diff --git a/scripts/rpmsetinit/compare_random_sets.py b/scripts/rpmsetinit/compare_random_sets.py
new file mode 100755
index 0000000..23afebc
--- /dev/null
+++ b/scripts/rpmsetinit/compare_random_sets.py
@@ -0,0 +1,125 @@
+#!/usr/bin/env python3
+"""Continuously compare set strings produced by set.c and newset.c."""
+
+from __future__ import annotations
+
+import random
+import shlex
+import subprocess
+import tempfile
+import time
+from pathlib import Path
+
+# Test parameters. Edit these constants directly; the script has no CLI options.
+MAX_N = 1_000
+MAX_M = 100
+BPP = 31
+ALPHABET = ".0123456789@ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz"
+CC = "cc"
+CFLAGS = ("-O2", "-std=gnu11", "-D_GNU_SOURCE")
+
+SCRIPT_DIR = Path(__file__).resolve().parent
+REPO_ROOT = SCRIPT_DIR.parent.parent
+OLD_SET_SOURCE = REPO_ROOT / "set.c"
+NEW_SET_SOURCE = REPO_ROOT / "reimplement" / "newset.c"
+MKSET_SOURCE = SCRIPT_DIR / "mkset.c"
+COMPAT_HEADER = SCRIPT_DIR / "newset_compat.h"
+ERROR_DIR = SCRIPT_DIR / "error"
+
+SET_HEADER = """\
+#ifndef ARSV_SET_H
+#define ARSV_SET_H
+
+struct set;
+struct set *set_new(void);
+void set_add(struct set *set, const char *symbol);
+const char *set_fini(struct set *set, int bpp);
+
+#endif
+"""
+
+
+def build_mkset(source: Path, output: Path, build_dir: Path) -> None:
+    command = [
+        CC,
+        *CFLAGS,
+        f"-I{build_dir}",
+        "-include",
+        str(COMPAT_HEADER),
+        str(source),
+        str(MKSET_SOURCE),
+        "-o",
+        str(output),
+    ]
+    completed = subprocess.run(command, text=True, capture_output=True)
+    if completed.returncode != 0:
+        raise RuntimeError(
+            f"Compilation failed: {shlex.join(command)}\n{completed.stderr}"
+        )
+
+
+def run_mkset(binary: Path, input_path: Path) -> str:
+    with input_path.open("r", encoding="ascii") as input_file:
+        completed = subprocess.run(
+            [str(binary), str(BPP)],
+            stdin=input_file,
+            text=True,
+            capture_output=True,
+        )
+    if completed.returncode != 0:
+        raise RuntimeError(
+            f"{binary.name} failed with code {completed.returncode}:\n"
+            f"{completed.stderr}"
+        )
+    return completed.stdout.strip()
+
+
+def generate_input(path: Path, n: int, m: int) -> None:
+    with path.open("w", encoding="ascii") as output:
+        for _ in range(n):
+            output.write("".join(random.choices(ALPHABET, k=m)))
+            output.write("\n")
+
+
+def main() -> None:
+    if MAX_N < 1 or MAX_M < 1:
+        raise ValueError("MAX_N and MAX_M must be at least 1")
+    if not 10 <= BPP <= 32:
+        raise ValueError("BPP must be in the range 10..32")
+
+    ERROR_DIR.mkdir(parents=True, exist_ok=True)
+
+    with tempfile.TemporaryDirectory(prefix="arsv-rpmsetinit-") as temporary:
+        build_dir = Path(temporary)
+        (build_dir / "rpmlib.h").touch()
+        (build_dir / "system.h").touch()
+        (build_dir / "set.h").write_text(SET_HEADER, encoding="ascii")
+
+        mkset = build_dir / "mkset"
+        mkset_new = build_dir / "mkset_new"
+        input_path = build_dir / "input.txt"
+
+        build_mkset(OLD_SET_SOURCE, mkset, build_dir)
+        build_mkset(NEW_SET_SOURCE, mkset_new, build_dir)
+
+        tests_completed = 0
+        while True:
+            n = random.randint(1, MAX_N)
+            m = random.randint(1, MAX_M)
+            print(f"tests={tests_completed} n={n} m={m}", flush=True)
+
+            generate_input(input_path, n, m)
+            new_result = run_mkset(mkset_new, input_path)
+            old_result = run_mkset(mkset, input_path)
+
+            tests_completed += 1
+            if new_result != old_result:
+                error_path = ERROR_DIR / (
+                    f"test_{tests_completed}_n{n}_m{m}_{time.time_ns()}.txt"
+                )
+                error_path.write_bytes(input_path.read_bytes())
+                print(f"mismatch: saved input to {error_path}", flush=True)
+
+
+if __name__ == "__main__":
+    main()