feat(ui): add filetype config for output buffer

Author: vapourismo

README.md

@@ -232,6 +232,7 @@ require('opencode').setup({
       use_vim_ui_select = false, -- If true, render questions/prompts with vim.ui.select instead of showing them inline in the output buffer.
     },
     output = {
+      filetype = 'opencode_output', -- Filetype assigned to the output buffer (default: 'opencode_output')
       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

@@ -137,6 +137,7 @@ M.defaults = {
       frames = { '⠋', '⠙', '⠹', '⠸', '⠼', '⠴', '⠦', '⠧', '⠇', '⠏' },
     },
     output = {
+      filetype = 'opencode_output',
       rendering = {
         markdown_debounce_ms = 250,
         on_data_rendered = nil,

lua/opencode/types.lua

@@ -178,6 +178,7 @@
 ---@field tools { show_output: boolean, show_reasoning_output: boolean }
 ---@field rendering OpencodeUIOutputRenderingConfig
 ---@field always_scroll_to_bottom boolean
+---@field filetype string
 
 ---@class OpencodeUIPickerConfig
 ---@field snacks_layout? snacks.picker.layout.Config

lua/opencode/ui/output_window.lua

@@ -6,7 +6,8 @@ M.namespace = vim.api.nvim_create_namespace('opencode_output')
 
 function M.create_buf()
   local output_buf = vim.api.nvim_create_buf(false, true)
-  vim.api.nvim_set_option_value('filetype', 'opencode_output', { buf = output_buf })
+  local filetype = config.ui.output.filetype or 'opencode_output'
+  vim.api.nvim_set_option_value('filetype', filetype, { buf = output_buf })
 
   local buffixwin = require('opencode.ui.buf_fix_win')
   buffixwin.fix_to_win(output_buf, function()

tests/unit/output_window_spec.lua

@@ -0,0 +1,42 @@
+local config = require('opencode.config')
+local output_window = require('opencode.ui.output_window')
+
+describe('output_window.create_buf', function()
+  local original_config
+
+  before_each(function()
+    original_config = vim.deepcopy(config.values)
+    config.values = vim.deepcopy(config.defaults)
+  end)
+
+  after_each(function()
+    config.values = original_config
+  end)
+
+  it('uses default output filetype', function()
+    config.setup({})
+    local buf = output_window.create_buf()
+
+    local filetype = vim.api.nvim_get_option_value('filetype', { buf = buf })
+    assert.equals('opencode_output', filetype)
+
+    pcall(vim.api.nvim_buf_delete, buf, { force = true })
+  end)
+
+  it('uses configured output filetype', function()
+    config.setup({
+      ui = {
+        output = {
+          filetype = 'markdown',
+        },
+      },
+    })
+
+    local buf = output_window.create_buf()
+    local filetype = vim.api.nvim_get_option_value('filetype', { buf = buf })
+
+    assert.equals('markdown', filetype)
+
+    pcall(vim.api.nvim_buf_delete, buf, { force = true })
+  end)
+end)