diff --git a/edit/server.py b/edit/server.py
index c606156..fa9568d 100644
--- a/edit/server.py
+++ b/edit/server.py
@@ -49,14 +49,34 @@ _GIT_DIR = os.environ.get("GIT_DIR")
 _git_lock = asyncio.Lock()
 
 
-async def _git_commit(file_path: Path, handle: str, verb: str) -> None:
-    rel = str(file_path.relative_to(_ROOT))
+def _git_env() -> dict:
     env = os.environ.copy()
     if _GIT_DIR:
         env["GIT_DIR"] = _GIT_DIR
         env["GIT_WORK_TREE"] = str(_ROOT)
     env.setdefault("GIT_COMMITTER_NAME", "bincio-wiki")
     env.setdefault("GIT_COMMITTER_EMAIL", "wiki@bincio.wiki")
+    return env
+
+
+async def _git_file_hash(file_path: Path) -> str:
+    rel = str(file_path.relative_to(_ROOT))
+    try:
+        proc = await asyncio.create_subprocess_exec(
+            "git", "log", "-1", "--format=%H", "--", rel,
+            cwd=str(_ROOT), env=_git_env(),
+            stdout=asyncio.subprocess.PIPE,
+            stderr=asyncio.subprocess.DEVNULL,
+        )
+        stdout, _ = await proc.communicate()
+        return stdout.decode().strip()
+    except Exception:
+        return ""
+
+
+async def _git_commit(file_path: Path, handle: str, verb: str) -> None:
+    rel = str(file_path.relative_to(_ROOT))
+    env = _git_env()
     try:
         async with _git_lock:
             add = await asyncio.create_subprocess_exec(
@@ -256,6 +276,7 @@ def _slug_to_path(slug: str, base: Path) -> Path:
 
 class PageBody(BaseModel):
     content: str
+    base_hash: str | None = None
 
 
 def _list(base: Path) -> list[str]:
@@ -263,11 +284,13 @@ def _list(base: Path) -> list[str]:
         return []
     return [str(p.relative_to(base).with_suffix("")) for p in sorted(base.rglob("*.md"))]
 
-def _get(slug: str, base: Path) -> JSONResponse:
+async def _get(slug: str, base: Path) -> JSONResponse:
     path = _slug_to_path(slug, base)
     if not path.exists():
         raise HTTPException(404, "Not found")
-    return JSONResponse({"slug": slug, "content": path.read_text(encoding="utf-8")})
+    content = path.read_text(encoding="utf-8")
+    base_hash = await _git_file_hash(path)
+    return JSONResponse({"slug": slug, "content": content, "base_hash": base_hash})
 
 def _save(slug: str, body: PageBody, base: Path) -> JSONResponse:
     path = _slug_to_path(slug, base)
@@ -295,8 +318,13 @@ async def get_page(slug: str, user: User = Depends(require_auth)) -> JSONRespons
 
 @app.post("/pages/{slug:path}")
 async def save_page(slug: str, body: PageBody, user: User = Depends(require_auth)) -> JSONResponse:
+    path = _slug_to_path(slug, pages_dir)
+    if body.base_hash is not None:
+        current = await _git_file_hash(path)
+        if current and current != body.base_hash:
+            raise HTTPException(409, "Pagina modificata da qualcun altro — ricarica prima di salvare")
     result = _save(slug, body, pages_dir)
-    await _git_commit(_slug_to_path(slug, pages_dir), user.handle, "edited")
+    await _git_commit(path, user.handle, "edited")
     return result
 
 @app.delete("/pages/{slug:path}")
@@ -319,8 +347,13 @@ async def get_story(slug: str, user: User = Depends(require_auth)) -> JSONRespon
 
 @app.post("/stories/{slug:path}")
 async def save_story(slug: str, body: PageBody, user: User = Depends(require_auth)) -> JSONResponse:
+    path = _slug_to_path(slug, stories_dir)
+    if body.base_hash is not None:
+        current = await _git_file_hash(path)
+        if current and current != body.base_hash:
+            raise HTTPException(409, "Pagina modificata da qualcun altro — ricarica prima di salvare")
     result = _save(slug, body, stories_dir)
-    await _git_commit(_slug_to_path(slug, stories_dir), user.handle, "edited")
+    await _git_commit(path, user.handle, "edited")
     return result
 
 @app.delete("/stories/{slug:path}")
diff --git a/site b/site
index d6eda09..1539bdb 160000
--- a/site
+++ b/site
@@ -1 +1 @@
-Subproject commit d6eda096d93063ad840de2f70a37de42997ffc39
+Subproject commit 1539bdb3a78146685af9e5d369b325c2119b29ec