diff --git a/cista/__init__.py b/cista/__init__.py
old mode 100755
new mode 100644
diff --git a/cista/__main__.py b/cista/__main__.py
old mode 100755
new mode 100644
index bbddc8d..05a42dc
--- a/cista/__main__.py
+++ b/cista/__main__.py
@@ -67,14 +67,14 @@ def _main():
         # Maybe run without arguments
         print(doc)
         print(
-            "No config file found! Get started with:\n  cista -l :8000 /path/to/files, or\n  cista -l example.com --import-droppy  # Uses Droppy files\n"
+            "No config file found! Get started with:\n  cista -l :8000 /path/to/files, or\n  cista -l example.com --import-droppy  # Uses Droppy files\n",
         )
         return 1
     settings = {}
     if import_droppy:
         if exists:
             raise ValueError(
-                f"Importing Droppy: First remove the existing configuration:\n  rm {config.conffile}"
+                f"Importing Droppy: First remove the existing configuration:\n  rm {config.conffile}",
             )
         settings = droppy.readconf()
     if path:
@@ -95,6 +95,7 @@ def _main():
     print(f"Serving {config.config.path} at {url}{extra}")
     # Run the server
     serve.run(dev=dev)
+    return 0
 
 
 def _confdir(args):
diff --git a/cista/api.py b/cista/api.py
index eb197a6..6b56f93 100644
--- a/cista/api.py
+++ b/cista/api.py
@@ -32,7 +32,7 @@ async def upload(req, ws):
         text = await ws.recv()
         if not isinstance(text, str):
             raise ValueError(
-                f"Expected JSON control, got binary len(data) = {len(text)}"
+                f"Expected JSON control, got binary len(data) = {len(text)}",
             )
         req = msgspec.json.decode(text, type=FileRange)
         pos = req.start
@@ -46,7 +46,6 @@ async def upload(req, ws):
         # Report success
         res = StatusMsg(status="ack", req=req)
         await asend(ws, res)
-        # await ws.drain()
 
 
 @bp.websocket("download")
@@ -58,7 +57,7 @@ async def download(req, ws):
         text = await ws.recv()
         if not isinstance(text, str):
             raise ValueError(
-                f"Expected JSON control, got binary len(data) = {len(text)}"
+                f"Expected JSON control, got binary len(data) = {len(text)}",
             )
         req = msgspec.json.decode(text, type=FileRange)
         pos = req.start
@@ -70,7 +69,6 @@ async def download(req, ws):
         # Report success
         res = StatusMsg(status="ack", req=req)
         await asend(ws, res)
-        # await ws.drain()
 
 
 @bp.websocket("control")
diff --git a/cista/app.py b/cista/app.py
old mode 100755
new mode 100644
index bb39b42..ea7a1ac
--- a/cista/app.py
+++ b/cista/app.py
@@ -1,15 +1,15 @@
+import asyncio
 import mimetypes
 from importlib.resources import files
 from urllib.parse import unquote
-
-import sanic.helpers
-import asyncio
-import brotli
-from blake3 import blake3
-from sanic import Blueprint, Sanic, raw, empty
-from sanic.exceptions import Forbidden, NotFound
 from wsgiref.handlers import format_date_time
 
+import brotli
+import sanic.helpers
+from blake3 import blake3
+from sanic import Blueprint, Sanic, empty, raw
+from sanic.exceptions import Forbidden, NotFound
+
 from cista import auth, config, session, watching
 from cista.api import bp
 from cista.util.apphelpers import handle_sanic_exception
diff --git a/cista/auth.py b/cista/auth.py
old mode 100755
new mode 100644
index e1974e3..1095194
--- a/cista/auth.py
+++ b/cista/auth.py
@@ -25,7 +25,7 @@ def login(username: str, password: str):
     try:
         u = config.config.users[un.decode()]
     except KeyError:
-        raise ValueError("Invalid username")
+        raise ValueError("Invalid username") from None
     # Verify password
     need_rehash = False
     if not u.hash:
@@ -41,7 +41,7 @@ def login(username: str, password: str):
         try:
             _argon.verify(u.hash, pw)
         except Exception:
-            raise ValueError("Invalid password")
+            raise ValueError("Invalid password") from None
         if _argon.check_needs_rehash(u.hash):
             need_rehash = True
     # Login successful
@@ -62,7 +62,7 @@ class LoginResponse(msgspec.Struct):
     error: str = ""
 
 
-def verify(request, privileged=False):
+def verify(request, *, privileged=False):
     """Raise Unauthorized or Forbidden if the request is not authorized"""
     if privileged:
         if request.ctx.user:
@@ -130,11 +130,14 @@ async def login_post(request):
         if not username or not password:
             raise KeyError
     except KeyError:
-        raise BadRequest("Missing username or password", context={"redirect": "/login"})
+        raise BadRequest(
+            "Missing username or password",
+            context={"redirect": "/login"},
+        ) from None
     try:
         user = login(username, password)
     except ValueError as e:
-        raise Forbidden(str(e), context={"redirect": "/login"})
+        raise Forbidden(str(e), context={"redirect": "/login"}) from e
 
     if "text/html" in request.headers.accept:
         res = redirect("/")
diff --git a/cista/config.py b/cista/config.py
old mode 100755
new mode 100644
index fa6fc9f..56aa708
--- a/cista/config.py
+++ b/cista/config.py
@@ -21,7 +21,7 @@ class Config(msgspec.Struct):
 class User(msgspec.Struct, omit_defaults=True):
     privileged: bool = False
     hash: str = ""
-    lastSeen: int = 0
+    lastSeen: int = 0  # noqa: N815
 
 
 class Link(msgspec.Struct, omit_defaults=True):
diff --git a/cista/droppy.py b/cista/droppy.py
old mode 100755
new mode 100644
index 5636266..3271611
--- a/cista/droppy.py
+++ b/cista/droppy.py
@@ -30,10 +30,12 @@ def _droppy_listeners(cf):
             host = listener["host"]
             if isinstance(host, list):
                 host = host[0]
+        except (KeyError, IndexError):
+            continue
+        else:
             if host in ("127.0.0.1", "::", "localhost"):
                 return f":{port}"
             return f"{host}:{port}"
-        except (KeyError, IndexError):
-            continue
+
     # If none matched, fallback to Droppy default
     return "0.0.0.0:8989"
diff --git a/cista/fileio.py b/cista/fileio.py
old mode 100755
new mode 100644
index 566aaea..8a821d2
--- a/cista/fileio.py
+++ b/cista/fileio.py
@@ -62,7 +62,9 @@ class FileServer:
     async def start(self):
         self.alink = AsyncLink()
         self.worker = asyncio.get_event_loop().run_in_executor(
-            None, self.worker_thread, self.alink.to_sync
+            None,
+            self.worker_thread,
+            self.alink.to_sync,
         )
         self.cache = LRUCache(File, capacity=10, maxage=5.0)
 
diff --git a/cista/protocol.py b/cista/protocol.py
old mode 100755
new mode 100644
index 4a5cf7c..f793345
--- a/cista/protocol.py
+++ b/cista/protocol.py
@@ -74,7 +74,10 @@ class Cp(ControlBase):
         for p in sel:
             # Note: copies as dst rather than in dst unless name is appended.
             shutil.copytree(
-                p, dst / p.name, dirs_exist_ok=True, ignore_dangling_symlinks=True
+                p,
+                dst / p.name,
+                dirs_exist_ok=True,
+                ignore_dangling_symlinks=True,
             )
 
 
diff --git a/cista/serve.py b/cista/serve.py
old mode 100755
new mode 100644
index 05c1232..1e3e167
--- a/cista/serve.py
+++ b/cista/serve.py
@@ -7,7 +7,7 @@ from sanic import Sanic
 from cista import config, server80
 
 
-def run(dev=False):
+def run(*, dev=False):
     """Run Sanic main process that spawns worker processes to serve HTTP requests."""
     from .app import app
 
@@ -38,7 +38,7 @@ def check_cert(certdir, domain):
         return
     # TODO: Use certbot to fetch a cert
     raise ValueError(
-        f"TLS certificate files privkey.pem and fullchain.pem needed in {certdir}"
+        f"TLS certificate files privkey.pem and fullchain.pem needed in {certdir}",
     )
 
 
@@ -47,15 +47,14 @@ def parse_listen(listen):
         unix = Path(listen).resolve()
         if not unix.parent.exists():
             raise ValueError(
-                f"Directory for unix socket does not exist: {unix.parent}/"
+                f"Directory for unix socket does not exist: {unix.parent}/",
             )
         return "http://localhost", {"unix": unix}
-    elif re.fullmatch(r"(\w+(-\w+)*\.)+\w{2,}", listen, re.UNICODE):
+    if re.fullmatch(r"(\w+(-\w+)*\.)+\w{2,}", listen, re.UNICODE):
         return f"https://{listen}", {"host": listen, "port": 443, "ssl": True}
-    else:
-        try:
-            addr, _port = listen.split(":", 1)
-            port = int(_port)
-        except Exception:
-            raise ValueError(f"Invalid listen address: {listen}")
-        return f"http://localhost:{port}", {"host": addr, "port": port}
+    try:
+        addr, _port = listen.split(":", 1)
+        port = int(_port)
+    except Exception:
+        raise ValueError(f"Invalid listen address: {listen}") from None
+    return f"http://localhost:{port}", {"host": addr, "port": port}
diff --git a/cista/session.py b/cista/session.py
old mode 100755
new mode 100644
diff --git a/cista/util/apphelpers.py b/cista/util/apphelpers.py
index 7043354..ee2562d 100644
--- a/cista/util/apphelpers.py
+++ b/cista/util/apphelpers.py
@@ -33,7 +33,8 @@ async def handle_sanic_exception(request, e):
     # Non-browsers get JSON errors
     if "text/html" not in request.headers.accept:
         return jres(
-            ErrorMsg({"code": code, "message": message, **context}), status=code
+            ErrorMsg({"code": code, "message": message, **context}),
+            status=code,
         )
     # Redirections flash the error message via cookies
     if "redirect" in context:
diff --git a/cista/util/asynclink.py b/cista/util/asynclink.py
old mode 100755
new mode 100644
index 85b98cc..dee1acb
--- a/cista/util/asynclink.py
+++ b/cista/util/asynclink.py
@@ -80,8 +80,9 @@ class SyncRequest:
         if exc:
             self.set_exception(exc)
             return True
-        elif not self.done:
+        if not self.done:
             self.set_result(None)
+        return None
 
     def set_result(self, value):
         """Set result value; mark as done."""
diff --git a/cista/util/lrucache.py b/cista/util/lrucache.py
old mode 100755
new mode 100644
index 528403f..89154dd
--- a/cista/util/lrucache.py
+++ b/cista/util/lrucache.py
@@ -41,7 +41,7 @@ class LRUCache:
             The corresponding item's handle.
         """
         # Take from cache or open a new one
-        for i, (k, f, ts) in enumerate(self.cache):
+        for i, (k, f, _ts) in enumerate(self.cache):  # noqa: B007
             if k == key:
                 self.cache.pop(i)
                 break
diff --git a/cista/watching.py b/cista/watching.py
old mode 100755
new mode 100644
index dbdbe78..5249d40
--- a/cista/watching.py
+++ b/cista/watching.py
@@ -80,8 +80,8 @@ def format_du():
                 "used": disk_usage.used,
                 "free": disk_usage.free,
                 "storage": tree[""].size,
-            }
-        }
+            },
+        },
     ).decode()
 
 
@@ -90,9 +90,9 @@ def format_tree():
     return msgspec.json.encode(
         {
             "update": [
-                UpdateEntry(id=root.id, size=root.size, mtime=root.mtime, dir=root.dir)
-            ]
-        }
+                UpdateEntry(id=root.id, size=root.size, mtime=root.mtime, dir=root.dir),
+            ],
+        },
     ).decode()
 
 
@@ -112,7 +112,7 @@ def walk(path: Path) -> DirEntry | FileEntry | None:
         }
         if tree:
             size = sum(v.size for v in tree.values())
-            mtime = max(mtime, max(v.mtime for v in tree.values()))
+            mtime = max(mtime, *(v.mtime for v in tree.values()))
         else:
             size = 0
         return DirEntry(id_, size, mtime, tree)
@@ -135,7 +135,8 @@ def update(relpath: PurePosixPath, loop):
 
 
 def update_internal(
-    relpath: PurePosixPath, new: DirEntry | FileEntry | None
+    relpath: PurePosixPath,
+    new: DirEntry | FileEntry | None,
 ) -> list[UpdateEntry]:
     path = "", *relpath.parts
     old = tree
@@ -181,9 +182,8 @@ def update_internal(
             u.size = new.size
         if u.mtime != new.mtime:
             u.mtime = new.mtime
-        if isinstance(new, DirEntry):
-            if u.dir == new.dir:
-                u.dir = new.dir
+        if isinstance(new, DirEntry) and u.dir == new.dir:
+            u.dir = new.dir
     else:
         del parent[name]
         u.deleted = True
diff --git a/pyproject.toml b/pyproject.toml
index 51ba9df..25b0b1d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,12 +7,13 @@ name = "cista"
 dynamic = ["version"]
 description = "Dropbox-like file server with modern web interface"
 readme = "README.md"
-license = ""
+license = "Public Domain"
 authors = [
     { name = "Vasanko" },
 ]
 classifiers = [
 ]
+requires-python = ">=3.11"
 dependencies = [
     "argon2-cffi",
     "blake3",
@@ -35,6 +36,7 @@ cista = "cista.__main__:main"
 [project.optional-dependencies]
 dev = [
     "pytest",
+    "ruff",
 ]
 
 [tool.hatchling]
@@ -65,7 +67,36 @@ testpaths = [
     "tests",
 ]
 
-[tool.isort]
-#src_paths = ["cista", "tests"]
-line_length = 120
-multi_line_output = 5
+[tool.ruff]
+select = ["ALL"]
+ignore = [
+    "A0",
+    "ARG001",
+    "ANN",
+    "B018",
+    "BLE001",
+    "C901",
+    "COM812",  # conflicts with ruff format
+    "D",
+    "E501",
+    "EM1",
+    "FIX002",
+    "ISC001",  # conflicts with ruff format
+    "PGH003",
+    "PLR0912",
+    "PLR2004",
+    "PLW0603",
+    "S101",
+    "SLF001",
+    "T201",
+    "TD0",
+    "TRY",
+]
+show-source = true
+show-fixes = true
+
+[tool.ruff.isort]
+known-first-party = ["cista"]
+
+[tool.ruff.per-file-ignores]
+"tests/*" = ["S", "ANN", "D", "INP"]
diff --git a/tests/test_control.py b/tests/test_control.py
index 06c3406..ebd77a8 100644
--- a/tests/test_control.py
+++ b/tests/test_control.py
@@ -7,7 +7,7 @@ from cista import config
 from cista.protocol import Cp, MkDir, Mv, Rename, Rm
 
 
-@pytest.fixture
+@pytest.fixture()
 def setup_temp_dir():
     with tempfile.TemporaryDirectory() as tmpdirname:
         config.config = config.Config(path=Path(tmpdirname), listen=":0")