fix(ui): prevent duplicate windows by implementing buffer-to-window binding

lua/opencode/api.lua

@@ -55,13 +55,29 @@ function M.paste_image()
   core.paste_image_from_clipboard()
 end
 
+--- Check if opencode windows are in the current tab page
+--- @return boolean
+local function are_windows_in_current_tab()
+  if not state.windows or not state.windows.output_win then
+    return false
+  end
+
+  local current_tab = vim.api.nvim_get_current_tabpage()
+  local ok, win_tab = pcall(vim.api.nvim_win_get_tabpage, state.windows.output_win)
+  return ok and win_tab == current_tab
+end
+
 M.toggle = Promise.async(function(new_session)
   -- When auto_hide input is enabled, always focus input; otherwise use last focused
   local focus = 'input' ---@cast focus 'input' | 'output'
   if not config.ui.input.auto_hide then
     focus = state.last_focused_opencode_window or 'input'
   end
-  if state.windows == nil then
+
+  if state.windows == nil or not are_windows_in_current_tab() then
+    if state.windows then
+      M.close()
+    end
     core.open({ new_session = new_session == true, focus = focus, start_insert = false }):await()
   else
     M.close()

lua/opencode/ui/autocmds.lua

@@ -75,18 +75,18 @@ function M.setup_autocmds(windows)
   end
 end
 
+---@param windows OpencodeWindowState?
 function M.setup_resize_handler(windows)
   local resize_group = vim.api.nvim_create_augroup('OpencodeResize', { clear = true })
   vim.api.nvim_create_autocmd('VimResized', {
     group = resize_group,
     callback = function()
       require('opencode.ui.topbar').render()
       require('opencode.ui.footer').update_window(windows)
-      require('opencode.ui.input_window').update_dimensions(windows)
-      require('opencode.ui.output_window').update_dimensions(windows)
+      input_window.update_dimensions(windows)
+      output_window.update_dimensions(windows)
     end,
   })
-
   vim.api.nvim_create_autocmd('WinResized', {
     group = resize_group,
     callback = function(args)

lua/opencode/ui/buf_fix_win.lua

@@ -0,0 +1,76 @@
+--- Prevents a buffer from appearing in multiple windows (opposite of 'winfixbuf')
+---
+--- This module solves the problem where buffers can appear in multiple windows
+--- despite having 'winfixbuf' set. The 'winfixbuf' option prevents a window from
+--- changing buffers, but doesn't prevent a buffer from appearing in multiple windows.
+---
+local M = {}
+local buff_to_win_map = {}
+local global_autocmd_setup = false
+
+local function close_duplicates(buf, get_win)
+  local intended = get_win()
+  if not intended or not vim.api.nvim_win_is_valid(intended) then
+    return
+  end
+
+  local wins = vim.fn.win_findbuf(buf)
+  if #wins > 1 then
+    vim.schedule(function()
+      for _, win in ipairs(wins) do
+        if win ~= intended and vim.api.nvim_win_is_valid(win) then
+          pcall(vim.api.nvim_win_close, win, true)
+        end
+      end
+    end)
+  end
+end
+
+local check_all_buffers = vim.schedule_wrap(function()
+  for buf, get_win in pairs(buff_to_win_map) do
+    if vim.api.nvim_buf_is_valid(buf) then
+      close_duplicates(buf, get_win)
+    else
+      buff_to_win_map[buf] = nil
+    end
+  end
+end)
+
+local function setup()
+  if global_autocmd_setup then
+    return
+  end
+  global_autocmd_setup = true
+
+  local augroup = vim.api.nvim_create_augroup('OpenCodeBufFixWin', { clear = false })
+  vim.api.nvim_create_autocmd({ 'WinNew', 'VimResized' }, {
+    group = augroup,
+    callback = check_all_buffers,
+  })
+  vim.api.nvim_create_autocmd('BufDelete', {
+    callback = function(args)
+      if args and args.buf then
+        buff_to_win_map[args.buf] = nil
+      end
+    end,
+  })
+end
+
+--- Protect a buffer from appearing in multiple windows
+---@param buf integer Buffer number
+---@param get_intended_window fun(): integer? Function returning intended window ID
+function M.fix_to_win(buf, get_intended_window)
+  setup()
+
+  buff_to_win_map[buf] = get_intended_window
+  local augroup = vim.api.nvim_create_augroup('OpenCodeBufFixWin_' .. buf, { clear = true })
+  vim.api.nvim_create_autocmd('BufWinEnter', {
+    group = augroup,
+    buffer = buf,
+    callback = function()
+      close_duplicates(buf, get_intended_window)
+    end,
+  })
+end
+
+return M

lua/opencode/ui/input_window.lua

@@ -62,6 +62,12 @@ end
 function M.create_buf()
   local input_buf = vim.api.nvim_create_buf(false, true)
   vim.api.nvim_set_option_value('filetype', 'opencode', { buf = input_buf })
+
+  local buffixwin = require('opencode.ui.buf_fix_win')
+  buffixwin.fix_to_win(input_buf, function()
+    return state.windows and state.windows.input_win
+  end)
+
   return input_buf
 end
 
@@ -261,6 +267,8 @@ function M.setup(windows)
   set_win_option('number', false, windows)
   set_win_option('relativenumber', false, windows)
   set_buf_option('buftype', 'nofile', windows)
+  set_buf_option('bufhidden', 'hide', windows)
+  set_buf_option('buflisted', false, windows)
   set_buf_option('swapfile', false, windows)
 
   if config.ui.position ~= 'current' then

lua/opencode/ui/output_window.lua

@@ -8,6 +8,12 @@ M.viewport_at_bottom = true
 function M.create_buf()
   local output_buf = vim.api.nvim_create_buf(false, true)
   vim.api.nvim_set_option_value('filetype', 'opencode_output', { buf = output_buf })
+
+  local buffixwin = require('opencode.ui.buf_fix_win')
+  buffixwin.fix_to_win(output_buf, function()
+    return state.windows and state.windows.output_win
+  end)
+
   return output_buf
 end
 
@@ -23,6 +29,7 @@ function M._build_output_win_config()
   }
 end
 
+---@param windows OpencodeWindowState?
 function M.mounted(windows)
   windows = windows or state.windows
   return windows and windows.output_buf and windows.output_win and vim.api.nvim_win_is_valid(windows.output_win)
@@ -96,7 +103,10 @@ function M.setup(windows)
   set_win_option('relativenumber', false, windows.output_win)
   set_buf_option('modifiable', false, windows.output_buf)
   set_buf_option('buftype', 'nofile', windows.output_buf)
+  set_buf_option('bufhidden', 'hide', windows.output_buf)
+  set_buf_option('buflisted', false, windows.output_buf)
   set_buf_option('swapfile', false, windows.output_buf)
+
   if config.ui.position ~= 'current' then
     set_win_option('winfixbuf', true, windows.output_win)
   end