refactor(renderer): add scroll-tracking suppression & incremental message patching

- add output_window.with_suppressed_scroll_tracking and
  output_window.is_scroll_tracking_suppressed to manage nested suppression scopes
- prevent autocmds and renderer logic from reacting to programmatic window calls
  by using suppression scopes
- make config.ui.output.max_rendered_messages honor nil (show full history) and
  adjust full-session rendering truncation logic
- implement nested message-level patching in renderer.buffer to patch only the
  changed parts inside a message block, preserving extmarks/actions and trailing padding
- introduce trigger_on_data_rendered_now to run the render callback immediately
  where appropriate while keeping the existing debounced on_data_rendered
- switch several scheduled renders to prefer incremental updates (avoid full renders)
- add tests for cursor tracking, suppression scopes, nested message patching, and
  full-session rendering behavior

Author: sudo-tee

README.md

@@ -234,6 +234,7 @@ require('opencode').setup({
     },
     output = {
       filetype = 'opencode_output', -- Filetype assigned to the output buffer (default: 'opencode_output')
+      max_rendered_messages = nil, -- Maximum number of messages kept in the full-session render. Set to nil to show all messages, or a number to truncate older history.
       tools = {
         show_output = true, -- Show tools output [diffs, cmd output, etc.] (default: true)
         show_reasoning_output = true, -- Show reasoning/thinking steps output (default: true)

lua/opencode/config.lua

@@ -139,6 +139,7 @@ M.defaults = {
     },
     output = {
       filetype = 'opencode_output',
+      max_rendered_messages = nil,
       rendering = {
         markdown_debounce_ms = 250,
         on_data_rendered = nil,

lua/opencode/types.lua

@@ -180,6 +180,7 @@
 ---@field rendering OpencodeUIOutputRenderingConfig
 ---@field always_scroll_to_bottom boolean
 ---@field filetype string
+---@field max_rendered_messages? integer|nil
 
 ---@class OpencodeUIPickerConfig
 ---@field snacks_layout? snacks.picker.layout.Config

lua/opencode/ui/output_window.lua

@@ -7,6 +7,27 @@ M.namespace = vim.api.nvim_create_namespace('opencode_output')
 
 local _update_depth = 0
 local _update_buf = nil
+local _scroll_tracking_suppressed = 0
+
+function M.with_suppressed_scroll_tracking(fn)
+  if type(fn) ~= 'function' then
+    return nil
+  end
+
+  _scroll_tracking_suppressed = _scroll_tracking_suppressed + 1
+  local ok, result = pcall(fn)
+  _scroll_tracking_suppressed = math.max(_scroll_tracking_suppressed - 1, 0)
+
+  if not ok then
+    error(result)
+  end
+
+  return result
+end
+
+function M.is_scroll_tracking_suppressed()
+  return _scroll_tracking_suppressed > 0
+end
 
 ---Begin a batch of buffer writes — toggle modifiable once for the whole batch.
 ---Returns true if the batch was opened (buffer is valid). Must be paired with end_update().
@@ -313,6 +334,10 @@ function M.setup_autocmds(windows, group)
     group = group,
     buffer = windows.output_buf,
     callback = function()
+      if M.is_scroll_tracking_suppressed() then
+        return
+      end
+
       if not windows.output_win or not vim.api.nvim_win_is_valid(windows.output_win) then
         return
       end

lua/opencode/ui/renderer.lua

@@ -15,7 +15,11 @@ local scheduler = require('opencode.ui.renderer.scheduler')
 
 local M = {}
 
-local DEFAULT_MAX_RENDERED_MESSAGES = 80
+local trigger_on_data_rendered
+
+local function with_suppressed_scroll_tracking(fn)
+  return output_window.with_suppressed_scroll_tracking(fn)
+end
 
 local function update_current_message_state(messages)
   local current_message = nil
@@ -74,7 +78,7 @@ end
 local function build_full_session_output(messages)
   local viewport_request = M.get_viewport_render_request()
   local revert_index = find_revert_index(messages)
-  local max_messages = config.ui.output.max_rendered_messages or DEFAULT_MAX_RENDERED_MESSAGES
+  local max_messages = config.ui.output.max_rendered_messages
 
   -- When a revert is active, show messages before the revert point (the reverted message itself is hidden)
   local visible_messages = messages
@@ -85,7 +89,10 @@ local function build_full_session_output(messages)
     end
   end
 
-  local tail_hidden_message_count = math.max(#visible_messages - max_messages, 0)
+  local tail_hidden_message_count = 0
+  if type(max_messages) == 'number' and max_messages > 0 then
+    tail_hidden_message_count = math.max(#visible_messages - max_messages, 0)
+  end
   local base_blocks = session_view.build_blocks(visible_messages, {
     max_messages = viewport_request and nil or max_messages,
     get_child_parts = function(session_id)
@@ -146,17 +153,21 @@ local function restore_output_view(visible_render, restore_state)
   view.col = math.max(view.col or 0, 0)
   view.leftcol = 0
 
-  return pcall(vim.api.nvim_win_call, output_win, function()
-    vim.fn.winrestview(view)
+  return pcall(with_suppressed_scroll_tracking, function()
+    vim.api.nvim_win_call(output_win, function()
+      vim.fn.winrestview(view)
+    end)
   end)
 end
 
 local function apply_visible_render(visible_render, should_scroll, restore_state)
-  if ctx.prev_visible_render and ctx.prev_visible_render.blocks then
-    backend.apply_patch(ctx.prev_visible_render, visible_render)
-  else
-    backend.apply_full(visible_render)
-  end
+  with_suppressed_scroll_tracking(function()
+    if ctx.prev_visible_render and ctx.prev_visible_render.blocks then
+      backend.apply_patch(ctx.prev_visible_render, visible_render)
+    else
+      backend.apply_full(visible_render)
+    end
+  end)
 
   local visible_keys = {}
   for _, block in ipairs(visible_render.blocks or {}) do
@@ -173,12 +184,16 @@ local function apply_visible_render(visible_render, should_scroll, restore_state
   }
 
   if restore_output_view(visible_render, restore_state) then
+    trigger_on_data_rendered()
     return
   end
 
   if should_scroll then
     M.scroll_to_bottom()
+    return
   end
+
+  trigger_on_data_rendered()
 end
 
 function M.get_viewport_render_request()
@@ -226,7 +241,7 @@ end
 -- can be stubbed cleanly (e.g. stub(renderer, '_render_full_session_data'))
 M.on_session_updated = events.on_session_updated
 
-local trigger_on_data_rendered = require('opencode.util').debounce(function()
+trigger_on_data_rendered = require('opencode.util').debounce(function()
   local cb_type = type(config.ui.output.rendering.on_data_rendered)
   if cb_type == 'boolean' then
     return
@@ -243,6 +258,23 @@ local trigger_on_data_rendered = require('opencode.util').debounce(function()
   end
 end, config.ui.output.rendering.markdown_debounce_ms or 250)
 
+local function trigger_on_data_rendered_now()
+  local cb_type = type(config.ui.output.rendering.on_data_rendered)
+  if cb_type == 'boolean' then
+    return
+  end
+  if not state.windows or not state.windows.output_buf or not state.windows.output_win then
+    return
+  end
+  if cb_type == 'function' then
+    pcall(config.ui.output.rendering.on_data_rendered, state.windows.output_buf, state.windows.output_win)
+  elseif vim.fn.exists(':RenderMarkdown') > 0 then
+    vim.cmd(':RenderMarkdown')
+  elseif vim.fn.exists(':Markview') > 0 then
+    vim.cmd(':Markview render ' .. state.windows.output_buf)
+  end
+end
+
 ---Reset all renderer state and clear the output buffer
 function M.reset()
   ctx:reset()
@@ -257,7 +289,7 @@ function M.reset()
   permission_window.clear_all()
   state.renderer.reset()
 
-  trigger_on_data_rendered()
+  trigger_on_data_rendered_now()
 end
 
 ---Unsubscribe from all events and reset
@@ -377,7 +409,7 @@ function M.perform_scheduled_render(snapshot)
     return
   end
 
-  local should_scroll = snapshot == nil or snapshot.full_render == true or next(snapshot.dirty_messages or {}) ~= nil
+  local should_scroll = snapshot == nil or snapshot.full_render == true or output_window.is_at_bottom()
   local viewport_request = M.get_viewport_render_request()
   local restore_state = viewport_request and {
     absolute_scroll_top = viewport_request.scroll_top,
@@ -447,17 +479,21 @@ function M.scroll_to_bottom(force)
     or prev_line_count == 0
     or config.ui.output.always_scroll_to_bottom
     or (function()
-         local ok_cursor, cursor = pcall(vim.api.nvim_win_get_cursor, output_win)
-         return ok_cursor and cursor and (cursor[1] >= prev_line_count or cursor[1] >= line_count)
-       end)()
+          local ok_cursor, cursor = pcall(vim.api.nvim_win_get_cursor, output_win)
+          return ok_cursor and cursor and (cursor[1] >= prev_line_count or cursor[1] >= line_count)
+        end)()
 
   if should_scroll then
-    local last_line = vim.api.nvim_buf_get_lines(output_buf, line_count - 1, line_count, false)[1] or ''
-    vim.api.nvim_win_set_cursor(output_win, { line_count, #last_line })
-    vim.api.nvim_win_call(output_win, function()
-      vim.cmd('normal! zb')
+    with_suppressed_scroll_tracking(function()
+      local last_line = vim.api.nvim_buf_get_lines(output_buf, line_count - 1, line_count, false)[1] or ''
+      vim.api.nvim_win_set_cursor(output_win, { line_count, #last_line })
+      vim.api.nvim_win_call(output_win, function()
+        vim.cmd('normal! zb')
+      end)
     end)
   end
+
+  trigger_on_data_rendered()
 end
 
 ---Re-render the permission display when focus changes (updates shortcut hints)
@@ -491,7 +527,6 @@ function M.on_emit_events_finished()
   if not rendered then
     M.perform_scheduled_render({ full_render = true, dirty_messages = {}, dirty_parts = {} })
   end
-  M.scroll_to_bottom()
 end
 
 ---Return all actions available at a given (0-indexed) line