diff --git a/lua/Trans/backend/offline.lua b/lua/Trans/backend/offline.lua
index a8e7613..0357b17 100644
--- a/lua/Trans/backend/offline.lua
+++ b/lua/Trans/backend/offline.lua
@@ -34,7 +34,6 @@ function M.query(data)
 
 
     data.result.offline = res and M.formatter(res) or false
-    return data
 end
 
 -- this is a awesome plugin
diff --git a/lua/Trans/core/backend.lua b/lua/Trans/core/backend.lua
index 9c7750c..ffd034a 100644
--- a/lua/Trans/core/backend.lua
+++ b/lua/Trans/core/backend.lua
@@ -4,6 +4,7 @@ local Trans = require('Trans')
 ---@class TransBackend
 ---@field query fun(data: TransData)---@async
 ---@field no_wait? boolean whether need to wait for the result
+---@field all_name string[] @all backend name
 ---@field name string @backend name
 
 
@@ -22,7 +23,9 @@ end
 
 ---@class Trans
 ---@field backend table<string, TransBackend>
-return setmetatable({}, {
+return setmetatable({
+    all_name = vim.tbl_keys(result),
+}, {
     __index = function(self, name)
         ---@type TransBackend
         local backend = require('Trans.backend.' .. name)
diff --git a/lua/Trans/core/buffer.lua b/lua/Trans/core/buffer.lua
index ec6ab1c..4eb5df9 100644
--- a/lua/Trans/core/buffer.lua
+++ b/lua/Trans/core/buffer.lua
@@ -1,4 +1,5 @@
 local api, fn = vim.api, vim.fn
+local Trans = require('Trans')
 
 ---@class TransBuffer
 ---@field bufnr integer buffer handle
@@ -7,19 +8,22 @@ local buffer = {}
 
 -- INFO : corountine can't invoke C function
 ---Clear all content in buffer
--- function buffer:wipe()
---     print('begin')
---     api.nvim_buf_set_lines(self.bufnr, 0, -1, false, {})
---     print('end')
--- end
+function buffer:wipe()
+    Trans.util.main_loop(function()
+        api.nvim_buf_set_lines(self.bufnr, 0, -1, false, {})
+    end)
+end
 
 ---Delete buffer [_start, _end] line content [one index]
 ---@param _start? integer start line index
 ---@param _end? integer end line index
-function buffer:del(_start, _end)
-    ---@diagnostic disable-next-line: cast-local-type
-    _start = _start or '$'
-    fn.deletebufline(self.bufnr, _start, _end)
+function buffer:deleteline(_start, _end)
+    Trans.util.main_loop(function()
+        ---@diagnostic disable-next-line: cast-local-type
+        _start = _start and _start - 1 or self:line_count() - 1
+        _end = _end and _end - 1 or _start + 1
+        api.nvim_buf_set_lines(self.bufnr, _start, _end, false, {})
+    end)
 end
 
 ---Set buffer option
@@ -113,37 +117,36 @@ end
 ---@param nodes string|table|table[] string -> as line content | table -> as a node | table[] -> as node[]
 ---@param one_index number? line number should be set[one index] or let it be nil to append
 function buffer:setline(nodes, one_index)
-    self:set('modifiable', true)
-
     one_index = one_index or self:line_count() + 1
     if one_index == 2 and self[1] == '' then one_index = 1 end
 
     if type(nodes) == 'string' then
         fn.setbufline(self.bufnr, one_index, nodes)
-    else
-        -- FIXME :set [nodes] type as node
-        if type(nodes[1]) == 'string' then
-            ---@diagnostic disable-next-line: assign-type-mismatch, param-type-mismatch
-            fn.setbufline(self.bufnr, one_index, nodes[1])
-            nodes:render(self, one_index, 0)
-        else
-            local strs = {}
-            local num = #nodes
-            for i = 1, num do
-                strs[i] = nodes[i][1]
-            end
-
-            fn.setbufline(self.bufnr, one_index, table.concat(strs))
-            local col = 0
-            for i = 1, num do
-                local node = nodes[i]
-                node:render(self, one_index, col)
-                col = col + #node[1]
-            end
-        end
+        return
     end
 
-    self:set('modifiable', false)
+    -- FIXME :set [nodes] type as node
+    if type(nodes[1]) == 'string' then
+        ---@diagnostic disable-next-line: assign-type-mismatch, param-type-mismatch
+        fn.setbufline(self.bufnr, one_index, nodes[1])
+        nodes:render(self, one_index, 0)
+        return
+    end
+
+
+    local strs = {}
+    local num = #nodes
+    for i = 1, num do
+        strs[i] = nodes[i][1]
+    end
+
+    fn.setbufline(self.bufnr, one_index, table.concat(strs))
+    local col = 0
+    for i = 1, num do
+        local node = nodes[i]
+        node:render(self, one_index, col)
+        col = col + #node[1]
+    end
 end
 
 buffer.__index = function(self, key)
@@ -171,7 +174,6 @@ end
 ---@param bufnr? integer buffer handle
 function buffer:init(bufnr)
     self.bufnr = bufnr or api.nvim_create_buf(false, false)
-    self:set('modifiable', false)
     self:set('filetype', 'Trans')
     self:set('buftype', 'nofile')
 end
diff --git a/lua/Trans/core/define.lua b/lua/Trans/core/define.lua
index 540ed0b..d78ba56 100644
--- a/lua/Trans/core/define.lua
+++ b/lua/Trans/core/define.lua
@@ -9,10 +9,10 @@ return {
         'visual',
         'input',
     },
-    backends = {
-        'offline',
-        'baidu',
-    },
+    -- backends = {
+    --     'offline',
+    --     'baidu',
+    -- },
     frontends = {
         'hover',
     }
diff --git a/lua/Trans/core/setup.lua b/lua/Trans/core/setup.lua
index cd4ec2f..63d76be 100644
--- a/lua/Trans/core/setup.lua
+++ b/lua/Trans/core/setup.lua
@@ -3,7 +3,7 @@ local Trans = require('Trans')
 local function set_strategy_opts(conf)
     local define       = Trans.define
     local all_modes    = define.modes
-    local all_backends = define.backends
+    local all_backends = Trans.backend.all_name
 
     local function parse_backend(backend)
         if type(backend) == 'string' then
diff --git a/lua/Trans/core/translate.lua b/lua/Trans/core/translate.lua
index d0c955c..980c77d 100644
--- a/lua/Trans/core/translate.lua
+++ b/lua/Trans/core/translate.lua
@@ -17,16 +17,14 @@ end
 local strategy = {
     fallback = function(data, update)
         local result = data.result
+
         for _, backend in ipairs(data.backends) do
             ---@cast backend TransBackend
             local name = backend.name
             backend.query(data)
 
-
-            if not backend.no_wait then
-                while result[name] == nil do
-                    update()
-                end
+            while result[name] == nil do
+                update()
             end
 
             if type(result[name]) == 'table' then
@@ -55,13 +53,19 @@ local function process(opts)
     end
 
     local data = Trans.data.new(opts)
-    local frontend = data.frontend
+    Trans.backend.offline.query(data)
+    local result = data.result['offline']
+    if not result then
+        result = strategy[Trans.conf.query](data, data.frontend:wait())
+        if not result then
+            -- data.frontend:fallback()
+            return
+        end
+    end
 
-    local result = strategy[Trans.conf.query](data, frontend:wait())
-    if not result then return end
 
     Trans.cache[data.str] = data
-    frontend:process(data, result)
+    data.frontend:process(data, result)
 end
 
 
diff --git a/lua/Trans/core/util.lua b/lua/Trans/core/util.lua
index bbc5663..f412262 100644
--- a/lua/Trans/core/util.lua
+++ b/lua/Trans/core/util.lua
@@ -115,6 +115,17 @@ function M.display_size(lines, width)
     return { height = ds_height, width = ds_width }
 end
 
+---Execute function in main loop
+---@param func function function to be executed
+function M.main_loop(func)
+    local co = coroutine.running()
+    vim.defer_fn(function()
+        func()
+        coroutine.resume(co)
+    end, 0)
+    coroutine.yield()
+end
+
 ---@class Trans
 ---@field util TransUtil
 return M
diff --git a/lua/Trans/frontend/hover/init.lua b/lua/Trans/frontend/hover/init.lua
index 2410adb..038f0a1 100644
--- a/lua/Trans/frontend/hover/init.lua
+++ b/lua/Trans/frontend/hover/init.lua
@@ -26,6 +26,7 @@ function M.new()
     }
     M.queue[#M.queue + 1] = new_instance
 
+    new_instance.buffer:deleteline(1)
     return setmetatable(new_instance, M)
 end
 
@@ -120,7 +121,6 @@ function M:wait()
 end
 
 --     -- FIXME :
---     -- buffer:wipe()
 --     -- vim.api.nvim_buf_set_lines(buffer.bufnr, 1, -1, true, {})
 --     -- print('jklajsdk')
 --     -- print(vim.fn.deletebufline(buffer.bufnr, 1))
@@ -132,16 +132,17 @@ end
 ---@param result TransResult
 ---@overload fun(result:TransResult)
 function M:process(data, result)
-    local buffer = self.buffer
-    print(vim.fn.deletebufline(buffer.bufnr, 1))
-    -- buffer[1] = ''
     -- local node = Trans.util.node
     -- local it, t, f = node.item, node.text, node.format
     -- self.buffer:setline(it('hello', 'MoreMsg'))
-    if self.pin then return end
 
     local opts = self.opts
+    if self.pin then return end
+
+    local buffer = self.buffer
     if not buffer:is_valid() then buffer:init() end
+    buffer:deleteline(1)
+
 
     if opts.auto_play then
         (data.from == 'en' and data.str or result.definition[1]):play()
@@ -170,6 +171,7 @@ function M:process(data, result)
     end
 
     window:set('wrap', true)
+    buffer:set('modifiable', false)
 
 
     local auto_close_events = opts.auto_close_events
@@ -182,21 +184,6 @@ function M:process(data, result)
             end,
         })
     end
-
-    -- vim.api.nvim_create_autocmd('User', {
-    --     pattern = 'TransHoverReady',
-    --     callback = function(opts)
-    --         vim.print(opts)
-    --         ---@type TransHover
-    --         local hover = opts.data
-    --     end,
-    --     desc = 'Auto Close Hover Window',
-    -- })
-
-    -- vim.api.nvim_exec_autocmds('User', {
-    --     pattern = 'TransHoverReady',
-    --     data = self,
-    -- })
 end
 
 ---Check if hover window and buffer are valid