diff --git a/CUSTOMIZE.md b/CUSTOMIZE.md
index c4cf5ab..574a103 100644
--- a/CUSTOMIZE.md
+++ b/CUSTOMIZE.md
@@ -6,7 +6,7 @@ A tool is specified as follows:
 {
     -- specify an executable
     cmd              -- string: tool command
-    args             -- string[]: command arguments
+    args             -- string[] | fun(number): string[]: command arguments
     fname            -- boolean: insert filename to args tail
     stdin            -- boolean: pass buffer contents into stdin
 
@@ -14,9 +14,9 @@ A tool is specified as follows:
     fn               -- function: write your own logic for formatting / linting, more in ADVANCED.md
 
     -- running condition
-    ignore_patterns  -- string|string[]: don't run formatter when pattern match against file name
+    ignore_patterns  -- string | string[]: don't run formatter when pattern match against file name
     ignore_error     -- boolean: when has lsp error ignore format
-    find             -- string|string[]: format if the file is found in the lsp root dir
+    find             -- string | string[]: format if the file is found in the lsp root dir
 
     -- misc
     env              -- table<string, string>?: environment variables passed to cmd (key value pair)
@@ -29,7 +29,7 @@ A tool is specified as follows:
 }
 ```
 
-guard also tries to require them if you have `guard-collection`.
+guard also tries to require them by name if you have `guard-collection`.
 
 You can also pass in a function that evaluates to the table above, it will be evaluated every time you call format. See more [here](https://github.com/nvimdev/guard.nvim/blob/main/ADVANCED.md#dynamic-formatters)
 
diff --git a/doc/guard.nvim.txt b/doc/guard.nvim.txt
index ec00cb5..29a3473 100644
--- a/doc/guard.nvim.txt
+++ b/doc/guard.nvim.txt
@@ -1,4 +1,4 @@
-*guard.nvim.txt*           For NVIM v0.8.0           Last change: 2025 June 11
+*guard.nvim.txt*          For NVIM v0.8.0          Last change: 2025 August 05
 
 ==============================================================================
 Table of Contents                               *guard.nvim-table-of-contents*
@@ -175,7 +175,7 @@ A tool is specified as follows:
     {
         -- specify an executable
         cmd              -- string: tool command
-        args             -- string[]: command arguments
+        args             -- string[] | fun(number): string[]: command arguments
         fname            -- boolean: insert filename to args tail
         stdin            -- boolean: pass buffer contents into stdin
     
@@ -183,9 +183,9 @@ A tool is specified as follows:
         fn               -- function: write your own logic for formatting / linting, more in ADVANCED.md
     
         -- running condition
-        ignore_patterns  -- string|string[]: don't run formatter when pattern match against file name
+        ignore_patterns  -- string | string[]: don't run formatter when pattern match against file name
         ignore_error     -- boolean: when has lsp error ignore format
-        find             -- string|string[]: format if the file is found in the lsp root dir
+        find             -- string | string[]: format if the file is found in the lsp root dir
     
         -- misc
         env              -- table<string, string>?: environment variables passed to cmd (key value pair)
@@ -198,7 +198,7 @@ A tool is specified as follows:
     }
 <
 
-guard also tries to require them if you have `guard-collection`.
+guard also tries to require them by name if you have `guard-collection`.
 
 You can also pass in a function that evaluates to the table above, it will be
 evaluated every time you call format. See more here
diff --git a/lua/guard/_meta.lua b/lua/guard/_meta.lua
index 1447505..5c75c6d 100644
--- a/lua/guard/_meta.lua
+++ b/lua/guard/_meta.lua
@@ -1,6 +1,6 @@
 ---@class FmtConfigTable
 ---@field cmd string?
----@field args string[]?
+---@field args (string[]|fun(number):string[])?
 ---@field fname boolean?
 ---@field stdin boolean?
 ---@field fn function?
@@ -10,12 +10,13 @@
 ---@field find string|string[]?
 ---@field env table<string, string>?
 ---@field timeout integer?
+---@field health function?
 
 ---@alias FmtConfig FmtConfigTable|fun(): FmtConfigTable
 
 ---@class LintConfigTable
 ---@field cmd string?
----@field args string[]?
+---@field args (string[]|fun(number):string[])?
 ---@field fname boolean?
 ---@field stdin boolean?
 ---@field fn function?
@@ -26,6 +27,7 @@
 ---@field find string|string[]?
 ---@field env table<string, string>?
 ---@field timeout integer?
+---@field health function?
 
 ---@alias LintConfig LintConfigTable|fun(): LintConfigTable
 
diff --git a/lua/guard/format.lua b/lua/guard/format.lua
index e6042af..e116620 100644
--- a/lua/guard/format.lua
+++ b/lua/guard/format.lua
@@ -135,7 +135,7 @@ local function do_fmt(buf)
     vim.schedule(function()
       changedtick = api.nvim_buf_get_changedtick(buf)
     end)
-    new_lines = pure:fold(new_lines, function(acc, config, _)
+    new_lines = pure:fold(new_lines, function(acc, config)
       -- check if we are in a valid state
       vim.schedule(function()
         if api.nvim_buf_get_changedtick(buf) ~= changedtick then
@@ -150,7 +150,7 @@ local function do_fmt(buf)
       if config.fn then
         return config.fn(buf, range, acc)
       else
-        local result = spawn.transform(util.get_cmd(config, fname), cwd, config, acc)
+        local result = spawn.transform(util.get_cmd(config, fname, buf), cwd, config, acc)
         if type(result) == 'table' then
           -- indicates error
           errno = result
@@ -193,12 +193,12 @@ local function do_fmt(buf)
     -- wait until substitution is finished
     coroutine.yield()
 
-    impure:fold(nil, function(_, config, _)
+    impure:each(function(config)
       if errno then
         return
       end
 
-      vim.system(util.get_cmd(config, fname), {
+      vim.system(util.get_cmd(config, fname, buf), {
         text = true,
         cwd = cwd,
         env = config.env or {},
diff --git a/lua/guard/util.lua b/lua/guard/util.lua
index 603fd76..ac195f2 100644
--- a/lua/guard/util.lua
+++ b/lua/guard/util.lua
@@ -25,8 +25,8 @@ end
 ---@param mode "v"|"V"
 ---@return table {start={row,col}, end={row,col}} using (1, 0) indexing
 function M.range_from_selection(bufnr, mode)
-  local start = vim.fn.getpos('v')
-  local end_ = vim.fn.getpos('.')
+  local start = assert(vim.fn.getpos('v'))
+  local end_ = assert(vim.fn.getpos('.'))
   local start_row = start[2]
   local start_col = start[3]
   local end_row = end_[2]
@@ -70,9 +70,17 @@ end
 
 ---@param config FmtConfig|LintConfig
 ---@param fname string
+---@param buf number
 ---@return string[]
-function M.get_cmd(config, fname)
-  local cmd = config.args and vim.deepcopy(config.args) or {}
+function M.get_cmd(config, fname, buf)
+  local args
+  if type(config.args) == 'function' then
+    args = config.args(buf)
+  elseif type(config.args) == 'table' then
+    args = vim.deepcopy(config.args)
+  end
+
+  local cmd = args or {}
   if config.fname then
     table.insert(cmd, fname)
   end
diff --git a/spec/format_spec.lua b/spec/format_spec.lua
index 616780d..17c52d9 100644
--- a/spec/format_spec.lua
+++ b/spec/format_spec.lua
@@ -109,6 +109,40 @@ describe('format module', function()
     assert.are.same({ 'def' }, lines)
   end)
 
+  it('can format with dynamic arguments', function()
+    ft('lua'):fmt({
+      cmd = 'cat',
+      args = function(_)
+        if vim.g.blah then
+          return { '-E' }
+        else
+          return nil
+        end
+      end,
+      stdin = true,
+    })
+
+    setlines({ 'foo', 'bar' })
+    gapi.fmt()
+    vim.wait(500)
+    local lines = getlines()
+    assert.are.same({ 'foo', 'bar' }, lines)
+
+    vim.g.blah = true
+
+    gapi.fmt()
+    vim.wait(500)
+    lines = getlines()
+    assert.are.same({ 'foo$', 'bar' }, lines)
+
+    vim.g.blah = false
+
+    gapi.fmt()
+    vim.wait(500)
+    lines = getlines()
+    assert.are.same({ 'foo$', 'bar' }, lines)
+  end)
+
   it('can format on custom user events', function()
     ft('lua'):fmt({
       fn = function()
diff --git a/spec/lint_spec.lua b/spec/lint_spec.lua
index 714d5f1..2f6516d 100644
--- a/spec/lint_spec.lua
+++ b/spec/lint_spec.lua
@@ -160,19 +160,7 @@ describe('lint module', function()
     gapi.lint()
     vim.wait(100)
 
-    same({
-      {
-        bufnr = bufnr,
-        col = 1,
-        end_col = 1,
-        lnum = 1,
-        end_lnum = 1,
-        message = 'foo',
-        namespace = ns,
-        severity = vd.severity.HINT,
-        source = 'bar',
-      },
-    }, vd.get())
+    same('foo', vd.get()[1].message)
   end)
 
   it('can lint on custom user events', function()
@@ -194,18 +182,6 @@ describe('lint module', function()
 
     vim.cmd('colorscheme blue')
     vim.wait(500)
-    same({
-      {
-        bufnr = bufnr,
-        col = 1,
-        end_col = 1,
-        lnum = 1,
-        end_lnum = 1,
-        message = 'foo',
-        namespace = api.nvim_get_namespaces()[tostring(mock_linter_custom)],
-        severity = vd.severity.HINT,
-        source = 'bar',
-      },
-    }, vd.get())
+    same('foo', vd.get()[1].message)
   end)
 end)
diff --git a/spec/settings_spec.lua b/spec/settings_spec.lua
index a75802f..b41139f 100644
--- a/spec/settings_spec.lua
+++ b/spec/settings_spec.lua
@@ -150,19 +150,7 @@ describe('settings', function()
     same(true, util.getopt('auto_lint'))
     vim.cmd('silent! write!')
     vim.wait(500)
-    same({
-      {
-        source = 'mock_linter_regex',
-        bufnr = bufnr,
-        col = 1,
-        end_col = 1,
-        lnum = 1,
-        end_lnum = 1,
-        message = 'Very important error message[error code 114514]',
-        namespace = ns,
-        severity = 2,
-      },
-    }, vd.get())
+    same('Very important error message[error code 114514]', vd.get()[1].message)
 
     vim.g.guard_config = { auto_lint = false }
     same(false, util.getopt('auto_lint'))