diff --git a/dmoj/executors/C.py b/dmoj/executors/C.py
index af4cb059f..afd1632d3 100644
--- a/dmoj/executors/C.py
+++ b/dmoj/executors/C.py
@@ -4,6 +4,7 @@
 class Executor(GCCMixin, CExecutor):
     command = 'gcc'
     std = 'c99'
+    ext_priority = 1
 
     test_program = """
 #include <stdio.h>
diff --git a/dmoj/executors/C11.py b/dmoj/executors/C11.py
index 43cdd20d5..14d57589e 100644
--- a/dmoj/executors/C11.py
+++ b/dmoj/executors/C11.py
@@ -5,6 +5,7 @@ class Executor(GCCMixin, CExecutor):
     command = 'gcc11'
     std = 'c11'
     command_paths = ['gcc']
+    ext_priority = 2
 
     test_program = """
 #include <stdio.h>
diff --git a/dmoj/executors/C23.py b/dmoj/executors/C23.py
index 60cdc7a2f..c53bcae3e 100644
--- a/dmoj/executors/C23.py
+++ b/dmoj/executors/C23.py
@@ -5,6 +5,7 @@ class Executor(GCCMixin, CExecutor):
     command = 'gcc23'
     std = 'c23'
     command_paths = ['gcc']
+    ext_priority = 4
 
     test_program = """
 #include <stdio.h>
diff --git a/dmoj/executors/CLANG.py b/dmoj/executors/CLANG.py
index e9b16c27e..2edabfc39 100644
--- a/dmoj/executors/CLANG.py
+++ b/dmoj/executors/CLANG.py
@@ -5,6 +5,7 @@ class Executor(ClangMixin, CExecutor):
     command = 'clang'
     std = 'c11'
     command_paths = [f'clang-{i}' for i in CLANG_VERSIONS] + ['clang']
+    ext_priority = 3
 
     test_program = """
 #include <stdio.h>
diff --git a/dmoj/executors/CLPP14.py b/dmoj/executors/CLPP14.py
index 1ab5c7fdf..6d29d734c 100644
--- a/dmoj/executors/CLPP14.py
+++ b/dmoj/executors/CLPP14.py
@@ -5,6 +5,7 @@ class Executor(ClangMixin, CPPExecutor):
     command = 'clang++'
     std = 'c++14'
     command_paths = [f'clang++-{i}' for i in CLANG_VERSIONS] + ['clang++']
+    ext_priority = 4
 
     test_program = """
 #include <iostream>
diff --git a/dmoj/executors/CLPP17.py b/dmoj/executors/CLPP17.py
index a25ef8d8f..462590ad8 100644
--- a/dmoj/executors/CLPP17.py
+++ b/dmoj/executors/CLPP17.py
@@ -5,6 +5,7 @@ class Executor(ClangMixin, CPPExecutor):
     command = 'clang++'
     std = 'c++17'
     command_paths = [f'clang++-{i}' for i in CLANG_VERSIONS] + ['clang++']
+    ext_priority = 6
 
     test_program = """
 #include <iostream>
diff --git a/dmoj/executors/CLPP20.py b/dmoj/executors/CLPP20.py
index cc5109bb2..82759f5be 100644
--- a/dmoj/executors/CLPP20.py
+++ b/dmoj/executors/CLPP20.py
@@ -5,6 +5,7 @@ class Executor(ClangMixin, CPPExecutor):
     command = 'clang++'
     std = 'c++20'
     command_paths = [f'clang++-{i}' for i in CLANG_VERSIONS] + ['clang++']
+    ext_priority = 8
 
     test_program = """
 #include <iostream>
diff --git a/dmoj/executors/CLPP23.py b/dmoj/executors/CLPP23.py
index 143d732a3..0599ce653 100644
--- a/dmoj/executors/CLPP23.py
+++ b/dmoj/executors/CLPP23.py
@@ -5,6 +5,7 @@ class Executor(ClangMixin, CPPExecutor):
     command = 'clang++'
     std = 'c++23'
     command_paths = [f'clang++-{i}' for i in CLANG_VERSIONS] + ['clang++']
+    ext_priority = 10
 
     test_program = """
 #include <iostream>
diff --git a/dmoj/executors/CPP03.py b/dmoj/executors/CPP03.py
index d945aa703..96db73554 100644
--- a/dmoj/executors/CPP03.py
+++ b/dmoj/executors/CPP03.py
@@ -4,6 +4,7 @@
 class Executor(GCCMixin, CPPExecutor):
     command = 'g++'
     std = 'c++03'
+    ext_priority = 1
     test_program = """
 #include <iostream>
 
diff --git a/dmoj/executors/CPP11.py b/dmoj/executors/CPP11.py
index 5ccbe8b97..14c281797 100644
--- a/dmoj/executors/CPP11.py
+++ b/dmoj/executors/CPP11.py
@@ -5,6 +5,7 @@ class Executor(GCCMixin, CPPExecutor):
     command = 'g++11'
     command_paths = ['g++-5', 'g++-4.9', 'g++-4.8', 'g++']
     std = 'c++11'
+    ext_priority = 2
     test_program = """
 #include <iostream>
 
diff --git a/dmoj/executors/CPP14.py b/dmoj/executors/CPP14.py
index 45a7ad818..27c09e701 100644
--- a/dmoj/executors/CPP14.py
+++ b/dmoj/executors/CPP14.py
@@ -5,6 +5,7 @@ class Executor(GCCMixin, CPPExecutor):
     command = 'g++14'
     command_paths = ['g++-5', 'g++']
     std = 'c++14'
+    ext_priority = 3
     test_program = """
 #include <iostream>
 
diff --git a/dmoj/executors/CPP17.py b/dmoj/executors/CPP17.py
index f190ecd7b..ee3f5f88d 100644
--- a/dmoj/executors/CPP17.py
+++ b/dmoj/executors/CPP17.py
@@ -5,6 +5,7 @@ class Executor(GCCMixin, CPPExecutor):
     command = 'g++17'
     command_paths = ['g++-7', 'g++']
     std = 'c++17'
+    ext_priority = 5
     test_program = """
 #include <iostream>
 
diff --git a/dmoj/executors/CPP20.py b/dmoj/executors/CPP20.py
index fb4729adb..4d92e2e1d 100644
--- a/dmoj/executors/CPP20.py
+++ b/dmoj/executors/CPP20.py
@@ -5,6 +5,7 @@ class Executor(GCCMixin, CPPExecutor):
     command = 'g++20'
     command_paths = ['g++-11', 'g++']
     std = 'c++20'
+    ext_priority = 7
     test_program = """
 #include <iostream>
 
diff --git a/dmoj/executors/CPP23.py b/dmoj/executors/CPP23.py
index d6e904545..fb9c6a5f8 100644
--- a/dmoj/executors/CPP23.py
+++ b/dmoj/executors/CPP23.py
@@ -5,6 +5,7 @@ class Executor(GCCMixin, CPPExecutor):
     command = 'g++23'
     command_paths = ['g++-13', 'g++']
     std = 'c++23'
+    ext_priority = 9
     test_program = """
 #include <iostream>
 
diff --git a/dmoj/executors/GAS32.py b/dmoj/executors/GAS32.py
index 3db690f8f..c1fab15ae 100644
--- a/dmoj/executors/GAS32.py
+++ b/dmoj/executors/GAS32.py
@@ -3,6 +3,7 @@
 
 class Executor(PlatformX86Mixin, GASExecutor):
     as_name = 'as_x86'
+    ext_priority = 1
 
     test_program = r""".intel_syntax noprefix
 
diff --git a/dmoj/executors/GAS64.py b/dmoj/executors/GAS64.py
index 1e22bf008..91336aefe 100644
--- a/dmoj/executors/GAS64.py
+++ b/dmoj/executors/GAS64.py
@@ -3,6 +3,7 @@
 
 class Executor(PlatformX64Mixin, GASExecutor):
     as_name = 'as_x64'
+    ext_priority = 2
 
     test_program = r""".intel_syntax noprefix
 
diff --git a/dmoj/executors/JAVA.py b/dmoj/executors/JAVA.py
index b859bc6b1..10efbd312 100644
--- a/dmoj/executors/JAVA.py
+++ b/dmoj/executors/JAVA.py
@@ -5,6 +5,7 @@ class Executor(JavacExecutor):
     compiler = 'javac'
     vm = 'java'
     jvm_regex = r'(?:java-|openjdk)(?:9|[1-9][0-9]+)'
+    ext_priority = 2
 
     test_program = """\
 import java.io.IOException;
diff --git a/dmoj/executors/JAVA8.py b/dmoj/executors/JAVA8.py
index ee816d8d3..ffa9e5a6a 100644
--- a/dmoj/executors/JAVA8.py
+++ b/dmoj/executors/JAVA8.py
@@ -7,6 +7,7 @@ class Executor(JavacExecutor):
     compiler = 'javac8'
     vm = 'java8'
     jvm_regex = r'java-8-|jdk-8-|openjdk8|oracle-java8'
+    ext_priority = 1
 
     test_program = """\
 import java.io.IOException;
diff --git a/dmoj/executors/NASM.py b/dmoj/executors/NASM.py
index af606deed..149fea830 100644
--- a/dmoj/executors/NASM.py
+++ b/dmoj/executors/NASM.py
@@ -3,6 +3,7 @@
 
 class Executor(PlatformX86Mixin, NASMExecutor):
     nasm_format = 'elf32'
+    ext_priority = 1
 
     test_program = """\
 section .text
diff --git a/dmoj/executors/NASM64.py b/dmoj/executors/NASM64.py
index 883c8daa7..ec4424e66 100644
--- a/dmoj/executors/NASM64.py
+++ b/dmoj/executors/NASM64.py
@@ -3,6 +3,7 @@
 
 class Executor(PlatformX64Mixin, NASMExecutor):
     nasm_format = 'elf64'
+    ext_priority = 2
 
     test_program = """\
 section .text
diff --git a/dmoj/executors/PY2.py b/dmoj/executors/PY2.py
index d19d78cf3..b67fc5eab 100644
--- a/dmoj/executors/PY2.py
+++ b/dmoj/executors/PY2.py
@@ -5,6 +5,7 @@ class Executor(PythonExecutor):
     command = 'python'
     command_paths = ['python2.7', 'python2', 'python']
     pygments_traceback_lexer = 'py2tb'
+    ext_priority = 1
     test_program = """
 import sys
 if sys.version_info.major == 2:
diff --git a/dmoj/executors/PY3.py b/dmoj/executors/PY3.py
index 1fcfb552e..3e87fdd2c 100644
--- a/dmoj/executors/PY3.py
+++ b/dmoj/executors/PY3.py
@@ -5,6 +5,7 @@ class Executor(PythonExecutor):
     command = 'python3'
     command_paths = [f'python{i}' for i in ['3.6', '3.5', '3.4', '3.3', '3.2', '3.1', '3']]
     pygments_traceback_lexer = 'py3tb'
+    ext_priority = 3
     test_program = """
 import sys
 if sys.version_info.major == 3:
diff --git a/dmoj/executors/PYPY.py b/dmoj/executors/PYPY.py
index e93c6e687..64777ff93 100644
--- a/dmoj/executors/PYPY.py
+++ b/dmoj/executors/PYPY.py
@@ -7,6 +7,7 @@
 class Executor(PythonExecutor):
     command = 'pypy'
     pygments_traceback_lexer = 'py2tb'
+    ext_priority = 2
     test_program = """
 import sys
 if sys.version_info.major == 2:
diff --git a/dmoj/executors/PYPY3.py b/dmoj/executors/PYPY3.py
index 5d59732bc..7cecfcd5e 100644
--- a/dmoj/executors/PYPY3.py
+++ b/dmoj/executors/PYPY3.py
@@ -4,6 +4,7 @@
 class Executor(PYPYExecutor):
     command = 'pypy3'
     pygments_traceback_lexer = 'py3tb'
+    ext_priority = 4
     test_program = """
 import sys
 if sys.version_info.major == 3:
diff --git a/dmoj/executors/__init__.py b/dmoj/executors/__init__.py
index b0971d3bd..cee8d6ac2 100644
--- a/dmoj/executors/__init__.py
+++ b/dmoj/executors/__init__.py
@@ -22,8 +22,8 @@ def by_ext(ext: str) -> Any:
         if name.lower() == ext:
             return executor
 
-    for executor in sorted(executors.values(), key=lambda executor: executor.Executor.name):
-        if executor.Executor.ext == ext:
+    for executor in sorted(executors.values(), key=lambda executor: executor.Executor.ext_priority, reverse=True):
+        if ext in executor.Executor.get_valid_exts():
             return executor
 
     raise KeyError('no executor for extension "%s"' % ext)
diff --git a/dmoj/executors/base_executor.py b/dmoj/executors/base_executor.py
index 25816e804..0c955b705 100644
--- a/dmoj/executors/base_executor.py
+++ b/dmoj/executors/base_executor.py
@@ -6,7 +6,7 @@
 import sys
 import tempfile
 import traceback
-from typing import Any, Callable, Dict, List, Optional, Tuple, Type, Union
+from typing import Any, Callable, Dict, List, Optional, Sequence, Tuple, Type, Union
 
 from dmoj.cptbox import IsolateTracer, TracedPopen, syscalls
 from dmoj.cptbox.filesystem_policies import ExactDir, ExactFile, FilesystemAccessRule, RecursiveDir
@@ -120,6 +120,7 @@ class BaseExecutor(metaclass=ExecutorMeta):
     test_memory = env.selftest_memory_limit
     version_regex = re.compile(r'.*?(\d+(?:\.\d+)+)', re.DOTALL)
     source_filename_format = '{problem_id}.{ext}'
+    ext_priority = 0  # When there are multiple versions of a similar runtime, bigger is newer
 
     address_grace = 65536
     data_grace = 0
@@ -483,3 +484,12 @@ def get_find_first_mapping(cls) -> Optional[Dict[str, List[str]]]:
     @classmethod
     def autoconfig(cls) -> AutoConfigOutput:
         return cls.autoconfig_find_first(cls.get_find_first_mapping())
+
+    @classmethod
+    def get_valid_exts(cls) -> Sequence[str]:
+        # This exists because sometimes we want to recognize more extensions than just `ext` for auxiliary files
+        return (cls.ext,)
+
+    @classmethod
+    def supports_multifile(cls) -> bool:
+        return False
diff --git a/dmoj/executors/c_like_executor.py b/dmoj/executors/c_like_executor.py
index e19ec963b..2e780df2f 100644
--- a/dmoj/executors/c_like_executor.py
+++ b/dmoj/executors/c_like_executor.py
@@ -1,7 +1,7 @@
 import os
 import re
 from collections import deque
-from typing import Dict, List, Optional, Type
+from typing import Dict, List, Optional, Sequence, Type
 
 from dmoj.cptbox import TracedPopen
 from dmoj.executors.base_executor import AutoConfigOutput, AutoConfigResult, VersionFlags
@@ -139,6 +139,10 @@ def initialize(cls) -> bool:
             cls.has_color = versions is not None and versions[0][1] is not None and versions[0][1] > (4, 9)
         return res
 
+    @classmethod
+    def supports_multifile(cls) -> bool:
+        return True
+
 
 class GCCMixin(CLikeExecutor):
     arch: str = 'gcc_target_arch'
@@ -161,6 +165,11 @@ def get_flags(self) -> List[str]:
     def get_version_flags(cls, command: str) -> List[VersionFlags]:
         return ['--version']
 
+    def create_files(self, problem_id: str, source_code: bytes, *args, **kwargs) -> None:
+        super().create_files(problem_id, source_code, *args, **kwargs)
+        # Clang/++ will complain if you pass header files, so we strip them out
+        self.source_paths = [source for source in self.source_paths if source.partition('.')[-1] not in ('h', 'hpp')]
+
 
 class CExecutor(CLikeExecutor):
     ext: str = 'c'
@@ -170,3 +179,8 @@ class CExecutor(CLikeExecutor):
 class CPPExecutor(CLikeExecutor):
     ext: str = 'cpp'
     is_signature_gradable = True
+
+    @classmethod
+    def get_valid_exts(cls) -> Sequence[str]:
+        # Recognize both `cpp` and `cc` as valid C++ extensions for auxiliary files
+        return 'cpp', 'cc'
diff --git a/dmoj/problem.py b/dmoj/problem.py
index fdc8c257a..ba1a94279 100644
--- a/dmoj/problem.py
+++ b/dmoj/problem.py
@@ -388,7 +388,7 @@ def _run_generator(self, gen: Union[str, ConfigNode], args: Optional[Iterable[st
         time_limit = env.generator_time_limit
         memory_limit = env.generator_memory_limit
         compiler_time_limit = env.generator_compiler_time_limit
-        lang = None  # Default to C/C++
+        lang = None  # Default to autodetection
 
         base = get_problem_root(self.problem.id)
         assert base is not None
diff --git a/dmoj/utils/helper_files.py b/dmoj/utils/helper_files.py
index 88be4bfbe..715ce4bd0 100644
--- a/dmoj/utils/helper_files.py
+++ b/dmoj/utils/helper_files.py
@@ -35,22 +35,6 @@ def compile_with_auxiliary_files(
         with open(filename, 'rb') as f:
             sources[os.path.basename(filename)] = f.read()
 
-    def find_runtime(*languages):
-        for grader in languages:
-            if grader in executors.executors:
-                return grader
-        return None
-
-    use_cpp = any(map(lambda name: os.path.splitext(name)[1] in ['.cpp', '.cc'], filenames))
-    use_c = any(map(lambda name: os.path.splitext(name)[1] in ['.c'], filenames))
-    if not lang:
-        if use_cpp:
-            lang = find_runtime('CPP20', 'CPP17', 'CPP14', 'CPP11', 'CPP03')
-        elif use_c:
-            lang = find_runtime('C11', 'C')
-
-    # TODO: remove above code once `from_filename` is smart enough to
-    # prioritize newer versions of runtimes
     if not lang:
         for filename in filenames:
             try:
@@ -69,15 +53,15 @@ def find_runtime(*languages):
         kwargs['compiler_time_limit'] = compiler_time_limit
 
     if hasattr(executor, 'flags'):
-        kwargs['flags'] = flags + list(executor.flags)
+        kwargs['flags'] = flags + executor.flags
 
-    # Optimize the common case.
-    if use_cpp or use_c:
+    # Check if the executor supports multifile compilation
+    if executor.supports_multifile():
         # Some auxiliary files (like those using testlib.h) take an extremely long time to compile, so we cache them.
         executor = executor('_aux_file', None, aux_sources=sources, cached=True, unbuffered=unbuffered, **kwargs)
     else:
         if len(sources) > 1:
-            raise InternalError('non-C/C++ auxiliary programs cannot be multi-file')
+            raise InternalError(f'{lang} auxiliary programs cannot be multi-file')
         executor = executor('_aux_file', list(sources.values())[0], cached=True, unbuffered=unbuffered, **kwargs)
 
     return executor
diff --git a/testsuite/bridged_interactor/interactor.cpp b/testsuite/bridged_interactor/interactor.cpp
index 904e424fe..0425e3210 100644
--- a/testsuite/bridged_interactor/interactor.cpp
+++ b/testsuite/bridged_interactor/interactor.cpp
@@ -11,17 +11,18 @@ int main(int argc, char *argv[]) {
   int N, guesses = 0;
   long long guess;
   fscanf(input_file, "%d", &N);
-  while (guess != N) {
+  while (true) {
     read(&guess);
+    guesses++;
     if (guess == N) {
       puts("OK");
+      break;
     } else if (guess > N) {
       puts("FLOATS");
     } else {
       puts("SINKS");
     }
     fflush(stdout);
-    guesses++;
   }
   if (guesses <= 31)
     return 0; // AC
diff --git a/testsuite/bridged_interactor_noflush/interactor.cpp b/testsuite/bridged_interactor_noflush/interactor.cpp
index 497e86892..761474008 100644
--- a/testsuite/bridged_interactor_noflush/interactor.cpp
+++ b/testsuite/bridged_interactor_noflush/interactor.cpp
@@ -11,16 +11,17 @@ int main(int argc, char *argv[]) {
   int N, guesses = 0;
   long long guess;
   fscanf(input_file, "%d", &N);
-  while (guess != N) {
+  while (true) {
     read(&guess);
+    guesses++;
     if (guess == N) {
       puts("OK");
+      break;
     } else if (guess > N) {
       puts("FLOATS");
     } else {
       puts("SINKS");
     }
-    guesses++;
   }
   if (guesses <= 31)
     return 0; // AC
diff --git a/testsuite/siggrade/tests/clang_signature_grading/sigtest.c b/testsuite/siggrade/tests/clang_signature_grading/sigtest.c
new file mode 100644
index 000000000..7daeddf6d
--- /dev/null
+++ b/testsuite/siggrade/tests/clang_signature_grading/sigtest.c
@@ -0,0 +1 @@
+bool is_valid(int n) { return n == 1; }
diff --git a/testsuite/siggrade/tests/clang_signature_grading/test.yml b/testsuite/siggrade/tests/clang_signature_grading/test.yml
new file mode 100644
index 000000000..2581334e4
--- /dev/null
+++ b/testsuite/siggrade/tests/clang_signature_grading/test.yml
@@ -0,0 +1,5 @@
+language: CLANG
+time: 2
+memory: 65536
+source: sigtest.c
+expect: AC