Repair standalone and historical-role fixtures after repository binding

docs/research/git-repository-root-binding.md

@@ -7,6 +7,32 @@ directory, including an ordinary linked worktree's `.git` file. Existing
 stored-object checks still disable replacement refs. Parent-process and
 package-verifier environments are unchanged.
 
+## Hosted validation limitation
+
+PR #5102 introduces working-source drift for the frozen
+`research/isolated-descendant-bytecode` package: its `SOURCES.json` still pins
+`scripts/check_research_commit.py` as an input, while this change updates that
+checker. The current package's `--check-only` therefore rejects with
+`working source drift: scripts/check_research_commit.py`. This is introduced
+by this PR, not a pre-existing failure. Its frozen package, pins and replay
+policy remain unchanged; this tooling repair does not establish a green
+historical scientific replay.
+
+The first hosted plan run (39932040857, job120342425789) reported eight test
+failures. One standalone cp1252 overlap fixture omitted the new shared-helper
+dependency; it now copies that dependency. Seven source-role assertions were
+masked by the unrelated checker drift. Their disposable fixture now restores
+the exact manifest-pinned checker blob, so they continue to test the intended
+`research_package.py` and source-history-test role transitions, including
+corrupt pins and unrelated input drift. This test setup correction does not
+change the actual frozen package's rejection described above.
+
+The affected 37 tests pass under normal and optimized Python after this fixture
+follow-up (10 descendant-role and 27 onboarding methods in each mode). The
+hosted planner command completes with 2,939 packages in 12 batches. The entire
+408-test hosted suite and those scientific replay batches were not rerun
+locally; hosted results remain separate from this targeted validation.
+
 ## Reproduced failure
 
 At canonical base `81e9bd69e4a5b00ba9c713a1620e36d576d5522e`, two real

tests/test_research_descendant_source_roles.py

@@ -39,6 +39,12 @@ def setUp(self):
             target = self.root / name
             target.parent.mkdir(parents=True, exist_ok=True)
             shutil.copyfile(ROOT / name, target)
+        # These tests vary HELPER/HISTORY_TEST source roles. Keep the unrelated
+        # checker input at this package's authenticated historical bytes; a live
+        # checker successor otherwise masks the predicate each test exercises.
+        checker = 'scripts/check_research_commit.py'
+        row = next(row for row in self.original['files'] if row['path'] == checker)
+        (self.root / checker).write_bytes(git(ROOT, 'cat-file', 'blob', row['git_blob']))
         git(self.root, 'init', '-q')
         objects = Path(git(ROOT, 'rev-parse', '--git-path', 'objects').decode().strip())
         if not objects.is_absolute():

tests/test_research_onboarding.py

@@ -37,6 +37,8 @@ def test_report_survives_a_cp1252_stdout(self):
             script = root / "scripts/find_overlap.py"
             script.parent.mkdir(parents=True)
             script.write_bytes((ROOT / "scripts/find_overlap.py").read_bytes())
+            (script.parent / "research_package.py").write_bytes(
+                (ROOT / "scripts/research_package.py").read_bytes())
             readme = root / "research/fixture/README.md"
             readme.parent.mkdir(parents=True)
             readme.write_text("Fixture contains κ", encoding="utf-8")