diff --git a/app/controllers/evaluators_controller.rb b/app/controllers/evaluators_controller.rb
index 1c61e1fa..5a636055 100644
--- a/app/controllers/evaluators_controller.rb
+++ b/app/controllers/evaluators_controller.rb
@@ -2,7 +2,7 @@ class EvaluatorsController < ApplicationController
 
   def permitted_params
     @_permitted_params ||= begin
-      permitted_attributes = [:name, :description, :source, :language_id]
+      permitted_attributes = [:name, :description, :source, :language_id, :interactive_processes]
       permitted_attributes << :owner_id if policy(@evaluator || Evaluator).transfer?
       params.require(:evaluator).permit(*permitted_attributes)
     end
diff --git a/app/models/evaluator.rb b/app/models/evaluator.rb
index 1011a1e2..f4629f69 100644
--- a/app/models/evaluator.rb
+++ b/app/models/evaluator.rb
@@ -6,5 +6,6 @@ class Evaluator < ActiveRecord::Base
   belongs_to :language
 
   validates :name, :presence => true
+  validates :interactive_processes, :presence => true, :numericality => { :greater_than_or_equal_to => 0, :less_than_or_equal_to => 2 }
 
 end
diff --git a/app/services/isolate.rb b/app/services/isolate.rb
index 07478662..27c5e8ba 100644
--- a/app/services/isolate.rb
+++ b/app/services/isolate.rb
@@ -12,8 +12,6 @@ class Isolate
   # 
   # Alternatively, the isolate box is passed as an argument to a block with an arity, which is not instance_exec-ed
   def self.box options = {}, &block
-    options.reverse_merge!(:cg => has_cgroups?).assert_valid_keys(:cg)
-    raise CGroupsUnavailableError if options[:cg] && !has_cgroups?
     isolate = self.new(options)
     yield isolate if block_given?
     true
@@ -50,6 +48,13 @@ def exec command, options = {}
     end
   end
 
+  # Spawn a single command in isolate context
+  def spawn_command command, options = {}
+    sandbox_command(command, options) do |command, options|
+      spawn(*command, options)
+    end
+  end
+
   # popen a single command in isolate context
   #
   # Example:
@@ -177,6 +182,8 @@ def read_pipe_limited(pipe, count)
   protected
 
   def initialize(options = {})
+    options.reverse_merge!(:cg => self.class.has_cgroups?).assert_valid_keys(:cg)
+    raise CGroupsUnavailableError if options[:cg] && !self.class.has_cgroups?
     @has_cgroup = !!options[:cg]
     @box_id = Kernel.send(:`, "isolock --lock -- #{"--cg" if has_cgroup?}").to_i
     raise LockError unless $?.success?
diff --git a/app/views/evaluators/_form.html.erb b/app/views/evaluators/_form.html.erb
index 33f4d741..d6f4fb28 100644
--- a/app/views/evaluators/_form.html.erb
+++ b/app/views/evaluators/_form.html.erb
@@ -27,6 +27,10 @@
     <%= f.label :language_id %><br>
     <%= f.select :language_id, grouped_options_for_select(Language.grouped_submission_options, @evaluator.language_id), :include_blank => true %>
   </div>
+  <div class="field">
+    <%= f.label :interactive_processes %><br />
+    <%= f.text_field :interactive_processes %>
+  </div>
   <div class="field">
     <%= f.label :owner_id %><br />
     <% if policy(@evaluator).transfer? %>
diff --git a/app/views/evaluators/show.html.erb b/app/views/evaluators/show.html.erb
index d91657de..3835fda5 100644
--- a/app/views/evaluators/show.html.erb
+++ b/app/views/evaluators/show.html.erb
@@ -10,6 +10,8 @@
   <p>
     <b>Language:</b>
     <%= @evaluator.language&.name %><br>
+    <b>Interactive processes:</b>
+    <%= @evaluator.interactive_processes %><br>
     <b>Source:</b>
     <%= predisplay @evaluator.source, language: @evaluator.language&.lexer %>
   </p>
diff --git a/app/workers/judge_submission_worker.rb b/app/workers/judge_submission_worker.rb
index febf86e8..4ed5ad88 100644
--- a/app/workers/judge_submission_worker.rb
+++ b/app/workers/judge_submission_worker.rb
@@ -135,7 +135,7 @@ def judge
   end
 
   private
-  attr_accessor :problem, :box, :tmpdir
+  attr_accessor :problem, :box, :interactive_boxes, :tmpdir
 
   def time_limit
     problem.time_limit || 0.001
@@ -155,18 +155,22 @@ def extra_time
   end
 
   def wall_time
-    time_limit*3+extra_time+5
+    time_limit*2+extra_time+1
   end
 
   def setup_judging
     self.problem = submission.problem
+    self.box = Isolate.new
+    self.interactive_boxes = Array.new(problem.evaluator&.interactive_processes || 0) { Isolate.new }
     Dir.mktmpdir do |tmpdir|
       self.tmpdir = tmpdir
-      Isolate.box do |box|
-        self.box = box
-        yield
-      end or raise Isolate::LockError, "Error locking box"
+      yield
     end
+  ensure
+    box.send(:destroy) if !box.nil?
+    interactive_boxes.each do |box|
+      box.send(:destroy) if !box.nil?
+    end if !interactive_boxes.nil?
   end
 
   def compile!(source, language, output)
@@ -178,15 +182,19 @@ def compile!(source, language, output)
   end
 
   def judge_test_case(test_case, run_command, eval_command, resource_limits)
-    FileUtils.copy(File.expand_path(exe_filename, tmpdir), box.expand_path(exe_filename))
-    result = run_test_case(test_case, run_command, resource_limits)
-    result['evaluator'] = evaluate_output(test_case, result['output'], result['output_size'], eval_command)
+    if problem.evaluator&.interactive_processes&.positive?
+      result = run_interactive(test_case, run_command, eval_command, resource_limits)
+    else
+      result = run_test_case(test_case, run_command, resource_limits)
+      result['evaluator'] = evaluate_output(test_case, result['output'], result['output_size'], eval_command)
+    end
     result['log'] = truncate_output(result['log']) # log only a small portion
     result['output'] = truncate_output(result['output'].slice(0,100)) # store only a small portion
     result
   end
 
   def run_test_case(test_case, run_command, resource_limits = {})
+    FileUtils.copy(File.expand_path(exe_filename, tmpdir), box.expand_path(exe_filename))
     stream_limit = OutputBaseLimit + test_case.output.bytesize*2
     run_opts = resource_limits.reverse_merge(:output_limit => stream_limit, :clean_utf8 => true)
     if submission.input.nil?
@@ -255,6 +263,144 @@ def evaluate_output(test_case, output, output_size, eval_command)
     box.clean!
   end
 
+  def run_interactive(test_case, run_command, eval_command, resource_limits)
+    stream_limit = OutputBaseLimit + test_case.output.bytesize*2
+    num_processes = problem.evaluator.interactive_processes
+
+    metafiles = []
+    boxfiles = []
+    logfiles = []
+    manager_pipes = []
+    user_pids = []
+
+    interactive_boxes.each_with_index do |box, index|
+      FileUtils.copy(File.expand_path(exe_filename, tmpdir), box.expand_path(exe_filename))
+      metafiles << Tempfile.new('metafile')
+      boxfiles << Tempfile.new('boxfile')
+      logfiles << box.tmpfile
+      manager_to_user = IO.pipe
+      user_to_manager = IO.pipe
+      manager_pipes << [user_to_manager[0], manager_to_user[1]]
+
+      run_opts = resource_limits.merge(:meta => metafiles.last.path, :err => boxfiles.last, :in => manager_to_user[0], :out => user_to_manager[1], :stderr => logfiles.last)
+      box_run_command = run_command
+      if num_processes > 1
+        box_run_command += " " + index.to_s
+      end
+      user_pids << box.spawn_command(box_run_command, run_opts)
+
+      manager_to_user[0].close
+      user_to_manager[1].close
+    end
+
+    expected = conditioned_output(test_case.output)
+    FileUtils.copy(File.expand_path(EvalFileName, tmpdir), box.expand_path(EvalFileName))
+    manager_resource_limits = { :mem => 524288, :time => num_processes * time_limit + 15, :wall_time => num_processes * wall_time + 30 }
+
+    eval_output = nil
+    eval_result = {}
+    str_to_pipe(expected) do |output_stream|
+      run_opts = manager_resource_limits.merge(:processes => true, 4 => output_stream, :stdin_data => test_case.input, :output_limit => OutputBaseLimit + test_case.output.bytesize*4, :clean_utf8 => true, :inherit_fds => true)
+      manager_pipes.each_with_index do |pipes, index|
+        run_opts.merge!(index * 2 + 5 => pipes[0], index * 2 + 6 => pipes[1])
+      end
+      (stdout,), (eval_result['log'],eval_result['log_size']), (eval_result['box'],), eval_result['meta'], status = box.capture5("#{eval_command}", run_opts)
+      eval_result['log'] = truncate_output(eval_result['log'])
+      eval_output = stdout.strip.split(nil,2)
+      eval_result['stat'] = status.exitstatus
+    end
+
+    manager_pipes.each do |pipes|
+      pipes[0].close
+      pipes[1].close
+    end
+
+    if eval_output.empty?
+      eval_result.delete('evaluation') # error
+    else
+      eval_result['evaluation'] = eval_output[0].to_d
+      eval_result['message'] = truncate_output(eval_output[1] || "")
+    end
+
+    r = { 'evaluator' => eval_result }
+
+    r['stat'] = 0
+    user_pids.each do |pid|
+      exit_status = Process.detach(pid).value.exitstatus
+      r['stat'] = r['stat'].nonzero? || exit_status
+    end
+
+    metafiles.each do |metafile|
+      metafile.open
+      meta = Isolate.parse_meta(metafile.read)
+
+      if r['meta'].nil?
+        r['meta'] = meta
+      else
+        # Merge execution stats
+        r['meta']['time'] += meta['time']
+        r['meta']['time-wall'] = [r['meta']['time-wall'], meta['time-wall']].max
+        r['meta']['cg-mem'] += meta['cg-mem'] if meta.has_key?('cg-mem')
+        r['meta']['max-rss'] += meta['max-rss']
+
+        # Use first non-OK status and related values
+        if r['meta']['status'] == 'OK' && meta['status'] != 'OK'
+          r['meta']['status'] = meta['status']
+          r['meta']['killed'] = meta['killed'] if meta.has_key?('killed')
+          r['meta']['exitcode'] = meta['exitcode'] if meta.has_key?('exitcode')
+          r['meta']['exitsig'] = meta['exitsig'] if meta.has_key?('exitsig')
+          r['meta']['message'] = meta['message'] if meta.has_key?('message')
+        end
+      end
+      metafile.close
+    end
+
+    # Check for MLE/TLE based on merged execution stats
+    if r['meta']['status'] == 'OK'
+      if (r['meta']['cg-mem'] || r['meta']['max-rss']).to_f > memory_limit*1024
+        r['meta']['status'] = 'SG'
+        r['meta']['exitsig'] = 9
+        r['meta']['message'] = "Memory Limit Exceeded"
+        r['meta']['cg-mem'] = [r['meta']['cg-mem'],memory_limit*1024].min if r['meta'].has_key?('cg-mem')
+        r['meta']['max-rss'] = [r['meta']['max-rss'],memory_limit*1024].min
+        r['stat'] = 1
+      elsif r['meta']['time'] > time_limit.to_f
+        r['meta']['status'] = 'TO'
+        r['meta']['message'] = "Time Limit Exceeded"
+        r['stat'] = 1
+      end
+    end
+
+    r['box'] = ''
+    boxfiles.each do |boxfile|
+      boxfile.open
+      r['box'] << boxfile.read
+      boxfile.close
+    end
+
+    r['log'] = ''
+    r['log_size'] = 0
+    interactive_boxes.zip(logfiles).each do |box, logfile|
+      stderr = File.open(box.expand_path(logfile)) { |f| box.read_pipe_limited(f, stream_limit) }
+      (log, log_size) = box.clean_utf8(stderr)
+      r['log'] << log
+      r['log_size'] += log_size
+    end
+    r['log'] = truncate_output(r['log'])
+
+    r['output'] = '' # no user output
+    r['output_size'] = 0
+
+    r['time'] = [r['meta']['time'],time_limit.to_f].min
+
+    return r
+  ensure
+    metafiles.each(&:close!)
+    boxfiles.each(&:close!)
+    interactive_boxes.each(&:clean!)
+    box.clean!
+  end
+
   def grade_test_set test_set, evaluated_test_cases
     result = {'cases' => []}
     pending, error, sig = false, false, false
diff --git a/db/migrate/20230225064438_add_interactive_processes_to_evaluators.rb b/db/migrate/20230225064438_add_interactive_processes_to_evaluators.rb
new file mode 100644
index 00000000..fdaa86fc
--- /dev/null
+++ b/db/migrate/20230225064438_add_interactive_processes_to_evaluators.rb
@@ -0,0 +1,5 @@
+class AddInteractiveProcessesToEvaluators < ActiveRecord::Migration
+  def change
+    add_column :evaluators, :interactive_processes, :integer, null: false, default: 0
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 0c980263..cb0af18d 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20230225054132) do
+ActiveRecord::Schema.define(version: 20230225064438) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -87,13 +87,14 @@
   end
 
   create_table "evaluators", force: :cascade do |t|
-    t.string   "name",                     null: false
-    t.text     "description", default: "", null: false
-    t.text     "source",      default: "", null: false
-    t.integer  "owner_id",                 null: false
+    t.string   "name",                               null: false
+    t.text     "description",           default: "", null: false
+    t.text     "source",                default: "", null: false
+    t.integer  "owner_id",                           null: false
     t.datetime "created_at"
     t.datetime "updated_at"
     t.integer  "language_id"
+    t.integer  "interactive_processes", default: 0,  null: false
   end
 
   create_table "file_attachments", force: :cascade do |t|