diff --git a/runtime/doc/lua.txt b/runtime/doc/lua.txt
index e9ceb47d3e..e855f2a59e 100644
--- a/runtime/doc/lua.txt
+++ b/runtime/doc/lua.txt
@@ -5208,13 +5208,13 @@ vim.version.range({spec})                                *vim.version.range()*
 
 
 ==============================================================================
-Lua module: vim._extui                                            *vim._extui*
+Lua module: vim._core.ui2                                      *vim._core.ui2*
 
 WARNING: This is an experimental interface intended to replace the message
 grid in the TUI.
 
 To enable the experimental UI (default opts shown): >lua
-    require('vim._extui').enable({
+    require('vim._core.ui2').enable({
      enable = true, -- Whether to enable or disable the UI.
      msg = { -- Options related to the message module.
        ---@type 'cmd'|'msg' Where to place regular messages, either in the
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index e40a89610e..2a98c30e58 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -397,7 +397,7 @@ UI
   address.
 • |:checkhealth| shows a summary in the header for every healthcheck.
 • |ui-multigrid| provides composition information and absolute coordinates.
-• `vim._extui` provides an experimental commandline and message UI intended to
+• `vim._core.ui2` provides an experimental commandline and message UI intended to
   replace the message grid in the TUI.
 • Error messages are more concise:
   • "Error detected while processing:" changed to "Error in:".
diff --git a/runtime/lua/vim/_core/ui2.lua b/runtime/lua/vim/_core/ui2.lua
new file mode 100644
index 0000000000..a8413fe51c
--- /dev/null
+++ b/runtime/lua/vim/_core/ui2.lua
@@ -0,0 +1,256 @@
+--- @brief
+---
+---WARNING: This is an experimental interface intended to replace the message
+---grid in the TUI.
+---
+---To enable the experimental UI (default opts shown):
+---```lua
+---require('vim._core.ui2').enable({
+---  enable = true, -- Whether to enable or disable the UI.
+---  msg = { -- Options related to the message module.
+---    ---@type 'cmd'|'msg' Where to place regular messages, either in the
+---    ---cmdline or in a separate ephemeral message window.
+---    target = 'cmd',
+---    timeout = 4000, -- Time a message is visible in the message window.
+---  },
+---})
+---```
+---
+---There are four separate window types used by this interface:
+---- "cmd": The cmdline window; also used for 'showcmd', 'showmode', 'ruler', and
+---  messages if 'cmdheight' > 0.
+---- "msg": The message window; used for messages when 'cmdheight' == 0.
+---- "pager": The pager window; used for |:messages| and certain messages
+---   that should be shown in full.
+---- "dialog": The dialog window; used for prompt messages that expect user input.
+---
+---These four windows are assigned the "cmd", "msg", "pager" and "dialog"
+---'filetype' respectively. Use a |FileType| autocommand to configure any local
+---options for these windows and their respective buffers.
+---
+---Rather than a |hit-enter-prompt|, messages shown in the cmdline area that do
+---not fit are appended with a `[+x]` "spill" indicator, where `x` indicates the
+---spilled lines. To see the full message, the |g<| command can be used.
+
+local api = vim.api
+local M = {
+  ns = api.nvim_create_namespace('nvim.ui2'),
+  augroup = api.nvim_create_augroup('nvim.ui2', {}),
+  cmdheight = vim.o.cmdheight, -- 'cmdheight' option value set by user.
+  redrawing = false, -- True when redrawing to display UI event.
+  wins = { cmd = -1, dialog = -1, msg = -1, pager = -1 },
+  bufs = { cmd = -1, dialog = -1, msg = -1, pager = -1 },
+  cfg = {
+    enable = true,
+    msg = { -- Options related to the message module.
+      ---@type 'cmd'|'msg' Where to place regular messages, either in the
+      ---cmdline or in a separate ephemeral message window.
+      target = 'cmd',
+      timeout = 4000, -- Time a message is visible in the message window.
+    },
+  },
+}
+--- @type vim.api.keyset.win_config
+local wincfg = { -- Default cfg for nvim_open_win().
+  relative = 'laststatus',
+  style = 'minimal',
+  col = 0,
+  row = 1,
+  width = 10000,
+  height = 1,
+  noautocmd = true,
+}
+
+local tab = 0
+---Ensure target buffers and windows are still valid.
+function M.check_targets()
+  local curtab = api.nvim_get_current_tabpage()
+  for i, type in ipairs({ 'cmd', 'dialog', 'msg', 'pager' }) do
+    local setopt = not api.nvim_buf_is_valid(M.bufs[type])
+    if setopt then
+      M.bufs[type] = api.nvim_create_buf(false, false)
+    end
+
+    if
+      tab ~= curtab
+      or not api.nvim_win_is_valid(M.wins[type])
+      or not api.nvim_win_get_config(M.wins[type]).zindex -- no longer floating
+    then
+      local cfg = vim.tbl_deep_extend('force', wincfg, {
+        focusable = type == 'pager',
+        mouse = type ~= 'cmd' and true or nil,
+        anchor = type ~= 'cmd' and 'SE' or nil,
+        hide = type ~= 'cmd' or M.cmdheight == 0 or nil,
+        border = type ~= 'msg' and 'none' or nil,
+        -- kZIndexMessages < cmd zindex < kZIndexCmdlinePopupMenu (grid_defs.h), pager below others.
+        zindex = 201 - i,
+        _cmdline_offset = type == 'cmd' and 0 or nil,
+      })
+      if tab ~= curtab and api.nvim_win_is_valid(M.wins[type]) then
+        cfg = api.nvim_win_get_config(M.wins[type])
+        api.nvim_win_close(M.wins[type], true)
+      end
+      M.wins[type] = api.nvim_open_win(M.bufs[type], false, cfg)
+      setopt = true
+    elseif api.nvim_win_get_buf(M.wins[type]) ~= M.bufs[type] then
+      api.nvim_win_set_buf(M.wins[type], M.bufs[type])
+      setopt = true
+    end
+
+    if setopt then
+      -- Set options without firing OptionSet and BufFilePost.
+      vim._with({ win = M.wins[type], noautocmd = true }, function()
+        local ignore = 'all,-FileType' .. (type == 'pager' and ',-TextYankPost' or '')
+        api.nvim_set_option_value('eventignorewin', ignore, { scope = 'local' })
+        api.nvim_set_option_value('wrap', true, { scope = 'local' })
+        api.nvim_set_option_value('linebreak', false, { scope = 'local' })
+        api.nvim_set_option_value('smoothscroll', true, { scope = 'local' })
+        api.nvim_set_option_value('breakindent', false, { scope = 'local' })
+        api.nvim_set_option_value('foldenable', false, { scope = 'local' })
+        api.nvim_set_option_value('showbreak', '', { scope = 'local' })
+        api.nvim_set_option_value('spell', false, { scope = 'local' })
+        api.nvim_set_option_value('swapfile', false, { scope = 'local' })
+        api.nvim_set_option_value('modifiable', true, { scope = 'local' })
+        api.nvim_set_option_value('bufhidden', 'hide', { scope = 'local' })
+        api.nvim_set_option_value('buftype', 'nofile', { scope = 'local' })
+        -- Use MsgArea except in the msg window. Hide Search highlighting except in the pager.
+        local search_hide = 'Search:,CurSearch:,IncSearch:'
+        local hl = 'Normal:MsgArea,' .. search_hide
+        if type == 'pager' then
+          hl = 'Normal:MsgArea'
+        elseif type == 'msg' then
+          hl = search_hide
+        end
+        api.nvim_set_option_value('winhighlight', hl, { scope = 'local' })
+      end)
+      api.nvim_buf_set_name(M.bufs[type], ('[%s]'):format(type:sub(1, 1):upper() .. type:sub(2)))
+      -- Fire FileType with window context to let the user reconfigure local options.
+      vim._with({ win = M.wins[type] }, function()
+        api.nvim_set_option_value('filetype', type, { scope = 'local' })
+      end)
+
+      if type == 'pager' then
+        -- Close pager with `q`, same as `checkhealth`
+        api.nvim_buf_set_keymap(M.bufs.pager, 'n', 'q', '<Cmd>wincmd c<CR>', {})
+      elseif type == M.cfg.msg.target then
+        M.msg.prev_msg = '' -- Will no longer be visible.
+      end
+    end
+  end
+  tab = curtab
+end
+
+local function ui_callback(redraw_msg, event, ...)
+  local handler = M.msg[event] or M.cmd[event]
+  M.check_targets()
+  handler(...)
+  -- Cmdline mode, non-fast message and non-empty showcmd require an immediate redraw.
+  if M.cmd[event] or redraw_msg or (event == 'msg_showcmd' and select(1, ...)[1]) then
+    M.redrawing = true
+    api.nvim__redraw({
+      flush = handler ~= M.cmd.cmdline_hide or nil,
+      cursor = handler == M.cmd[event] and true or nil,
+      win = handler == M.cmd[event] and M.wins.cmd or nil,
+    })
+    M.redrawing = false
+  end
+end
+local scheduled_ui_callback = vim.schedule_wrap(ui_callback)
+
+---@nodoc
+function M.enable(opts)
+  vim.validate('opts', opts, 'table', true)
+  if opts.msg then
+    vim.validate('opts.msg.pos', opts.msg.pos, 'nil', true, 'nil: "pos" moved to opts.target')
+    vim.validate('opts.msg.box', opts.msg.box, 'nil', true, 'nil: "timeout" moved to opts.msg')
+    vim.validate('opts.msg.target', opts.msg.target, function(tar)
+      return tar == 'cmd' or tar == 'msg'
+    end, "'cmd'|'msg'")
+  end
+  M.cfg = vim.tbl_deep_extend('keep', opts, M.cfg)
+  M.cmd = require('vim._core.ui2.cmdline')
+  M.msg = require('vim._core.ui2.messages')
+
+  if M.cfg.enable == false then
+    -- Detach and cleanup windows, buffers and autocommands.
+    for _, win in pairs(M.wins) do
+      if api.nvim_win_is_valid(win) then
+        api.nvim_win_close(win, true)
+      end
+    end
+    for _, buf in pairs(M.bufs) do
+      if api.nvim_buf_is_valid(buf) then
+        api.nvim_buf_delete(buf, {})
+      end
+    end
+    api.nvim_clear_autocmds({ group = M.augroup })
+    vim.ui_detach(M.ns)
+    return
+  end
+
+  vim.ui_attach(M.ns, { ext_messages = true, set_cmdheight = false }, function(event, ...)
+    if not (M.msg[event] or M.cmd[event]) then
+      return
+    end
+    -- Ensure cmdline is placed after a scheduled message in block mode.
+    if vim.in_fast_event() or (event == 'cmdline_show' and M.cmd.srow > 0) then
+      scheduled_ui_callback(false, event, ...)
+    else
+      ui_callback(event == 'msg_show', event, ...)
+    end
+    return true
+  end)
+
+  -- The visibility and appearance of the cmdline and message window is
+  -- dependent on some option values. Reconfigure windows when option value
+  -- has changed and after VimEnter when the user configured value is known.
+  -- TODO: Reconsider what is needed when this module is enabled by default early in startup.
+  local function check_cmdheight(value)
+    M.check_targets()
+    -- 'cmdheight' set; (un)hide cmdline window and set its height.
+    local cfg = { height = math.max(value, 1), hide = value == 0 }
+    api.nvim_win_set_config(M.wins.cmd, cfg)
+    -- Change message position when 'cmdheight' was or becomes 0.
+    if value == 0 or M.cmdheight == 0 then
+      M.cfg.msg.target = value == 0 and 'msg' or 'cmd'
+      M.msg.prev_msg = ''
+    end
+    M.cmdheight = value
+  end
+
+  if vim.v.vim_did_enter == 0 then
+    vim.schedule(function()
+      check_cmdheight(vim.o.cmdheight)
+    end)
+  end
+
+  api.nvim_create_autocmd('OptionSet', {
+    group = M.augroup,
+    pattern = { 'cmdheight' },
+    callback = function()
+      check_cmdheight(vim.v.option_new)
+      M.msg.set_pos()
+    end,
+    desc = 'Set cmdline and message window dimensions for changed option values.',
+  })
+
+  api.nvim_create_autocmd({ 'VimResized', 'TabEnter' }, {
+    group = M.augroup,
+    callback = function()
+      M.msg.set_pos()
+    end,
+    desc = 'Set cmdline and message window dimensions after shell resize or tabpage change.',
+  })
+
+  api.nvim_create_autocmd('WinEnter', {
+    callback = function()
+      local win = api.nvim_get_current_win()
+      if vim.tbl_contains(M.wins, win) and api.nvim_win_get_config(win).hide then
+        vim.cmd.wincmd('p')
+      end
+    end,
+    desc = 'Make sure hidden UI window is never current.',
+  })
+end
+
+return M
diff --git a/runtime/lua/vim/_extui/cmdline.lua b/runtime/lua/vim/_core/ui2/cmdline.lua
similarity index 77%
rename from runtime/lua/vim/_extui/cmdline.lua
rename to runtime/lua/vim/_core/ui2/cmdline.lua
index de538b3a65..4f648de2ae 100644
--- a/runtime/lua/vim/_extui/cmdline.lua
+++ b/runtime/lua/vim/_core/ui2/cmdline.lua
@@ -1,6 +1,6 @@
-local ext = require('vim._extui.shared')
+local ui = require('vim._core.ui2')
 local api, fn = vim.api, vim.fn
----@class vim._extui.cmdline
+---@class vim._core.ui2.cmdline
 local M = {
   highlighter = nil, ---@type vim.treesitter.highlighter?
   indent = 0, -- Current indent for block event.
@@ -17,7 +17,7 @@ local M = {
 ---@param hide boolean Whether to hide or show the window.
 ---@param height integer (Text)height of the cmdline window.
 local function win_config(win, hide, height)
-  if ext.cmdheight == 0 and api.nvim_win_get_config(win).hide ~= hide then
+  if ui.cmdheight == 0 and api.nvim_win_get_config(win).hide ~= hide then
     api.nvim_win_set_config(win, { hide = hide, height = not hide and height or nil })
   elseif api.nvim_win_get_height(win) ~= height then
     api.nvim_win_set_height(win, height)
@@ -28,10 +28,10 @@ local function win_config(win, hide, height)
     vim._with({ noautocmd = true, o = { splitkeep = 'screen' } }, function()
       vim.o.cmdheight = height
     end)
-    ext.msg.set_pos()
+    ui.msg.set_pos()
   elseif M.wmnumode ~= (M.prompt and fn.pumvisible() == 0 and fn.wildmenumode() or 0) then
     M.wmnumode = (M.wmnumode == 1 and 0 or 1)
-    ext.msg.set_pos()
+    ui.msg.set_pos()
   end
 end
 
@@ -53,7 +53,7 @@ local function set_text(content, prompt)
     cmdbuff = cmdbuff .. chunk[2]
   end
   lines[#lines] = ('%s%s '):format(lines[#lines], fn.strtrans(cmdbuff))
-  api.nvim_buf_set_lines(ext.bufs.cmd, M.srow, -1, false, lines)
+  api.nvim_buf_set_lines(ui.bufs.cmd, M.srow, -1, false, lines)
 end
 
 --- Set the cmdline buffer text and cursor position.
@@ -67,24 +67,24 @@ end
 ---@param hl_id integer
 function M.cmdline_show(content, pos, firstc, prompt, indent, level, hl_id)
   M.level, M.indent, M.prompt = level, indent, M.prompt or #prompt > 0
-  if M.highlighter == nil or M.highlighter.bufnr ~= ext.bufs.cmd then
-    local parser = assert(vim.treesitter.get_parser(ext.bufs.cmd, 'vim', {}))
+  if M.highlighter == nil or M.highlighter.bufnr ~= ui.bufs.cmd then
+    local parser = assert(vim.treesitter.get_parser(ui.bufs.cmd, 'vim', {}))
     M.highlighter = vim.treesitter.highlighter.new(parser)
   end
   -- Only enable TS highlighter for Ex commands (not search or filter commands).
-  M.highlighter.active[ext.bufs.cmd] = firstc == ':' and M.highlighter or nil
-  if ext.msg.cmd.msg_row ~= -1 then
-    ext.msg.msg_clear()
+  M.highlighter.active[ui.bufs.cmd] = firstc == ':' and M.highlighter or nil
+  if ui.msg.cmd.msg_row ~= -1 then
+    ui.msg.msg_clear()
   end
-  ext.msg.virt.last = { {}, {}, {}, {} }
+  ui.msg.virt.last = { {}, {}, {}, {} }
 
   set_text(content, ('%s%s%s'):format(firstc, prompt, (' '):rep(indent)))
   if promptlen > 0 and hl_id > 0 then
-    api.nvim_buf_set_extmark(ext.bufs.cmd, ext.ns, 0, 0, { hl_group = hl_id, end_col = promptlen })
+    api.nvim_buf_set_extmark(ui.bufs.cmd, ui.ns, 0, 0, { hl_group = hl_id, end_col = promptlen })
   end
 
-  local height = math.max(ext.cmdheight, api.nvim_win_text_height(ext.wins.cmd, {}).all)
-  win_config(ext.wins.cmd, false, height)
+  local height = math.max(ui.cmdheight, api.nvim_win_text_height(ui.wins.cmd, {}).all)
+  win_config(ui.wins.cmd, false, height)
   M.cmdline_pos(pos)
 end
 
@@ -94,7 +94,7 @@ end
 ---@param shift boolean
 --@param level integer
 function M.cmdline_special_char(c, shift)
-  api.nvim_win_call(ext.wins.cmd, function()
+  api.nvim_win_call(ui.wins.cmd, function()
     api.nvim_put({ c }, shift and '' or 'c', false, false)
   end)
 end
@@ -110,12 +110,12 @@ function M.cmdline_pos(pos)
     curpos[1], curpos[2] = M.erow + 1, promptlen + pos
     -- Add matchparen highlighting to non-prompt part of cmdline.
     if pos > 0 and fn.exists('#matchparen#CursorMoved') == 1 then
-      api.nvim_win_set_cursor(ext.wins.cmd, { curpos[1], curpos[2] - 1 })
-      vim._with({ win = ext.wins.cmd, wo = { eventignorewin = '' } }, function()
+      api.nvim_win_set_cursor(ui.wins.cmd, { curpos[1], curpos[2] - 1 })
+      vim._with({ win = ui.wins.cmd, wo = { eventignorewin = '' } }, function()
         api.nvim_exec_autocmds('CursorMoved', {})
       end)
     end
-    api.nvim_win_set_cursor(ext.wins.cmd, curpos)
+    api.nvim_win_set_cursor(ui.wins.cmd, curpos)
   end
 end
 
@@ -128,21 +128,21 @@ function M.cmdline_hide(level, abort)
     return -- No need to hide when still in nested cmdline or cmdline_block.
   end
 
-  fn.clearmatches(ext.wins.cmd) -- Clear matchparen highlights.
-  api.nvim_win_set_cursor(ext.wins.cmd, { 1, 0 })
+  fn.clearmatches(ui.wins.cmd) -- Clear matchparen highlights.
+  api.nvim_win_set_cursor(ui.wins.cmd, { 1, 0 })
   if abort then
     -- Clear cmd buffer for aborted command (non-abort is left visible).
-    api.nvim_buf_set_lines(ext.bufs.cmd, 0, -1, false, {})
+    api.nvim_buf_set_lines(ui.bufs.cmd, 0, -1, false, {})
   end
 
   local clear = vim.schedule_wrap(function(was_prompt)
     -- Avoid clearing prompt window when it is re-entered before the next event
     -- loop iteration. E.g. when a non-choice confirm button is pressed.
     if was_prompt and not M.prompt then
-      api.nvim_buf_set_lines(ext.bufs.cmd, 0, -1, false, {})
-      api.nvim_buf_set_lines(ext.bufs.dialog, 0, -1, false, {})
-      api.nvim_win_set_config(ext.wins.dialog, { hide = true })
-      vim.on_key(nil, ext.msg.dialog_on_key)
+      api.nvim_buf_set_lines(ui.bufs.cmd, 0, -1, false, {})
+      api.nvim_buf_set_lines(ui.bufs.dialog, 0, -1, false, {})
+      api.nvim_win_set_config(ui.wins.dialog, { hide = true })
+      vim.on_key(nil, ui.msg.dialog_on_key)
     end
     -- Messages emitted as a result of a typed command are treated specially:
     -- remember if the cmdline was used this event loop iteration.
@@ -154,7 +154,7 @@ function M.cmdline_hide(level, abort)
   clear(M.prompt)
 
   M.prompt, M.level, curpos[1], curpos[2] = false, 0, 0, 0
-  win_config(ext.wins.cmd, true, ext.cmdheight)
+  win_config(ui.wins.cmd, true, ui.cmdheight)
 end
 
 --- Set multi-line cmdline buffer text.
diff --git a/runtime/lua/vim/_extui/messages.lua b/runtime/lua/vim/_core/ui2/messages.lua
similarity index 78%
rename from runtime/lua/vim/_extui/messages.lua
rename to runtime/lua/vim/_core/ui2/messages.lua
index 7b699eee48..4c6991f0fd 100644
--- a/runtime/lua/vim/_extui/messages.lua
+++ b/runtime/lua/vim/_core/ui2/messages.lua
@@ -1,8 +1,8 @@
 local api, fn, o = vim.api, vim.fn, vim.o
-local ext = require('vim._extui.shared')
+local ui = require('vim._core.ui2')
 
 ---@alias Msg { extid: integer, timer: uv.uv_timer_t? }
----@class vim._extui.messages
+---@class vim._core.ui2.messages
 local M = {
   -- Message window. Used for regular messages with 'cmdheight' == 0 or,
   -- cfg.msg.target == 'msg'. Automatically resizes to the text dimensions up to
@@ -40,16 +40,16 @@ local M = {
 
 local cmd_on_key ---@type integer? Set to vim.on_key namespace while cmdline is expanded.
 -- An external redraw indicates the start of a new batch of messages in the cmdline.
-api.nvim_set_decoration_provider(ext.ns, {
+api.nvim_set_decoration_provider(ui.ns, {
   on_start = function()
-    M.cmd.ids = (ext.redrawing or cmd_on_key) and M.cmd.ids or {}
+    M.cmd.ids = (ui.redrawing or cmd_on_key) and M.cmd.ids or {}
   end,
 })
 
 function M.msg:close()
   self.width, M.virt.msg[M.virt.idx.dupe][1] = 1, nil
-  if api.nvim_win_is_valid(ext.wins.msg) then
-    api.nvim_win_set_config(ext.wins.msg, { hide = true })
+  if api.nvim_win_is_valid(ui.wins.msg) then
+    api.nvim_win_set_config(ui.wins.msg, { hide = true })
   end
 end
 
@@ -63,18 +63,18 @@ function M.msg:start_timer(buf, id)
   end
   self.ids[id].timer = vim.defer_fn(function()
     local extid = api.nvim_buf_is_valid(buf) and self.ids[id] and self.ids[id].extid
-    local mark = extid and api.nvim_buf_get_extmark_by_id(buf, ext.ns, extid, { details = true })
+    local mark = extid and api.nvim_buf_get_extmark_by_id(buf, ui.ns, extid, { details = true })
     self.ids[id] = nil
     if not mark or not mark[1] then
       return
     end
     -- Clear prev_msg when line that may have dupe marker is removed.
     local erow = api.nvim_buf_line_count(buf) - 1
-    M.prev_msg = ext.cfg.msg.target == 'msg' and mark[3].end_row == erow and '' or M.prev_msg
+    M.prev_msg = ui.cfg.msg.target == 'msg' and mark[3].end_row == erow and '' or M.prev_msg
 
     -- Remove message (including potentially leftover empty line).
     api.nvim_buf_set_text(buf, mark[1], mark[2], mark[3].end_row, mark[3].end_col, {})
-    if fn.col({ mark[1] + 1, '$' }, ext.wins.msg) == 1 then
+    if fn.col({ mark[1] + 1, '$' }, ui.wins.msg) == 1 then
       api.nvim_buf_set_lines(buf, mark[1], mark[1] + 1, false, {})
     end
 
@@ -84,7 +84,7 @@ function M.msg:start_timer(buf, id)
     else
       self:close()
     end
-  end, ext.cfg.msg.timeout)
+  end, ui.cfg.msg.timeout)
 end
 
 --- Place or delete a virtual text mark in the cmdline or message window.
@@ -92,7 +92,7 @@ end
 ---@param type 'last'|'msg'|'top'|'bot'
 ---@param tar? 'cmd'|'msg'|'dialog'
 local function set_virttext(type, tar)
-  if (type == 'last' and (ext.cmdheight == 0 or M.virt.delayed)) or cmd_on_key then
+  if (type == 'last' and (ui.cmdheight == 0 or M.virt.delayed)) or cmd_on_key then
     return -- Don't show virtual text while cmdline is expanded or delaying for error.
   end
 
@@ -105,17 +105,17 @@ local function set_virttext(type, tar)
       width = width + api.nvim_strwidth(chunk[2])
     end
   end
-  tar = tar or type == 'msg' and ext.cfg.msg.target or 'cmd'
+  tar = tar or type == 'msg' and ui.cfg.msg.target or 'cmd'
 
   if M.virt.ids[type] and #chunks == 0 then
-    api.nvim_buf_del_extmark(ext.bufs[tar], ext.ns, M.virt.ids[type])
+    api.nvim_buf_del_extmark(ui.bufs[tar], ui.ns, M.virt.ids[type])
     M.cmd.last_col = type == 'last' and o.columns or M.cmd.last_col
     M.virt.ids[type] = nil
   elseif #chunks > 0 then
-    local win = ext.wins[tar]
+    local win = ui.wins[tar]
     local line = (tar == 'msg' or type == 'top') and 'w0' or type == 'bot' and 'w$'
-    local srow = line and fn.line(line, ext.wins.dialog) - 1
-    local erow = tar == 'cmd' and math.min(M.cmd.msg_row, api.nvim_buf_line_count(ext.bufs.cmd) - 1)
+    local srow = line and fn.line(line, ui.wins.dialog) - 1
+    local erow = tar == 'cmd' and math.min(M.cmd.msg_row, api.nvim_buf_line_count(ui.bufs.cmd) - 1)
     local texth = api.nvim_win_text_height(win, {
       max_height = (type == 'top' or type == 'bot') and 1 or api.nvim_win_get_height(win),
       start_row = srow or nil,
@@ -147,20 +147,20 @@ local function set_virttext(type, tar)
 
       -- Give virt_text the same highlight as the message tail.
       local pos, opts = { row, col }, { details = true, overlap = true, type = 'highlight' }
-      local hl = api.nvim_buf_get_extmarks(ext.bufs[tar], ext.ns, pos, pos, opts)
+      local hl = api.nvim_buf_get_extmarks(ui.bufs[tar], ui.ns, pos, pos, opts)
       for _, chunk in ipairs(hl[1] and chunks or {}) do
         chunk[2] = hl[1][4].hl_group
       end
     else
       local mode = #M.virt.last[M.virt.idx.mode]
       local pad = o.columns - width ---@type integer
-      local newlines = math.max(0, ext.cmdheight - texth.all)
+      local newlines = math.max(0, ui.cmdheight - texth.all)
       row = row + newlines
       M.cmd.last_col = mode > 0 and 0 or o.columns - (newlines > 0 and 0 or width)
 
       if newlines > 0 then
         -- Add empty lines to place virt_text on the last screen row.
-        api.nvim_buf_set_lines(ext.bufs.cmd, -1, -1, false, fn['repeat']({ '' }, newlines))
+        api.nvim_buf_set_lines(ui.bufs.cmd, -1, -1, false, fn['repeat']({ '' }, newlines))
         col = 0
       else
         if scol > M.cmd.last_col then
@@ -179,7 +179,7 @@ local function set_virttext(type, tar)
           col = vcol <= 0 and 0 or fn.virtcol2col(win, row + 1, vcol)
           M.prev_msg = mode > 0 and '' or M.prev_msg
           M.virt.msg = mode > 0 and { {}, {} } or M.virt.msg
-          api.nvim_buf_set_text(ext.bufs.cmd, row, col, row, -1, { mode > 0 and ' ' or '' })
+          api.nvim_buf_set_text(ui.bufs.cmd, row, col, row, -1, { mode > 0 and ' ' or '' })
         end
 
         pad = pad - ((mode > 0 or col == 0) and 0 or math.min(M.cmd.last_col, scol))
@@ -188,7 +188,7 @@ local function set_virttext(type, tar)
       set_virttext('msg') -- Readjust to new M.cmd.last_col or clear for mode.
     end
 
-    M.virt.ids[type] = api.nvim_buf_set_extmark(ext.bufs[tar], ext.ns, row, col, {
+    M.virt.ids[type] = api.nvim_buf_set_extmark(ui.bufs[tar], ui.ns, row, col, {
       virt_text = chunks,
       virt_text_pos = 'overlay',
       right_gravity = false,
@@ -205,22 +205,22 @@ local hlopts = { undo_restore = false, invalidate = true, priority = 1 }
 local function expand_msg(src)
   -- Copy and clear message from src to enlarged cmdline that is dismissed by any
   -- key press, or append to pager in case that is already open (not hidden).
-  local hidden = api.nvim_win_get_config(ext.wins.pager).hide
+  local hidden = api.nvim_win_get_config(ui.wins.pager).hide
   local tar = hidden and 'cmd' or 'pager'
   if tar ~= src then
-    local srow = hidden and 0 or api.nvim_buf_line_count(ext.bufs.pager)
+    local srow = hidden and 0 or api.nvim_buf_line_count(ui.bufs.pager)
     local opts = { details = true, type = 'highlight' }
-    local marks = api.nvim_buf_get_extmarks(ext.bufs[src], -1, 0, -1, opts)
-    local lines = api.nvim_buf_get_lines(ext.bufs[src], 0, -1, false)
-    api.nvim_buf_set_lines(ext.bufs[src], 0, -1, false, {})
-    api.nvim_buf_set_lines(ext.bufs[tar], srow, -1, false, lines)
+    local marks = api.nvim_buf_get_extmarks(ui.bufs[src], -1, 0, -1, opts)
+    local lines = api.nvim_buf_get_lines(ui.bufs[src], 0, -1, false)
+    api.nvim_buf_set_lines(ui.bufs[src], 0, -1, false, {})
+    api.nvim_buf_set_lines(ui.bufs[tar], srow, -1, false, lines)
     for _, mark in ipairs(marks) do
       hlopts.end_col, hlopts.hl_group = mark[4].end_col, mark[4].hl_group
-      api.nvim_buf_set_extmark(ext.bufs[tar], ext.ns, srow + mark[2], mark[3], hlopts)
+      api.nvim_buf_set_extmark(ui.bufs[tar], ui.ns, srow + mark[2], mark[3], hlopts)
     end
 
-    if tar == 'cmd' and ext.cmd.highlighter then
-      ext.cmd.highlighter.active[ext.bufs.cmd] = nil
+    if tar == 'cmd' and ui.cmd.highlighter then
+      ui.cmd.highlighter.active[ui.bufs.cmd] = nil
     elseif tar == 'pager' then
       api.nvim_command('norm! G')
     end
@@ -230,7 +230,7 @@ local function expand_msg(src)
     M.msg:close()
   else
     for _, id in pairs(M.virt.ids) do
-      api.nvim_buf_del_extmark(ext.bufs.cmd, ext.ns, id)
+      api.nvim_buf_del_extmark(ui.bufs.cmd, ui.ns, id)
     end
   end
   M.set_pos(tar)
@@ -246,25 +246,25 @@ local cmd_timer ---@type uv.uv_timer_t? Timer resetting cmdline state next event
 ---@param append boolean
 ---@param id integer|string
 function M.show_msg(tar, content, replace_last, append, id)
-  local mark, msg, cr, dupe, buf = {}, '', false, 0, ext.bufs[tar]
+  local mark, msg, cr, dupe, buf = {}, '', false, 0, ui.bufs[tar]
 
   if M[tar] then -- tar == 'cmd'|'msg'
     local extid = M[tar].ids[id] and M[tar].ids[id].extid
-    if tar == ext.cfg.msg.target then
+    if tar == ui.cfg.msg.target then
       -- Save the concatenated message to identify repeated messages.
       for _, chunk in ipairs(content) do
         msg = msg .. chunk[2]
       end
-      dupe = (not extid and msg == M.prev_msg and ext.cmd.srow == 0 and M.dupe + 1 or 0)
+      dupe = (not extid and msg == M.prev_msg and ui.cmd.srow == 0 and M.dupe + 1 or 0)
     end
 
     cr = next(M[tar].ids) ~= nil and msg:sub(1, 1) == '\r'
     replace_last = next(M[tar].ids) ~= nil and not extid and (replace_last or dupe > 0)
     extid = extid or replace_last and M[tar].ids[M.prev_id] and M[tar].ids[M.prev_id].extid
-    mark = extid and api.nvim_buf_get_extmark_by_id(buf, ext.ns, extid, { details = true }) or {}
+    mark = extid and api.nvim_buf_get_extmark_by_id(buf, ui.ns, extid, { details = true }) or {}
 
     -- Ensure cmdline is clear when writing the first message.
-    if tar == 'cmd' and dupe == 0 and not next(M.cmd.ids) and ext.cmd.srow == 0 then
+    if tar == 'cmd' and dupe == 0 and not next(M.cmd.ids) and ui.cmd.srow == 0 then
       api.nvim_buf_set_lines(buf, 0, -1, false, {})
     end
   end
@@ -278,7 +278,7 @@ function M.show_msg(tar, content, replace_last, append, id)
   ---@type integer Start row after last line in the target buffer, unless
   ---this is the first message, or in case of a repeated or replaced message.
   local row = mark[1]
-    or (M[tar] and not next(M[tar].ids) and ext.cmd.srow == 0 and 0)
+    or (M[tar] and not next(M[tar].ids) and ui.cmd.srow == 0 and 0)
     or (line_count - ((replace_last or cr or append) and 1 or 0))
   local curline = (cr or append) and api.nvim_buf_get_lines(buf, row, row + 1, false)[1]
   local start_row, width = row, M.msg.width
@@ -307,7 +307,7 @@ function M.show_msg(tar, content, replace_last, append, id)
 
       if chunk[3] > 0 then
         hlopts.end_col, hlopts.hl_group = end_col, chunk[3]
-        api.nvim_buf_set_extmark(buf, ext.ns, row, col, hlopts)
+        api.nvim_buf_set_extmark(buf, ui.ns, row, col, hlopts)
       end
 
       if pat == '\n' then
@@ -322,12 +322,12 @@ function M.show_msg(tar, content, replace_last, append, id)
     -- Keep track of message span to replace by ID.
     local opts = { end_row = row, end_col = col, invalidate = true, undo_restore = false }
     M[tar].ids[id] = M[tar].ids[id] or {}
-    M[tar].ids[id].extid = api.nvim_buf_set_extmark(buf, ext.ns, start_row, start_col, opts)
+    M[tar].ids[id].extid = api.nvim_buf_set_extmark(buf, ui.ns, start_row, start_col, opts)
   end
 
   if tar == 'msg' then
-    api.nvim_win_set_width(ext.wins.msg, width)
-    local texth = api.nvim_win_text_height(ext.wins.msg, { start_row = start_row, end_row = row })
+    api.nvim_win_set_width(ui.wins.msg, width)
+    local texth = api.nvim_win_text_height(ui.wins.msg, { start_row = start_row, end_row = row })
     if texth.all > math.ceil(o.lines * 0.5) then
       expand_msg(tar)
     else
@@ -336,23 +336,23 @@ function M.show_msg(tar, content, replace_last, append, id)
       M.msg:start_timer(buf, id)
     end
   elseif tar == 'cmd' and dupe == 0 then
-    fn.clearmatches(ext.wins.cmd) -- Clear matchparen highlights.
-    if ext.cmd.srow > 0 then
+    fn.clearmatches(ui.wins.cmd) -- Clear matchparen highlights.
+    if ui.cmd.srow > 0 then
       -- In block mode the cmdheight is already dynamic, so just print the full message
       -- regardless of height. Put cmdline below message.
-      ext.cmd.srow = row + 1
+      ui.cmd.srow = row + 1
     else
-      api.nvim_win_set_cursor(ext.wins.cmd, { 1, 0 }) -- ensure first line is visible
-      if ext.cmd.highlighter then
-        ext.cmd.highlighter.active[buf] = nil
+      api.nvim_win_set_cursor(ui.wins.cmd, { 1, 0 }) -- ensure first line is visible
+      if ui.cmd.highlighter then
+        ui.cmd.highlighter.active[buf] = nil
       end
       -- Place [+x] indicator for lines that spill over 'cmdheight'.
-      local texth = api.nvim_win_text_height(ext.wins.cmd, {})
-      local spill = texth.all > ext.cmdheight and (' [+%d]'):format(texth.all - ext.cmdheight)
+      local texth = api.nvim_win_text_height(ui.wins.cmd, {})
+      local spill = texth.all > ui.cmdheight and (' [+%d]'):format(texth.all - ui.cmdheight)
       M.virt.msg[M.virt.idx.spill][1] = spill and { 0, spill } or nil
       M.cmd.msg_row = texth.end_row
 
-      if texth.all > ext.cmdheight then
+      if texth.all > ui.cmdheight then
         expand_msg(tar)
       end
     end
@@ -387,7 +387,7 @@ end
 function M.msg_show(kind, content, replace_last, _, append, id)
   if kind == 'empty' then
     -- A sole empty message clears the cmdline.
-    if ext.cfg.msg.target == 'cmd' and not next(M.cmd.ids) and ext.cmd.srow == 0 then
+    if ui.cfg.msg.target == 'cmd' and not next(M.cmd.ids) and ui.cmd.srow == 0 then
       M.msg_clear()
     end
   elseif kind == 'search_count' then
@@ -398,20 +398,20 @@ function M.msg_show(kind, content, replace_last, _, append, id)
     M.virt.last[M.virt.idx.search] = content
     M.virt.last[M.virt.idx.cmd] = { { 0, (' '):rep(11) } }
     set_virttext('last')
-  elseif (ext.cmd.prompt or kind == 'wildlist') and ext.cmd.srow == 0 then
+  elseif (ui.cmd.prompt or kind == 'wildlist') and ui.cmd.srow == 0 then
     -- Route to dialog that stays open so long as the cmdline prompt is active.
-    replace_last = api.nvim_win_get_config(ext.wins.dialog).hide or kind == 'wildlist'
+    replace_last = api.nvim_win_get_config(ui.wins.dialog).hide or kind == 'wildlist'
     if kind == 'wildlist' then
-      api.nvim_buf_set_lines(ext.bufs.dialog, 0, -1, false, {})
-      ext.cmd.prompt = true -- Ensure dialog is closed when cmdline is hidden.
+      api.nvim_buf_set_lines(ui.bufs.dialog, 0, -1, false, {})
+      ui.cmd.prompt = true -- Ensure dialog is closed when cmdline is hidden.
     end
     M.show_msg('dialog', content, replace_last, append, id)
     M.set_pos('dialog')
   else
     -- Set the entered search command in the cmdline (if available).
-    local tar = kind == 'search_cmd' and 'cmd' or ext.cfg.msg.target
+    local tar = kind == 'search_cmd' and 'cmd' or ui.cfg.msg.target
     if tar == 'cmd' then
-      if ext.cmdheight == 0 or (ext.cmd.level > 0 and ext.cmd.srow == 0) then
+      if ui.cmdheight == 0 or (ui.cmd.level > 0 and ui.cmd.srow == 0) then
         return -- Do not overwrite an active cmdline unless in block mode.
       end
       -- Store the time when an important message was emitted in order to not overwrite
@@ -431,10 +431,10 @@ end
 
 ---Clear currently visible messages.
 function M.msg_clear()
-  api.nvim_buf_set_lines(ext.bufs.cmd, 0, -1, false, {})
-  api.nvim_buf_set_lines(ext.bufs.msg, 0, -1, false, {})
-  api.nvim_win_set_config(ext.wins.msg, { hide = true })
-  M[ext.cfg.msg.target].ids, M.dupe, M.cmd.msg_row, M.msg.width = {}, 0, -1, 1
+  api.nvim_buf_set_lines(ui.bufs.cmd, 0, -1, false, {})
+  api.nvim_buf_set_lines(ui.bufs.msg, 0, -1, false, {})
+  api.nvim_win_set_config(ui.wins.msg, { hide = true })
+  M[ui.cfg.msg.target].ids, M.dupe, M.cmd.msg_row, M.msg.width = {}, 0, -1, 1
   M.prev_msg, M.virt.msg = '', { {}, {} }
 end
 
@@ -442,7 +442,7 @@ end
 ---
 ---@param content MsgContent
 function M.msg_showmode(content)
-  M.virt.last[M.virt.idx.mode] = ext.cmd.level > 0 and {} or content
+  M.virt.last[M.virt.idx.mode] = ui.cmd.level > 0 and {} or content
   M.virt.last[M.virt.idx.search] = {}
   set_virttext('last')
 end
@@ -461,7 +461,7 @@ end
 ---
 ---@param content MsgContent
 function M.msg_ruler(content)
-  M.virt.last[M.virt.idx.ruler] = ext.cmd.level > 0 and {} or content
+  M.virt.last[M.virt.idx.ruler] = ui.cmd.level > 0 and {} or content
   set_virttext('last')
 end
 
@@ -483,7 +483,7 @@ function M.msg_history_show(entries, prev_cmd)
     M.msg_clear()
   end
 
-  api.nvim_buf_set_lines(ext.bufs.pager, 0, -1, false, {})
+  api.nvim_buf_set_lines(ui.bufs.pager, 0, -1, false, {})
   for i, entry in ipairs(entries) do
     M.show_msg('pager', entry[2], i == 1, entry[3], 0)
   end
@@ -500,10 +500,10 @@ function M.set_pos(type)
     local texth = type and api.nvim_win_text_height(win, {}) or {}
     local top = { vim.opt.fcs:get().msgsep or ' ', 'MsgSeparator' }
     cfg.height = type and math.min(texth.all, math.ceil(o.lines * 0.5))
-    cfg.border = win ~= ext.wins.msg and { '', top, '', '', '', '', '', '' } or nil
+    cfg.border = win ~= ui.wins.msg and { '', top, '', '', '', '', '', '' } or nil
     cfg.focusable = type == 'cmd' or nil
-    cfg.row = (win == ext.wins.msg and 0 or 1) - ext.cmd.wmnumode
-    cfg.row = cfg.row - ((win == ext.wins.pager and o.laststatus == 3) and 1 or 0)
+    cfg.row = (win == ui.wins.msg and 0 or 1) - ui.cmd.wmnumode
+    cfg.row = cfg.row - ((win == ui.wins.pager and o.laststatus == 3) and 1 or 0)
     api.nvim_win_set_config(win, cfg)
 
     if type == 'cmd' and not cmd_on_key then
@@ -518,32 +518,32 @@ function M.set_pos(type)
           return
         end
         vim.schedule(function()
-          local entered = api.nvim_get_current_win() == ext.wins.cmd
+          local entered = api.nvim_get_current_win() == ui.wins.cmd
           cmd_on_key = nil
-          if api.nvim_win_is_valid(ext.wins.cmd) then
-            api.nvim_win_close(ext.wins.cmd, true)
+          if api.nvim_win_is_valid(ui.wins.cmd) then
+            api.nvim_win_close(ui.wins.cmd, true)
           end
-          ext.check_targets()
+          ui.check_targets()
           -- Show or clear the message depending on if the pager was opened.
-          if entered or not api.nvim_win_get_config(ext.wins.pager).hide then
+          if entered or not api.nvim_win_get_config(ui.wins.pager).hide then
             M.virt.msg[M.virt.idx.spill][1] = nil
-            api.nvim_buf_set_lines(ext.bufs.cmd, 0, -1, false, {})
+            api.nvim_buf_set_lines(ui.bufs.cmd, 0, -1, false, {})
             if entered then
               api.nvim_command('norm! g<') -- User entered the cmdline window: open the pager.
             end
-          elseif ext.cfg.msg.target == 'cmd' and ext.cmd.level <= 0 then
-            ext.check_targets()
+          elseif ui.cfg.msg.target == 'cmd' and ui.cmd.level <= 0 then
+            ui.check_targets()
             set_virttext('msg')
           end
           api.nvim__redraw({ flush = true }) -- NOTE: redundant unless cmdline was opened.
         end)
-        vim.on_key(nil, ext.ns)
-      end, ext.ns)
+        vim.on_key(nil, ui.ns)
+      end, ui.ns)
     elseif type == 'dialog' then
       -- Add virtual [+x] text to indicate scrolling is possible.
       local function set_top_bot_spill()
-        local topspill = fn.line('w0', ext.wins.dialog) - 1
-        local botspill = api.nvim_buf_line_count(ext.bufs.dialog) - fn.line('w$', ext.wins.dialog)
+        local topspill = fn.line('w0', ui.wins.dialog) - 1
+        local botspill = api.nvim_buf_line_count(ui.bufs.dialog) - fn.line('w$', ui.wins.dialog)
         M.virt.top[1][1] = topspill > 0 and { 0, (' [+%d]'):format(topspill) } or nil
         set_virttext('top', 'dialog')
         M.virt.bot[1][1] = botspill > 0 and { 0, (' [+%d]'):format(botspill) } or nil
@@ -567,17 +567,17 @@ function M.set_pos(type)
           f = [[\<C-F>]],
           b = [[\<C-B>]],
         }
-        local info = page_keys[key] and fn.getwininfo(ext.wins.dialog)[1]
-        if info and (key ~= 'f' or info.botline < api.nvim_buf_line_count(ext.bufs.dialog)) then
-          fn.win_execute(ext.wins.dialog, ('exe "norm! %s"'):format(page_keys[key]))
+        local info = page_keys[key] and fn.getwininfo(ui.wins.dialog)[1]
+        if info and (key ~= 'f' or info.botline < api.nvim_buf_line_count(ui.bufs.dialog)) then
+          fn.win_execute(ui.wins.dialog, ('exe "norm! %s"'):format(page_keys[key]))
           set_top_bot_spill()
-          return fn.getwininfo(ext.wins.dialog)[1].topline ~= info.topline and '' or nil
+          return fn.getwininfo(ui.wins.dialog)[1].topline ~= info.topline and '' or nil
         end
       end)
     elseif type == 'msg' then
       -- Ensure last line is visible and first line is at top of window.
       local row = (texth.all > cfg.height and texth.end_row or 0) + 1
-      api.nvim_win_set_cursor(ext.wins.msg, { row, 0 })
+      api.nvim_win_set_cursor(ui.wins.msg, { row, 0 })
     elseif type == 'pager' then
       if fn.getcmdwintype() ~= '' then
         -- Cannot leave the cmdwin to enter the pager, so close it.
@@ -588,15 +588,15 @@ function M.set_pos(type)
 
       -- Cmdwin is actually closed one event iteration later so schedule in case it was open.
       vim.schedule(function()
-        api.nvim_set_current_win(ext.wins.pager)
+        api.nvim_set_current_win(ui.wins.pager)
         -- Make pager relative to cmdwin when it is opened, restore when it is closed.
         api.nvim_create_autocmd({ 'WinEnter', 'CmdwinEnter', 'CmdwinLeave' }, {
           callback = function(ev)
-            if api.nvim_win_is_valid(ext.wins.pager) then
+            if api.nvim_win_is_valid(ui.wins.pager) then
               local config = ev.event == 'CmdwinLeave' and cfg
                 or ev.event == 'WinEnter' and { hide = true }
                 or { relative = 'win', win = 0, row = 0, col = 0 }
-              api.nvim_win_set_config(ext.wins.pager, config)
+              api.nvim_win_set_config(ui.wins.pager, config)
             end
             return ev.event == 'WinEnter'
           end,
@@ -606,7 +606,7 @@ function M.set_pos(type)
     end
   end
 
-  for t, win in pairs(ext.wins) do
+  for t, win in pairs(ui.wins) do
     local cfg = (t == type or (type == nil and t ~= 'cmd'))
       and api.nvim_win_is_valid(win)
       and api.nvim_win_get_config(win)
diff --git a/runtime/lua/vim/_extui.lua b/runtime/lua/vim/_extui.lua
deleted file mode 100644
index 4d72325dd5..0000000000
--- a/runtime/lua/vim/_extui.lua
+++ /dev/null
@@ -1,152 +0,0 @@
---- @brief
----
----WARNING: This is an experimental interface intended to replace the message
----grid in the TUI.
----
----To enable the experimental UI (default opts shown):
----```lua
----require('vim._extui').enable({
----  enable = true, -- Whether to enable or disable the UI.
----  msg = { -- Options related to the message module.
----    ---@type 'cmd'|'msg' Where to place regular messages, either in the
----    ---cmdline or in a separate ephemeral message window.
----    target = 'cmd',
----    timeout = 4000, -- Time a message is visible in the message window.
----  },
----})
----```
----
----There are four separate window types used by this interface:
----- "cmd": The cmdline window; also used for 'showcmd', 'showmode', 'ruler', and
----  messages if 'cmdheight' > 0.
----- "msg": The message window; used for messages when 'cmdheight' == 0.
----- "pager": The pager window; used for |:messages| and certain messages
----   that should be shown in full.
----- "dialog": The dialog window; used for prompt messages that expect user input.
----
----These four windows are assigned the "cmd", "msg", "pager" and "dialog"
----'filetype' respectively. Use a |FileType| autocommand to configure any local
----options for these windows and their respective buffers.
----
----Rather than a |hit-enter-prompt|, messages shown in the cmdline area that do
----not fit are appended with a `[+x]` "spill" indicator, where `x` indicates the
----spilled lines. To see the full message, the |g<| command can be used.
-
-local api = vim.api
-local ext = require('vim._extui.shared')
-ext.msg = require('vim._extui.messages')
-ext.cmd = require('vim._extui.cmdline')
-local M = {}
-
-local function ui_callback(redraw_msg, event, ...)
-  local handler = ext.msg[event] or ext.cmd[event]
-  ext.check_targets()
-  handler(...)
-  -- Cmdline mode, non-fast message and non-empty showcmd require an immediate redraw.
-  if ext.cmd[event] or redraw_msg or (event == 'msg_showcmd' and select(1, ...)[1]) then
-    ext.redrawing = true
-    api.nvim__redraw({
-      flush = handler ~= ext.cmd.cmdline_hide or nil,
-      cursor = handler == ext.cmd[event] and true or nil,
-      win = handler == ext.cmd[event] and ext.wins.cmd or nil,
-    })
-    ext.redrawing = false
-  end
-end
-local scheduled_ui_callback = vim.schedule_wrap(ui_callback)
-
----@nodoc
-function M.enable(opts)
-  vim.validate('opts', opts, 'table', true)
-  if opts.msg then
-    vim.validate('opts.msg.pos', opts.msg.pos, 'nil', true, 'nil: "pos" moved to opts.target')
-    vim.validate('opts.msg.box', opts.msg.box, 'nil', true, 'nil: "timeout" moved to opts.msg')
-    vim.validate('opts.msg.target', opts.msg.target, function(tar)
-      return tar == 'cmd' or tar == 'msg'
-    end, "'cmd'|'msg'")
-  end
-  ext.cfg = vim.tbl_deep_extend('keep', opts, ext.cfg)
-
-  if ext.cfg.enable == false then
-    -- Detach and cleanup windows, buffers and autocommands.
-    for _, win in pairs(ext.wins) do
-      if api.nvim_win_is_valid(win) then
-        api.nvim_win_close(win, true)
-      end
-    end
-    for _, buf in pairs(ext.bufs) do
-      if api.nvim_buf_is_valid(buf) then
-        api.nvim_buf_delete(buf, {})
-      end
-    end
-    api.nvim_clear_autocmds({ group = ext.augroup })
-    vim.ui_detach(ext.ns)
-    return
-  end
-
-  vim.ui_attach(ext.ns, { ext_messages = true, set_cmdheight = false }, function(event, ...)
-    if not (ext.msg[event] or ext.cmd[event]) then
-      return
-    end
-    -- Ensure cmdline is placed after a scheduled message in block mode.
-    if vim.in_fast_event() or (event == 'cmdline_show' and ext.cmd.srow > 0) then
-      scheduled_ui_callback(false, event, ...)
-    else
-      ui_callback(event == 'msg_show', event, ...)
-    end
-    return true
-  end)
-
-  -- The visibility and appearance of the cmdline and message window is
-  -- dependent on some option values. Reconfigure windows when option value
-  -- has changed and after VimEnter when the user configured value is known.
-  -- TODO: Reconsider what is needed when this module is enabled by default early in startup.
-  local function check_cmdheight(value)
-    ext.check_targets()
-    -- 'cmdheight' set; (un)hide cmdline window and set its height.
-    local cfg = { height = math.max(value, 1), hide = value == 0 }
-    api.nvim_win_set_config(ext.wins.cmd, cfg)
-    -- Change message position when 'cmdheight' was or becomes 0.
-    if value == 0 or ext.cmdheight == 0 then
-      ext.cfg.msg.target = value == 0 and 'msg' or 'cmd'
-      ext.msg.prev_msg = ''
-    end
-    ext.cmdheight = value
-  end
-
-  if vim.v.vim_did_enter == 0 then
-    vim.schedule(function()
-      check_cmdheight(vim.o.cmdheight)
-    end)
-  end
-
-  api.nvim_create_autocmd('OptionSet', {
-    group = ext.augroup,
-    pattern = { 'cmdheight' },
-    callback = function()
-      check_cmdheight(vim.v.option_new)
-      ext.msg.set_pos()
-    end,
-    desc = 'Set cmdline and message window dimensions for changed option values.',
-  })
-
-  api.nvim_create_autocmd({ 'VimResized', 'TabEnter' }, {
-    group = ext.augroup,
-    callback = function()
-      ext.msg.set_pos()
-    end,
-    desc = 'Set cmdline and message window dimensions after shell resize or tabpage change.',
-  })
-
-  api.nvim_create_autocmd('WinEnter', {
-    callback = function()
-      local win = api.nvim_get_current_win()
-      if vim.tbl_contains(ext.wins, win) and api.nvim_win_get_config(win).hide then
-        vim.cmd.wincmd('p')
-      end
-    end,
-    desc = 'Make sure hidden extui window is never current.',
-  })
-end
-
-return M
diff --git a/runtime/lua/vim/_extui/shared.lua b/runtime/lua/vim/_extui/shared.lua
deleted file mode 100644
index bacfc68cca..0000000000
--- a/runtime/lua/vim/_extui/shared.lua
+++ /dev/null
@@ -1,111 +0,0 @@
-local api = vim.api
-local M = {
-  msg = nil, ---@type vim._extui.messages
-  cmd = nil, ---@type vim._extui.cmdline
-  ns = api.nvim_create_namespace('nvim._ext_ui'),
-  augroup = api.nvim_create_augroup('nvim._ext_ui', {}),
-  cmdheight = vim.o.cmdheight, -- 'cmdheight' option value set by user.
-  redrawing = false, -- True when redrawing to display UI event.
-  wins = { cmd = -1, dialog = -1, msg = -1, pager = -1 },
-  bufs = { cmd = -1, dialog = -1, msg = -1, pager = -1 },
-  cfg = {
-    enable = true,
-    msg = { -- Options related to the message module.
-      ---@type 'cmd'|'msg' Where to place regular messages, either in the
-      ---cmdline or in a separate ephemeral message window.
-      target = 'cmd',
-      timeout = 4000, -- Time a message is visible in the message window.
-    },
-  },
-}
---- @type vim.api.keyset.win_config
-local wincfg = { -- Default cfg for nvim_open_win().
-  relative = 'laststatus',
-  style = 'minimal',
-  col = 0,
-  row = 1,
-  width = 10000,
-  height = 1,
-  noautocmd = true,
-}
-
-local tab = 0
----Ensure target buffers and windows are still valid.
-function M.check_targets()
-  local curtab = api.nvim_get_current_tabpage()
-  for i, type in ipairs({ 'cmd', 'dialog', 'msg', 'pager' }) do
-    local setopt = not api.nvim_buf_is_valid(M.bufs[type])
-    if setopt then
-      M.bufs[type] = api.nvim_create_buf(false, false)
-    end
-
-    if
-      tab ~= curtab
-      or not api.nvim_win_is_valid(M.wins[type])
-      or not api.nvim_win_get_config(M.wins[type]).zindex -- no longer floating
-    then
-      local cfg = vim.tbl_deep_extend('force', wincfg, {
-        focusable = type == 'pager',
-        mouse = type ~= 'cmd' and true or nil,
-        anchor = type ~= 'cmd' and 'SE' or nil,
-        hide = type ~= 'cmd' or M.cmdheight == 0 or nil,
-        border = type ~= 'msg' and 'none' or nil,
-        -- kZIndexMessages < cmd zindex < kZIndexCmdlinePopupMenu (grid_defs.h), pager below others.
-        zindex = 201 - i,
-        _cmdline_offset = type == 'cmd' and 0 or nil,
-      })
-      if tab ~= curtab and api.nvim_win_is_valid(M.wins[type]) then
-        cfg = api.nvim_win_get_config(M.wins[type])
-        api.nvim_win_close(M.wins[type], true)
-      end
-      M.wins[type] = api.nvim_open_win(M.bufs[type], false, cfg)
-      setopt = true
-    elseif api.nvim_win_get_buf(M.wins[type]) ~= M.bufs[type] then
-      api.nvim_win_set_buf(M.wins[type], M.bufs[type])
-      setopt = true
-    end
-
-    if setopt then
-      -- Set options without firing OptionSet and BufFilePost.
-      vim._with({ win = M.wins[type], noautocmd = true }, function()
-        local ignore = 'all,-FileType' .. (type == 'pager' and ',-TextYankPost' or '')
-        api.nvim_set_option_value('eventignorewin', ignore, { scope = 'local' })
-        api.nvim_set_option_value('wrap', true, { scope = 'local' })
-        api.nvim_set_option_value('linebreak', false, { scope = 'local' })
-        api.nvim_set_option_value('smoothscroll', true, { scope = 'local' })
-        api.nvim_set_option_value('breakindent', false, { scope = 'local' })
-        api.nvim_set_option_value('foldenable', false, { scope = 'local' })
-        api.nvim_set_option_value('showbreak', '', { scope = 'local' })
-        api.nvim_set_option_value('spell', false, { scope = 'local' })
-        api.nvim_set_option_value('swapfile', false, { scope = 'local' })
-        api.nvim_set_option_value('modifiable', true, { scope = 'local' })
-        api.nvim_set_option_value('bufhidden', 'hide', { scope = 'local' })
-        api.nvim_set_option_value('buftype', 'nofile', { scope = 'local' })
-        -- Use MsgArea except in the msg window. Hide Search highlighting except in the pager.
-        local search_hide = 'Search:,CurSearch:,IncSearch:'
-        local hl = 'Normal:MsgArea,' .. search_hide
-        if type == 'pager' then
-          hl = 'Normal:MsgArea'
-        elseif type == 'msg' then
-          hl = search_hide
-        end
-        api.nvim_set_option_value('winhighlight', hl, { scope = 'local' })
-      end)
-      api.nvim_buf_set_name(M.bufs[type], ('[%s]'):format(type:sub(1, 1):upper() .. type:sub(2)))
-      -- Fire FileType with window context to let the user reconfigure local options.
-      vim._with({ win = M.wins[type] }, function()
-        api.nvim_set_option_value('filetype', type, { scope = 'local' })
-      end)
-
-      if type == 'pager' then
-        -- Close pager with `q`, same as `checkhealth`
-        api.nvim_buf_set_keymap(M.bufs.pager, 'n', 'q', '<Cmd>wincmd c<CR>', {})
-      elseif type == M.cfg.msg.target then
-        M.msg.prev_msg = '' -- Will no longer be visible.
-      end
-    end
-  end
-  tab = curtab
-end
-
-return M
diff --git a/src/gen/gen_vimdoc.lua b/src/gen/gen_vimdoc.lua
index e90158d502..1e483cc7fc 100755
--- a/src/gen/gen_vimdoc.lua
+++ b/src/gen/gen_vimdoc.lua
@@ -184,14 +184,14 @@ local config = {
       'version.lua',
 
       -- Sections at the end, in a specific order:
-      '_extui.lua',
+      'ui2.lua',
     },
     files = {
       'runtime/lua/vim/_core/editor.lua',
       'runtime/lua/vim/_core/options.lua',
       'runtime/lua/vim/_core/shared.lua',
       'runtime/lua/vim/_core/system.lua',
-      'runtime/lua/vim/_extui.lua',
+      'runtime/lua/vim/_core/ui2.lua',
       'runtime/lua/vim/_inspector.lua',
       'runtime/lua/vim/_meta/base64.lua',
       'runtime/lua/vim/_meta/builtin.lua',
@@ -235,6 +235,7 @@ local config = {
     end,
     section_name = {
       ['_inspector.lua'] = 'inspector',
+      ['ui2.lua'] = '_core.ui2',
     },
     section_fmt = function(name)
       name = name:lower()
diff --git a/test/functional/core/main_spec.lua b/test/functional/core/main_spec.lua
index 400b27a278..a3dd2b537f 100644
--- a/test/functional/core/main_spec.lua
+++ b/test/functional/core/main_spec.lua
@@ -227,6 +227,7 @@ describe('vim._core', function()
       'vim._core.shared',
       'vim._core.stringbuffer',
       'vim._core.system',
+      'vim._core.ui2',
       'vim._core.util',
       'vim._init_packages',
       'vim.filetype',
diff --git a/test/functional/ui/cmdline2_spec.lua b/test/functional/ui/cmdline2_spec.lua
index 7c25d9a976..a2f31e8115 100644
--- a/test/functional/ui/cmdline2_spec.lua
+++ b/test/functional/ui/cmdline2_spec.lua
@@ -16,7 +16,7 @@ describe('cmdline2', function()
       [101] = { background = Screen.colors.Yellow, foreground = Screen.colors.Grey0 },
     })
     exec_lua(function()
-      require('vim._extui').enable({})
+      require('vim._core.ui2').enable({})
     end)
   end)
 
@@ -245,7 +245,7 @@ describe('cmdline2', function()
     clear({
       args = {
         '--clean',
-        '+lua require("vim._extui").enable({})',
+        '+lua require("vim._core.ui2").enable({})',
         "+call feedkeys(':')",
       },
     })
diff --git a/test/functional/ui/messages2_spec.lua b/test/functional/ui/messages2_spec.lua
index 12c8b13f13..78c4c3b569 100644
--- a/test/functional/ui/messages2_spec.lua
+++ b/test/functional/ui/messages2_spec.lua
@@ -15,11 +15,11 @@ describe('messages2', function()
       [100] = { foreground = Screen.colors.Magenta1, bold = true },
     })
     exec_lua(function()
-      require('vim._extui').enable({})
+      require('vim._core.ui2').enable({})
     end)
   end)
   after_each(function()
-    -- Since vim._extui lasts until Nvim exits, there may be unfinished timers.
+    -- Since ui2 module lasts until Nvim exits, there may be unfinished timers.
     -- Close unfinished timers to avoid 2s delay on exit with ASAN or TSAN.
     exec_lua(function()
       vim.uv.walk(function(handle)
diff --git a/test/functional/vimscript/screenchar_spec.lua b/test/functional/vimscript/screenchar_spec.lua
index cb43c189c3..ba653d9942 100644
--- a/test/functional/vimscript/screenchar_spec.lua
+++ b/test/functional/vimscript/screenchar_spec.lua
@@ -105,7 +105,7 @@ describe('screenchar() and family respect floating windows', function()
     end)
 
     it('from ui2', function()
-      n.exec_lua('require("vim._extui").enable({ enable = true })')
+      n.exec_lua('require("vim._core.ui2").enable({ enable = true })')
       command('echo "foo"')
 
       assert_screen_funcs()