diff --git a/docs/research/research-package-guide.md b/docs/research/research-package-guide.md
index 4aea949036..9e0ae8fb87 100644
--- a/docs/research/research-package-guide.md
+++ b/docs/research/research-package-guide.md
@@ -95,6 +95,30 @@ Each gets a fresh runner and explicit commands. It does not run every historical
 `verify.py`. New hooks do not replace existing cold-replay obligations, and a
 passing metadata check is not acceptance of a mathematical result.
 
+## Check publication bytes
+
+After committing a package and before publishing it, optionally compare its
+working files and declared inputs with the exact commit:
+
+```sh
+python3 scripts/check_research_commit.py --package research/my-experiment
+# For a different publication commit:
+python3 scripts/check_research_commit.py --package research/my-experiment --ref COMMIT
+```
+
+Git attributes or clean filters can make a valid local source-hash receipt
+describe different bytes from those committed, even when `git diff` is empty.
+This read-only check compares raw bytes and reports missing, extra or changed
+files. It includes tracked and nonignored untracked package files plus the
+explicit `VERIFY.json` inputs, and rejects committed links/submodules.
+Ignored runtime files and undeclared external dependencies are outside scope.
+
+If a mismatch is intentional, use an explicitly documented source adapter;
+otherwise correct the working bytes or publication commit and rerun the
+affected verifier before regenerating its receipt. The preflight never changes
+files or normalizes scientific evidence. Passing it does not run the verifier,
+validate the mathematics, or establish equivalence to a hosted CI environment.
+
 ## Optional workflow feedback
 
 If something helped or obstructed the session, add a few sentences to your PR
diff --git a/scripts/check_research_commit.py b/scripts/check_research_commit.py
new file mode 100644
index 0000000000..20f0ebef09
--- /dev/null
+++ b/scripts/check_research_commit.py
@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+"""Compare package working bytes with a commit before publishing hash receipts.
+
+This is a byte-transport preflight, not a research verifier or CI-equivalence
+claim. Prepared for ywz65 with OpenAI Codex assistance. Apache-2.0.
+"""
+import argparse
+from contextlib import closing
+import hashlib
+import json
+from pathlib import Path
+import re
+import subprocess
+
+from research_package import canonical_relative_path, git, git_blobs, relative_file, require
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+def check(root, package, ref='HEAD'):
+    require(re.fullmatch(r'research/[a-z0-9][a-z0-9-]*', package), 'package must be research/<slug>')
+    manifest = json.loads(relative_file(root, package+'/VERIFY.json').read_text(encoding='utf-8'))
+    require(isinstance(manifest, dict), 'VERIFY.json must be an object')
+    inputs = manifest.get('inputs')
+    require(isinstance(inputs, list), 'declare input paths in VERIFY.json')
+    for name in inputs:
+        canonical_relative_path(name)
+    commit = git(root, 'rev-parse', '--verify', '--end-of-options', ref+'^{commit}').decode('ascii').strip()
+    # Literal pathspecs keep wildcard filenames from selecting other files.
+    records = git(root, '--literal-pathspecs', 'ls-tree', '-r', '-z', '--full-tree',
+                  commit, '--', package, *inputs).split(b'\0')
+    entries = {}
+    for record in records:
+        if not record:
+            continue
+        header, raw_name = record.split(b'\t', 1)
+        mode, kind, obj = header.split()
+        name = raw_name.decode('utf-8')
+        require(mode in (b'100644', b'100755') and kind == b'blob',
+                'commit contains a non-regular file: '+name)
+        entries[name] = obj.decode('ascii')
+    # New nonignored local checkers must not disappear from the publication.
+    local = git(root, '--literal-pathspecs', 'ls-files', '-c', '-o', '--exclude-standard',
+                '-z', '--', package).decode('utf-8').split('\0')
+    expected = {name for name in local if name} | set(inputs)
+    require(set(entries) == expected, 'working/commit file inventory differs: '+
+            ', '.join(sorted(set(entries) ^ expected)))
+    names = sorted(entries)
+    require(names, 'empty package inventory')
+    with closing(git_blobs(root, [entries[name] for name in names])) as blobs:
+        # Advance the blob iterator once past its last yield, so its final
+        # Git exit-status check runs before reporting success.
+        for (_, committed), name in zip(blobs, names):
+            working = relative_file(root, name).read_bytes()
+            require(working == committed,
+                    'working/commit bytes differ: '+name+' (working SHA256 '+
+                    hashlib.sha256(working).hexdigest()+', commit SHA256 '+
+                    hashlib.sha256(committed).hexdigest()+')')
+    return {'commit':commit, 'files':len(names), 'package':package}
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument('--package', required=True)
+    parser.add_argument('--ref', default='HEAD', help='commit to publish; default HEAD')
+    args = parser.parse_args()
+    try:
+        result = check(ROOT, args.package, args.ref)
+    except (OSError, ValueError, TypeError, subprocess.SubprocessError) as exc:
+        parser.exit(1, str(exc)+'\n')
+    print('PASS_RESEARCH_COMMIT_BYTES '+json.dumps(result))
+
+
+if __name__ == '__main__':
+    main()
diff --git a/tests/test_research_commit_bytes.py b/tests/test_research_commit_bytes.py
new file mode 100644
index 0000000000..3b367bfbc3
--- /dev/null
+++ b/tests/test_research_commit_bytes.py
@@ -0,0 +1,156 @@
+"""Actual Git object/working-tree controls for the publication byte preflight."""
+from pathlib import Path
+import json
+import subprocess
+import sys
+import tempfile
+import unittest
+from unittest.mock import patch
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT/'scripts'))
+import check_research_commit as checker
+sys.path.pop(0)
+
+
+class CommitBytesTests(unittest.TestCase):
+    def setUp(self):
+        self.tmp = tempfile.TemporaryDirectory()
+        self.addCleanup(self.tmp.cleanup)
+        self.root = Path(self.tmp.name)
+        self.package = 'research/fixture'
+        self.path = self.root/self.package
+        self.path.mkdir(parents=True)
+        self.git('init', '-q')
+        self.git('config', 'user.name', 'Fixture')
+        self.git('config', 'user.email', 'fixture@example.invalid')
+        self.git('config', 'core.autocrlf', 'false')
+        self.write('.gitattributes', b'*.lean text eol=lf\n')
+        self.write('research/fixture/VERIFY.json', b'{"inputs":["input.bin"]}\n')
+        self.write('research/fixture/Proof.lean', b'import Std\nexample : True := by trivial\n')
+        self.write('input.bin', b'\x00\r\n\xff')
+        self.commit()
+
+    def git(self, *args):
+        return subprocess.check_output(['git', *args], cwd=self.root, stderr=subprocess.PIPE)
+
+    def write(self, name, data):
+        path = self.root/name
+        path.parent.mkdir(parents=True, exist_ok=True)
+        path.write_bytes(data)
+
+    def commit(self):
+        self.git('add', '.')
+        self.git('commit', '-qm', 'fixture')
+        return self.git('rev-parse', 'HEAD').decode().strip()
+
+    def check(self, ref='HEAD'):
+        return checker.check(self.root, self.package, ref)
+
+    def test_exact_bytes_and_binary_input_pass(self):
+        self.assertEqual(self.check()['files'], 3)
+
+    def test_actual_git_normalization_is_detected_then_fixed(self):
+        path = self.path/'Proof.lean'
+        path.write_bytes(path.read_bytes().replace(b'\n', b'\r\n'))
+        self.git('add', '.')
+        # Git reports no change although a raw source-hash receipt would
+        # describe bytes different from those in a normal LF checkout.
+        self.assertEqual(self.git('diff', '--cached', '--name-only'), b'')
+        with self.assertRaisesRegex(ValueError, 'bytes differ.*Proof.lean'):
+            self.check()
+        path.write_bytes(path.read_bytes().replace(b'\r\n', b'\n'))
+        self.check()
+
+    def test_untracked_and_staged_new_files_are_not_in_commit(self):
+        self.write(self.package+'/helper.py', b'pass\n')
+        for staged in (False, True):
+            if staged:
+                self.git('add', '.')
+            with self.assertRaisesRegex(ValueError, 'inventory differs.*helper.py'):
+                self.check()
+        self.commit()
+        self.assertEqual(self.check()['files'], 4)
+
+    def test_input_drift_and_missing_working_file(self):
+        self.write('input.bin', b'changed')
+        with self.assertRaisesRegex(ValueError, 'bytes differ.*input.bin'):
+            self.check()
+        (self.root/'input.bin').unlink()
+        with self.assertRaisesRegex(ValueError, 'missing or external file'):
+            self.check()
+
+    def test_older_ref_and_deleted_package_file(self):
+        old = self.git('rev-parse', 'HEAD').decode().strip()
+        self.write(self.package+'/Proof.lean', b'import Std\n')
+        self.commit()
+        self.check()
+        with self.assertRaisesRegex(ValueError, 'bytes differ.*Proof.lean'):
+            self.check(old)
+        (self.path/'Proof.lean').unlink()
+        with self.assertRaisesRegex(ValueError, 'missing or external file'):
+            self.check()
+
+    def test_ignored_runtime_artifacts_are_outside_scope(self):
+        self.write('.gitignore', b'__pycache__/\n')
+        self.commit()
+        self.write(self.package+'/__pycache__/check.pyc', b'temporary')
+        self.assertEqual(self.check()['files'], 3)
+
+    def test_commit_symlink_is_rejected_without_following_it(self):
+        # Set Git mode directly: no Windows symlink privilege is required.
+        self.write(self.package+'/link', b'Proof.lean')
+        obj = self.git('hash-object', '-w', self.package+'/link').decode().strip()
+        self.git('update-index', '--add', '--cacheinfo', '120000', obj, self.package+'/link')
+        self.git('commit', '-qm', 'symbolic link')
+        with self.assertRaisesRegex(ValueError, 'non-regular file'):
+            self.check()
+
+    def test_invalid_package_and_missing_input_commit_reject(self):
+        with self.assertRaisesRegex(ValueError, 'package must'):
+            checker.check(self.root, '../outside')
+        self.write('new.bin', b'data')
+        self.write(self.package+'/VERIFY.json', b'{"inputs":["new.bin"]}\n')
+        with self.assertRaisesRegex(ValueError, 'inventory differs'):
+            self.check()
+
+    def test_unicode_and_wildcard_characters_are_literal_input_paths(self):
+        name = 'data/δ [α].bin'
+        self.write(name, b'exact')
+        self.write('data/δ α.bin', b'decoy')
+        self.write(self.package+'/VERIFY.json',
+                   json.dumps({'inputs':[name]}).encode('utf-8'))
+        self.commit()
+        self.assertEqual(self.check()['files'], 3)
+
+    def test_cli_pass_fail_and_read_only_behavior(self):
+        for name in ('check_research_commit.py', 'research_package.py'):
+            self.write('scripts/'+name, (ROOT/'scripts'/name).read_bytes())
+        self.commit()
+        script = self.root/'scripts/check_research_commit.py'
+        before = self.git('rev-parse', 'HEAD'), self.git('ls-files', '--stage', '-z')
+        command = [sys.executable, '-B', str(script), '--package', self.package]
+        good = subprocess.run(command, cwd=self.root, capture_output=True, timeout=30)
+        self.assertEqual(good.returncode, 0, good.stderr)
+        self.assertIn(b'PASS_RESEARCH_COMMIT_BYTES', good.stdout)
+        self.write('input.bin', b'drift')
+        bad = subprocess.run(command, cwd=self.root, capture_output=True, timeout=30)
+        self.assertEqual(bad.returncode, 1)
+        self.assertIn(b'working/commit bytes differ: input.bin', bad.stderr)
+        self.assertEqual(before, (self.git('rev-parse', 'HEAD'), self.git('ls-files', '--stage', '-z')))
+        self.assertEqual((self.root/'input.bin').read_bytes(), b'drift')
+
+    def test_blob_reader_final_failure_is_not_skipped(self):
+        original = checker.git_blobs
+
+        def failed_after_payloads(root, specs):
+            yield from original(root, specs)
+            raise ValueError('reader final exit failure')
+
+        with patch.object(checker, 'git_blobs', side_effect=failed_after_payloads):
+            with self.assertRaisesRegex(ValueError, 'reader final exit failure'):
+                self.check()
+
+
+if __name__ == '__main__':
+    unittest.main()