feat(timeline-picker): Implement basic timeline picker

This is the first commit, the fork action is not yet implemented

Author: sudo-tee

README.md

@@ -680,6 +680,26 @@ function M.undo(messageId)
     end)
 end
 
+function M.timeline()
+  local user_messages = {}
+  for _, msg in ipairs(state.messages or {}) do
+    if msg.info.role == 'user' then
+      table.insert(user_messages, msg)
+    end
+  end
+  if #user_messages == 0 then
+    vim.notify('No user messages in the current session', vim.log.levels.WARN)
+    return
+  end
+
+  local timeline_picker = require('opencode.ui.timeline_picker')
+  timeline_picker.pick(user_messages, function(selected_msg)
+    if selected_msg then
+      require('opencode.ui.navigation').goto_message_by_id(selected_msg.info.id)
+    end
+  end)
+end
+
 -- Returns the ID of the next user message after the current undo point
 -- This is a port of the opencode tui logic
 -- https://github.com/sst/opencode/blob/dev/packages/tui/internal/components/chat/messages.go#L1199
@@ -1074,6 +1094,11 @@ M.commands = {
       end
     end,
   },
+
+  timeline = {
+    desc = 'Open timeline picker to navigate/undo/redo/fork to message',
+    fn = M.timeline,
+  },
 }
 
 M.slash_commands_map = {
@@ -1089,6 +1114,7 @@ M.slash_commands_map = {
   ['/redo'] = { fn = M.redo, desc = 'Redo last action' },
   ['/sessions'] = { fn = M.select_session, desc = 'Select session' },
   ['/share'] = { fn = M.share, desc = 'Share current session' },
+  ['/timeline'] = { fn = M.timeline, desc = 'Open timeline picker' },
   ['/undo'] = { fn = M.undo, desc = 'Undo last action' },
   ['/unshare'] = { fn = M.unshare, desc = 'Unshare current session' },
 }

lua/opencode/api.lua

@@ -75,6 +75,10 @@ M.defaults = {
       delete_session = { '<C-d>' },
       new_session = { '<C-n>' },
     },
+    timeline_picker = {
+      undo = { '<C-u>', mode = { 'i', 'n' } },
+      fork = { '<C-f>', mode = { 'i', 'n' } },
+    },
   },
   ui = {
     position = 'right',

lua/opencode/config.lua

@@ -77,6 +77,10 @@
 ---@field delete_session OpencodeKeymapEntry
 ---@field new_session OpencodeKeymapEntry
 
+---@class OpencodeTimelinePickerKeymap
+---@field undo OpencodeKeymapEntry
+---@field fork OpencodeKeymapEntry
+
 ---@class OpencodeCompletionFileSourcesConfig
 ---@field enabled boolean
 ---@field preferred_cli_tool 'server'|'fd'|'fdfind'|'rg'|'git'

lua/opencode/types.lua

@@ -20,6 +20,24 @@ local function is_message_header(details)
   return first_virt_text[1] == header_user_icon or first_virt_text[1] == header_assistant_icon
 end
 
+function M.goto_message_by_id(message_id)
+  require('opencode.ui.ui').focus_output()
+  local windows = state.windows or {}
+  local win = windows.output_win
+  local buf = windows.output_buf
+
+  if not win or not buf then
+    return
+  end
+
+  local rendered_msg = require('opencode.ui.renderer').get_rendered_message(message_id)
+  if not rendered_msg or not rendered_msg.line_start then
+    return
+  end
+  local sep_offset = 2
+  vim.api.nvim_win_set_cursor(win, { rendered_msg.line_start + sep_offset, 0 })
+end
+
 function M.goto_next_message()
   require('opencode.ui.ui').focus_output()
   local windows = state.windows or {}

lua/opencode/ui/navigation.lua

@@ -962,4 +962,15 @@ function M._update_stats_from_message(message)
   end
 end
 
+---Get rendered message by ID
+---@param message_id string Message ID
+---@return RenderedMessage|nil Rendered message or nil if not found
+function M.get_rendered_message(message_id)
+  local rendered_msg = M._render_state:get_message(message_id)
+  if rendered_msg then
+    return rendered_msg
+  end
+  return nil
+end
+
 return M

lua/opencode/ui/renderer.lua

@@ -1,5 +1,6 @@
 local M = {}
 local picker = require('opencode.ui.picker')
+local config = require('lua.opencode.config')
 
 local picker_title = function()
   local config = require('opencode.config') --[[@as OpencodeConfig]]
@@ -37,7 +38,9 @@ local function format_session(session)
     table.insert(parts, modified)
   end
 
-  table.insert(parts, 'ID: ' .. (session.id or 'N/A'))
+  if config.debug then
+    table.insert(parts, 'ID: ' .. (session.id or 'N/A'))
+  end
   return table.concat(parts, ' ~ ')
 end