perf(renderer): suppress TextChanged during flushes, reduce deepcopy and extmark allocs

- Wrap apply_pending and end_bulk_mode writes in eventignore='all' so
  render-markdown only fires from the explicit request_on_data_rendered
  call, not once per nvim_buf_set_lines during streaming or session load
- set_lines noautocmd opts removed; bulk caller sets eventignore directly
  via begin_update/end_update, keeping the API clean
- set_extmarks: skip deepcopy for marks with no start_col and no end_row
  offset needed (~99% of extmarks), eliminating 125k copies per session load
- add_vertical_border: build extmark_opts once per call instead of per line
- get_markdown_filetype: memoize vim.filetype.match results by filename
- accumulate_bulk_extmarks helper deduplicates 3x copy-pasted extmark loop
- Remove dead bulk_message_positions/bulk_part_positions tracking fields
- Remove unused write_formatted_data export and dead append_part_now bulk branch
- Hoist lines_equal/extmarks_equal out of format_message closure; replace
  vim.inspect comparison with vim.deep_equal

Author: sudo-tee

lua/opencode/ui/formatter.lua

@@ -61,7 +61,6 @@ function M._format_revert_message(session_data, start_idx)
   local message_text = stats.messages == 1 and 'message' or 'messages'
   local tool_text = stats.tool_calls == 1 and 'tool call' or 'tool calls'
 
-  output:add_lines(M.separator)
   output:add_line(
     string.format('> %d %s reverted, %d %s reverted', stats.messages, message_text, stats.tool_calls, tool_text)
   )
@@ -95,12 +94,14 @@ function M._format_revert_message(session_data, start_idx)
       end
     end
   end
+
+  output:add_empty_line()
   return output
 end
 
 local function add_action(output, text, action_type, args, key, line)
   -- actions use api-indexing (e.g. 0 indexed)
-  line = (line or output:get_line_count()) - 1
+  line = (line or output:get_line_count()) - 2
   output:add_action({
     text = text,
     type = action_type,
@@ -154,6 +155,11 @@ end
 function M.format_message_header(message)
   local output = Output.new()
 
+  if message.info and message.info.id == '__opencode_revert_message__' then
+    output:add_lines(M.separator)
+    return output
+  end
+
   output:add_lines(M.separator)
   local role = message.info.role or 'unknown'
   local icon = message.info.role == 'user' and icons.get('header_user') or icons.get('header_assistant')
@@ -167,18 +173,13 @@ function M.format_message_header(message)
   local display_name
   if role == 'assistant' then
     local mode = message.info.mode
-    if mode and mode ~= '' then
-      display_name = mode:upper()
-    else
-      -- For the most recent assistant message, show current_mode if mode is missing
-      -- This handles new messages that haven't been stamped yet
-      local is_last_message = #state.messages == 0 or message.info.id == state.messages[#state.messages].info.id
-      if is_last_message and state.current_mode and state.current_mode ~= '' then
+      if mode and mode ~= '' then
+        display_name = mode:upper()
+      elseif state.current_mode and state.current_mode ~= '' then
         display_name = state.current_mode:upper()
       else
         display_name = 'ASSISTANT'
       end
-    end
   else
     display_name = role:upper()
   end
@@ -291,11 +292,32 @@ end
 ---@param output Output Output object to write to
 ---@param part OpencodeMessagePart
 function M._format_selection_context(output, part)
+  local part_message = part._message_context
   local json = context_module.decode_json_context(part.text or '', 'selection')
   if not json then
     return
   end
-  local start_line = output:get_line_count()
+  local start_line = output:get_line_count() + 1
+
+  if part_message and part_message.parts then
+    for i, message_part in ipairs(part_message.parts) do
+      if message_part.id == part.id then
+        local previous_part = part_message.parts[i - 1]
+        if previous_part and previous_part.type == 'text' and previous_part.synthetic then
+          local has_selection = context_module.decode_json_context(previous_part.text or '', 'selection') ~= nil
+          local has_cursor = context_module.decode_json_context(previous_part.text or '', 'cursor-data') ~= nil
+          local diagnostics = context_module.decode_json_context(previous_part.text or '', 'diagnostics')
+          local has_diagnostics = diagnostics and diagnostics.content and type(diagnostics.content) == 'table' and #diagnostics.content > 0
+
+          if has_selection or has_cursor or has_diagnostics then
+            start_line = output:get_line_count()
+          end
+        end
+        break
+      end
+    end
+  end
+
   output:add_lines(vim.split(json.content or '', '\n'))
   output:add_empty_line()
 
@@ -359,6 +381,75 @@ function M._format_diagnostics_context(output, part)
   M.add_vertical_border(output, start_line, end_line, 'OpencodeMessageRoleUser', -3)
 end
 
+local function get_visible_user_part_kind(part)
+  if not part then
+    return nil
+  end
+
+  if part.type == 'file' and part.filename and part.filename ~= '' then
+    return 'file'
+  end
+
+  if part.type ~= 'text' or not part.text or part.text == '' then
+    return nil
+  end
+
+  if not part.synthetic then
+    return 'text'
+  end
+
+  if context_module.decode_json_context(part.text, 'selection') then
+    return 'selection'
+  end
+
+  if context_module.decode_json_context(part.text, 'cursor-data') then
+    return 'cursor-data'
+  end
+
+  local diagnostics = context_module.decode_json_context(part.text, 'diagnostics')
+  if diagnostics and diagnostics.content and type(diagnostics.content) == 'table' and #diagnostics.content > 0 then
+    return 'diagnostics'
+  end
+
+  return nil
+end
+
+local function get_user_part_neighbors(message, part)
+  if not message or not message.parts or not part or not part.id then
+    return nil, nil
+  end
+
+  local current_index = nil
+  for i, message_part in ipairs(message.parts) do
+    if message_part.id == part.id then
+      current_index = i
+      break
+    end
+  end
+
+  if not current_index then
+    return nil, nil
+  end
+
+  local previous_kind = nil
+  for i = current_index - 1, 1, -1 do
+    previous_kind = get_visible_user_part_kind(message.parts[i])
+    if previous_kind then
+      break
+    end
+  end
+
+  local next_kind = nil
+  for i = current_index + 1, #message.parts do
+    next_kind = get_visible_user_part_kind(message.parts[i])
+    if next_kind then
+      break
+    end
+  end
+
+  return previous_kind, next_kind
+end
+
 ---Format and display the file path in the context
 ---@param output Output Output object to write to
 ---@param path string|nil File path
@@ -450,19 +541,14 @@ end
 ---@param win_col number
 ---@param text_hl_group? string Optional highlight group for the background/foreground of text lines
 function M.add_vertical_border(output, start_line, end_line, hl_group, win_col, text_hl_group)
+  local extmark_opts = {
+    virt_text = { { require('opencode.ui.icons').get('border'), hl_group } },
+    virt_text_pos = 'overlay',
+    virt_text_win_col = win_col,
+    virt_text_repeat_linebreak = true,
+    line_hl_group = text_hl_group or nil,
+  }
   for line = start_line, end_line do
-    local extmark_opts = {
-      virt_text = { { require('opencode.ui.icons').get('border'), hl_group } },
-      virt_text_pos = 'overlay',
-      virt_text_win_col = win_col,
-      virt_text_repeat_linebreak = true,
-    }
-
-    -- Add line highlight if text_hl_group is provided
-    if text_hl_group then
-      extmark_opts.line_hl_group = text_hl_group
-    end
-
     output:add_extmark(line - 1, extmark_opts --[[@as OutputExtmark]])
   end
 end
@@ -486,17 +572,30 @@ function M.format_part(part, message, is_last_part, get_child_parts)
   if role == 'user' then
     if part.type == 'text' and part.text then
       if part.synthetic == true then
+        part._message_context = message
         M._format_selection_context(output, part)
         M._format_cursor_data_context(output, part)
         M._format_diagnostics_context(output, part)
+        part._message_context = nil
       else
         M._format_user_prompt(output, vim.trim(part.text), message)
         content_added = true
       end
     elseif part.type == 'file' then
       local file_line = M._format_context_file(output, part.filename)
       if file_line then
-        M.add_vertical_border(output, file_line - 1, file_line, 'OpencodeMessageRoleUser', -3)
+        local previous_kind, next_kind = get_user_part_neighbors(message, part)
+        local previous_is_context = previous_kind == 'selection'
+          or previous_kind == 'cursor-data'
+          or previous_kind == 'diagnostics'
+
+        if next_kind == 'text' or (previous_is_context and not next_kind) then
+          M.add_vertical_border(output, file_line - 1, file_line, 'OpencodeMessageRoleUser', -3)
+        elseif next_kind == 'file' then
+          M.add_vertical_border(output, file_line, file_line + 1, 'OpencodeMessageRoleUser', -3)
+        else
+          M.add_vertical_border(output, file_line, file_line, 'OpencodeMessageRoleUser', -3)
+        end
         content_added = true
       end
     end

lua/opencode/ui/output_window.lua

@@ -292,25 +292,23 @@ function M.set_lines(lines, start_line, end_line)
   start_line = start_line or 0
   end_line = end_line or -1
 
-  -- Avoid rewriting unchanged lines to prevent flashing/flicker when
-  -- re-rendering formatted parts (e.g. markdown). Compare the target range
-  -- with the existing buffer lines and skip the write when identical.
-  local ok, existing = pcall(vim.api.nvim_buf_get_lines, buf, start_line, end_line, false)
-  if ok and existing then
-    local same = true
-    if #existing ~= #lines then
-      same = false
-    else
+  -- Skip identical content outside of batch mode to avoid unnecessary writes
+  -- that cause flicker (e.g. when a markdown plugin re-renders an unchanged part).
+  -- Inside begin_update/end_update the caller controls exactly what is written,
+  -- so the check would be redundant and expensive.
+  if _update_depth == 0 then
+    local ok, existing = pcall(vim.api.nvim_buf_get_lines, buf, start_line, end_line, false)
+    if ok and existing and #existing == #lines then
+      local same = true
       for i = 1, #lines do
         if existing[i] ~= lines[i] then
           same = false
           break
         end
       end
-    end
-
-    if same then
-      return
+      if same then
+        return
+      end
     end
   end
 
@@ -355,19 +353,34 @@ function M.set_extmarks(extmarks, line_offset)
 
   local output_buf = windows.output_buf
 
-  for line_idx, marks in pairs(extmarks) do
+  local line_indices = vim.tbl_keys(extmarks)
+  table.sort(line_indices)
+
+  for _, line_idx in ipairs(line_indices) do
+    local marks = extmarks[line_idx]
+    table.sort(marks, function(a, b)
+      local ma = type(a) == 'function' and a() or a
+      local mb = type(b) == 'function' and b() or b
+      return (ma.priority or 0) > (mb.priority or 0)
+    end)
+
     for _, mark in ipairs(marks) do
-      local actual_mark = type(mark) == 'function' and mark() or mark
+      local m = type(mark) == 'function' and mark() or mark
       local target_line = line_offset + line_idx --[[@as integer]]
-      if actual_mark.end_row then
-        actual_mark.end_row = actual_mark.end_row + line_offset
-      end
-      local start_col = actual_mark.start_col
-      if actual_mark.start_col then
-        actual_mark.start_col = nil
+      local start_col = m.start_col
+      -- Only deepcopy when we need to mutate: start_col must be removed from the
+      -- opts table, and end_row must be offset when line_offset is non-zero.
+      -- The vast majority of extmarks (border virt_text) have neither field, so
+      -- we avoid 100k+ deepcopy calls during a full session render.
+      if start_col ~= nil or (m.end_row ~= nil and line_offset ~= 0) then
+        m = vim.deepcopy(m)
+        m.start_col = nil
+        if m.end_row then
+          m.end_row = m.end_row + line_offset
+        end
       end
-      ---@cast actual_mark vim.api.keyset.set_extmark
-      pcall(vim.api.nvim_buf_set_extmark, output_buf, M.namespace, target_line, start_col or 0, actual_mark)
+      ---@cast m vim.api.keyset.set_extmark
+      pcall(vim.api.nvim_buf_set_extmark, output_buf, M.namespace, target_line, start_col or 0, m)
     end
   end
 end