feat(session-picker): add full message preview with formatter rendering

README.md

@@ -116,7 +116,7 @@ Install the plugin with your favorite package manager. See the [Configuration](#
 ```lua
 -- Default configuration with all available options
 require('opencode').setup({
-  preferred_picker = nil, -- 'telescope', 'fzf', 'mini.pick', 'snacks', 'select', if nil, it will use the best available picker. Note mini.pick does not support multiple selections
+  preferred_picker = nil, -- 'telescope'/'telescope.nvim', 'fzf'/'fzf-lua', 'mini.pick', 'snacks'/'snacks.nvim', 'select', if nil, it will use the best available picker. Note mini.pick does not support multiple selections
   preferred_completion = nil, -- 'blink', 'nvim-cmp','vim_complete' if nil, it will use the best available completion
   default_global_keymaps = true, -- If false, disables all default global keymaps
   default_mode = 'build', -- 'build' or 'plan' or any custom configured. @see [OpenCode Agents](https://opencode.ai/docs/modes/)

lua/opencode/api_client.lua

@@ -292,9 +292,16 @@ end
 --- List messages for a session
 --- @param id string Session ID (required)
 --- @param directory string|nil Directory path
+--- @param opts? { limit?: number } Optional query parameters
 --- @return Promise<OpencodeMessage[]>
-function OpencodeApiClient:list_messages(id, directory)
-  return self:_call('/session/' .. id .. '/message', 'GET', nil, { directory = directory })
+function OpencodeApiClient:list_messages(id, directory, opts)
+  local query = { directory = directory }
+  if opts then
+    for k, v in pairs(opts) do
+      query[k] = v
+    end
+  end
+  return self:_call('/session/' .. id .. '/message', 'GET', nil, query)
 end
 
 --- Create and send a new message to a session

lua/opencode/session.lua

@@ -94,13 +94,14 @@ end)
 
 ---Get messages for a session
 ---@param session Session
+---@param opts? { limit?: number } Optional query parameters (e.g. limit)
 ---@return Promise<OpencodeMessage[]>
-function M.get_messages(session)
+function M.get_messages(session, opts)
   if not session then
     return Promise.new():resolve(nil)
   end
 
-  return state.api_client:list_messages(session.id)
+  return state.api_client:list_messages(session.id, nil, opts)
 end
 
 ---Get snapshot IDs from a message's parts

lua/opencode/types.lua

@@ -356,7 +356,7 @@
 ---@field fn? fun(args:string[]|nil):nil|Promise<any>|any
 
 ---@class OpencodeConfig
----@field preferred_picker 'telescope' | 'fzf' | 'mini.pick' | 'snacks' | 'select' | nil
+---@field preferred_picker 'telescope' | 'telescope.nvim' | 'fzf' | 'fzf-lua' | 'mini.pick' | 'snacks' | 'snacks.nvim' | 'select' | nil
 ---@field default_global_keymaps boolean
 ---@field default_mode 'build' | 'plan' | string -- Default mode
 ---@field default_system_prompt string | nil

lua/opencode/ui/base_picker.lua

@@ -17,10 +17,17 @@ local Promise = require('opencode.promise')
 ---@field title string|fun(): string The picker title
 ---@field width? number Optional width for the picker (defaults to config or current window width)
 ---@field multi_selection? table<string, boolean> Actions that support multi-selection
----@field preview? "file"|"none"|false Preview mode: "file" for file preview, "none" or false to disable
+---@field preview? "file"|"custom"|"none"|false Preview mode: "file" for file preview, "custom" for custom preview via preview_fn, "none" or false to disable
+---@field preview_fn? fun(item: any, target: PickerPreviewTarget): nil Custom preview function, called when preview = 'custom' and a selection changes
 ---@field layout_opts? OpencodeUIPickerConfig
 ---@field close? fun() Close the picker programmatically (set by the backend)
 
+---@class PickerPreviewTarget
+---@field get_bufnr fun(self: PickerPreviewTarget): integer?
+---@field is_valid fun(self: PickerPreviewTarget): boolean
+---@field set_lines fun(self: PickerPreviewTarget, lines: string[]): nil
+---@field with_window fun(self: PickerPreviewTarget, fn: fun(): nil): nil
+
 ---@class TelescopeEntry
 ---@field value any
 ---@field display fun(entry: TelescopeEntry): string[]
@@ -57,6 +64,64 @@ local Promise = require('opencode.promise')
 local M = {}
 local picker = require('opencode.ui.picker')
 
+---@param bufnr integer?
+---@return PickerPreviewTarget
+local function create_buffer_preview_target(bufnr)
+  return {
+    get_bufnr = function()
+      return bufnr
+    end,
+    is_valid = function()
+      return bufnr ~= nil and vim.api.nvim_buf_is_valid(bufnr)
+    end,
+    set_lines = function(_, lines)
+      if bufnr == nil or not vim.api.nvim_buf_is_valid(bufnr) then
+        return
+      end
+      local modifiable = vim.bo[bufnr].modifiable
+      vim.bo[bufnr].modifiable = true
+      vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
+      vim.bo[bufnr].modifiable = modifiable
+    end,
+    with_window = function(_, fn)
+      if bufnr == nil or not vim.api.nvim_buf_is_valid(bufnr) then
+        return
+      end
+      local win = vim.fn.bufwinid(bufnr)
+      if win ~= -1 then
+        vim.api.nvim_win_call(win, fn)
+      end
+    end,
+  }
+end
+
+---@param ctx snacks.picker.preview.ctx
+---@return PickerPreviewTarget
+local function create_snacks_preview_target(ctx)
+  return {
+    get_bufnr = function()
+      return ctx.buf
+    end,
+    is_valid = function()
+      return ctx.buf ~= nil and vim.api.nvim_buf_is_valid(ctx.buf)
+    end,
+    set_lines = function(_, lines)
+      if ctx.preview and ctx.preview.set_lines then
+        ctx.preview:set_lines(lines)
+      elseif ctx.buf and vim.api.nvim_buf_is_valid(ctx.buf) then
+        create_buffer_preview_target(ctx.buf):set_lines(lines)
+      end
+    end,
+    with_window = function(_, fn)
+      if ctx.win and vim.api.nvim_win_is_valid(ctx.win) then
+        vim.api.nvim_win_call(ctx.win, fn)
+        return
+      end
+      create_buffer_preview_target(ctx.buf):with_window(fn)
+    end,
+  }
+end
+
 ---Build title with action legend
 ---@param base_title string The base title
 ---@param actions table<string, PickerAction> The available actions
@@ -146,7 +211,22 @@ local function telescope_ui(opts)
     prompt_title = opts.title,
     finder = finders.new_table({ results = opts.items, entry_maker = make_entry }),
     sorter = conf.generic_sorter({}),
-    previewer = opts.preview == 'file' and require('telescope.previewers').vim_buffer_vimgrep.new({}) or nil,
+    previewer = (function()
+      if opts.preview == 'file' then
+        return require('telescope.previewers').vim_buffer_vimgrep.new({})
+      elseif opts.preview == 'custom' and opts.preview_fn then
+        return require('telescope.previewers').new_buffer_previewer({
+          define_preview = function(self, entry)
+            if not entry then
+              return
+            end
+            opts.preview_fn(entry.value, create_buffer_preview_target(self.state.bufnr))
+          end,
+        })
+      else
+        return nil
+      end
+    end)(),
     layout_config = opts.width and {
         width = opts.width + 7, -- extra space for telescope UI
       } or nil,
@@ -252,8 +332,35 @@ local function fzf_ui(opts)
         ['--delimiter'] = '\x01', -- use SOH as delimiter (invisible char)
       },
       _headers = { 'actions' },
-      -- Enable builtin previewer for file preview support
-      previewer = opts.preview == 'file' and 'builtin' or nil,
+      previewer = (function()
+        if opts.preview == 'file' then
+          return 'builtin'
+        elseif opts.preview == 'custom' and opts.preview_fn then
+          return {
+            _ctor = function()
+              local previewer = require('fzf-lua.previewer.builtin').buffer_or_file:extend()
+              function previewer:populate_preview_buf(entry_str)
+                if not self.win or not self.win:validate_preview() then
+                  return
+                end
+                local idx_str = entry_str:match('^(%d+)\x01')
+                local idx = tonumber(idx_str)
+                if not idx or not opts.items[idx] then
+                  return
+                end
+                -- Create scratch buffer, attach to preview window first
+                -- so preview_fn can use bufwinid for window-local ops (folds)
+                local buf = self:get_tmp_buffer()
+                self:set_preview_buf(buf, true) -- min_winopts=true
+                opts.preview_fn(opts.items[idx], create_buffer_preview_target(buf))
+              end
+              return previewer
+            end,
+          }
+        else
+          return nil
+        end
+      end)(),
       fn_fzf_index = function(line)
         -- Extract the numeric index prefix before the SOH delimiter
         local idx_str = line:match('^(%d+)\x01')
@@ -490,30 +597,36 @@ end
 local function snacks_picker_ui(opts)
   local Snacks = require('snacks')
 
-  local has_preview = opts.preview == 'file'
+  local has_custom_preview = opts.preview == 'custom' and opts.preview_fn ~= nil
+  local has_preview = opts.preview == 'file' or has_custom_preview
 
   local title = type(opts.title) == 'function' and opts.title() or opts.title
   ---@cast title string
 
   local layout_opts = opts.layout_opts and opts.layout_opts.snacks_layout or nil
 
   local selection_made = false
+  local default_layout = {
+    preset = has_custom_preview and 'default' or 'select',
+    config = function(layout)
+      local width = opts.width and (opts.width + 3) or nil -- extra space for snacks UI
+      if not has_preview then
+        layout.layout.width = width
+        layout.layout.max_width = width
+        layout.layout.min_width = width
+      end
+    end,
+  }
+  if opts.preview == 'file' then
+    default_layout.preview = 'main'
+  elseif not has_preview then
+    default_layout.preview = false
+  end
 
   ---@type snacks.picker.Config
   local snack_opts = {
     title = title,
-    layout = layout_opts or {
-      preview = has_preview and 'main' or false,
-      preset = 'select',
-      config = function(layout)
-        local width = opts.width and (opts.width + 3) or nil -- extra space for snacks UI
-        if not has_preview then
-          layout.layout.width = width
-          layout.layout.max_width = width
-          layout.layout.min_width = width
-        end
-      end,
-    },
+    layout = layout_opts or default_layout,
     finder = function()
       return opts.items
     end,
@@ -560,9 +673,15 @@ local function snacks_picker_ui(opts)
     },
   }
 
-  -- Add file preview if enabled
-  if has_preview then
+  if opts.preview == 'file' then
     snack_opts.preview = 'file'
+  elseif has_custom_preview then
+    snack_opts.preview = function(ctx)
+      if ctx.item then
+        ctx.preview:reset()
+        opts.preview_fn(ctx.item, create_snacks_preview_target(ctx))
+      end
+    end
   else
     snack_opts.preview = function()
       return false

lua/opencode/ui/output_window.lua

@@ -482,22 +482,20 @@ function M.clear_extmarks(start_line, end_line, clear_all)
   pcall(vim.api.nvim_buf_clear_namespace, windows.output_buf, clear_all and -1 or M.namespace, start_line, end_line)
 end
 
----Apply extmarks to the output buffer
+---Apply extmarks to any buffer (reusable for preview buffers)
+---@param bufnr integer Target buffer
 ---@param extmarks table<number, OutputExtmark[]> Extmarks indexed by line
 ---@param line_offset? integer Line offset to apply to extmarks, defaults to 0
-function M.set_extmarks(extmarks, line_offset)
+function M.apply_extmarks(bufnr, extmarks, line_offset)
   if not extmarks or type(extmarks) ~= 'table' then
     return
   end
-  local windows = state.windows
-  if not windows or not windows.output_buf or not vim.api.nvim_buf_is_valid(windows.output_buf) then
+  if not bufnr or not vim.api.nvim_buf_is_valid(bufnr) then
     return
   end
 
   line_offset = line_offset or 0
 
-  local output_buf = windows.output_buf
-
   local line_indices = vim.tbl_keys(extmarks)
   table.sort(line_indices)
 
@@ -525,11 +523,26 @@ function M.set_extmarks(extmarks, line_offset)
         end
       end
       ---@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)
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, M.namespace, target_line, start_col or 0, m)
     end
   end
 end
 
+---Apply extmarks to the output buffer
+---@param extmarks table<number, OutputExtmark[]> Extmarks indexed by line
+---@param line_offset? integer Line offset to apply to extmarks, defaults to 0
+function M.set_extmarks(extmarks, line_offset)
+  if not extmarks or type(extmarks) ~= 'table' then
+    return
+  end
+  local windows = state.windows
+  if not windows or not windows.output_buf or not vim.api.nvim_buf_is_valid(windows.output_buf) then
+    return
+  end
+
+  M.apply_extmarks(windows.output_buf, extmarks, line_offset)
+end
+
 ---@param start_line integer
 ---@param end_line integer
 function M.highlight_changed_lines(start_line, end_line)

lua/opencode/ui/picker.lua

@@ -1,15 +1,25 @@
 local M = {}
 
+local picker_aliases = {
+  ['fzf-lua'] = 'fzf',
+  ['snacks.nvim'] = 'snacks',
+  ['telescope.nvim'] = 'telescope',
+}
+
+local function normalize_picker_name(name)
+  if name == 'select' then
+    return nil
+  end
+
+  return picker_aliases[name] or name
+end
+
 function M.get_best_picker()
   local config = require('opencode.config')
 
   local preferred_picker = config.preferred_picker
   if preferred_picker and type(preferred_picker) == 'string' and preferred_picker ~= '' then
-    if preferred_picker == 'select' then
-      return nil
-    end
-
-    return preferred_picker
+    return normalize_picker_name(preferred_picker)
   end
 
   if pcall(require, 'telescope') then