diff --git a/lua/opencode/ui/output_window.lua b/lua/opencode/ui/output_window.lua
index dbceb3cd..cef27422 100644
--- a/lua/opencode/ui/output_window.lua
+++ b/lua/opencode/ui/output_window.lua
@@ -79,6 +79,8 @@ end
 ---@return integer
 function M.create_buf()
   local output_buf = vim.api.nvim_create_buf(false, true)
+  local filetype = config.ui.output.filetype or 'opencode_output'
+  vim.api.nvim_set_option_value('filetype', filetype, { buf = output_buf })
 
   state.ui.set_output_folds(build_fold_state({}))
 
diff --git a/lua/opencode/ui/ui.lua b/lua/opencode/ui/ui.lua
index ea96e60d..4ede7e9b 100644
--- a/lua/opencode/ui/ui.lua
+++ b/lua/opencode/ui/ui.lua
@@ -454,12 +454,6 @@ function M.create_windows()
   windows.input_win = win_ids.input_win
   windows.output_win = win_ids.output_win
   windows.tab_strip_win = win_ids.tab_strip_win
-
-  local filetype = config.ui.output.filetype or 'opencode_output'
-  vim.api.nvim_win_call(windows.output_win, function()
-    vim.api.nvim_set_option_value('filetype', filetype, { buf = windows.output_buf })
-  end)
-
   windows.saved_width_ratio = state.last_window_width_ratio
 
   input_window.setup(windows)
diff --git a/tests/unit/output_window_spec.lua b/tests/unit/output_window_spec.lua
index e3917529..741d15c6 100644
--- a/tests/unit/output_window_spec.lua
+++ b/tests/unit/output_window_spec.lua
@@ -17,32 +17,26 @@ local function parse_fillchars(value)
   return result
 end
 
-describe('ui.create_windows output filetype', function()
-  local ui = require('opencode.ui.ui')
+describe('output_window.create_buf', function()
   local original_config
-  local windows
 
   before_each(function()
     original_config = vim.deepcopy(config.values)
     config.values = vim.deepcopy(config.defaults)
-    state.ui.set_windows(nil)
   end)
 
   after_each(function()
-    if windows then
-      pcall(ui.close_windows, windows, false)
-      windows = nil
-    end
-    state.ui.set_windows(nil)
     config.values = original_config
   end)
 
   it('uses default output filetype', function()
     config.setup({})
-    windows = ui.create_windows()
+    local buf = output_window.create_buf()
 
-    local filetype = vim.api.nvim_get_option_value('filetype', { buf = windows.output_buf })
+    local filetype = vim.api.nvim_get_option_value('filetype', { buf = buf })
     assert.equals('opencode_output', filetype)
+
+    pcall(vim.api.nvim_buf_delete, buf, { force = true })
   end)
 
   it('uses configured output filetype', function()
@@ -54,10 +48,12 @@ describe('ui.create_windows output filetype', function()
       },
     })
 
-    windows = ui.create_windows()
-    local filetype = vim.api.nvim_get_option_value('filetype', { buf = windows.output_buf })
+    local buf = output_window.create_buf()
+    local filetype = vim.api.nvim_get_option_value('filetype', { buf = buf })
 
     assert.equals('markdown', filetype)
+
+    pcall(vim.api.nvim_buf_delete, buf, { force = true })
   end)
 end)