UQCUNfwe4dokeOqMcW', 'Cajero', 'Test', 'cajero', '[]', 1, 0)
+            """);
+
+        var response = await _client.PostAsJsonAsync("/api/v1/auth/login",
+            new { username = "cajero_getbyid", password = "@Diego550@" });
+        response.EnsureSuccessStatusCode();
+        var json = await response.Content.ReadFromJsonAsync<JsonElement>();
+        return json.GetProperty("accessToken").GetString()!;
+    }
+
+    [Fact]
+    public async Task GET_Users_Id_200_Returns_Detail_Shape()
+    {
+        var token = await GetAdminTokenAsync();
+        var adminId = await GetAdminIdAsync();
+        var request = new HttpRequestMessage(HttpMethod.Get, $"/api/v1/users/{adminId}");
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+
+        var response = await _client.SendAsync(request);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var json = await response.Content.ReadFromJsonAsync<JsonElement>();
+        Assert.Equal(adminId, json.GetProperty("id").GetInt32());
+        Assert.Equal("admin", json.GetProperty("username").GetString());
+        Assert.True(json.TryGetProperty("nombre", out _));
+        Assert.True(json.TryGetProperty("rol", out _));
+        Assert.True(json.TryGetProperty("activo", out _));
+        Assert.True(json.TryGetProperty("mustChangePassword", out _));
+    }
+
+    [Fact]
+    public async Task GET_Users_Id_DoesNotContain_PasswordHash_In_Response()
+    {
+        var token = await GetAdminTokenAsync();
+        var adminId = await GetAdminIdAsync();
+        var request = new HttpRequestMessage(HttpMethod.Get, $"/api/v1/users/{adminId}");
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+
+        var response = await _client.SendAsync(request);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var rawJson = await response.Content.ReadAsStringAsync();
+        Assert.DoesNotContain("passwordHash", rawJson, StringComparison.OrdinalIgnoreCase);
+        Assert.DoesNotContain("permisosJson", rawJson, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public async Task GET_Users_Id_9999_Returns_404()
+    {
+        var token = await GetAdminTokenAsync();
+        var request = new HttpRequestMessage(HttpMethod.Get, "/api/v1/users/9999");
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+
+        var response = await _client.SendAsync(request);
+
+        Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task GET_Users_Id_No_Auth_Returns_401()
+    {
+        var response = await _client.GetAsync("/api/v1/users/1");
+        Assert.Equal(HttpStatusCode.Unauthorized, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task GET_Users_Id_No_Permission_Returns_403()
+    {
+        var token = await GetCajeroTokenAsync();
+        var request = new HttpRequestMessage(HttpMethod.Get, "/api/v1/users/1");
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+
+        var response = await _client.SendAsync(request);
+
+        Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
+    }
+}
diff --git a/tests/SIGCM2.Api.Tests/Usuarios/ListUsuariosEndpointTests.cs b/tests/SIGCM2.Api.Tests/Usuarios/ListUsuariosEndpointTests.cs
new file mode 100644
index 0000000..8180731
--- /dev/null
+++ b/tests/SIGCM2.Api.Tests/Usuarios/ListUsuariosEndpointTests.cs
@@ -0,0 +1,152 @@
+using System.Net;
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+using System.Text.Json;
+using Dapper;
+using Microsoft.Data.SqlClient;
+using SIGCM2.TestSupport;
+
+namespace SIGCM2.Api.Tests.Usuarios;
+
+/// <summary>
+/// Integration tests for GET /api/v1/users (UDT-008 B3).
+/// </summary>
+[Collection("ApiIntegration")]
+public sealed class ListUsuariosEndpointTests : IAsyncLifetime
+{
+    private const string TestConnectionString =
+        "Server=TECNICA3;Database=SIGCM2_Test;User Id=desarrollo;Password=desarrollo2026;TrustServerCertificate=True;";
+
+    private readonly HttpClient _client;
+    private readonly SqlTestFixture _db;
+
+    public ListUsuariosEndpointTests(TestWebAppFactory factory)
+    {
+        _client = factory.CreateClient();
+        _db = new SqlTestFixture(TestConnectionString);
+    }
+
+    public async Task InitializeAsync() => await _db.InitializeAsync();
+    public async Task DisposeAsync() => await _db.DisposeAsync();
+
+    private async Task<string> GetAdminTokenAsync()
+    {
+        var response = await _client.PostAsJsonAsync("/api/v1/auth/login",
+            new { username = "admin", password = "@Diego550@" });
+        response.EnsureSuccessStatusCode();
+        var json = await response.Content.ReadFromJsonAsync<JsonElement>();
+        return json.GetProperty("accessToken").GetString()!;
+    }
+
+    private async Task<string> GetCajeroTokenAsync()
+    {
+        // Seed a cajero user
+        await using var conn = new SqlConnection(TestConnectionString);
+        await conn.OpenAsync();
+        await conn.ExecuteAsync("""
+            IF NOT EXISTS (SELECT 1 FROM dbo.Usuario WHERE Username = 'cajero_test')
+            INSERT INTO dbo.Usuario (Username, PasswordHash, Nombre, Apellido, Rol, PermisosJson, Activo, MustChangePassword)
+            VALUES ('cajero_test', '$2a$12$rmq6tlSAQ8WXhR2CwLCSeuwCJKz/.8Eab95UQCUNfwe4dokeOqMcW', 'Cajero', 'Test', 'cajero', '[]', 1, 0)
+            """);
+
+        var response = await _client.PostAsJsonAsync("/api/v1/auth/login",
+            new { username = "cajero_test", password = "@Diego550@" });
+        response.EnsureSuccessStatusCode();
+        var json = await response.Content.ReadFromJsonAsync<JsonElement>();
+        return json.GetProperty("accessToken").GetString()!;
+    }
+
+    // ── happy path ────────────────────────────────────────────────────────────
+
+    [Fact]
+    public async Task GET_Users_200_Returns_Paged_Shape()
+    {
+        var token = await GetAdminTokenAsync();
+        var request = new HttpRequestMessage(HttpMethod.Get, "/api/v1/users");
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+
+        var response = await _client.SendAsync(request);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var json = await response.Content.ReadFromJsonAsync<JsonElement>();
+        Assert.True(json.TryGetProperty("items", out _));
+        Assert.True(json.TryGetProperty("page", out _));
+        Assert.True(json.TryGetProperty("pageSize", out _));
+        Assert.True(json.TryGetProperty("total", out _));
+    }
+
+    [Fact]
+    public async Task GET_Users_Default_PageSize_Is_20()
+    {
+        var token = await GetAdminTokenAsync();
+        var request = new HttpRequestMessage(HttpMethod.Get, "/api/v1/users");
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+
+        var response = await _client.SendAsync(request);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var json = await response.Content.ReadFromJsonAsync<JsonElement>();
+        Assert.Equal(20, json.GetProperty("pageSize").GetInt32());
+        Assert.Equal(1, json.GetProperty("page").GetInt32());
+    }
+
+    [Fact]
+    public async Task GET_Users_Filter_Rol_Admin_Returns_Only_Admins()
+    {
+        var token = await GetAdminTokenAsync();
+        var request = new HttpRequestMessage(HttpMethod.Get, "/api/v1/users?rol=admin");
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+
+        var response = await _client.SendAsync(request);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var json = await response.Content.ReadFromJsonAsync<JsonElement>();
+        var items = json.GetProperty("items").EnumerateArray().ToList();
+        Assert.All(items, item => Assert.Equal("admin", item.GetProperty("rol").GetString()));
+    }
+
+    [Fact]
+    public async Task GET_Users_PageSize_0_Returns_400()
+    {
+        var token = await GetAdminTokenAsync();
+        var request = new HttpRequestMessage(HttpMethod.Get, "/api/v1/users?pageSize=0");
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+
+        var response = await _client.SendAsync(request);
+
+        Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task GET_Users_Page_0_Returns_400()
+    {
+        var token = await GetAdminTokenAsync();
+        var request = new HttpRequestMessage(HttpMethod.Get, "/api/v1/users?page=0");
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+
+        var response = await _client.SendAsync(request);
+
+        Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
+    }
+
+    // ── auth ──────────────────────────────────────────────────────────────────
+
+    [Fact]
+    public async Task GET_Users_No_Auth_Returns_401()
+    {
+        var response = await _client.GetAsync("/api/v1/users");
+        Assert.Equal(HttpStatusCode.Unauthorized, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task GET_Users_No_Permission_Returns_403()
+    {
+        var token = await GetCajeroTokenAsync();
+        var request = new HttpRequestMessage(HttpMethod.Get, "/api/v1/users");
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+
+        var response = await _client.SendAsync(request);
+
+        Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
+    }
+}
diff --git a/tests/SIGCM2.Application.Tests/Usuarios/GetUsuarioByIdQueryHandlerTests.cs b/tests/SIGCM2.Application.Tests/Usuarios/GetUsuarioByIdQueryHandlerTests.cs
new file mode 100644
index 0000000..b9a7fe3
--- /dev/null
+++ b/tests/SIGCM2.Application.Tests/Usuarios/GetUsuarioByIdQueryHandlerTests.cs
@@ -0,0 +1,61 @@
+using NSubstitute;
+using SIGCM2.Application.Abstractions.Persistence;
+using SIGCM2.Application.Usuarios.GetById;
+using SIGCM2.Domain.Entities;
+using SIGCM2.Domain.Exceptions;
+
+namespace SIGCM2.Application.Tests.Usuarios;
+
+public class GetUsuarioByIdQueryHandlerTests
+{
+    private readonly IUsuarioRepository _repo = Substitute.For<IUsuarioRepository>();
+    private readonly GetUsuarioByIdQueryHandler _handler;
+
+    public GetUsuarioByIdQueryHandlerTests()
+    {
+        _handler = new GetUsuarioByIdQueryHandler(_repo);
+    }
+
+    [Fact]
+    public async Task Handle_Returns_UsuarioDetailDto_When_Found()
+    {
+        var usuario = new Usuario(5, "jperez", "$2a$12$hash", "Juan", "Pérez", "j@x.com", "cajero", "[]", true,
+            fechaModificacion: null, ultimoLogin: null, mustChangePassword: false);
+
+        _repo.GetDetailAsync(5, Arg.Any<CancellationToken>()).Returns(usuario);
+
+        var result = await _handler.Handle(new GetUsuarioByIdQuery(5));
+
+        Assert.Equal(5, result.Id);
+        Assert.Equal("jperez", result.Username);
+        Assert.Equal("Juan", result.Nombre);
+        Assert.Equal("Pérez", result.Apellido);
+        Assert.Equal("j@x.com", result.Email);
+        Assert.Equal("cajero", result.Rol);
+        Assert.True(result.Activo);
+        Assert.False(result.MustChangePassword);
+    }
+
+    [Fact]
+    public async Task Handle_DoesNotReturn_PasswordHash_In_Dto()
+    {
+        var usuario = new Usuario(5, "jperez", "$2a$12$SECRETHASH", "Juan", "Pérez", null, "cajero", "[]", true);
+        _repo.GetDetailAsync(5, Arg.Any<CancellationToken>()).Returns(usuario);
+
+        var result = await _handler.Handle(new GetUsuarioByIdQuery(5));
+
+        // UsuarioDetailDto must not expose PasswordHash
+        var props = typeof(UsuarioDetailDto).GetProperties().Select(p => p.Name);
+        Assert.DoesNotContain("PasswordHash", props);
+        Assert.DoesNotContain("PermisosJson", props);
+    }
+
+    [Fact]
+    public async Task Handle_Throws_UsuarioNotFoundException_When_Not_Found()
+    {
+        _repo.GetDetailAsync(9999, Arg.Any<CancellationToken>()).Returns((Usuario?)null);
+
+        await Assert.ThrowsAsync<UsuarioNotFoundException>(
+            () => _handler.Handle(new GetUsuarioByIdQuery(9999)));
+    }
+}
diff --git a/tests/SIGCM2.Application.Tests/Usuarios/ListUsuariosQueryHandlerTests.cs b/tests/SIGCM2.Application.Tests/Usuarios/ListUsuariosQueryHandlerTests.cs
new file mode 100644
index 0000000..31bdef6
--- /dev/null
+++ b/tests/SIGCM2.Application.Tests/Usuarios/ListUsuariosQueryHandlerTests.cs
@@ -0,0 +1,119 @@
+using NSubstitute;
+using SIGCM2.Application.Abstractions.Persistence;
+using SIGCM2.Application.Common;
+using SIGCM2.Application.Usuarios.List;
+using SIGCM2.Domain.Exceptions;
+
+namespace SIGCM2.Application.Tests.Usuarios;
+
+public class ListUsuariosQueryHandlerTests
+{
+    private readonly IUsuarioRepository _repo = Substitute.For<IUsuarioRepository>();
+    private readonly ListUsuariosQueryHandler _handler;
+
+    public ListUsuariosQueryHandlerTests()
+    {
+        _handler = new ListUsuariosQueryHandler(_repo);
+    }
+
+    [Fact]
+    public async Task Handle_Returns_PagedResult_With_Items()
+    {
+        var items = new List<UsuarioListItem>
+        {
+            new(1, "admin", "Admin", "Sys", null, "admin", true, null, null)
+        };
+        var paged = new PagedResult<UsuarioListItem>(items, 1, 20, 1);
+
+        _repo.GetPagedAsync(Arg.Any<UsuariosQuery>(), Arg.Any<CancellationToken>())
+            .Returns(paged);
+
+        var query = new ListUsuariosQuery(1, 20, null, null, null);
+        var result = await _handler.Handle(query);
+
+        Assert.Equal(1, result.Total);
+        Assert.Single(result.Items);
+    }
+
+    [Fact]
+    public async Task Handle_Clamps_PageSize_Above_100_To_100()
+    {
+        _repo.GetPagedAsync(Arg.Any<UsuariosQuery>(), Arg.Any<CancellationToken>())
+            .Returns(new PagedResult<UsuarioListItem>([], 1, 100, 0));
+
+        var query = new ListUsuariosQuery(1, 200, null, null, null);
+        await _handler.Handle(query);
+
+        await _repo.Received(1).GetPagedAsync(
+            Arg.Is<UsuariosQuery>(q => q.PageSize == 100),
+            Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task Handle_Clamps_Page_Below_1_To_1()
+    {
+        _repo.GetPagedAsync(Arg.Any<UsuariosQuery>(), Arg.Any<CancellationToken>())
+            .Returns(new PagedResult<UsuarioListItem>([], 1, 20, 0));
+
+        var query = new ListUsuariosQuery(0, 20, null, null, null);
+        await _handler.Handle(query);
+
+        await _repo.Received(1).GetPagedAsync(
+            Arg.Is<UsuariosQuery>(q => q.Page == 1),
+            Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task Handle_Passes_Rol_Filter()
+    {
+        _repo.GetPagedAsync(Arg.Any<UsuariosQuery>(), Arg.Any<CancellationToken>())
+            .Returns(new PagedResult<UsuarioListItem>([], 1, 20, 0));
+
+        var query = new ListUsuariosQuery(1, 20, "admin", null, null);
+        await _handler.Handle(query);
+
+        await _repo.Received(1).GetPagedAsync(
+            Arg.Is<UsuariosQuery>(q => q.Rol == "admin"),
+            Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task Handle_Passes_Activo_Filter()
+    {
+        _repo.GetPagedAsync(Arg.Any<UsuariosQuery>(), Arg.Any<CancellationToken>())
+            .Returns(new PagedResult<UsuarioListItem>([], 1, 20, 0));
+
+        var query = new ListUsuariosQuery(1, 20, null, false, null);
+        await _handler.Handle(query);
+
+        await _repo.Received(1).GetPagedAsync(
+            Arg.Is<UsuariosQuery>(q => q.Activo == false),
+            Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task Handle_Passes_Search_Filter()
+    {
+        _repo.GetPagedAsync(Arg.Any<UsuariosQuery>(), Arg.Any<CancellationToken>())
+            .Returns(new PagedResult<UsuarioListItem>([], 1, 20, 0));
+
+        var query = new ListUsuariosQuery(1, 20, null, null, "juan");
+        await _handler.Handle(query);
+
+        await _repo.Received(1).GetPagedAsync(
+            Arg.Is<UsuariosQuery>(q => q.Search == "juan"),
+            Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task Handle_Returns_Empty_When_No_Items()
+    {
+        _repo.GetPagedAsync(Arg.Any<UsuariosQuery>(), Arg.Any<CancellationToken>())
+            .Returns(new PagedResult<UsuarioListItem>([], 1, 20, 0));
+
+        var result = await _handler.Handle(new ListUsuariosQuery(1, 20, null, null, null));
+
+        Assert.Equal(0, result.Total);
+        Assert.Empty(result.Items);
+    }
+}