feat: Add prompt_guard status indicator to output buffer topbar

- Create new prompt_guard_indicator module to track prompt guard status
- Display guard status icon on top left of output buffer when denied
- Add 1-second timer to update indicator when output buffer is visible
- Add OpencodeGuardDenied highlight group for guard status
- Support both light and dark themes with appropriate colors

The indicator helps users quickly see if their prompts will be accepted before
attempting to send a message to the opencode server.

Author: guillaumeboehm

lua/opencode/ui/highlight.lua

@@ -22,6 +22,7 @@ function M.setup()
     vim.api.nvim_set_hl(0, 'OpencodeContextualActions', { bg = '#90A4AE', fg = '#1976D2', bold = true, default = true })
     vim.api.nvim_set_hl(0, 'OpencodeInputLegend', { bg = '#757575', fg = '#424242', bold = false, default = true })
     vim.api.nvim_set_hl(0, 'OpencodeHint', { link = 'Comment', default = true })
+    vim.api.nvim_set_hl(0, 'OpencodeGuardDenied', { fg = '#F44336', bold = true, default = true })
   else
     vim.api.nvim_set_hl(0, 'OpencodeBorder', { fg = '#616161', default = true })
     vim.api.nvim_set_hl(0, 'OpencodeBackground', { link = 'Normal', default = true })
@@ -41,6 +42,7 @@ function M.setup()
     vim.api.nvim_set_hl(0, 'OpencodeContextualActions', { bg = '#3b4261', fg = '#61AFEF', bold = true, default = true })
     vim.api.nvim_set_hl(0, 'OpencodeInputLegend', { bg = '#616161', fg = '#CCCCCC', bold = false, default = true })
     vim.api.nvim_set_hl(0, 'OpencodeHint', { link = 'Comment', default = true })
+    vim.api.nvim_set_hl(0, 'OpencodeGuardDenied', { fg = '#EF5350', bold = true, default = true })
   end
 end
 

lua/opencode/ui/output_window.lua

@@ -1,5 +1,7 @@
 local state = require('opencode.state')
 local config = require('opencode.config')
+local Timer = require('opencode.ui.timer')
+local topbar = require('opencode.ui.topbar')
 
 local M = {}
 M.namespace = vim.api.nvim_create_namespace('opencode_output')
@@ -155,6 +157,36 @@ function M.setup_keymaps(windows)
 end
 
 function M.setup_autocmds(windows, group)
+  local guard_timer = nil
+
+  local function start_guard_timer()
+    if guard_timer then
+      return -- Timer already running
+    end
+    guard_timer = Timer.new({
+      interval = 1000, -- 1 second
+      repeat_timer = true,
+      on_tick = function()
+        if state.windows and vim.api.nvim_win_is_valid(state.windows.output_win) then
+          topbar.render()
+          return true
+        end
+        return false
+      end,
+    })
+    guard_timer:start_and_tick()
+  end
+
+  local function stop_guard_timer()
+    if guard_timer then
+      guard_timer:stop()
+      guard_timer = nil
+    end
+  end
+
+  -- Start the timer when the window is created (visible) and tick immediately
+  start_guard_timer()
+
   vim.api.nvim_create_autocmd('WinEnter', {
     group = group,
     buffer = windows.output_buf,
@@ -175,6 +207,15 @@ function M.setup_autocmds(windows, group)
     end,
   })
 
+  -- Stop the timer when the window is closed
+  vim.api.nvim_create_autocmd('WinClosed', {
+    group = group,
+    pattern = tostring(windows.output_win),
+    callback = function()
+      stop_guard_timer()
+    end,
+  })
+
   state.subscribe('current_permission', function()
     require('opencode.keymap').toggle_permission_keymap(windows.output_buf)
   end)

lua/opencode/ui/prompt_guard_indicator.lua

@@ -0,0 +1,35 @@
+local M = {}
+
+local state = require('opencode.state')
+local config = require('opencode.config')
+local util = require('opencode.util')
+local icons = require('opencode.ui.icons')
+
+---Get the current prompt guard status
+---@return boolean allowed
+---@return string|nil error_message
+function M.get_status()
+  return util.check_prompt_allowed(config.prompt_guard)
+end
+
+---Check if guard will deny prompts
+---@return boolean denied
+function M.is_denied()
+  local allowed, _ = M.get_status()
+  return not allowed
+end
+
+---Get formatted indicator string with highlight (empty if allowed)
+---@return string formatted_indicator
+function M.get_formatted()
+  if not M.is_denied() then
+    -- Prompts are allowed - don't show anything
+    return ''
+  end
+
+  -- Prompts will be denied - show red indicator
+  local icon = icons.get('status_off')
+  return string.format('%%#OpencodeGuardDenied#%s%%*', icon)
+end
+
+return M

lua/opencode/ui/timer.lua

@@ -48,6 +48,12 @@ function Timer:start()
   end
 end
 
+--- Start the timer and immediately execute the callback
+function Timer:start_and_tick()
+  self:start()
+  self.on_tick(unpack(self.args))
+end
+
 function Timer:stop()
   if not self._uv_timer then
     return

lua/opencode/ui/topbar.lua

@@ -2,6 +2,8 @@ local M = {}
 
 local state = require('opencode.state')
 local config_file = require('opencode.config_file')
+local prompt_guard_indicator = require('opencode.ui.prompt_guard_indicator')
+local icons = require('opencode.ui.icons')
 
 local LABELS = {
   NEW_SESSION_TITLE = 'New session',
@@ -40,17 +42,45 @@ local function get_mode_highlight()
   end
 end
 
-local function create_winbar_text(description, model_info, mode_info, win_width)
-  local available_width = win_width - 2 -- 2 padding spaces
-
-  -- If total length exceeds available width, truncate description
-  if #description + 1 + #model_info + #mode_info + 1 > available_width then
-    local space_for_desc = available_width - (#model_info + #mode_info + 1) - 4 -- -4 for "... "
-    description = description:sub(1, space_for_desc) .. '... '
+local function create_winbar_text(description, model_info, mode_info, show_guard_indicator, win_width)
+  -- Calculate how many visible characters we have
+  -- Format: " [GUARD] description padding model_info MODE "
+  -- Where [GUARD] is optional (1 char + 1 space = 2 visible chars)
+  
+  local guard_prefix = ''
+  local guard_visible_width = 0
+  
+  if show_guard_indicator then
+    local guard_icon = icons.get('status_off')
+    guard_prefix = string.format('%%#OpencodeGuardDenied#%s%%* ', guard_icon)
+    guard_visible_width = 2 -- icon + space
   end
-
-  local padding = string.rep(' ', available_width - #description - #model_info - #mode_info - 1)
-  return string.format(' %s%s%s %s ', description, padding, model_info, get_mode_highlight() .. mode_info .. '%*')
+  
+  -- Total available width for all content
+  local total_width = win_width
+  
+  -- Calculate used width: leading space + guard + trailing space + model + mode
+  local mode_info_str = get_mode_highlight() .. mode_info .. '%*'
+  local mode_visible_width = #mode_info
+  local model_visible_width = #model_info
+  
+  -- Reserve space: 1 (leading) + guard_visible_width + 1 (space before description) + 1 (space before model) + model + mode
+  local reserved_width = 1 + guard_visible_width + 1 + 1 + model_visible_width + mode_visible_width
+  
+  -- Available width for description and padding
+  local available_for_desc = total_width - reserved_width
+  
+  -- Truncate description if needed
+  if #description > available_for_desc then
+    description = description:sub(1, math.max(1, available_for_desc - 4)) .. '...'
+  end
+  
+  -- Calculate padding to right-align model and mode
+  local desc_and_padding_width = available_for_desc
+  local padding_width = desc_and_padding_width - #description
+  local padding = string.rep(' ', math.max(0, padding_width))
+  
+  return string.format(' %s%s%s%s %s', guard_prefix, description, padding, model_info, mode_info_str)
 end
 
 local function update_winbar_highlights(win_id)
@@ -96,8 +126,10 @@ function M.render()
     end
     -- topbar needs to at least have a value to make sure footer is positioned correctly
     vim.wo[win].winbar = ' '
+
+    local show_guard_indicator = prompt_guard_indicator.is_denied()
     vim.wo[win].winbar =
-      create_winbar_text(get_session_desc(), format_model_info(), format_mode_info(), vim.api.nvim_win_get_width(win))
+      create_winbar_text(get_session_desc(), format_model_info(), format_mode_info(), show_guard_indicator, vim.api.nvim_win_get_width(win))
 
     update_winbar_highlights(win)
   end)