diff --git a/README.md b/README.md
index ba7e58f..625e2bc 100644
--- a/README.md
+++ b/README.md
@@ -15,6 +15,6 @@ updateproject backend    # one part
 newproject ~/projects/my-thing --parts backend,frontend,caddy --backend python --frontend svelte --serve bun --defaults
 ```
 
-One part alone is rendered at the root of the project; two parts live in `backend/` and `frontend/`. After rendering, `make env` creates `.env` and every `docker-compose.override.yml` from their examples. Templates are cloned from `https://git.kotikot.com/templates` unless `TEMPLATES_DIR` points at a directory with local checkouts; `TEMPLATES_REF=HEAD` renders their working trees instead of the latest tag.
+One part alone is rendered at the root of the project; two parts live in `backend/` and `frontend/`. After rendering, `make env` creates `.env` and every `docker-compose.override.yml` from their examples. `updateproject` needs a clean working tree and commits each part's update separately, so the next part starts from a clean tree again; conflicts stay in those commits for you to resolve. Templates are cloned from `https://git.kotikot.com/templates` unless `TEMPLATES_DIR` points at a directory with local checkouts; `TEMPLATES_REF=HEAD` renders their working trees instead of the latest tag.
 
 Requires `uv`; `bun`, `docker` and `pre-commit` are used by the generated projects.
diff --git a/templates.py b/templates.py
index 2673a47..63fda66 100644
--- a/templates.py
+++ b/templates.py
@@ -90,15 +90,26 @@ def new(args: argparse.Namespace) -> None:
         subprocess.run(["make", "env"], cwd=dest, check=True)
 
 
+def git_dirty() -> bool:
+    result = subprocess.run(["git", "status", "--porcelain"], capture_output=True, text=True, check=False)
+    return bool(result.stdout.strip())
+
+
 def update(args: argparse.Namespace) -> None:
     answers = sorted(Path(".copier").glob("*.yml"))
     if args.parts:
         answers = [Path(".copier") / f"{p}.yml" for p in args.parts]
     if not answers:
         sys.exit("no .copier/*.yml here")
+    if git_dirty():
+        sys.exit("working tree is dirty, commit or stash first")
     for file in answers:
         run_update(".", answers_file=str(file), unsafe=True, overwrite=True,
                    skip_answered=not args.ask, defaults=args.defaults, vcs_ref=REF)
+        if git_dirty():
+            subprocess.run(["git", "add", "-A"], check=True)
+            subprocess.run(["git", "commit", "-qm", f"Update {file.stem} template"], check=True)
+            print(f"committed {file.stem} update")
 
 
 def main() -> None: