feat(ui/output): add compact assistant headers

Add config.ui.output.compact_assistant_headers (boolean) to collapse consecutive
assistant headers in the same mode into a minimal header showing only a
right-aligned timestamp. Update formatter to accept a previous message and
render minimal headers when appropriate. Add RenderState:get_previous_message,
renderer navigation helpers, and pass the previous rendered message in
renderer.flush. Update types, defaults, README example, and tests.

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')
+      compact_assistant_headers = false, -- Collapse consecutive assistant headers in the same mode to a right-aligned timestamp only
       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',
+      compact_assistant_headers = false,
       rendering = {
         markdown_debounce_ms = 250,
         on_data_rendered = nil,

lua/opencode/types.lua

@@ -181,6 +181,7 @@
 ---@field rendering OpencodeUIOutputRenderingConfig
 ---@field always_scroll_to_bottom boolean
 ---@field filetype string
+---@field compact_assistant_headers boolean
 
 ---@class OpencodeUIPickerConfig
 ---@field snacks_layout? snacks.picker.layout.Config

lua/opencode/ui/formatter.lua

@@ -157,16 +157,16 @@ function M._format_error(output, message)
 end
 
 ---@param message OpencodeMessage
+---@param previous_message? OpencodeMessage
 ---@return Output
-function M.format_message_header(message)
+function M.format_message_header(message, previous_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')
 
@@ -190,21 +190,42 @@ function M.format_message_header(message)
     display_name = role:upper()
   end
 
-  output:add_extmark(output:get_line_count() - 1, {
-    virt_text = {
-      { icon, role_hl },
-      { ' ' },
-      { display_name, role_hl },
-      { model_text, 'OpencodeHint' },
-      { debug_text, 'OpencodeHint' },
-    },
-    virt_text_win_col = -3,
-    priority = 10,
-  } --[[@as OutputExtmark]])
+  local same_mode_as_previous = false
+  if config.ui.output.compact_assistant_headers and role == 'assistant' and previous_message then
+    local previous_role = previous_message.info and previous_message.info.role or nil
+    local previous_mode = previous_message.info and previous_message.info.mode or state.current_mode
+    local current_mode = message.info.mode or state.current_mode
+    same_mode_as_previous = previous_role == 'assistant'
+      and current_mode
+      and previous_mode
+      and current_mode ~= ''
+      and previous_mode ~= ''
+      and current_mode == previous_mode
+  end
+
+  if not same_mode_as_previous then
+    output:add_lines(M.separator)
+  else
+    output:add_line('')
+  end
+
+  if not same_mode_as_previous then
+    output:add_extmark(output:get_line_count() - 1, {
+      virt_text = {
+        { icon, role_hl },
+        { ' ' },
+        { display_name, role_hl },
+        { model_text, 'OpencodeHint' },
+        { debug_text, 'OpencodeHint' },
+      },
+      virt_text_win_col = -3,
+      priority = 10,
+    } --[[@as OutputExtmark]])
+  end
 
   if time then
     output:add_extmark(output:get_line_count() - 1, {
-      virt_text = { { ' ' .. util.format_time(time), 'OpencodeHint' } },
+      virt_text = { { (same_mode_as_previous and '' or ' ') .. util.format_time(time), 'OpencodeHint' } },
       virt_text_pos = 'right_align',
       priority = 9,
     } --[[@as OutputExtmark]])

lua/opencode/ui/render_state.lua

@@ -207,6 +207,23 @@ function RenderState:get_message(message_id)
   return self._messages[message_id]
 end
 
+---@param messages OpencodeMessage[]
+---@param message_id string
+---@return RenderedMessage?
+function RenderState:get_previous_message(messages, message_id)
+  for i = #messages, 1, -1 do
+    local message = messages[i]
+    if message and message.info and message.info.id == message_id then
+      if i <= 1 then
+        return nil
+      end
+      local previous_message = messages[i - 1]
+      return previous_message and previous_message.info and self._messages[previous_message.info.id] or nil
+    end
+  end
+  return nil
+end
+
 ---@param message_id string
 ---@param part OpencodeMessagePart
 function RenderState:upsert_orphan_part(message_id, part)

lua/opencode/ui/renderer.lua

@@ -249,4 +249,34 @@ function M.get_rendered_message(message_id)
   return ctx.render_state:get_message(message_id) or nil
 end
 
+---@param current_line integer
+---@return RenderedMessage|nil
+function M.get_next_rendered_message(current_line)
+  local next_message = nil
+
+  for _, message in ipairs(state.messages or {}) do
+    local rendered = message.info and message.info.id and ctx.render_state:get_message(message.info.id) or nil
+    if rendered and rendered.line_start and rendered.line_start + 1 > current_line then
+      next_message = rendered
+      break
+    end
+  end
+
+  return next_message
+end
+
+---@param current_line integer
+---@return RenderedMessage|nil
+function M.get_prev_rendered_message(current_line)
+  for i = #(state.messages or {}), 1, -1 do
+    local message = state.messages[i]
+    local rendered = message and message.info and message.info.id and ctx.render_state:get_message(message.info.id) or nil
+    if rendered and rendered.line_start and rendered.line_start + 1 < current_line then
+      return rendered
+    end
+  end
+
+  return nil
+end
+
 return M

lua/opencode/ui/renderer/flush.lua

@@ -291,7 +291,8 @@ local function format_message(message_id)
   end
 
   local prev = ctx.formatted_messages[message_id]
-  local formatted = formatter.format_message_header(message)
+  local previous_rendered = ctx.render_state:get_previous_message(state.messages or {}, message_id)
+  local formatted = formatter.format_message_header(message, previous_rendered and previous_rendered.message or nil)
 
   if prev and lines_equal(prev.lines, formatted.lines) and extmarks_equal(prev.extmarks, formatted.extmarks) then
     -- no visible change

tests/unit/formatter_spec.lua

@@ -3,12 +3,14 @@ local config = require('opencode.config')
 local formatter = require('opencode.ui.formatter')
 local Output = require('opencode.ui.output')
 local state = require('opencode.state')
+local util = require('opencode.util')
 
 describe('formatter', function()
   before_each(function()
     config.setup({
       ui = {
         output = {
+          compact_assistant_headers = false,
           tools = {
             show_output = true,
           },
@@ -296,6 +298,76 @@ describe('formatter', function()
     assert.are.equal('BUILD', output.extmarks[1][1].virt_text[3][1])
   end)
 
+  it('renders minimal same-mode assistant headers with only right-aligned time', function()
+    config.setup({
+      ui = {
+        output = {
+          compact_assistant_headers = true,
+        },
+      },
+    })
+
+    local output = formatter.format_message_header({
+      info = {
+        id = 'msg_current',
+        role = 'assistant',
+        sessionID = 'ses_1',
+        mode = 'build',
+        time = {
+          created = 1,
+        },
+      },
+      parts = {},
+    }, {
+      info = {
+        id = 'msg_prev',
+        role = 'assistant',
+        sessionID = 'ses_1',
+        mode = 'build',
+      },
+      parts = {},
+    })
+
+    assert.are.same({ '', '' }, output.lines)
+    assert.is_truthy(output.extmarks[0])
+    assert.are.equal(util.format_time(1), output.extmarks[0][1].virt_text[1][1])
+    assert.are.equal('right_align', output.extmarks[0][1].virt_text_pos)
+  end)
+
+  it('keeps full assistant headers when the mode changes', function()
+    config.setup({
+      ui = {
+        output = {
+          compact_assistant_headers = true,
+        },
+      },
+    })
+
+    local output = formatter.format_message_header({
+      info = {
+        id = 'msg_current',
+        role = 'assistant',
+        sessionID = 'ses_1',
+        mode = 'build',
+        time = {
+          created = 1,
+        },
+      },
+      parts = {},
+    }, {
+      info = {
+        id = 'msg_prev',
+        role = 'assistant',
+        sessionID = 'ses_1',
+        mode = 'plan',
+      },
+      parts = {},
+    })
+
+    assert.are.same({ '----', '', '' }, output.lines)
+    assert.are.equal('BUILD', output.extmarks[1][1].virt_text[3][1])
+  end)
+
   it('anchors task child-session action to the rendered task block', function()
     local message = {
       info = {