diff --git a/app/controllers/posts_controller.rb b/app/controllers/posts_controller.rb
index c09c81b76..3af0df2d9 100644
--- a/app/controllers/posts_controller.rb
+++ b/app/controllers/posts_controller.rb
@@ -140,16 +140,15 @@ class PostsController < ApplicationController
 
         if post.errors.any?
           @message = post.errors.full_messages.join("; ")
-          render :template => "static/error", :status => 500
-        else
-          response_params = {:q => params[:tags_query], :pool_id => params[:pool_id], post_set_id: params[:post_set_id]}
-          response_params.reject!{|key, value| value.blank?}
-          redirect_to post_path(post, response_params)
+          if flash[:notice].present?
+            flash[:notice] += "\n\n" + @message
+          else
+            flash[:notice] = @message
+          end
         end
-      end
-
-      format.json do
-        render :json => post
+        response_params = { q: params[:tags_query], pool_id: params[:pool_id], post_set_id: params[:post_set_id] }
+        response_params.compact_blank!
+        redirect_to post_path(post, response_params)
       end
     end
   end
diff --git a/app/javascript/src/javascripts/posts.js b/app/javascript/src/javascripts/posts.js
index 8de86766a..cd0d48592 100644
--- a/app/javascript/src/javascripts/posts.js
+++ b/app/javascript/src/javascripts/posts.js
@@ -757,9 +757,12 @@ Post.update = function (post_id, params) {
         Post.notice_update("dec");
         Post.update_data(data);
       },
-      error: function () {
+      error: function (data) {
         Post.notice_update("dec");
-        $(window).trigger("danbooru:error", "There was an error updating <a href=\"/posts/" + post_id + "\">post #" + post_id + "</a>");
+        const message = $
+          .map(data.responseJSON.errors, function (msg) { return msg; })
+          .join("; ");
+        $(window).trigger("danbooru:error", `There was an error updating <a href="/posts/${post_id}">post #${post_id}</a>: ${message}`);
       },
     });
   });
diff --git a/app/models/pool.rb b/app/models/pool.rb
index be510f40c..0aa60bb24 100644
--- a/app/models/pool.rb
+++ b/app/models/pool.rb
@@ -194,8 +194,9 @@ class Pool < ApplicationRecord
     post_ids_before = post_ids_before_last_save || post_ids_was
     added = post_ids - post_ids_before
     return unless added.size > 0
-    if post_ids.size > 1_000
-      errors.add(:base, "Pools can have up to 1,000 posts each")
+    max = Danbooru.config.pool_post_limit(CurrentUser.user)
+    if post_ids.size > max
+      errors.add(:base, "Pools can only have up to #{ActiveSupport::NumberHelper.number_to_delimited(max)} posts each")
       false
     else
       true
@@ -211,6 +212,7 @@ class Pool < ApplicationRecord
       reload
       self.skip_sync = true
       update(post_ids: post_ids + [post.id])
+      raise(ActiveRecord::Rollback) unless valid?
       self.skip_sync = false
       post.add_pool!(self)
       post.save
@@ -232,6 +234,7 @@ class Pool < ApplicationRecord
       reload
       self.skip_sync = true
       update(post_ids: post_ids - [post.id])
+      raise(ActiveRecord::Rollback) unless valid?
       self.skip_sync = false
       post.remove_pool!(self)
       post.save
diff --git a/app/models/post.rb b/app/models/post.rb
index 10af8a718..436d37433 100644
--- a/app/models/post.rb
+++ b/app/models/post.rb
@@ -730,40 +730,76 @@ class Post < ApplicationRecord
       @post_metatags.each do |tag|
         case tag
         when /^-pool:(\d+)$/i
-          pool = Pool.find_by_id($1.to_i)
-          pool.remove!(self) if pool
+          pool = Pool.find_by(id: $1.to_i)
+          if pool
+            pool.remove!(self)
+            if pool.errors.any?
+              errors.add(:base, pool.errors.full_messages.join("; "))
+            end
+          end
 
         when /^-pool:(.+)$/i
-          pool = Pool.find_by_name($1)
-          pool.remove!(self) if pool
+          pool = Pool.find_by(name: $1)
+          if pool
+            pool.remove!(self)
+            if pool.errors.any?
+              errors.add(:base, pool.errors.full_messages.join("; "))
+            end
+          end
 
         when /^pool:(\d+)$/i
-          pool = Pool.find_by_id($1.to_i)
-          pool.add!(self) if pool
+          pool = Pool.find_by(id: $1.to_i)
+          if pool
+            pool.add!(self)
+            if pool.errors.any?
+              errors.add(:base, pool.errors.full_messages.join("; "))
+            end
+          end
 
-        when /^pool:(.+)$/i
-          pool = Pool.find_by_name($1)
-          pool.add!(self) if pool
-
-        when /^newpool:(.+)$/i
-          pool = Pool.find_by_name($1)
-          pool.add!(self) if pool
+        when /^(?:new)?pool:(.+)$/i
+          pool = Pool.find_by(name: $1)
+          if pool
+            pool.add!(self)
+            if pool.errors.any?
+              errors.add(:base, pool.errors.full_messages.join("; "))
+            end
+          end
 
         when /^set:(\d+)$/i
-          set = PostSet.find_by_id($1.to_i)
-          set.add!(self) if set&.can_edit_posts?(CurrentUser.user)
+          set = PostSet.find_by(id: $1.to_i)
+          if set&.can_edit_posts?(CurrentUser.user)
+            set.add!(self)
+            if set.errors.any?
+              errors.add(:base, set.errors.full_messages.join("; "))
+            end
+          end
 
         when /^-set:(\d+)$/i
-          set = PostSet.find_by_id($1.to_i)
-          set.remove!(self) if set&.can_edit_posts?(CurrentUser.user)
+          set = PostSet.find_by(id: $1.to_i)
+          if set&.can_edit_posts?(CurrentUser.user)
+            set.remove!(self)
+            if set.errors.any?
+              errors.add(:base, set.errors.full_messages.join("; "))
+            end
+          end
 
         when /^set:(.+)$/i
-          set = PostSet.find_by_shortname($1)
-          set.add!(self) if set&.can_edit_posts?(CurrentUser.user)
+          set = PostSet.find_by(shortname: $1)
+          if set&.can_edit_posts?(CurrentUser.user)
+            set.add!(self)
+            if set.errors.any?
+              errors.add(:base, set.errors.full_messages.join("; "))
+            end
+          end
 
         when /^-set:(.+)$/i
-          set = PostSet.find_by_shortname($1)
-          set.remove!(self) if set&.can_edit_posts?(CurrentUser.user)
+          set = PostSet.find_by(shortname: $1)
+          if set&.can_edit_posts?(CurrentUser.user)
+            set.remove!(self)
+            if set.errors.any?
+              errors.add(:base, set.errors.full_messages.join("; "))
+            end
+          end
 
         when /^child:none$/i
           children.each do |post|
diff --git a/app/models/post_set.rb b/app/models/post_set.rb
index abcd7e13e..1af91525e 100644
--- a/app/models/post_set.rb
+++ b/app/models/post_set.rb
@@ -136,8 +136,9 @@ class PostSet < ApplicationRecord
       post_ids_before = post_ids_before_last_save || post_ids_was
       added = post_ids - post_ids_before
       return unless added.size > 0
-      if post_ids.size > 10_000
-        errors.add(:base, "Sets can have up to 10,000 posts each")
+      max = Danbooru.config.set_post_limit(CurrentUser.user)
+      if post_ids.size > max
+        errors.add(:base, "Sets can only have up to #{ActiveSupport::NumberHelper.number_to_delimited(max)} posts each")
         false
       else
         true
@@ -203,6 +204,7 @@ class PostSet < ApplicationRecord
         reload
         self.skip_sync = true
         update(post_ids: post_ids + [post.id])
+        raise(ActiveRecord::Rollback) unless valid?
         post.add_set!(self, true)
         post.save
       end
@@ -219,6 +221,7 @@ class PostSet < ApplicationRecord
         reload
         self.skip_sync = true
         update(post_ids: post_ids - [post.id])
+        raise(ActiveRecord::Rollback) unless valid?
         post.remove_set!(self)
         post.save
       end
diff --git a/config/danbooru_default_config.rb b/config/danbooru_default_config.rb
index 1a345f44e..fd3cadda5 100644
--- a/config/danbooru_default_config.rb
+++ b/config/danbooru_default_config.rb
@@ -337,6 +337,14 @@ module Danbooru
       20_000
     end
 
+    def pool_post_limit(_user)
+      1_000
+    end
+
+    def set_post_limit(_user) # rubocop:disable Naming/AccessorMethodName
+      10_000
+    end
+
     def discord_site
     end
 
diff --git a/test/unit/post_test.rb b/test/unit/post_test.rb
index 9f8f8624c..70ddc8a75 100644
--- a/test/unit/post_test.rb
+++ b/test/unit/post_test.rb
@@ -2269,4 +2269,99 @@ class PostTest < ActiveSupport::TestCase
       end
     end
   end
+
+  context "Metatags:" do
+    context "set:" do
+      setup do
+        @set = create(:post_set, creator: @user)
+        @post = create(:post)
+      end
+
+      context "with an id" do
+        should "work" do
+          @post.update(tag_string_diff: "set:#{@set.id}")
+          assert_equal([@post.id], @set.reload.post_ids)
+          assert_equal("set:#{@set.id}", @post.pool_string)
+        end
+
+        should "gracefully fail if the set is full" do
+          Danbooru.config.stubs(:set_post_limit).returns(0)
+          @post.update(tag_string_diff: "set:#{@set.id}")
+          assert_equal(["Sets can only have up to 0 posts each"], @post.errors.full_messages)
+          assert_equal([], @set.reload.post_ids)
+          assert_equal("", @post.pool_string)
+        end
+      end
+
+      context "with a shortname" do
+        should "work" do
+          @post.update(tag_string_diff: "set:#{@set.shortname}")
+          assert_equal([@post.id], @set.reload.post_ids)
+          assert_equal("set:#{@set.id}", @post.pool_string)
+        end
+
+        should "gracefully fail if the set is full" do
+          Danbooru.config.stubs(:set_post_limit).returns(0)
+          @post.update(tag_string_diff: "set:#{@set.shortname}")
+          assert_equal(["Sets can only have up to 0 posts each"], @post.errors.full_messages)
+          assert_equal([], @set.reload.post_ids)
+          assert_equal("", @post.pool_string)
+        end
+      end
+    end
+
+    context "pool:" do
+      setup do
+        @pool = create(:pool)
+        @post = create(:post)
+      end
+
+      context "with an id" do
+        should "work" do
+          @post.update(tag_string_diff: "pool:#{@pool.id}")
+          assert_equal([@post.id], @pool.reload.post_ids)
+          assert_equal("pool:#{@pool.id}", @post.pool_string)
+        end
+
+        should "gracefully fail if the pool is full" do
+          Danbooru.config.stubs(:pool_post_limit).returns(0)
+          @post.update(tag_string_diff: "pool:#{@pool.id}")
+          assert_equal(["Pools can only have up to 0 posts each"], @post.errors.full_messages)
+          assert_equal([], @pool.reload.post_ids)
+          assert_equal("", @post.pool_string)
+        end
+      end
+
+      context "with a name" do
+        should "work" do
+          @post.update(tag_string_diff: "pool:#{@pool.name}")
+          assert_equal([@post.id], @pool.reload.post_ids)
+          assert_equal("pool:#{@pool.id}", @post.pool_string)
+        end
+
+        should "gracefully fail if the pool is full" do
+          Danbooru.config.stubs(:pool_post_limit).returns(0)
+          @post.update(tag_string_diff: "pool:#{@pool.name}")
+          assert_equal(["Pools can only have up to 0 posts each"], @post.errors.full_messages)
+          assert_equal([], @pool.reload.post_ids)
+          assert_equal("", @post.pool_string)
+        end
+      end
+    end
+
+    context "newpool:" do
+      setup do
+        @post = create(:post)
+      end
+
+      should "work" do
+        assert_difference("Pool.count", 1) do
+          @post.update(tag_string_diff: "newpool:test")
+        end
+        @pool = Pool.last
+        assert_equal([@post.id], @pool.reload.post_ids)
+        assert_equal("pool:#{@pool.id}", @post.pool_string)
+      end
+    end
+  end
 end