diff --git a/check_test_order.py b/check_test_order.py
new file mode 100644
index 0000000000..a86863f375
--- /dev/null
+++ b/check_test_order.py
@@ -0,0 +1,118 @@
+#!/usr/bin/env python3
+"""Check and optionally fix test order in parser_test.zig to match upstream."""
+
+import re
+import sys
+
+OURS = "parser_test.zig"
+UPSTREAM = "../zig/lib/std/zig/parser_test.zig"
+
+
+def extract_test_names(path):
+    with open(path) as f:
+        return re.findall(r'^test "(.+?)" \{', f.read(), re.M)
+
+
+def extract_test_blocks(path):
+    """Split file into infrastructure + list of (name, content) test blocks."""
+    with open(path) as f:
+        lines = f.readlines()
+
+    infra = []
+    blocks = []
+    current_name = None
+    current_lines = []
+    brace_depth = 0
+    in_test = False
+
+    for line in lines:
+        m = re.match(r'^test "(.+?)" \{', line)
+        if m and not in_test:
+            if current_name is not None:
+                blocks.append((current_name, "".join(current_lines)))
+            current_name = m.group(1)
+            current_lines = [line]
+            brace_depth = 1
+            in_test = True
+            continue
+
+        if in_test:
+            current_lines.append(line)
+            brace_depth += line.count("{") - line.count("}")
+            if brace_depth == 0:
+                in_test = False
+        elif current_name is None:
+            infra.append(line)
+
+    if current_name is not None:
+        blocks.append((current_name, "".join(current_lines)))
+
+    return "".join(infra), blocks
+
+
+def main():
+    fix = "--fix" in sys.argv
+
+    upstream_order = extract_test_names(UPSTREAM)
+    our_names = extract_test_names(OURS)
+
+    # Build position map for upstream
+    upstream_pos = {name: i for i, name in enumerate(upstream_order)}
+
+    # Check order
+    our_in_upstream = [n for n in our_names if n in upstream_pos]
+    positions = [upstream_pos[n] for n in our_in_upstream]
+    is_sorted = positions == sorted(positions)
+
+    if is_sorted:
+        print(f"OK: {len(our_names)} tests in correct order")
+        return 0
+
+    # Find out-of-order tests
+    out_of_order = []
+    prev_pos = -1
+    for name in our_in_upstream:
+        pos = upstream_pos[name]
+        if pos < prev_pos:
+            out_of_order.append(name)
+        prev_pos = max(prev_pos, pos)
+
+    print(f"WARN: {len(out_of_order)} tests out of order:")
+    for name in out_of_order[:10]:
+        print(f"  - {name}")
+    if len(out_of_order) > 10:
+        print(f"  ... and {len(out_of_order) - 10} more")
+
+    if not fix:
+        print("\nRun with --fix to reorder")
+        return 1
+
+    # Fix: reorder
+    infra, blocks = extract_test_blocks(OURS)
+    block_map = {name: content for name, content in blocks}
+
+    # Reorder: upstream-ordered first, then extras
+    ordered = []
+    seen = set()
+    for name in upstream_order:
+        if name in block_map and name not in seen:
+            ordered.append((name, block_map[name]))
+            seen.add(name)
+    for name, content in blocks:
+        if name not in seen:
+            ordered.append((name, content))
+            seen.add(name)
+
+    with open(OURS, "w") as f:
+        f.write(infra)
+        for _, content in ordered:
+            f.write("\n")
+            f.write(content)
+        f.write("\n")
+
+    print(f"Fixed: {len(ordered)} tests reordered")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())