diff --git a/lua/cp/cache.lua b/lua/cp/cache.lua
index 5c56ef8..86d806f 100644
--- a/lua/cp/cache.lua
+++ b/lua/cp/cache.lua
@@ -92,6 +92,26 @@ function M.get_contest_data(platform, contest_id)
   return cache_data[platform][contest_id]
 end
 
+---Get all cached contest IDs for a platform
+---@param platform string
+---@return string[]
+function M.get_cached_contest_ids(platform)
+  vim.validate({
+    platform = { platform, 'string' },
+  })
+
+  if not cache_data[platform] then
+    return {}
+  end
+
+  local contest_ids = {}
+  for contest_id, _ in pairs(cache_data[platform]) do
+    table.insert(contest_ids, contest_id)
+  end
+  table.sort(contest_ids)
+  return contest_ids
+end
+
 ---@param platform string
 ---@param contest_id string
 ---@param problems Problem[]
diff --git a/lua/cp/commands/init.lua b/lua/cp/commands/init.lua
index fa4f658..f48727d 100644
--- a/lua/cp/commands/init.lua
+++ b/lua/cp/commands/init.lua
@@ -59,16 +59,15 @@ local function parse_command(args)
       local debug = false
       local test_index = nil
 
-      for i = 2, #args do
-        local arg = args[i]
-        if arg == '--debug' then
+      if #args == 2 then
+        if args[2] == '--debug' then
           debug = true
         else
-          local idx = tonumber(arg)
+          local idx = tonumber(args[2])
           if not idx then
             return {
               type = 'error',
-              message = ("Invalid argument '%s': expected test number or --debug"):format(arg),
+              message = ("Invalid argument '%s': expected test number or --debug"):format(args[2]),
             }
           end
           if idx < 1 or idx ~= math.floor(idx) then
@@ -76,6 +75,30 @@ local function parse_command(args)
           end
           test_index = idx
         end
+      elseif #args == 3 then
+        local idx = tonumber(args[2])
+        if not idx then
+          return {
+            type = 'error',
+            message = ("Invalid argument '%s': expected test number"):format(args[2]),
+          }
+        end
+        if idx < 1 or idx ~= math.floor(idx) then
+          return { type = 'error', message = ("'%s' is not a valid test index"):format(idx) }
+        end
+        if args[3] ~= '--debug' then
+          return {
+            type = 'error',
+            message = ("Invalid argument '%s': expected --debug"):format(args[3]),
+          }
+        end
+        test_index = idx
+        debug = true
+      elseif #args > 3 then
+        return {
+          type = 'error',
+          message = 'Too many arguments. Usage: :CP ' .. first .. ' [test_num] [--debug]',
+        }
       end
 
       return { type = 'action', action = first, test_index = test_index, debug = debug }
diff --git a/plugin/cp.lua b/plugin/cp.lua
index 5d4df32..b4954a4 100644
--- a/plugin/cp.lua
+++ b/plugin/cp.lua
@@ -22,12 +22,30 @@ end, {
       num_args = num_args + 1
     end
 
+    local function filter_candidates(candidates)
+      return vim.tbl_filter(function(cmd)
+        return cmd:find(ArgLead, 1, true) == 1
+      end, candidates)
+    end
+
+    local function get_enabled_languages(platform)
+      local config = require('cp.config').get_config()
+      if platform and config.platforms[platform] then
+        return config.platforms[platform].enabled_languages
+      end
+      return vim.tbl_keys(config.languages)
+    end
+
     if num_args == 2 then
       local candidates = {}
       local state = require('cp.state')
       local platform = state.get_platform()
       local contest_id = state.get_contest_id()
 
+      vim.list_extend(candidates, platforms)
+      table.insert(candidates, 'cache')
+      table.insert(candidates, 'pick')
+
       if platform and contest_id then
         vim.list_extend(candidates, actions)
         local cache = require('cp.cache')
@@ -39,44 +57,75 @@ end, {
           table.sort(ids)
           vim.list_extend(candidates, ids)
         end
-      else
-        vim.list_extend(candidates, platforms)
-        table.insert(candidates, 'cache')
-        table.insert(candidates, 'pick')
       end
 
-      return vim.tbl_filter(function(cmd)
-        return cmd:find(ArgLead, 1, true) == 1
-      end, candidates)
+      return filter_candidates(candidates)
     elseif num_args == 3 then
-      if args[2] == 'cache' then
-        return vim.tbl_filter(function(cmd)
-          return cmd:find(ArgLead, 1, true) == 1
-        end, { 'clear', 'read' })
+      if vim.tbl_contains(platforms, args[2]) then
+        local cache = require('cp.cache')
+        cache.load()
+        local contests = cache.get_cached_contest_ids(args[2])
+        return filter_candidates(contests)
+      elseif args[2] == 'cache' then
+        return filter_candidates({ 'clear', 'read' })
       elseif args[2] == 'interact' then
-        local cands = utils.cwd_executables()
-        return vim.tbl_filter(function(cmd)
-          return cmd:find(ArgLead, 1, true) == 1
-        end, cands)
+        return filter_candidates(utils.cwd_executables())
+      elseif args[2] == 'run' or args[2] == 'panel' then
+        local state = require('cp.state')
+        local platform = state.get_platform()
+        local contest_id = state.get_contest_id()
+        local problem_id = state.get_problem_id()
+        local candidates = { '--debug' }
+        if platform and contest_id and problem_id then
+          local cache = require('cp.cache')
+          cache.load()
+          local test_cases = cache.get_test_cases(platform, contest_id, problem_id)
+          if test_cases then
+            for i = 1, #test_cases do
+              table.insert(candidates, tostring(i))
+            end
+          end
+        end
+        return filter_candidates(candidates)
+      elseif args[2] == 'next' or args[2] == 'prev' or args[2] == 'pick' then
+        return filter_candidates({ '--lang' })
+      else
+        local state = require('cp.state')
+        if state.get_platform() and state.get_contest_id() then
+          return filter_candidates({ '--lang' })
+        end
       end
     elseif num_args == 4 then
       if args[2] == 'cache' and args[3] == 'clear' then
-        return vim.tbl_filter(function(cmd)
-          return cmd:find(ArgLead, 1, true) == 1
-        end, platforms)
+        return filter_candidates(platforms)
+      elseif args[3] == '--lang' then
+        local platform = require('cp.state').get_platform()
+        return filter_candidates(get_enabled_languages(platform))
+      elseif (args[2] == 'run' or args[2] == 'panel') and tonumber(args[3]) then
+        return filter_candidates({ '--debug' })
       elseif vim.tbl_contains(platforms, args[2]) then
         local cache = require('cp.cache')
         cache.load()
         local contest_data = cache.get_contest_data(args[2], args[3])
+        local candidates = { '--lang' }
         if contest_data and contest_data.problems then
-          local candidates = {}
           for _, problem in ipairs(contest_data.problems) do
             table.insert(candidates, problem.id)
           end
-          return vim.tbl_filter(function(cmd)
-            return cmd:find(ArgLead, 1, true) == 1
-          end, candidates)
         end
+        return filter_candidates(candidates)
+      end
+    elseif num_args == 5 then
+      if vim.tbl_contains(platforms, args[2]) then
+        if args[4] == '--lang' then
+          return filter_candidates(get_enabled_languages(args[2]))
+        else
+          return filter_candidates({ '--lang' })
+        end
+      end
+    elseif num_args == 6 then
+      if vim.tbl_contains(platforms, args[2]) and args[5] == '--lang' then
+        return filter_candidates(get_enabled_languages(args[2]))
       end
     end
     return {}