feat(ui): default expr-based output folds closed and apply fold ranges immediately

- Set default foldlevel to 0 for expr-based output so folds start closed.
- Replace manual window/fold manipulation with a safe window-call that triggers a fold recalc (zX)
  only when the output window is valid and displays the output buffer.
- Persist fold ranges to buffer var opencode_folds.
- Add unit tests asserting default closed folds and immediate application of fold ranges.

Author: sudo-tee

lua/opencode/ui/formatter/tools/todowrite.lua

@@ -25,7 +25,9 @@ function M.format(output, part)
   end
 
   local statuses = { in_progress = '-', completed = 'x', pending = ' ' }
-  local todos = part.state and part.state.input and part.state.input.todos or {}
+  local todos = part.state and part.state.input and type(part.state.input.todos) == 'table' and part.state.input.todos
+    or {}
+
   for _, item in ipairs(todos) do
     output:add_line(string.format('- [%s] %s ', statuses[item.status], item.content))
   end

lua/opencode/ui/output_window.lua

@@ -189,7 +189,7 @@ function M.setup(windows)
   window_options.set_window_option('foldmethod', 'expr', windows.output_win)
   window_options.set_window_option('foldexpr', 'v:lua.opencode_fold_expr()', windows.output_win)
   window_options.set_window_option('foldenable', true, windows.output_win)
-  window_options.set_window_option('foldlevel', 99, windows.output_win)
+  window_options.set_window_option('foldlevel', 0, windows.output_win)
   window_options.set_window_option('foldcolumn', '1', windows.output_win)
   window_options.set_window_option('foldtext', 'v:lua.opencode_fold_text()', windows.output_win)
 
@@ -324,32 +324,18 @@ _G.opencode_fold_text = M.fold_text
 ---@param fold_ranges table<{from: number, to: number}>
 function M.set_folds(fold_ranges)
   local windows = state.windows
-  local output_win = windows and windows.output_win
   if not windows or not windows.output_buf or not vim.api.nvim_buf_is_valid(windows.output_buf) then
     return
   end
 
   local folds = fold_ranges or {}
-  vim.api.nvim_buf_set_var(windows.output_buf, 'opencode_folds', folds)
-
-  if output_win and vim.api.nvim_win_is_valid(output_win) then
-    local win = output_win
-    local buf = windows.output_buf
-    local folds = fold_ranges or {}
-    vim.schedule(function()
-      if vim.api.nvim_win_is_valid(win) and vim.api.nvim_buf_is_valid(buf) then
-        local prev_win = vim.api.nvim_get_current_win()
-        vim.api.nvim_set_current_win(win)
-        local orig_foldmethod = vim.api.nvim_get_option_value('foldmethod', { win = win })
-        vim.api.nvim_set_option_value('foldmethod', 'manual', { win = win })
-        for _, range in ipairs(folds) do
-          if range.from < range.to then
-            vim.cmd(string.format('%d,%dfold', range.from, range.to))
-          end
-        end
-        vim.api.nvim_set_option_value('foldmethod', orig_foldmethod, { win = win })
-        vim.api.nvim_set_current_win(prev_win)
-      end
+  local buf = windows.output_buf
+  local win = windows.output_win
+  vim.api.nvim_buf_set_var(buf, 'opencode_folds', folds)
+
+  if win and vim.api.nvim_win_is_valid(win) and vim.api.nvim_win_get_buf(win) == buf then
+    pcall(vim.api.nvim_win_call, win, function()
+      vim.cmd('silent! normal! zX')
     end)
   end
 end

lua/opencode/ui/topbar.lua

@@ -83,7 +83,7 @@ function M.render()
 
     vim.wo[win].winbar = ' '
 
-    local desc = get_session_desc()
+    local desc = get_session_desc():gsub('%%', '%%%%')
     local token_info = format_token_info()
     local winbar_str = create_winbar_text(desc, token_info, vim.api.nvim_win_get_width(win))
     vim.wo[win].winbar = winbar_str

tests/unit/output_window_spec.lua

@@ -143,6 +143,27 @@ describe('output_window.setup', function()
     local cursorline = vim.api.nvim_get_option_value('cursorline', { win = win })
     assert.is_false(cursorline)
   end)
+
+  it('defaults folds to closed for expr-based output folds', function()
+    output_window.setup({ output_buf = buf, output_win = win })
+
+    local foldlevel = vim.api.nvim_get_option_value('foldlevel', { win = win })
+
+    assert.equals(0, foldlevel)
+  end)
+
+  it('applies closed folds immediately when fold ranges change', function()
+    output_window.setup({ output_buf = buf, output_win = win })
+    output_window.set_lines({ 'a', 'b', 'c', 'd' })
+
+    output_window.set_folds({ { from = 1, to = 3 } })
+
+    local foldclosed = vim.api.nvim_win_call(win, function()
+      return vim.fn.foldclosed(1)
+    end)
+
+    assert.equals(1, foldclosed)
+  end)
 end)
 
 describe('output_window extmarks', function()