diff --git a/tests/restyle.py b/tests/restyle.py
new file mode 100755
index 0000000000..909f089a3c
--- /dev/null
+++ b/tests/restyle.py
@@ -0,0 +1,270 @@
+#!/usr/bin/env python
+
+import argparse
+import os
+import sys
+import pathlib
+import subprocess
+import contextlib
+
+from dataclasses import dataclass
+
+
+GIT_ROOT = pathlib.Path(
+    subprocess.check_output(
+        ["git", "rev-parse", "--show-toplevel"], universal_newlines=True
+    ).strip()
+)
+
+
+def clang_format(clang_format, config, files):
+    if not files:
+        raise ValueError("Files list cannot be empty")
+
+    cmd = [clang_format, "--verbose", f"--style=file:{config.as_posix()}", "-i"]
+    cmd.extend(files)
+
+    subprocess.run(cmd, check=True)
+
+
+def ls_files(patterns):
+    """Git-only search, but rather poor at matching complex patterns (at least w/ <=py3.12)"""
+    proc = subprocess.run(
+        ["git", "--no-pager", "ls-files"],
+        capture_output=True,
+        check=True,
+        universal_newlines=True,
+    )
+
+    out = []
+    for line in proc.stdout.split("\n"):
+        path = pathlib.Path(line.strip())
+        if any(path.match(pattern) for pattern in patterns):
+            out.append(path)
+
+    return out
+
+
+def find_files(patterns):
+    """Filesystem search, matches both git and non-git files"""
+    return [
+        file
+        for pattern in patterns
+        for file in [found for found in GIT_ROOT.rglob(pattern)]
+    ]
+
+
+def find_core_files():
+    """Returns a subset of Core files that should be formatted"""
+    return [
+        file
+        for file in find_files(
+            (
+                "cores/esp8266/Lwip*",
+                "libraries/ESP8266mDNS/**/*",
+                "libraries/Wire/**/*",
+                "libraries/lwIP*/**/*",
+                "cores/esp8266/debug*",
+                "cores/esp8266/core_esp8266_si2c*",
+                "cores/esp8266/StreamString*",
+                "cores/esp8266/StreamSend*",
+                "libraries/Netdump/**/*",
+                "tests/**/*",
+            )
+        )
+        if file.is_file()
+        and file.suffix in (".c", ".cpp", ".h", ".hpp")
+        and not GIT_ROOT / "tests/host/bin" in file.parents
+        and not GIT_ROOT / "tests/host/common/catch.hpp" == file
+    ]
+
+
+def find_arduino_files():
+    """Returns every .ino file available in the repository, excluding submodule ones"""
+    return [
+        ino
+        for library in find_files(("libraries/*",))
+        if library.is_dir() and not (library / ".git").exists()
+        for ino in library.rglob("**/*.ino")
+    ]
+
+
+FILES_PRESETS = {
+    "core": find_core_files,
+    "arduino": find_arduino_files,
+}
+
+
+@dataclass
+class Changed:
+    file: str
+    hunk: list[str]
+    lines: list[int]
+
+
+class Context:
+    def __init__(self):
+        self.append_hunk = False
+        self.deleted = False
+        self.file = ""
+        self.hunk = []
+        self.markers = []
+
+    def reset(self):
+        self.__init__()
+
+    def reset_with_line(self, line):
+        self.reset()
+        self.hunk.append(line)
+
+    def pop(self, out, line):
+        if self.file and self.hunk and self.markers:
+            out.append(
+                Changed(file=self.file, hunk="\n".join(self.hunk), lines=self.markers)
+            )
+
+        self.reset_with_line(line)
+
+
+def changed_files():
+    """
+    Naive git-diff output parser. Generates list[Changed] for every file changed after clang-format.
+    """
+    proc = subprocess.run(
+        ["git", "--no-pager", "diff"],
+        capture_output=True,
+        check=True,
+        universal_newlines=True,
+    )
+
+    ctx = Context()
+    out = []
+
+    # TODO: pygit2?
+    # ref. https://github.com/cpp-linter/cpp-linter/blob/main/cpp_linter/git/__init__.py ::parse_diff
+    # ref. https://github.com/libgit2/pygit2/blob/master/src/diff.c ::parse_diff
+    for line in proc.stdout.split("\n"):
+        # '--- a/path/to/changed/file' most likely
+        # '--- a/dev/null' aka created file. should be ignored, same as removed ones
+        if line.startswith("---"):
+            ctx.pop(out, line)
+            ctx.deleted = "/dev/null" in file
+
+        # '+++ b/path/to/changed/file' most likely
+        # '+++ /dev/null' aka removed file
+        elif not ctx.deleted and line.startswith("+++"):
+            ctx.hunk.append(line)
+
+            _, file = line.split(" ")
+            ctx.deleted = "/dev/null" in file
+            if not ctx.deleted:
+                ctx.file = file[2:]
+
+        # @@ from-file-line-numbers to-file-line-numbers @@
+        elif not ctx.deleted and line.startswith("@@"):
+            ctx.hunk.append(line)
+
+            _, _, numbers, _ = line.split(" ", 3)
+            if "," in numbers:
+                numbers, _ = numbers.split(",")  # drop count
+
+            numbers = numbers.replace("+", "")
+            numbers = numbers.replace("-", "")
+
+            ctx.markers.append(int(numbers))
+            ctx.append_hunk = True
+
+        # capture diff for the summary
+        elif ctx.append_hunk and line.startswith(("+", "-", " ")):
+            ctx.hunk.append(line)
+
+    ctx.pop(out, line)
+
+    return out
+
+
+def errors_changed(changed: Changed):
+    all_lines = ", ".join(str(x) for x in changed.lines)
+    for line in changed.lines:
+        print(
+            f"::error file={changed.file},title=Run tests/restyle.sh and re-commit {changed.file},line={line}::File {changed.file} failed clang-format style check. (lines {all_lines})"
+        )
+
+
+SUMMARY_PATH = pathlib.Path(os.environ.get("GITHUB_STEP_SUMMARY", os.devnull))
+SUMMARY_OUTPUT = SUMMARY_PATH.open("a")
+
+
+def summary_diff(changed: Changed):
+    with contextlib.redirect_stdout(SUMMARY_OUTPUT):
+        print(f"# {changed.file} (suggested change)")
+        print("```diff")
+        print(changed.hunk)
+        print("```")
+
+
+def stdout_diff():
+    subprocess.run(["git", "--no-pager", "diff"])
+
+
+def assert_unchanged():
+    subprocess.run(
+        ["git", "diff", "--exit-code"], check=True, stdout=subprocess.DEVNULL
+    )
+
+
+def run_format(args):
+    targets = []
+
+    for include in args.include:
+        targets.append(
+            (GIT_ROOT / f"tests/clang-format-{include}.yaml", FILES_PRESETS[include]())
+        )
+
+    if not targets:
+        targets.append((args.config, args.files))
+
+    for target in targets:
+        clang_format(args.clang_format, *target)
+
+
+def run_assert(args):
+    for changed in changed_files():
+        if args.with_errors:
+            errors_changed(changed)
+        if args.with_summary:
+            summary_diff(changed)
+
+    if args.with_diff:
+        stdout_diff()
+
+    assert_unchanged()
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+
+    cmd = parser.add_subparsers(required=True)
+    format_ = cmd.add_parser("format")
+    format_.set_defaults(func=run_format)
+    format_.add_argument("--clang-format", default="clang-format")
+
+    fmt = format_.add_subparsers(required=True)
+
+    preset = fmt.add_parser("preset")
+    preset.add_argument(
+        "--include", action="append", required=True, choices=tuple(FILES_PRESETS.keys())
+    )
+
+    files = fmt.add_parser("files")
+    files.add_argument("--config", type=pathlib.Path, required=True)
+    files.add_argument("files", type=pathlib.Path, nargs="+")
+
+    assert_ = cmd.add_parser("assert")
+    assert_.set_defaults(func=run_assert)
+    assert_.add_argument("--with-diff", action="store_true")
+    assert_.add_argument("--with-errors", action="store_true")
+    assert_.add_argument("--with-summary", action="store_true")
+
+    args = parser.parse_args()
+    args.func(args)
diff --git a/tests/restyle.sh b/tests/restyle.sh
index ce8e906a76..6e10cab6a2 100755
--- a/tests/restyle.sh
+++ b/tests/restyle.sh
@@ -1,5 +1,5 @@
 #!/bin/sh
-# requires clang-format, git, python3 with pyyaml
+# requires python3, git, and runnable clang-format (specified below)
 
 set -e -x
 
@@ -11,51 +11,13 @@ test -d ${root}/libraries
 # default to v15, latest stable version from ubuntu-latest Github Actions image
 CLANG_FORMAT=${CLANG_FORMAT:-clang-format-15}
 
-#########################################
-# 'all' variable should be "cores/esp8266 libraries"
-
-all=${1:-"
-cores/esp8266/Lwip*
-libraries/ESP8266mDNS
-libraries/Wire
-libraries/lwIP*
-cores/esp8266/debug*
-cores/esp8266/core_esp8266_si2c.cpp
-cores/esp8266/StreamString.*
-cores/esp8266/StreamSend.*
-libraries/Netdump
-tests
-"}
-
-#########################################
-# restyling core & libraries
-
 cd $root
-
-style=${root}/tests/clang-format-core.yaml
-for target in $all; do
-    if [ -d "$target" ]; then
-        find $target \
-            '(' -name "*.cpp" -o -name "*.c" -o -name "*.h" ')' \
-            -exec $CLANG_FORMAT --verbose --style="file:$style" -i {} \;
-    else
-        $CLANG_FORMAT --verbose --style="file:$style" -i $target
-    fi
-done
-
-#########################################
-# restyling arduino examples
-
-# TODO should not be matched, these are formatted externally
-# exclude=$(git submodule --quiet foreach git rev-parse --show-toplevel | grep libraries)
-
-if [ -z $1 ] ; then
-    style=${root}/tests/clang-format-arduino.yaml
-    find libraries \
-        -path libraries/ESP8266SdFat -prune -o \
-        -path libraries/Ethernet -prune -o \
-        -path libraries/SoftwareSerial -prune -o \
-        -name '*.ino' -exec $CLANG_FORMAT --verbose --style="file:$style" -i {} \;
+python $root/tests/restyle.py format --clang-format=$CLANG_FORMAT preset --include core --include arduino
+
+if [ $CI = "true" ] ; then
+    echo foo
+    python $root/tests/restyle.py assert --with-summary --with-errors
+else
+    echo bar
+    python $root/tests/restyle.py assert --with-diff
 fi
-
-#########################################