diff --git a/Gemfile b/Gemfile
index f0736381..96ffa020 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,8 +5,11 @@
 # tiempo buscando soporte para musl
 if ENV['RAILS_ENV'] == 'production'
   source 'https://gems.sutty.nl'
+  ruby '2.7.2'
 else
   source 'https://rubygems.org'
+  # Cambiar en Dockerfile también
+  ruby '2.7.1'
 end
 
 git_source(:github) do |repo_name|
@@ -14,8 +17,6 @@ git_source(:github) do |repo_name|
   "https://github.com/#{repo_name}.git"
 end
 
-# Cambiar en Dockerfile también
-ruby '2.7.2'
 
 gem 'dotenv-rails', require: 'dotenv/rails-now'
 
@@ -71,6 +72,7 @@ gem 'redis', require: %w[redis redis/connection/hiredis]
 gem 'redis-rails'
 gem 'rubyzip'
 gem 'rugged'
+gem 'concurrent-ruby-ext'
 gem 'sucker_punch'
 gem 'symbol-fstring', require: 'fstring/all'
 gem 'terminal-table'
diff --git a/Gemfile.lock b/Gemfile.lock
index ae912f98..8d4da435 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -10,60 +10,60 @@ GEM
   remote: https://rubygems.org/
   remote: https://gems.sutty.nl/
   specs:
-    actioncable (6.1.1)
-      actionpack (= 6.1.1)
-      activesupport (= 6.1.1)
+    actioncable (6.1.2.1)
+      actionpack (= 6.1.2.1)
+      activesupport (= 6.1.2.1)
       nio4r (~> 2.0)
       websocket-driver (>= 0.6.1)
-    actionmailbox (6.1.1)
-      actionpack (= 6.1.1)
-      activejob (= 6.1.1)
-      activerecord (= 6.1.1)
-      activestorage (= 6.1.1)
-      activesupport (= 6.1.1)
+    actionmailbox (6.1.2.1)
+      actionpack (= 6.1.2.1)
+      activejob (= 6.1.2.1)
+      activerecord (= 6.1.2.1)
+      activestorage (= 6.1.2.1)
+      activesupport (= 6.1.2.1)
       mail (>= 2.7.1)
-    actionmailer (6.1.1)
-      actionpack (= 6.1.1)
-      actionview (= 6.1.1)
-      activejob (= 6.1.1)
-      activesupport (= 6.1.1)
+    actionmailer (6.1.2.1)
+      actionpack (= 6.1.2.1)
+      actionview (= 6.1.2.1)
+      activejob (= 6.1.2.1)
+      activesupport (= 6.1.2.1)
       mail (~> 2.5, >= 2.5.4)
       rails-dom-testing (~> 2.0)
-    actionpack (6.1.1)
-      actionview (= 6.1.1)
-      activesupport (= 6.1.1)
+    actionpack (6.1.2.1)
+      actionview (= 6.1.2.1)
+      activesupport (= 6.1.2.1)
       rack (~> 2.0, >= 2.0.9)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.2.0)
-    actiontext (6.1.1)
-      actionpack (= 6.1.1)
-      activerecord (= 6.1.1)
-      activestorage (= 6.1.1)
-      activesupport (= 6.1.1)
+    actiontext (6.1.2.1)
+      actionpack (= 6.1.2.1)
+      activerecord (= 6.1.2.1)
+      activestorage (= 6.1.2.1)
+      activesupport (= 6.1.2.1)
       nokogiri (>= 1.8.5)
-    actionview (6.1.1)
-      activesupport (= 6.1.1)
+    actionview (6.1.2.1)
+      activesupport (= 6.1.2.1)
       builder (~> 3.1)
       erubi (~> 1.4)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.1, >= 1.2.0)
-    activejob (6.1.1)
-      activesupport (= 6.1.1)
+    activejob (6.1.2.1)
+      activesupport (= 6.1.2.1)
       globalid (>= 0.3.6)
-    activemodel (6.1.1)
-      activesupport (= 6.1.1)
-    activerecord (6.1.1)
-      activemodel (= 6.1.1)
-      activesupport (= 6.1.1)
-    activestorage (6.1.1)
-      actionpack (= 6.1.1)
-      activejob (= 6.1.1)
-      activerecord (= 6.1.1)
-      activesupport (= 6.1.1)
+    activemodel (6.1.2.1)
+      activesupport (= 6.1.2.1)
+    activerecord (6.1.2.1)
+      activemodel (= 6.1.2.1)
+      activesupport (= 6.1.2.1)
+    activestorage (6.1.2.1)
+      actionpack (= 6.1.2.1)
+      activejob (= 6.1.2.1)
+      activerecord (= 6.1.2.1)
+      activesupport (= 6.1.2.1)
       marcel (~> 0.3.1)
       mimemagic (~> 0.3.2)
-    activesupport (6.1.1)
+    activesupport (6.1.2.1)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (>= 1.6, < 2)
       minitest (>= 5.1)
@@ -86,7 +86,7 @@ GEM
     bcrypt (3.1.16)
     benchmark-ips (2.8.4)
     bindex (0.8.1)
-    blazer (2.4.1)
+    blazer (2.4.2)
       activerecord (>= 5)
       chartkick (>= 3.2)
       railties (>= 5)
@@ -108,18 +108,20 @@ GEM
     childprocess (3.0.0)
     coderay (1.1.3)
     colorator (1.1.0)
-    commonmarker (0.21.1)
+    commonmarker (0.21.2)
       ruby-enum (~> 0.5)
     concurrent-ruby (1.1.8)
+    concurrent-ruby-ext (1.1.8)
+      concurrent-ruby (= 1.1.8)
     crass (1.0.6)
-    database_cleaner (2.0.0)
+    database_cleaner (2.0.1)
       database_cleaner-active_record (~> 2.0.0)
     database_cleaner-active_record (2.0.0)
       activerecord (>= 5.a)
       database_cleaner-core (~> 2.0.0)
-    database_cleaner-core (2.0.0)
+    database_cleaner-core (2.0.1)
     dead_end (1.1.4)
-    derailed_benchmarks (2.0.0)
+    derailed_benchmarks (2.0.1)
       benchmark-ips (~> 2)
       dead_end
       get_process_mem (~> 0)
@@ -127,6 +129,7 @@ GEM
       memory_profiler (>= 0, < 2)
       mini_histogram (>= 0.3.0)
       rack (>= 1)
+      rack-test
       rake (> 10, < 14)
       ruby-statistics (>= 2.1)
       thor (>= 0.19, < 2)
@@ -287,7 +290,7 @@ GEM
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
       ruby_dep (~> 1.2)
-    lockbox (0.6.1)
+    lockbox (0.6.2)
     lograge (0.11.2)
       actionpack (>= 4)
       activesupport (>= 4)
@@ -313,7 +316,7 @@ GEM
       jekyll-feed (~> 0.9)
       jekyll-seo-tag (~> 2.1)
     minitest (5.14.3)
-    mobility (1.0.5)
+    mobility (1.1.0)
       i18n (>= 0.6.10, < 2)
       request_store (~> 1.0)
     netaddr (2.0.4)
@@ -331,7 +334,7 @@ GEM
     popper_js (1.16.0)
     prometheus_exporter (0.7.0)
       webrick
-    pry (0.13.1)
+    pry (0.14.0)
       coderay (~> 1.1)
       method_source (~> 1.0)
     public_suffix (4.0.6)
@@ -360,20 +363,20 @@ GEM
       jekyll-relative-urls (~> 0.0)
       jekyll-seo-tag (~> 2.1)
       jekyll-turbolinks (~> 0)
-    rails (6.1.1)
-      actioncable (= 6.1.1)
-      actionmailbox (= 6.1.1)
-      actionmailer (= 6.1.1)
-      actionpack (= 6.1.1)
-      actiontext (= 6.1.1)
-      actionview (= 6.1.1)
-      activejob (= 6.1.1)
-      activemodel (= 6.1.1)
-      activerecord (= 6.1.1)
-      activestorage (= 6.1.1)
-      activesupport (= 6.1.1)
+    rails (6.1.2.1)
+      actioncable (= 6.1.2.1)
+      actionmailbox (= 6.1.2.1)
+      actionmailer (= 6.1.2.1)
+      actionpack (= 6.1.2.1)
+      actiontext (= 6.1.2.1)
+      actionview (= 6.1.2.1)
+      activejob (= 6.1.2.1)
+      activemodel (= 6.1.2.1)
+      activerecord (= 6.1.2.1)
+      activestorage (= 6.1.2.1)
+      activesupport (= 6.1.2.1)
       bundler (>= 1.15.0)
-      railties (= 6.1.1)
+      railties (= 6.1.2.1)
       sprockets-rails (>= 2.0.0)
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
@@ -385,9 +388,9 @@ GEM
       railties (>= 6.0.0, < 7)
     rails_warden (0.6.0)
       warden (>= 1.2.0)
-    railties (6.1.1)
-      actionpack (= 6.1.1)
-      activesupport (= 6.1.1)
+    railties (6.1.2.1)
+      actionpack (= 6.1.2.1)
+      activesupport (= 6.1.2.1)
       method_source
       rake (>= 0.8.7)
       thor (~> 1.0)
@@ -457,7 +460,7 @@ GEM
       i18n
     ruby-filemagic (0.7.2)
     ruby-progressbar (1.11.0)
-    ruby-statistics (2.1.2)
+    ruby-statistics (2.1.3)
     ruby-vips (2.0.17)
       ffi (~> 1.9)
     ruby_dep (1.5.0)
@@ -537,7 +540,7 @@ GEM
       unicode-display_width (~> 1.1, >= 1.1.1)
     thor (1.1.0)
     tilt (2.0.10)
-    timecop (0.9.2)
+    timecop (0.9.4)
     turbolinks (5.2.1)
       turbolinks-source (~> 5.2)
     turbolinks-source (5.2.0)
@@ -583,6 +586,7 @@ DEPENDENCIES
   brakeman
   capybara (~> 2.13)
   commonmarker
+  concurrent-ruby-ext
   database_cleaner
   derailed_benchmarks
   devise
@@ -660,7 +664,7 @@ DEPENDENCIES
   yaml_db!
 
 RUBY VERSION
-   ruby 2.7.2p137
+   ruby 2.7.1p83
 
 BUNDLED WITH
    2.1.4
diff --git a/Makefile b/Makefile
index 7e5cf70a..66638fbb 100644
--- a/Makefile
+++ b/Makefile
@@ -9,10 +9,10 @@ assets := package.json yarn.lock $(shell find app/assets/ app/javascript/ -type
 
 alpine_version := 3.12
 
-public/packs/manifest.json: $(assets)
+public/packs/manifest.json.br: $(assets)
 	PANEL_URL=https://panel.sutty.nl RAILS_ENV=production NODE_ENV=production bundle exec rake assets:precompile assets:clean
 
-assets: public/packs/manifest.json
+assets: public/packs/manifest.json.br
 
 serve: /etc/hosts
 	bundle exec rails s -b "ssl://0.0.0.0:3000?key=../sutty.local/domain/$(SUTTY).key&cert=../sutty.local/domain/$(SUTTY).crt"
@@ -82,7 +82,7 @@ $(dirs):
 /etc/hosts: always
 	@echo "Chequeando si es necesario agregar el dominio local $(SUTTY)"
 	@grep -q " $(SUTTY)$$" $@ || echo -e "127.0.0.1 $(SUTTY)\n::1 $(SUTTY)" | sudo tee -a $@
-	@grep -q " api.$(SUTTY)$$" $@ || echo -e "127.0.0.1 api.$(SUTTY)\n::1 $(SUTTY)" | sudo tee -a $@
-	@grep -q " panel.$(SUTTY)$$" $@ || echo -e "127.0.0.1 panel.$(SUTTY)\n::1 $(SUTTY)" | sudo tee -a $@
+	@grep -q " api.$(SUTTY)$$" $@ || echo -e "127.0.0.1 api.$(SUTTY)\n::1 api.$(SUTTY)" | sudo tee -a $@
+	@grep -q " panel.$(SUTTY)$$" $@ || echo -e "127.0.0.1 panel.$(SUTTY)\n::1 panel.$(SUTTY)" | sudo tee -a $@
 
 .PHONY: always
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 2f09ceab..9893daa6 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -4,7 +4,7 @@
 class ApplicationController < ActionController::Base
   include ExceptionHandler
 
-  protect_from_forgery with: :exception
+  protect_from_forgery with: :exception, prepend: true
 
   before_action :prepare_exception_notifier
   before_action :configure_permitted_parameters, if: :devise_controller?
diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index a389327a..23b4c995 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -73,7 +73,7 @@ module ApplicationHelper
 
   # Opciones por defecto para el campo de un formulario
   def field_options(attribute, metadata, **extra)
-    required = metadata.required || extra[:required]
+    required = extra.key?(:required) ? extra[:required] : metadata.required
 
     {
       class: "form-control #{invalid(metadata.post, attribute)} #{extra[:class]}",
diff --git a/app/javascript/packs/application.js b/app/javascript/packs/application.js
index 7295446d..4c232fd6 100644
--- a/app/javascript/packs/application.js
+++ b/app/javascript/packs/application.js
@@ -107,4 +107,13 @@ document.addEventListener('turbolinks:load', () => {
     // Ocultar el area
     textArea.style.display = 'none'
   })
+
+  // Validar fechas en navegadores que no soportan date
+  document.querySelectorAll('input[type="date"]').forEach(date => {
+    if (date.type === 'date') return
+
+    date.addEventListener('change', event => {
+      date.setCustomValidity(date.validity.patternMismatch ? date.dataset.patternMismatch : '')
+    })
+  })
 })
diff --git a/app/jobs/maintenance_job.rb b/app/jobs/maintenance_job.rb
index 114ff77b..4c411d0e 100644
--- a/app/jobs/maintenance_job.rb
+++ b/app/jobs/maintenance_job.rb
@@ -22,15 +22,13 @@ class MaintenanceJob < ApplicationJob
 
     # XXX: Parece que [0] es más rápido que []#first
     Usuarie.all.pluck(:email, :lang).each do |u|
-      begin
-        MaintenanceMailer.with(maintenance: maintenance,
-                               email: u[0],
-                               lang: u[1]).public_send(mailer).deliver_now
-      rescue Net::SMTPServerBusy => e
-        # Algunas direcciones no son válidas, no queremos detener el
-        # envío pero sí enterarnos cuáles son
-        ExceptionNotifier.notify_exception e
-      end
+      MaintenanceMailer.with(maintenance: maintenance,
+                             email: u[0],
+                             lang: u[1]).public_send(mailer).deliver_now
+    rescue Net::SMTPServerBusy => e
+      # Algunas direcciones no son válidas, no queremos detener el
+      # envío pero sí enterarnos cuáles son
+      ExceptionNotifier.notify_exception(e, data: { maintenance_id: maintenance_id, email: u[0] })
     end
   end
 end
diff --git a/app/models/layout.rb b/app/models/layout.rb
index c05a02f6..2d68273a 100644
--- a/app/models/layout.rb
+++ b/app/models/layout.rb
@@ -9,6 +9,10 @@ Layout = Struct.new(:site, :name, :meta, :metadata, keyword_init: true) do
     name.to_s
   end
 
+  def attributes
+    @attributes ||= metadata.keys.map(&:to_sym)
+  end
+
   # Busca la traducción del Layout en el sitio o intenta humanizarlo
   # según Rails.
   #
diff --git a/app/models/metadata_array.rb b/app/models/metadata_array.rb
index a1ff8c72..5c0b16f7 100644
--- a/app/models/metadata_array.rb
+++ b/app/models/metadata_array.rb
@@ -7,15 +7,22 @@ class MetadataArray < MetadataTemplate
     super || []
   end
 
+  # Los Arrays no se pueden cifrar todavía
+  # TODO: Cifrar y decifrar arrays
+  def private?
+    false
+  end
+
   private
 
+  # TODO: Sanitizar otros valores
+  # XXX: Por qué eliminamos el punto del final?
   def sanitize(values)
     values.map do |v|
-      if v.is_a? String
-        super(v).sub(/\.\z/, '')
-      else
-        v
+      case v
+      when String then super(v).sub(/\.\z/, '')
+      else v
       end
-    end
+    end.select(&:present?)
   end
 end
diff --git a/app/models/metadata_belongs_to.rb b/app/models/metadata_belongs_to.rb
index 21195470..0626ba0c 100644
--- a/app/models/metadata_belongs_to.rb
+++ b/app/models/metadata_belongs_to.rb
@@ -3,6 +3,13 @@
 # Almacena el UUID de otro Post y actualiza el valor en el Post
 # relacionado.
 class MetadataBelongsTo < MetadataRelatedPosts
+  def value_was=(new_value)
+    @belongs_to = nil
+    @belonged_to = nil
+
+    super(new_value)
+  end
+
   # TODO: Convertir algunos tipos de valores en módulos para poder
   # implementar varios tipos de campo sin repetir código
   #
@@ -23,36 +30,36 @@ class MetadataBelongsTo < MetadataRelatedPosts
 
   # Guardar y guardar la relación inversa también, eliminando la
   # relación anterior si existía.
-  #
-  # XXX: Esto es un poco enclenque, porque habría que guardar tres
-  # archivos en lugar de uno solo e indicarle al artículo que tiene uno
-  # o muchos que busque los datos actualizados filtrando.  Pero también
-  # nos ahorra recursos en la búsqueda al cachear la información.  En
-  # una relación HABTM también vamos a hacer lo mismo.
   def save
-    return super unless inverse? && !included?
+    super
 
-    # Evitar que se cambie el orden de la relación
-    belonged_to&.dig(inverse)&.value&.delete post.uuid.value if belonged_to != belongs_to
+    # Si no hay relación inversa, no hacer nada más
+    return true unless changed?
+    return true unless inverse?
 
-    belongs_to[inverse].value << post.uuid.value unless belongs_to[inverse].value.include? post.uuid.value
+    # Si estamos cambiando la relación, tenemos que eliminar la relación
+    # anterior
+    belonged_to[inverse].value.delete post.uuid.value if changed? && belonged_to.present?
+
+    # No duplicar las relaciones
+    belongs_to[inverse].value << post.uuid.value unless belongs_to.blank? || included?
 
     true
   end
 
   # El Post actual está incluido en la relación inversa?
   def included?
-    belongs_to[inverse].value.include? post.uuid.value
+    belongs_to[inverse].value.include?(post.uuid.value)
   end
 
   # Hay una relación inversa y el artículo existe?
   def inverse?
-    inverse.present? && belongs_to.present?
+    inverse.present?
   end
 
   # El campo que es la relación inversa de este
   def inverse
-    layout.metadata.dig name, 'inverse'
+    @inverse ||= layout.metadata.dig(name, 'inverse')&.to_sym
   end
 
   # El Post relacionado con este artículo
@@ -62,15 +69,14 @@ class MetadataBelongsTo < MetadataRelatedPosts
   def belongs_to
     return if value.blank?
 
-    @belongs_to ||= {}
-    @belongs_to[value] ||= posts.find(value, uuid: true)
+    @belongs_to ||= posts.find(value, uuid: true)
   end
 
-  # El anterior artículo relacionado
+  # El artículo relacionado anterior
   def belonged_to
-    return if document.data[name.to_s].blank?
+    return if value_was.blank?
 
-    @belonged_to ||= posts.find(document.data[name.to_s], uuid: true)
+    @belonged_to ||= posts.find(value_was, uuid: true)
   end
 
   def related_posts?
@@ -83,11 +89,13 @@ class MetadataBelongsTo < MetadataRelatedPosts
 
   private
 
-  def sanitize(uuid)
-    uuid.gsub(/[^a-f0-9\-]/, '')
+  def post_exists?
+    return true if sanitize(value).blank?
+
+    sanitize(value).present? && belongs_to.present?
   end
 
-  def post_exists?
-    !value.blank? && posts.find(sanitize(value), uuid: true)
+  def sanitize(uuid)
+    uuid.to_s.gsub(/[^a-f0-9\-]/i, '')
   end
 end
diff --git a/app/models/metadata_document_date.rb b/app/models/metadata_document_date.rb
index 036877ae..39e68735 100644
--- a/app/models/metadata_document_date.rb
+++ b/app/models/metadata_document_date.rb
@@ -7,10 +7,14 @@ class MetadataDocumentDate < MetadataTemplate
     Date.today.to_time
   end
 
+  def value_from_document
+    document.date
+  end
+
   # El valor puede ser un Date, Time o una String en el formato
   # "yyyy-mm-dd"
   def value
-    return (self[:value] = document.date || default_value) if self[:value].nil?
+    return (self[:value] = value_from_document || default_value) if self[:value].nil?
 
     self[:value] = Date.iso8601(self[:value]).to_time if self[:value].is_a? String
 
diff --git a/app/models/metadata_factory.rb b/app/models/metadata_factory.rb
index 8cac1c86..c33f1f18 100644
--- a/app/models/metadata_factory.rb
+++ b/app/models/metadata_factory.rb
@@ -2,9 +2,14 @@
 
 # Devuelve metadatos de cierto tipo
 class MetadataFactory
-  def self.build(**args)
-    @@factory_cache ||= {}
-    @@factory_cache[args[:type]] ||= ('Metadata' + args[:type].to_s.camelcase).constantize
-    @@factory_cache[args[:type]].new(args)
+  class << self
+    def build(**args)
+      classify(args[:type]).new(**args)
+    end
+
+    def classify(type)
+      @factory_cache ||= {}
+      @factory_cache[type] ||= ('Metadata' + type.to_s.camelcase).constantize
+    end
   end
 end
diff --git a/app/models/metadata_file.rb b/app/models/metadata_file.rb
index fcabf05d..8fecf553 100644
--- a/app/models/metadata_file.rb
+++ b/app/models/metadata_file.rb
@@ -73,10 +73,14 @@ class MetadataFile < MetadataTemplate
     end
   end
 
+  def key_from_path
+    path.dirname.basename.to_s
+  end
+
   private
 
   def path?
-    !value['path'].blank?
+    value['path'].present?
   end
 
   def filemagic
@@ -100,10 +104,6 @@ class MetadataFile < MetadataTemplate
     end
   end
 
-  def key_from_path
-    path.dirname.basename.to_s
-  end
-
   # Hacemos un link duro para colocar el archivo dentro del repositorio
   # y no duplicar el espacio que ocupan.  Esto requiere que ambos
   # directorios estén dentro del mismo punto de montaje.
diff --git a/app/models/metadata_has_and_belongs_to_many.rb b/app/models/metadata_has_and_belongs_to_many.rb
index e08c9917..f14827ec 100644
--- a/app/models/metadata_has_and_belongs_to_many.rb
+++ b/app/models/metadata_has_and_belongs_to_many.rb
@@ -10,40 +10,7 @@
 # el libro actual.  La relación belongs_to tiene que traer todes les
 # autores que tienen este libro.  La relación es bidireccional, no hay
 # diferencia entre has_many y belongs_to.
-class MetadataHasAndBelongsToMany < MetadataBelongsTo
-  def default_value
-    []
-  end
-
-  # Posts a los que pertenece.  Memoizamos por value para obtener
-  # siempre la última relación.
-  #
-  # Buscamos todos los Post contenidos en el valor actual.  No
-  # garantizamos el orden.
-  #
-  # @return [PostRelation] Posts
-  def belongs_to
-    @belongs_to ||= {}
-    @belongs_to[value.hash.to_s] ||= posts.where(uuid: value)
-  end
-
-  # Devuelve la lista de Posts relacionados con este buscándolos en la
-  # relación inversa.  #save debería mantenerlos sincronizados.
-  #
-  # @return [PostRelation]
-  def has_many
-    @has_many ||= {}
-    @has_many[value.hash.to_s] ||= posts.where(inverse.to_sym => post.uuid.value)
-  end
-  alias had_many has_many
-
-  # Posts a los que pertenecía
-  #
-  # @return [PostRelation] Posts
-  def belonged_to
-    @belonged_to ||= posts.where(uuid: document.data.fetch(name.to_s, []))
-  end
-
+class MetadataHasAndBelongsToMany < MetadataHasMany
   # Mantiene la relación inversa si existe.
   #
   # La relación belongs_to se mantiene actualizada en la modificación
@@ -52,39 +19,33 @@ class MetadataHasAndBelongsToMany < MetadataBelongsTo
   # Buscamos en belongs_to la relación local, si se eliminó hay que
   # quitarla de la relación remota, sino hay que agregarla.
   def save
-    return true unless changed?
-
+    # XXX: No usamos super
     self[:value] = sanitize value
 
-    return true unless inverse? && !included?
+    return true unless changed?
+    return true unless inverse?
 
-    (belonged_to - belongs_to).each do |p|
-      p[inverse].value.delete post.uuid.value
+    (had_many - has_many).each do |remove|
+      remove[inverse]&.value&.delete post.uuid.value
     end
 
-    (belongs_to - belonged_to).each do |p|
-      p[inverse].value << post.uuid.value
+    (has_many - had_many).each do |add|
+      next unless add[inverse]
+      next if add[inverse].value.include? post.uuid.value
+
+      add[inverse].value << post.uuid.value
     end
 
     true
   end
 
-  def sanitize(sanitizable)
-    sanitizable.map do |v|
-      super v
-    end
-  end
+  private
 
-  def post_exists?
-    return true if empty? && can_be_empty?
-
-    !belongs_to.empty?
-  end
-
-  # Todos los artículos relacionados incluyen a este?
-  def included?
-    belongs_to.map do |p|
-      p[inverse].value.include? post.uuid.value
-    end.all?
+  # Igual que en MetadataRelatedPosts
+  # TODO: Mover a un módulo
+  def sanitize(uuid)
+    super(uuid.map do |u|
+      u.to_s.gsub(/[^a-f0-9\-]/i, '')
+    end)
   end
 end
diff --git a/app/models/metadata_has_many.rb b/app/models/metadata_has_many.rb
index cf7a1b0a..61354011 100644
--- a/app/models/metadata_has_many.rb
+++ b/app/models/metadata_has_many.rb
@@ -6,22 +6,32 @@
 # Localmente tenemos un Array de UUIDs.  Remotamente tenemos una String
 # apuntando a un Post, que se mantiene actualizado como el actual.
 class MetadataHasMany < MetadataRelatedPosts
-  # Todos los Post relacionados según la relación remota
-  def has_many_remote
-    @has_many_remote ||= posts.where(inverse => post.uuid.value)
+  # Invalidar la relación anterior
+  def value_was=(new_value)
+    @had_many = nil
+    @has_many = nil
+
+    super(new_value)
+  end
+
+  def validate
+    super
+
+    errors << I18n.t('metadata.has_many.missing_posts') unless posts_exist?
+
+    errors.empty?
   end
 
   # Todos los Post relacionados
   def has_many
-    @has_many ||= {}
-    @has_many[value.hash.to_s] ||= posts.where(uuid: value)
+    @has_many ||= posts.where(uuid: value)
   end
 
   # La relación anterior
   def had_many
-    return [] if document.data[name.to_s].blank?
+    return [] if value_was.blank?
 
-    @had_many ||= posts.where(uuid: document.data[name.to_s])
+    @had_many ||= posts.where(uuid: value_was)
   end
 
   def inverse?
@@ -38,18 +48,17 @@ class MetadataHasMany < MetadataRelatedPosts
   # Actualizar las relaciones inversas.  Hay que buscar la diferencia
   # entre had y has_many.
   def save
+    super
+
     return true unless changed?
-
-    self[:value] = sanitize value
-
     return true unless inverse?
 
     (had_many - has_many).each do |remove|
-      remove[inverse].value = remove[inverse].default_value
+      remove[inverse]&.value = remove[inverse].default_value
     end
 
     (has_many - had_many).each do |add|
-      add[inverse].value = post.uuid.value
+      add[inverse]&.value = post.uuid.value
     end
 
     true
@@ -63,11 +72,7 @@ class MetadataHasMany < MetadataRelatedPosts
     @related_methods ||= %i[has_many had_many].freeze
   end
 
-  private
-
-  def sanitize(sanitizable)
-    sanitizable.map do |uuid|
-      uuid.gsub(/[^a-f0-9\-]/, '')
-    end
+  def posts_exist?
+    has_many.size == sanitize(value).size
   end
 end
diff --git a/app/models/metadata_lang.rb b/app/models/metadata_lang.rb
index da13d902..93ef87cc 100644
--- a/app/models/metadata_lang.rb
+++ b/app/models/metadata_lang.rb
@@ -6,8 +6,12 @@ class MetadataLang < MetadataTemplate
     super || I18n.locale
   end
 
+  def value_from_document
+    document.collection.label
+  end
+
   def value
-    self[:value] ||= document.collection.label || default_value
+    self[:value] ||= value_from_document || default_value
   end
 
   def values
diff --git a/app/models/metadata_path.rb b/app/models/metadata_path.rb
index 6dede4b5..3c93cca6 100644
--- a/app/models/metadata_path.rb
+++ b/app/models/metadata_path.rb
@@ -7,8 +7,12 @@ class MetadataPath < MetadataTemplate
     File.join(site.path, "_#{lang}", "#{date}-#{slug}#{ext}")
   end
 
+  # El valor no vuelve desde el documento
+  def value_from_document
+    document.path
+  end
+
   def value
-    @value_was ||= default_value
     self[:value] = default_value
   end
   alias absolute value
diff --git a/app/models/metadata_related_posts.rb b/app/models/metadata_related_posts.rb
index 6712ce2b..324ba4ff 100644
--- a/app/models/metadata_related_posts.rb
+++ b/app/models/metadata_related_posts.rb
@@ -31,4 +31,10 @@ class MetadataRelatedPosts < MetadataArray
   def filter
     layout.metadata.dig(name, 'filter')&.to_h&.symbolize_keys || {}
   end
+
+  def sanitize(uuid)
+    super(uuid.map do |u|
+      u.to_s.gsub(/[^a-f0-9\-]/i, '')
+    end)
+  end
 end
diff --git a/app/models/metadata_slug.rb b/app/models/metadata_slug.rb
index 1f12475c..09da23f9 100644
--- a/app/models/metadata_slug.rb
+++ b/app/models/metadata_slug.rb
@@ -25,11 +25,7 @@ require 'jekyll/utils'
 class MetadataSlug < MetadataTemplate
   # Trae el slug desde el título si existe o una string al azar
   def default_value
-    if title
-      Jekyll::Utils.slugify(title)
-    else
-      SecureRandom.hex
-    end
+    title ? Jekyll::Utils.slugify(title) : SecureRandom.uuid
   end
 
   def value
@@ -40,6 +36,9 @@ class MetadataSlug < MetadataTemplate
 
   # Devuelve el título a menos que sea privado y no esté vacío
   def title
-    post.title&.value&.to_s unless post.title.private? && !post.title&.value&.blank?
+    return if post.title&.private?
+    return if post.title&.value&.blank?
+
+    post.title&.value&.to_s
   end
 end
diff --git a/app/models/metadata_template.rb b/app/models/metadata_template.rb
index e7e2edb8..8fa5a971 100644
--- a/app/models/metadata_template.rb
+++ b/app/models/metadata_template.rb
@@ -7,8 +7,6 @@
 MetadataTemplate = Struct.new(:site, :document, :name, :label, :type,
                               :value, :help, :required, :errors, :post,
                               :layout, keyword_init: true) do
-  attr_reader :value_was
-
   # Queremos que los artículos nuevos siempre cacheen, si usamos el UUID
   # siempre vamos a obtener un item nuevo.
   def cache_key
@@ -25,13 +23,26 @@ MetadataTemplate = Struct.new(:site, :document, :name, :label, :type,
     cache_key + '-' + cache_version
   end
 
+  # XXX: Deberíamos sanitizar durante la asignación?
   def value=(new_value)
     @value_was = value
     self[:value] = new_value
   end
 
+  # Siempre obtener el valor actual y solo obtenerlo del documento una
+  # vez.
+  def value_was
+    return @value_was if instance_variable_defined? '@value_was'
+
+    @value_was = value_from_document
+  end
+
+  def value_from_document
+    @value_from_document ||= document.data[name.to_s]
+  end
+
   def changed?
-    !value_was.nil? && value_was != value
+    value_was != value
   end
 
   # Obtiene el valor del JekyllDocument
@@ -59,7 +70,7 @@ MetadataTemplate = Struct.new(:site, :document, :name, :label, :type,
   # Valor actual o por defecto.  Al memoizarlo podemos modificarlo
   # usando otros métodos que el de asignación.
   def value
-    self[:value] ||= if (data = document.data[name.to_s]).present?
+    self[:value] ||= if (data = value_from_document).present?
                        private? ? decrypt(data) : data
                      else
                        default_value
@@ -112,6 +123,8 @@ MetadataTemplate = Struct.new(:site, :document, :name, :label, :type,
   # En caso de que algún campo necesite realizar acciones antes de ser
   # guardado
   def save
+    return true unless changed?
+
     self[:value] = sanitize value
     self[:value] = encrypt(value) if private?
 
@@ -123,12 +136,12 @@ MetadataTemplate = Struct.new(:site, :document, :name, :label, :type,
   end
 
   def related_methods
-    raise NotImplementedError
+    @related_methods ||= [].freeze
   end
 
   # Determina si el campo es privado y debería ser cifrado
   def private?
-    !!layout.metadata.dig(name, 'private')
+    layout.metadata.dig(name, 'private').present?
   end
 
   private
@@ -172,7 +185,7 @@ MetadataTemplate = Struct.new(:site, :document, :name, :label, :type,
 
     box.decrypt_str value.to_s
   rescue Lockbox::DecryptionError => e
-    ExceptionNotifier.notify_exception(e)
+    ExceptionNotifier.notify_exception(e, data: { site: site.name, post: post.path.absolute, name: name })
 
     I18n.t('lockbox.help.decryption_error')
   end
diff --git a/app/models/post.rb b/app/models/post.rb
index 39de2db8..8fc11b9a 100644
--- a/app/models/post.rb
+++ b/app/models/post.rb
@@ -3,9 +3,11 @@
 # Esta clase representa un post en un sitio jekyll e incluye métodos
 # para modificarlos y crear nuevos.
 #
-# rubocop:disable Metrics/ClassLength
-# rubocop:disable Style/MissingRespondToMissing
-class Post < OpenStruct
+# * Los metadatos se tienen que cargar dinámicamente, solo usamos los
+# que necesitamos
+#
+#
+class Post
   # Atributos por defecto
   DEFAULT_ATTRIBUTES = %i[site document layout].freeze
   # Otros atributos que no vienen en los metadatos
@@ -13,6 +15,8 @@ class Post < OpenStruct
   PUBLIC_ATTRIBUTES = %i[lang date uuid].freeze
   ATTR_SUFFIXES = %w[? =].freeze
 
+  attr_reader :attributes, :errors, :layout, :site, :document
+
   class << self
     # Obtiene el layout sin leer el Document
     #
@@ -31,41 +35,20 @@ class Post < OpenStruct
   #
   def initialize(**args)
     default_attributes_missing(**args)
-    super(**args)
 
     # Genera un método con todos los atributos disponibles
-    self.attributes = layout.metadata.keys.map(&:to_sym) + PUBLIC_ATTRIBUTES
-    self.errors = {}
+    @layout = args[:layout]
+    @site = args[:site]
+    @document = args[:document]
+    @attributes = layout.attributes + PUBLIC_ATTRIBUTES
+    @errors = {}
+    @metadata = {}
 
-    # Genera un atributo por cada uno de los campos de la plantilla,
-    # MetadataFactory devuelve un tipo de campo por cada campo.  A
-    # partir de ahí se pueden obtener los valores actuales y una lista
-    # de valores por defecto.
-    #
-    # XXX: En el primer intento de hacerlo más óptimo, movimos esta
-    # lógica a instanciación bajo demanda, pero no solo no logramos
-    # optimizar sino que aumentamos el tiempo de carga :/
-    layout.metadata.each_pair do |name, template|
-      send "#{name}=".to_sym,
-           MetadataFactory.build(document: document,
-                                 post: self,
-                                 site: site,
-                                 name: name.to_sym,
-                                 value: args[name.to_sym],
-                                 layout: layout,
-                                 type: template['type'],
-                                 label: template['label'],
-                                 help: template['help'],
-                                 required: template['required'])
+    # Inicializar valores
+    attributes.each do |attr|
+      public_send(attr)&.value = args[attr] if args.key?(attr)
     end
 
-    # TODO: Llamar dinámicamente
-    load_lang!
-    load_slug!
-    load_date!
-    load_path!
-    load_uuid!
-
     # XXX: No usamos Post#read porque a esta altura todavía no sabemos
     # nada del Document
     document.read! if File.exist? document.path
@@ -108,7 +91,8 @@ class Post < OpenStruct
       html.css('img').each do |img|
         next if %r{\Ahttps?://} =~ img.attributes['src']
 
-        img.attributes['src'].value = Rails.application.routes.url_helpers.site_static_file_url(site, file: img.attributes['src'].value)
+        img.attributes['src'].value = Rails.application.routes.url_helpers.site_static_file_url(site,
+                                                                                                file: img.attributes['src'].value)
       end
 
       # Notificar a les usuaries que están viendo una previsualización
@@ -152,29 +136,65 @@ class Post < OpenStruct
     @modified_at ||= Time.now
   end
 
-  # Solo ejecuta la magia de OpenStruct si el campo existe en la
-  # plantilla
-  #
-  # XXX: Reemplazarlo por nuestro propio método, mantener todo lo demás
-  # compatible con OpenStruct
-  #
-  # XXX: rubocop dice que tenemos que usar super cuando ya lo estamos
-  # usando...
-  def method_missing(mid, *args)
+  def [](attr)
+    public_send attr
+  end
+
+  # Define metadatos a demanda
+  def method_missing(name, *_args)
     # Limpiar el nombre del atributo, para que todos los ayudantes
     # reciban el método en limpio
-    name = attribute_name mid
-
     unless attribute? name
       raise NoMethodError, I18n.t('exceptions.post.no_method',
-                                  method: mid)
+                                  method: name)
     end
 
-    # OpenStruct
-    super(mid, *args)
+    define_singleton_method(name) do
+      template = layout.metadata[name.to_s]
 
-    # Devolver lo mismo que devuelve el método después de definirlo
-    send(mid, *args)
+      @metadata[name] ||=
+        MetadataFactory.build(document: document,
+                              post: self,
+                              site: site,
+                              name: name,
+                              layout: layout,
+                              type: template['type'],
+                              label: template['label'],
+                              help: template['help'],
+                              required: template['required'])
+    end
+
+    public_send name
+  end
+
+  # TODO: Mover a method_missing
+  def slug
+    @metadata[:slug] ||= MetadataSlug.new(document: document, site: site, layout: layout, name: :slug, type: :slug,
+                                          post: self, required: true)
+  end
+
+  # TODO: Mover a method_missing
+  def date
+    @metadata[:date] ||= MetadataDocumentDate.new(document: document, site: site, layout: layout, name: :date,
+                                                  type: :document_date, post: self, required: true)
+  end
+
+  # TODO: Mover a method_missing
+  def path
+    @metadata[:path] ||= MetadataPath.new(document: document, site: site, layout: layout, name: :path, type: :path,
+                                          post: self, required: true)
+  end
+
+  # TODO: Mover a method_missing
+  def lang
+    @metadata[:lang] ||= MetadataLang.new(document: document, site: site, layout: layout, name: :lang, type: :lang,
+                                          post: self, required: true)
+  end
+
+  # TODO: Mover a method_missing
+  def uuid
+    @metadata[:uuid] ||= MetadataUuid.new(document: document, site: site, layout: layout, name: :uuid, type: :uuid,
+                                          post: self, required: true)
   end
 
   # Detecta si es un atributo válido o no, a partir de la tabla de la
@@ -189,11 +209,14 @@ class Post < OpenStruct
     included
   end
 
-  # Devuelve los strong params para el layout
+  # Devuelve los strong params para el layout.
+  #
+  # XXX: Nos gustaría no tener que instanciar Metadata acá, pero depende
+  # del valor por defecto que a su vez depende de Layout.
   def params
     attributes.map do |attr|
-      send(attr).to_param
-    end
+      public_send(attr)&.to_param
+    end.compact
   end
 
   # Genera el post con metadatos en YAML
@@ -201,8 +224,8 @@ class Post < OpenStruct
   # TODO: Cachear por un minuto
   def full_content
     body = ''
-    yaml = layout.metadata.keys.map(&:to_sym).map do |metadata|
-      template = send(metadata)
+    yaml = layout.attributes.map do |attr|
+      template = public_send attr
 
       unless template.front_matter?
         body += "\n\n"
@@ -212,7 +235,7 @@ class Post < OpenStruct
 
       next if template.empty?
 
-      [metadata.to_s, template.value]
+      [attr.to_s, template.value]
     end.compact.to_h
 
     # TODO: Convertir a Metadata?
@@ -281,7 +304,7 @@ class Post < OpenStruct
 
   # Detecta si el artículo es válido para guardar
   def valid?
-    self.errors = {}
+    @errors = {}
 
     layout.metadata.keys.map(&:to_sym).each do |metadata|
       template = send(metadata)
@@ -339,9 +362,7 @@ class Post < OpenStruct
   # Levanta un error si al construir el artículo no pasamos un atributo.
   def default_attributes_missing(**args)
     DEFAULT_ATTRIBUTES.each do |attr|
-      i18n = I18n.t("exceptions.post.#{attr}_missing")
-
-      raise ArgumentError, i18n unless args[attr].present?
+      raise ArgumentError, I18n.t("exceptions.post.#{attr}_missing") unless args[attr].present?
     end
   end
 
@@ -349,57 +370,11 @@ class Post < OpenStruct
     document.data.fetch('usuaries', [])
   end
 
-  # Obtiene el nombre del atributo a partir del nombre del método
-  def attribute_name(attr)
-    # XXX: Los simbolos van al final
-    @attribute_name_cache ||= {}
-    @attribute_name_cache[attr] ||= ATTR_SUFFIXES.reduce(attr.to_s) do |a, suffix|
-      a.chomp suffix
-    end.to_sym
-  end
-
-  def load_slug!
-    self.slug = MetadataSlug.new(document: document, site: site,
-                                 layout: layout, name: :slug, type: :slug,
-                                 post: self,
-                                 required: true)
-  end
-
-  def load_date!
-    self.date = MetadataDocumentDate.new(document: document, site: site,
-                                         layout: layout, name: :date,
-                                         type: :document_date,
-                                         post: self,
-                                         required: true)
-  end
-
-  def load_path!
-    self.path = MetadataPath.new(document: document, site: site,
-                                 layout: layout, name: :path,
-                                 type: :path, post: self,
-                                 required: true)
-  end
-
-  def load_lang!
-    self.lang = MetadataLang.new(document: document, site: site,
-                                 layout: layout, name: :lang,
-                                 type: :lang, post: self,
-                                 required: true)
-  end
-
-  def load_uuid!
-    self.uuid = MetadataUuid.new(document: document, site: site,
-                                 layout: layout, name: :uuid,
-                                 type: :uuid, post: self,
-                                 required: true)
-  end
-
   # Ejecuta la acción de guardado en cada atributo
+  # TODO: Solo guardar los que se modificaron
   def save_attributes!
     attributes.map do |attr|
-      send(attr).save
+      public_send(attr).save
     end.all?
   end
 end
-# rubocop:enable Metrics/ClassLength
-# rubocop:enable Style/MissingRespondToMissing
diff --git a/app/models/post_relation.rb b/app/models/post_relation.rb
index 7ea9aef6..850a83dc 100644
--- a/app/models/post_relation.rb
+++ b/app/models/post_relation.rb
@@ -4,10 +4,11 @@
 # artículos como si estuviésemos usando ActiveRecord.
 class PostRelation < Array
   # No necesitamos cambiar el sitio
-  attr_reader :site
+  attr_reader :site, :lang
 
-  def initialize(site:)
+  def initialize(site:, lang:)
     @site = site
+    @lang = lang
     # Proseguimos la inicialización sin valores por defecto
     super()
   end
@@ -15,7 +16,7 @@ class PostRelation < Array
   # Genera un artículo nuevo con los parámetros que le pasemos y lo suma
   # al array
   def build(**args)
-    args[:lang] ||= I18n.locale
+    args[:lang] = lang
     args[:document] ||= build_document(collection: args[:lang])
     args[:layout] = build_layout(args[:layout])
 
@@ -94,7 +95,7 @@ class PostRelation < Array
 
     @where ||= {}
     @where[args.hash.to_s] ||= begin
-      PostRelation.new(site: site).concat(select do |post|
+      PostRelation.new(site: site, lang: lang).concat(select do |post|
         result = args.map do |attr, value|
           next unless post.attribute?(attr)
 
@@ -123,7 +124,7 @@ class PostRelation < Array
   # @return [PostRelation]
   alias array_select select
   def select(&block)
-    PostRelation.new(site: site).concat array_select(&block)
+    PostRelation.new(site: site, lang: lang).concat array_select(&block)
   end
 
   # Intenta guardar todos y devuelve true si pudo
diff --git a/app/models/site.rb b/app/models/site.rb
index 6c930836..4ec0b9f9 100644
--- a/app/models/site.rb
+++ b/app/models/site.rb
@@ -225,6 +225,7 @@ class Site < ApplicationRecord
 
     # Traemos los posts del idioma actual por defecto
     lang ||= I18n.locale
+    lang   = lang.to_sym
 
     # Crea un Struct dinámico con los valores de los locales, si
     # llegamos a pasar un idioma que no existe vamos a tener una
@@ -233,7 +234,7 @@ class Site < ApplicationRecord
 
     return @posts[lang] unless @posts[lang].blank?
 
-    @posts[lang] = PostRelation.new site: self
+    @posts[lang] = PostRelation.new site: self, lang: lang
 
     # No fallar si no existe colección para este idioma
     # XXX: queremos fallar silenciosamente?
@@ -250,7 +251,7 @@ class Site < ApplicationRecord
   #
   # @return PostRelation
   def docs
-    @docs ||= PostRelation.new(site: self).push(locales.flat_map do |locale|
+    @docs ||= PostRelation.new(site: self, lang: :docs).push(locales.flat_map do |locale|
       posts(lang: locale)
     end).flatten!
   end
diff --git a/app/models/site/static_file_migration.rb b/app/models/site/static_file_migration.rb
index 798601a5..614f63dd 100644
--- a/app/models/site/static_file_migration.rb
+++ b/app/models/site/static_file_migration.rb
@@ -42,6 +42,7 @@ class Site
               metadata = doc.public_send(field)
 
               next if metadata.value['path'].blank?
+              next if ActiveStorage::Blob.find_by(key: metadata.key_from_path)
 
               path = Pathname.new(metadata.value['path'])
 
diff --git a/app/services/post_service.rb b/app/services/post_service.rb
index 571588cb..bc8def1c 100644
--- a/app/services/post_service.rb
+++ b/app/services/post_service.rb
@@ -36,6 +36,8 @@ PostService = Struct.new(:site, :usuarie, :post, :params, keyword_init: true) do
     post.usuaries << usuarie
     params[:post][:draft] = true if site.invitade? usuarie
 
+    # Es importante que el artículo se guarde primero y luego los
+    # relacionados.
     commit(action: :updated, file: update_related_posts) if post.update(post_params)
 
     # Devolver el post aunque no se haya salvado para poder rescatar los
@@ -111,23 +113,24 @@ PostService = Struct.new(:site, :usuarie, :post, :params, keyword_init: true) do
   # Actualiza los artículos relacionados según los métodos que los
   # metadatos declaren.
   #
+  # Este método se asegura que todos los artículos se guardan una sola
+  # vez.
+  #
   # @return [Array] Lista de archivos modificados
   def update_related_posts
-    files = [post.path.absolute]
+    posts = Set.new
 
     post.attributes.each do |a|
-      next unless post[a].related_posts?
-
       post[a].related_methods.each do |m|
         next unless post[a].respond_to? m
 
         # La respuesta puede ser una PostRelation también
-        [post[a].public_send(m)].flatten.compact.uniq.each do |p|
-          files << p.path.absolute if p.save(validate: false)
-        end
+        posts.merge [post[a].public_send(m)].flatten.compact
       end
     end
 
-    files
+    posts.map do |p|
+      p.path.absolute if p.save(validate: false)
+    end.compact << post.path.absolute
   end
 end
diff --git a/app/views/posts/attribute_ro/_has_and_belongs_to_many.haml b/app/views/posts/attribute_ro/_has_and_belongs_to_many.haml
index d7186718..d6b51a7a 100644
--- a/app/views/posts/attribute_ro/_has_and_belongs_to_many.haml
+++ b/app/views/posts/attribute_ro/_has_and_belongs_to_many.haml
@@ -2,5 +2,5 @@
   %th= post_label_t(attribute, post: post)
   %td
     %ul{ dir: dir, lang: locale }
-      - metadata.belongs_to.each do |p|
+      - metadata.has_many.each do |p|
         %li= link_to p.title.value, site_post_path(site, p.id)
diff --git a/app/views/posts/attributes/_array.haml b/app/views/posts/attributes/_array.haml
index 73e96dea..da9ec654 100644
--- a/app/views/posts/attributes/_array.haml
+++ b/app/views/posts/attributes/_array.haml
@@ -1,5 +1,6 @@
 .form-group
   = label_tag "#{base}_#{attribute}", post_label_t(attribute, post: post)
+  = hidden_field_tag "#{base}[#{attribute}][]", ''
 
   .taggable{ dir: dir, lang: locale, data: { values: metadata.value.to_json,
     name: "#{base}[#{attribute}][]", list: id_for_datalist(attribute),
diff --git a/app/views/posts/attributes/_belongs_to.haml b/app/views/posts/attributes/_belongs_to.haml
index 06594742..2d17c3fb 100644
--- a/app/views/posts/attributes/_belongs_to.haml
+++ b/app/views/posts/attributes/_belongs_to.haml
@@ -1,13 +1,7 @@
 .form-group
   = label_tag "#{base}_#{attribute}", post_label_t(attribute, post: post)
-  = text_field base, attribute, value: metadata.value,
-    dir: dir, lang: locale, list: id_for_datalist(attribute),
-    pattern: metadata.values.values.join('|'), autocomplete: 'off',
-    **field_options(attribute, metadata)
+  = select_tag(plain_field_name_for(base, attribute),
+    options_for_select(metadata.values, metadata.value),
+    **field_options(attribute, metadata), include_blank: true)
   = render 'posts/attribute_feedback',
     post: post, attribute: attribute, metadata: metadata
-
-  -# TODO: Ocultar el UUID
-  %datalist{ id: id_for_datalist(attribute) }
-    - metadata.values.each_pair do |key, value|
-      %option{ value: value }= key
diff --git a/app/views/posts/attributes/_date.haml b/app/views/posts/attributes/_date.haml
index 38c4f500..1347c59c 100644
--- a/app/views/posts/attributes/_date.haml
+++ b/app/views/posts/attributes/_date.haml
@@ -1,6 +1,7 @@
 .form-group
   = label_tag "#{base}_#{attribute}", post_label_t(attribute, post: post)
   = date_field base, attribute, value: metadata.value.to_date.strftime('%F'),
-    **field_options(attribute, metadata)
+    **field_options(attribute, metadata), pattern: '\d{4}-\d{2}-\d{2}',
+    data: { 'pattern-mismatch': t('metadata.date.invalid_format') }
   = render 'posts/attribute_feedback',
     post: post, attribute: attribute, metadata: metadata
diff --git a/app/views/posts/attributes/_document_date.haml b/app/views/posts/attributes/_document_date.haml
index 65516718..1be997cc 100644
--- a/app/views/posts/attributes/_document_date.haml
+++ b/app/views/posts/attributes/_document_date.haml
@@ -1,6 +1,7 @@
 .form-group
   = label_tag "#{base}_#{attribute}", post_label_t(attribute, post: post)
   = date_field base, attribute, value: metadata.value.strftime('%F'),
-    **field_options(attribute, metadata)
+    **field_options(attribute, metadata), pattern: '\d{4}-\d{2}-\d{2}',
+    data: { 'pattern-mismatch': t('metadata.date.invalid_format') }
   = render 'posts/attribute_feedback',
     post: post, attribute: attribute, metadata: metadata
diff --git a/app/views/posts/attributes/_file.haml b/app/views/posts/attributes/_file.haml
index 56adb239..54f87b5b 100644
--- a/app/views/posts/attributes/_file.haml
+++ b/app/views/posts/attributes/_file.haml
@@ -34,6 +34,6 @@
   = text_field(*field_name_for(base, attribute, :description),
     value: metadata.value['description'],
     dir: dir, lang: locale,
-    **field_options(attribute, metadata))
+    **field_options(attribute, metadata, required: false))
   = render 'posts/attribute_feedback',
     post: post, attribute: [attribute, :description], metadata: metadata
diff --git a/app/views/posts/attributes/_has_and_belongs_to_many.haml b/app/views/posts/attributes/_has_and_belongs_to_many.haml
index d39d124d..e36b6552 100644
--- a/app/views/posts/attributes/_has_and_belongs_to_many.haml
+++ b/app/views/posts/attributes/_has_and_belongs_to_many.haml
@@ -1,5 +1,6 @@
 .form-group
   = label_tag "#{base}_#{attribute}", post_label_t(attribute, post: post)
+  = hidden_field_tag "#{base}[#{attribute}][]", ''
 
   .mapable{ dir: dir, lang: locale,
     data: { values: metadata.value.to_json,
diff --git a/app/views/posts/attributes/_has_many.haml b/app/views/posts/attributes/_has_many.haml
index d39d124d..e36b6552 100644
--- a/app/views/posts/attributes/_has_many.haml
+++ b/app/views/posts/attributes/_has_many.haml
@@ -1,5 +1,6 @@
 .form-group
   = label_tag "#{base}_#{attribute}", post_label_t(attribute, post: post)
+  = hidden_field_tag "#{base}[#{attribute}][]", ''
 
   .mapable{ dir: dir, lang: locale,
     data: { values: metadata.value.to_json,
diff --git a/app/views/posts/attributes/_image.haml b/app/views/posts/attributes/_image.haml
index 06503700..2824b4c9 100644
--- a/app/views/posts/attributes/_image.haml
+++ b/app/views/posts/attributes/_image.haml
@@ -32,7 +32,7 @@
   = text_field(*field_name_for(base, attribute, :description),
     value: metadata.value['description'],
     dir: dir, lang: locale,
-    **field_options(attribute, metadata))
+    **field_options(attribute, metadata, required: false))
   = render 'posts/attribute_feedback',
     post: post, attribute: [attribute, :description], metadata: metadata
 
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 7aa061c3..6e050249 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -48,6 +48,10 @@ en:
       end_in_the_past: "Event end can't happen before the start"
     belongs_to:
       missing_post: "Couldn't find the related post"
+    has_many:
+      missing_posts: "Couldn't find some related posts"
+    date:
+      invalid_format: "It seems that your browser doesn't support dates and the date is on the incorrect format, please use yyyy-mm-dd, ie. 2021-01-31"
   exceptions:
     post:
       site_missing: 'Needs an instance of Site'
@@ -460,7 +464,7 @@ en:
         label: Language
       date:
         label: Date
-        help: Publication date for this post.  If you use a date in the future the post won't be published until then.
+        help: Date for this post.  If you use a date in the future the post won't be published until you publish changes on that day.
       required:
         label: ' (required)'
         feedback: 'This field cannot be empty!'
diff --git a/config/locales/es.yml b/config/locales/es.yml
index 7a35ee5b..309b40ea 100644
--- a/config/locales/es.yml
+++ b/config/locales/es.yml
@@ -48,6 +48,10 @@ es:
       end_in_the_past: 'El fin del evento no puede ser anterior al comienzo'
     belongs_to:
       missing_post: 'No se pudo encontrar el artículo relacionado'
+    has_many:
+      missing_posts: 'No se pudieron encontrar algunos artículos relacionados'
+    date:
+      invalid_format: 'Parece que tu navegador no soporta fechas y la fecha no está en el formato correcto, por favor usa aaaa-mm-dd, por ejemplo: 2021-01-31'
   exceptions:
     post:
       site_missing: 'Necesita una instancia de Site'
@@ -469,7 +473,7 @@ es:
         label: Idioma
       date:
         label: Fecha
-        help: La fecha de publicación del artículo.  Si colocas una fecha en el futuro no se publicará hasta ese día.
+        help: La fecha del artículo.  Si colocas una fecha en el futuro no se publicará hasta que publiques cambios ese día.
       required:
         label: ' (requerido)'
         feedback: '¡Este campo no puede estar vacío!'
diff --git a/test/controllers/posts_controller_test.rb b/test/controllers/posts_controller_test.rb
index 376c740f..b8c9f560 100644
--- a/test/controllers/posts_controller_test.rb
+++ b/test/controllers/posts_controller_test.rb
@@ -143,21 +143,26 @@ class PostsControllerTest < ActionDispatch::IntegrationTest
   end
 
   test 'se pueden reordenar' do
-    lang = I18n.available_locales.sample
-    posts = @site.posts(lang: lang)
+    lang = { lang: @site.locales.sample }
+
+    (rand * 10).round.times do
+      @site.posts(**lang).create title: SecureRandom.hex, description: SecureRandom.hex
+    end
+
+    posts = @site.posts(**lang)
     reorder = Hash[posts.map { |p| p.uuid.value }.shuffle.each_with_index.to_a]
 
     post site_posts_reorder_url(@site),
          headers: @authorization,
-         params: { post: { lang: lang, reorder: reorder } }
+         params: { post: { lang: lang[:lang], reorder: reorder } }
 
     @site = Site.find @site.id
 
-    assert_equal I18n.t('post_service.reorder'),
-                 @site.repository.rugged.head.target.message
     assert_equal reorder,
-                 Hash[@site.posts(lang: lang).map do |p|
+                 Hash[@site.posts(**lang).map do |p|
                    [p.uuid.value, p.order.value]
                  end]
+    assert_equal I18n.t('post_service.reorder'),
+                 @site.repository.rugged.head.target.message
   end
 end
diff --git a/test/models/post_test.rb b/test/models/post_test.rb
index 67dd1a24..ab7dd510 100644
--- a/test/models/post_test.rb
+++ b/test/models/post_test.rb
@@ -95,11 +95,6 @@ class PostTest < ActiveSupport::TestCase
     end
   end
 
-  test 'attribute_name' do
-    assert_equal :hola, @post.send(:attribute_name, :hola)
-    assert_equal :hola, @post.send(:attribute_name, :hola?)
-  end
-
   test 'se puede cambiar el slug' do
     @post.title.value = SecureRandom.hex
     assert_not @post.slug.changed?