diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e3113fd8880..3c666df08fd 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,7 +26,7 @@ jobs:
         run: |
           tools/ci/check_json.sh
           tools/ci/build_tgui.sh
-          tools/ci/check_grep.sh
+          python3 tools/ci/check_grep2.py
           python3 tools/ci/check_line_endings.py
           python3 tools/ci/check_file_names.py
           python3 tools/ci/unticked_files.py ${GITHUB_WORKSPACE}
diff --git a/tools/ci/check_grep2.py b/tools/ci/check_grep2.py
new file mode 100644
index 00000000000..6fbcbe6d4f1
--- /dev/null
+++ b/tools/ci/check_grep2.py
@@ -0,0 +1,132 @@
+import glob
+import re
+import os
+import sys
+import time
+from collections import namedtuple
+
+Failure = namedtuple("Failure", ["lineno", "message"])
+
+RED = "\033[0;31m"
+GREEN = "\033[0;32m"
+BLUE = "\033[0;34m"
+NC = "\033[0m"  # No Color
+
+IGNORE_515_PROC_MARKER_FILENAME = "__byond_version_compat.dm"
+CHECK_515_PROC_MARKER_RE = re.compile(r"\.proc/")
+def check_515_proc_syntax(lines):
+    for idx, line in enumerate(lines):
+        if CHECK_515_PROC_MARKER_RE.match(line):
+            return Failure(idx + 1, "Outdated proc reference use detected in code. Please use proc reference helpers.")
+
+
+CHECK_SPACE_INDENTATION_RE = re.compile(r"^ {2,}[^\*]")
+def check_space_indentation(lines):
+    """
+    Check specifically for space-significant indentation. Excludes dmdoc
+    block comment lines so long as there is an asterisk immediately after the
+    leading spaces.
+
+    >>> bool(check_space_indentation(["  foo"]))
+    True
+
+    >>> bool(check_space_indentation(["\\tfoo"]))
+    False
+    >>> bool(check_space_indentation(["  * foo"]))
+    False
+    """
+    for idx, line in enumerate(lines):
+        if CHECK_SPACE_INDENTATION_RE.match(line):
+            return Failure(idx + 1, "Space indentation detected, please use tab indentation.")
+
+
+CHECK_MIXED_INDENTATION_RE = re.compile(r"^(\t+ | +\t)\s*[^\s\*]")
+def check_mixed_indentation(lines):
+    """
+    Check specifically for leading whitespace which contains a mix of tab and
+    space characters. Excludes dmdoc block comment lines so long as there is an
+    asterisk immediately after the leading whitespace.
+
+    >>> bool(check_mixed_indentation(["\\t\\t foo"]))
+    True
+    >>> bool(check_mixed_indentation(["\\t \\t foo"]))
+    True
+    >>> bool(check_mixed_indentation(["\\t // foo"]))
+    True
+    >>> bool(check_mixed_indentation([" \\tfoo"]))
+    True
+    >>> bool(check_mixed_indentation(["  \\t  foo"]))
+    True
+
+    >>> bool(check_mixed_indentation(["\\t  * foo"]))
+    False
+    >>> bool(check_mixed_indentation(["\\t\\t* foo"]))
+    False
+    >>> bool(check_mixed_indentation(["\\t \\t  * foo"]))
+    False
+    """
+    for idx, line in enumerate(lines):
+        if CHECK_MIXED_INDENTATION_RE.match(line):
+            return Failure(idx + 1, "Mixed <tab><space> indentation detected, please stick to tab indentation.")
+
+
+def check_trailing_newlines(lines):
+    if not lines:
+        return
+
+    last_line = [x for x in lines][-1]
+    if not last_line.endswith("\n"):
+        return Failure(len(lines), "Missing a trailing newline")
+
+
+GLOBAL_VARS_RE = re.compile(r"^/*var/")
+def check_global_vars(lines):
+    for idx, line in enumerate(lines):
+        if GLOBAL_VARS_RE.match(line):
+            return Failure(idx + 1, "Unmanaged global var use detected in code, please use the helpers.")
+
+
+PROC_ARGS_WITH_VAR_PREFIX_RE = re.compile(r"^/[\w/]\S+\(.*(var/|, ?var/.*).*\)")
+def check_proc_args_with_var_prefix(lines):
+    for idx, line in enumerate(lines):
+        if PROC_ARGS_WITH_VAR_PREFIX_RE.match(line):
+            return Failure(idx + 1, "Changed files contains a proc argument starting with 'var'.")
+
+
+CODE_CHECKS = [
+    check_space_indentation,
+    check_mixed_indentation,
+    check_trailing_newlines,
+    check_global_vars,
+    check_proc_args_with_var_prefix,
+]
+
+
+if __name__ == "__main__":
+    print("check_grep2 started")
+
+    exit_code = 0
+    start = time.time()
+
+    for code_filepath in glob.glob("**/*.dm", recursive=True):
+        with open(code_filepath, encoding="UTF-8") as code:
+            filename = code_filepath.split(os.path.sep)[-1]
+            # 515 proc syntax check is unique in running on all files but one,
+            # but I'm not going to make some disproportionately generic "check"
+            # that also validates that the test should be run, so it just goes
+            # here.
+            if filename != IGNORE_515_PROC_MARKER_FILENAME:
+                if failure := check_515_proc_syntax(code):
+                    exit_code = 1
+                    print(f"{code_filepath}:{failure.lineno}: {RED}{failure.message}{NC}")
+
+            for check in CODE_CHECKS:
+                code.seek(0)
+                if failure := check(code):
+                    exit_code = 1
+                    print(f"{code_filepath}:{failure.lineno}: {RED}{failure.message}{NC}")
+
+    end = time.time()
+    print(f"\ncheck_grep2 tests completed in {end - start:.2f}s\n")
+
+    sys.exit(exit_code)