diff --git a/term/.config/nvim/init.lua b/term/.config/nvim/init.lua
index 3638c14..25ed79c 100644
--- a/term/.config/nvim/init.lua
+++ b/term/.config/nvim/init.lua
@@ -44,6 +44,8 @@ require("basic-settings")
 -- ============================================================================
 require("lazy").setup("plugins")
 
+require("diff-base")
+
 -- ============================================================================
 -- STEP 4: LSP KEYMAPS
 -- ============================================================================
diff --git a/term/.config/nvim/lua/diff-base.lua b/term/.config/nvim/lua/diff-base.lua
new file mode 100644
index 0000000..4ecb65e
--- /dev/null
+++ b/term/.config/nvim/lua/diff-base.lua
@@ -0,0 +1,112 @@
+local git = require("neo-tree.git")
+local parser = require("neo-tree.git.parser")
+local git_cmd = require("neo-tree.git.cmd")
+local utils = require("neo-tree.utils")
+
+local diff_base = nil
+local status_cache = {}
+local orig_find_status
+
+local function find_worktree_root()
+	local root = git.find_worktree_info(vim.fn.getcwd())
+	if not root then
+		local buf = vim.api.nvim_buf_get_name(0)
+		if buf ~= "" then
+			root = git.find_worktree_info(buf)
+		end
+	end
+	return root
+end
+
+local function run_git(args)
+	local result = vim.system(args):wait()
+	if result.code ~= 0 then
+		return nil
+	end
+	return result.stdout
+end
+
+local function compute_status(wr, base)
+	local args = git_cmd.with_args({ "-C", wr, "diff", base, "--name-status", "-z" })
+	local out = run_git(args)
+	if not out then
+		vim.notify("DiffBase: invalid ref " .. base, vim.log.levels.WARN)
+		return nil
+	end
+	local status = parser.parse_diff_name_status_output(wr, false, utils.gsplit_plain(out, "\000"))
+	local ut = run_git(git_cmd.with_args({ "-C", wr, "ls-files", "--others", "--exclude-standard", "-z" }))
+	if ut then
+		for _, p in ipairs(parser.parse_ls_files_output(wr, utils.gsplit_plain(ut, "\000"))) do
+			status[p] = "?"
+		end
+	end
+	return status
+end
+
+local function patch()
+	if not orig_find_status then
+		orig_find_status = git.find_existing_status_code
+	end
+	git.find_existing_status_code = function(path, base_lookup)
+		if diff_base then
+			local wr, _ = git.find_existing_worktree(path)
+			local cached = wr and status_cache[wr]
+			local hit = cached and cached[path]
+			if hit then
+				return hit, true
+			end
+		end
+		return orig_find_status(path, base_lookup)
+	end
+end
+
+local function set(base)
+	base = base or ""
+	if base == "" or base == "HEAD" then
+		diff_base = nil
+		status_cache = {}
+		pcall(function()
+			require("gitsigns").change_base(nil, true)
+		end)
+		local e = require("neo-tree.events")
+		vim.schedule(function()
+			e.fire_event(e.GIT_EVENT, {})
+		end)
+		vim.notify("DiffBase: reset to HEAD")
+		return
+	end
+	local wr = find_worktree_root()
+	if not wr then
+		vim.notify("DiffBase: not in a git repo", vim.log.levels.WARN)
+		return
+	end
+	local s = compute_status(wr, base)
+	if not s then
+		return
+	end
+	diff_base = base
+	status_cache[wr] = s
+	pcall(function()
+		require("gitsigns").change_base(base, true)
+	end)
+	patch()
+	local events = require("neo-tree.events")
+	if git.worktrees[wr] then
+		git.worktrees[wr].status = s
+	end
+	vim.schedule(function()
+		events.fire_event(events.GIT_STATUS_CHANGED, { git_root = wr, git_status = s, base = base })
+	end)
+	vim.notify("DiffBase: set to " .. base)
+end
+
+vim.api.nvim_create_user_command("DiffBase", function(opts)
+	set(opts.args)
+end, {
+	nargs = "?",
+	complete = function(l)
+		return vim.tbl_filter(function(s)
+			return s:find(l, 1, true) == 1
+		end, { "HEAD", "HEAD~1", "HEAD~2", "HEAD~3", "main", "master", "origin/main", "origin/master" })
+	end,
+})