--- a/devito/arch/compiler.py
+++ b/devito/arch/compiler.py
@@ -145,6 +145,14 @@
 
 
 class Compiler(GCCToolchain):
+    # codepy >=2025.1 turned GCCToolchain into a frozen dataclass, which
+    # forbids attribute assignment.  Override the frozen __setattr__ /
+    # __delattr__ so that Compiler (and its subclasses) can keep setting
+    # attributes imperatively.
+    def __setattr__(self, name, value):
+        object.__setattr__(self, name, value)
+    def __delattr__(self, name):
+        object.__delattr__(self, name)
     """
     Base class for all compiler classes.
 
@@ -196,7 +204,11 @@
         else:
             self._name = maybe_name
 
-        super().__init__(**kwargs)
+        # codepy >=2025.1: GCCToolchain is a frozen dataclass whose __init__
+        # requires all fields as positional args.  Skip it entirely and
+        # initialise the fields that Compiler never sets itself.
+        self.o_ext = '.o'
+        self.features = set()
 
         self.__lookup_cmds__()
         self._cpp = kwargs.get('cpp', self._default_cpp)
@@ -355,12 +367,12 @@
                 ) from e
         debug(f"Make <{' '.join(args)}>")
 
-    def _cmdline(self, files, object=False):
+    def _cmdline(self, files, *, is_object=False):
         """
         Sanitize command line to remove all shell string escape such as
         mpicc/mpicxx would add, e.g., `-Wl\\,-rpath,/path/to/lib`.
         """
-        cc_line = super()._cmdline(files, object=object)
+        cc_line = super()._cmdline(files, is_object=is_object)
         return [s.replace('\\', '') for s in cc_line]
 
     def jit_compile(self, soname, code):
@@ -417,9 +429,11 @@
         # when running the test suite in parallel)
         with warnings.catch_warnings():
             warnings.simplefilter('ignore')
-            _, _, _, recompiled = compile_from_string(self, target, code, src_file,
-                                                      cache_dir=cache_dir, debug=debug,
-                                                      sleep_delay=sleep_delay)
+            # codepy >=2025.1: source_name is now keyword-only.
+            _, _, _, recompiled = compile_from_string(
+                self, target, code, source_name=src_file,
+                cache_dir=cache_dir, debug=debug,
+                sleep_delay=sleep_delay)
 
         return recompiled, src_file