diff --git a/cista/config.py b/cista/config.py
index 03fbfdd..093d0c2 100644
--- a/cista/config.py
+++ b/cista/config.py
@@ -7,9 +7,11 @@ from contextlib import suppress
 from functools import wraps
 from hashlib import sha256
 from pathlib import Path, PurePath
-from time import time
+from time import sleep, time
+from typing import Callable, Concatenate, Literal, ParamSpec
 
 import msgspec
+import msgspec.toml
 
 
 class Config(msgspec.Struct):
@@ -22,6 +24,13 @@ class Config(msgspec.Struct):
     links: dict[str, Link] = {}
 
 
+# Typing: arguments for config-modifying functions
+P = ParamSpec("P")
+ResultStr = Literal["modified", "created", "read"]
+RawModifyFunc = Callable[Concatenate[Config, P], Config]
+ModifyPublic = Callable[P, ResultStr]
+
+
 class User(msgspec.Struct, omit_defaults=True):
     privileged: bool = False
     hash: str = ""
@@ -34,11 +43,13 @@ class Link(msgspec.Struct, omit_defaults=True):
     expires: int = 0
 
 
-config = None
-conffile = None
+# Global variables - initialized during application startup
+config: Config
+conffile: Path
 
 
-def init_confdir():
+def init_confdir() -> None:
+    global conffile
     if p := os.environ.get("CISTA_HOME"):
         home = Path(p)
     else:
@@ -49,8 +60,6 @@ def init_confdir():
     if not home.is_dir():
         home.mkdir(parents=True, exist_ok=True)
         home.chmod(0o700)
-
-    global conffile
     conffile = home / "db.toml"
 
 
@@ -77,10 +86,10 @@ def dec_hook(typ, obj):
     raise TypeError
 
 
-def config_update(modify):
+def config_update(
+    modify: RawModifyFunc,
+) -> ResultStr | Literal["collision"]:
     global config
-    if conffile is None:
-        init_confdir()
     tmpname = conffile.with_suffix(".tmp")
     try:
         f = tmpname.open("xb")
@@ -95,7 +104,7 @@ def config_update(modify):
             c = msgspec.toml.decode(old, type=Config, dec_hook=dec_hook)
         except FileNotFoundError:
             old = b""
-            c = None
+            c = Config(path=Path(), listen="", secret=secrets.token_hex(12))
         c = modify(c)
         new = msgspec.toml.encode(c, enc_hook=enc_hook)
         if old == new:
@@ -118,17 +127,23 @@ def config_update(modify):
     return "modified" if old else "created"
 
 
-def modifies_config(modify):
-    """Decorator for functions that modify the config file"""
+def modifies_config(
+    modify: Callable[Concatenate[Config, P], Config],
+) -> Callable[P, ResultStr]:
+    """Decorator for functions that modify the config file
+
+    The decorated function takes as first arg Config and returns it modified.
+    The wrapper handles atomic modification and returns a string indicating the result.
+    """
 
     @wraps(modify)
-    def wrapper(*args, **kwargs):
-        def m(c):
+    def wrapper(*args: P.args, **kwargs: P.kwargs) -> ResultStr:
+        def m(c: Config) -> Config:
             return modify(c, *args, **kwargs)
 
         # Retry modification in case of write collision
         while (c := config_update(m)) == "collision":
-            time.sleep(0.01)
+            sleep(0.01)
         return c
 
     return wrapper
@@ -136,8 +151,7 @@ def modifies_config(modify):
 
 def load_config():
     global config
-    if conffile is None:
-        init_confdir()
+    init_confdir()
     config = msgspec.toml.decode(conffile.read_bytes(), type=Config, dec_hook=dec_hook)
 
 
@@ -145,7 +159,7 @@ def load_config():
 def update_config(conf: Config, changes: dict) -> Config:
     """Create/update the config with new values, respecting changes done by others."""
     # Encode into dict, update values with new, convert to Config
-    settings = {} if conf is None else msgspec.to_builtins(conf, enc_hook=enc_hook)
+    settings = msgspec.to_builtins(conf, enc_hook=enc_hook)
     settings.update(changes)
     return msgspec.convert(settings, Config, dec_hook=dec_hook)
 
@@ -155,8 +169,13 @@ def update_user(conf: Config, name: str, changes: dict) -> Config:
     """Create/update a user with new values, respecting changes done by others."""
     # Encode into dict, update values with new, convert to Config
     try:
-        u = conf.users[name].__copy__()
-    except (KeyError, AttributeError):
+        # Copy user by converting to dict and back
+        u = msgspec.convert(
+            msgspec.to_builtins(conf.users[name], enc_hook=enc_hook),
+            User,
+            dec_hook=dec_hook,
+        )
+    except KeyError:
         u = User()
     if "password" in changes:
         from . import auth
@@ -165,7 +184,7 @@ def update_user(conf: Config, name: str, changes: dict) -> Config:
         del changes["password"]
     udict = msgspec.to_builtins(u, enc_hook=enc_hook)
     udict.update(changes)
-    settings = msgspec.to_builtins(conf, enc_hook=enc_hook) if conf else {"users": {}}
+    settings = msgspec.to_builtins(conf, enc_hook=enc_hook)
     settings["users"][name] = msgspec.convert(udict, User, dec_hook=dec_hook)
     return msgspec.convert(settings, Config, dec_hook=dec_hook)
 
@@ -173,6 +192,7 @@ def update_user(conf: Config, name: str, changes: dict) -> Config:
 @modifies_config
 def del_user(conf: Config, name: str) -> Config:
     """Delete named user account."""
-    ret = conf.__copy__()
-    ret.users.pop(name)
-    return ret
+    # Create a copy by converting to dict and back
+    settings = msgspec.to_builtins(conf, enc_hook=enc_hook)
+    settings["users"].pop(name)
+    return msgspec.convert(settings, Config, dec_hook=dec_hook)