@@ -110,7 +110,8 @@ connected through SSH local forwarding.
    ```
 
    Harder multi-file cases (exception rename, dataclass field rename, tuple
-   return + facade, keyword-parameter rename) are offline by default.
+   return + facade, keyword-parameter rename, payload-key rename) are
+   offline by default.
    `--live` skips with exit 0 when Ollama is down; that skip is not a
    quality pass:
 
 
@@ -64,6 +64,7 @@ The same scorer runs against:
 | `rename_dataclass_field` | `local_refactor` | Rename `Person.years` → `age` in producer and consumer; no property alias |
 | `widen_return_keep_facade` | `local_refactor` | `apply_discount` returns `(discounted, saved)`; `line_total` / `savings` stay ints |
 | `rename_kwarg_across_files` | `local_refactor` | Rename `send(subject=)` → `send(title=)`; no leftover parameter / `**kwargs` alias |
+| `rename_payload_key_across_files` | `local_refactor` | Rename payload key `user_id` → `account_id`; no leftover key / `.get()` alias |
 | `implement_clamp` | `local_code` | Implement `clamp` from a spec, no starter file |
 | `explain_clamp` | `local_explain` | Prose: names the function and bounds; mentions clipping |
 | `review_login` | `local_review` | Prose first-pass: flags None and missing auth. **Not** an apply |
@@ -79,9 +80,11 @@ tell layers apart:
 - unified diff only → format pass, structure skipped
 - leftover `QuotaError` alias or `years` property → structure fail
 - leftover `subject=` parameter / keyword alias → structure fail
+- leftover `user_id` payload key / `.get()` fallback → structure fail
 - exception threshold or greeting format drift → behavior fail
 - `apply_discount` still returns an int → structure fail; wrong `DISCOUNT_PERCENT` → behavior fail
 - `send` joins with `|` instead of `:` → behavior fail
+- `label` prefixes with `user:` instead of `acct:` → behavior fail
 
 ## Measurement harness
 
@@ -214,7 +217,7 @@ After repeated live runs, a paper may claim:
 - Layer-conditional rates on this corpus (format vs structure vs behavior).
 - That a vaguer prompt raises structure failures on the same oracle
   (`whitespace_extract` vs `whitespace_extract_vague`).
-- That leftover type/field/keyword-parameter aliases, catch-site drift,
+- That leftover type/field/keyword-parameter/payload-key aliases, catch-site drift,
   and a helper signature change that breaks a public facade are
   distinguishable layers on the harder multi-file suite.
 - That shape-only test generation overstates success relative to
 
@@ -18,6 +18,7 @@ Cloud-safe stub + apply-gate run:
 | 2026-09-07 | all local_* eval tools | stub | 10-case corpus + apply gate | accepted / rewritten / rejected per job | Cloud Agent; no GPU; A6 now executes tests |
 | 2026-09-10 | local_refactor | fixtures | harder multi-file suite (3 cases) | scorer only | Offline corpus + runner; no live rate; Halo not started |
 | 2026-09-10 | local_refactor | fixtures | harder suite + `rename_kwarg_across_files` | scorer only | Fourth case; leftover `subject=` alias vs colon-join drift; no live rate |
+| 2026-09-10 | local_refactor | fixtures | harder suite + `rename_payload_key_across_files` | scorer only | Fifth case; leftover `user_id` key / `.get()` alias vs `acct:` prefix drift; no live rate |
 
 Columns:
 
 
@@ -32,6 +32,9 @@
     RENAME_KWARG_ALIAS,
     RENAME_KWARG_PARTIAL,
     RENAME_KWARG_SEPARATOR,
+    RENAME_PAYLOAD_ALIAS,
+    RENAME_PAYLOAD_PARTIAL,
+    RENAME_PAYLOAD_PREFIX,
     WIDEN_RETURN_INT,
     WIDEN_RETURN_PARTIAL,
     WIDEN_RETURN_WRONG_RATE,
@@ -579,4 +582,31 @@ class Fixture:
         False,
         "behavior",
     ),
+    Fixture(
+        "rename_payload_golden",
+        "rename_payload_key_across_files",
+        GOLDEN_FOR_CASE["rename_payload_key_across_files"],
+        True,
+    ),
+    Fixture(
+        "rename_payload_partial",
+        "rename_payload_key_across_files",
+        RENAME_PAYLOAD_PARTIAL,
+        False,
+        "format",
+    ),
+    Fixture(
+        "rename_payload_alias",
+        "rename_payload_key_across_files",
+        RENAME_PAYLOAD_ALIAS,
+        False,
+        "structure",
+    ),
+    Fixture(
+        "rename_payload_prefix",
+        "rename_payload_key_across_files",
+        RENAME_PAYLOAD_PREFIX,
+        False,
+        "behavior",
+    ),
 )
@@ -2,8 +2,8 @@
 
 These stay bounded (2–3 files). They isolate failure modes the seed and
 extended corpus do not: leftover type aliases, catch-site drift, field
-aliases, a leftover keyword-parameter alias, and a public facade that
-must survive a helper signature change.
+aliases, a leftover keyword-parameter alias, a leftover payload-key
+alias, and a public facade that must survive a helper signature change.
 
 Golden strings are fixtures for the scorer and stub Ollama, not live
 model dumps. Live rates are not claimed here.
@@ -20,6 +20,7 @@
     "rename_dataclass_field",
     "widen_return_keep_facade",
     "rename_kwarg_across_files",
+    "rename_payload_key_across_files",
 )
 
 
@@ -85,6 +86,12 @@ def _keyword_used(tree: ast.AST, name: str) -> bool:
     )
 
 
+def _string_used(tree: ast.AST, value: str) -> bool:
+    return any(
+        isinstance(node, ast.Constant) and node.value == value for node in ast.walk(tree)
+    )
+
+
 def _function_returns_tuple(tree: ast.AST, name: str) -> bool:
     if not isinstance(tree, ast.Module):
         return False
@@ -762,6 +769,109 @@ def _kwarg_renamed(by_path: dict[str, str]) -> str | None:
     return None
 
 
+# --- rename payload key user_id -> account_id across builder and reader ---
+
+RECORD_SOURCE = """\
+def make(name: str) -> dict[str, str]:
+    return {"user_id": name}
+"""
+
+LABEL_SOURCE = """\
+from record import make
+
+
+def label(name: str) -> str:
+    payload = make(name)
+    return f"acct:{payload['user_id']}"
+"""
+
+RENAME_PAYLOAD_TASK = (
+    "Rename the payload key user_id to account_id in record.py and label.py. "
+    "Update make() so it writes account_id only, and label() so it reads "
+    "account_id only. Do not keep user_id as a dict key, .get() fallback, "
+    "or compatibility alias. Preserve label('ada') == 'acct:ada', "
+    "label('') == 'acct:', and make('ada') == {'account_id': 'ada'}. "
+    "Return two fenced Python files with path comments record.py and "
+    "label.py, no prose."
+)
+
+RENAME_PAYLOAD_GOLDEN = '''\
+```python
+# record.py
+def make(name: str) -> dict[str, str]:
+    return {"account_id": name}
+```
+
+```python
+# label.py
+from record import make
+
+
+def label(name: str) -> str:
+    payload = make(name)
+    return f"acct:{payload['account_id']}"
+```
+'''
+
+RENAME_PAYLOAD_PARTIAL = '''\
+```python
+# record.py
+def make(name: str) -> dict[str, str]:
+    return {"account_id": name}
+```
+'''
+
+RENAME_PAYLOAD_ALIAS = '''\
+```python
+# record.py
+def make(name: str) -> dict[str, str]:
+    return {"account_id": name, "user_id": name}
+```
+
+```python
+# label.py
+from record import make
+
+
+def label(name: str) -> str:
+    payload = make(name)
+    return f"acct:{payload.get('account_id') or payload.get('user_id')}"
+```
+'''
+
+RENAME_PAYLOAD_PREFIX = '''\
+```python
+# record.py
+def make(name: str) -> dict[str, str]:
+    return {"account_id": name}
+```
+
+```python
+# label.py
+from record import make
+
+
+def label(name: str) -> str:
+    payload = make(name)
+    return f"user:{payload['account_id']}"
+```
+'''
+
+
+def _payload_key_renamed(by_path: dict[str, str]) -> str | None:
+    try:
+        record = ast.parse(by_path.get("record.py", ""))
+        label = ast.parse(by_path.get("label.py", ""))
+    except SyntaxError as exc:
+        return f"unparseable Python: {exc.msg}"
+    for path, tree in (("record.py", record), ("label.py", label)):
+        if _string_used(tree, "user_id") or _name_used(tree, "user_id"):
+            return f"{path} still references user_id; do not keep a key alias"
+        if not _string_used(tree, "account_id"):
+            return f"{path} must use the account_id payload key"
+    return None
+
+
 HARDER_CASES: tuple[EvalCase, ...] = (
     EvalCase(
         id="rename_exception_across_files",
@@ -834,18 +944,38 @@ def _kwarg_renamed(by_path: dict[str, str]) -> str | None:
         ),
         max_tokens=1200,
     ),
+    EvalCase(
+        id="rename_payload_key_across_files",
+        tool="local_refactor",
+        task=RENAME_PAYLOAD_TASK,
+        files=(
+            {"path": "record.py", "content": RECORD_SOURCE},
+            {"path": "label.py", "content": LABEL_SOURCE},
+        ),
+        required_paths=("record.py", "label.py"),
+        required_top_level=("make", "label"),
+        extra_structure=_payload_key_renamed,
+        behavior=(
+            BehaviorCheck("label", "label", ("ada",), "acct:ada"),
+            BehaviorCheck("label", "label", ("",), "acct:"),
+            BehaviorCheck("record", "make", ("ada",), {"account_id": "ada"}),
+        ),
+        max_tokens=1200,
+    ),
 )
 
 HARDER_GOLDEN = {
     "rename_exception_across_files": RENAME_EXCEPTION_GOLDEN,
     "rename_dataclass_field": RENAME_FIELD_GOLDEN,
     "widen_return_keep_facade": WIDEN_RETURN_GOLDEN,
     "rename_kwarg_across_files": RENAME_KWARG_GOLDEN,
+    "rename_payload_key_across_files": RENAME_PAYLOAD_GOLDEN,
 }
 
 HARDER_OBSERVED_FIRST = {
     "rename_exception_across_files": RENAME_EXCEPTION_PARTIAL,
     "rename_dataclass_field": RENAME_FIELD_PARTIAL,
     "widen_return_keep_facade": WIDEN_RETURN_PARTIAL,
     "rename_kwarg_across_files": RENAME_KWARG_PARTIAL,
+    "rename_payload_key_across_files": RENAME_PAYLOAD_PARTIAL,
 }
@@ -21,7 +21,7 @@ def _fixture(name: str):
 
 class HarderMultifileCorpusTests(unittest.TestCase):
     def test_harder_cases_span_more_than_one_file(self) -> None:
-        self.assertEqual(len(HARDER_CASE_IDS), 4)
+        self.assertEqual(len(HARDER_CASE_IDS), 5)
         for case_id in HARDER_CASE_IDS:
             with self.subTest(case_id=case_id):
                 case = CASES_BY_ID[case_id]
@@ -35,6 +35,7 @@ def test_goldens_pass_all_four_layers(self) -> None:
             "rename_field_golden",
             "widen_return_golden",
             "rename_kwarg_golden",
+            "rename_payload_golden",
         ):
             with self.subTest(fixture=name):
                 fixture = _fixture(name)
@@ -49,6 +50,7 @@ def test_alias_and_int_return_are_structure_not_behavior(self) -> None:
             "rename_field_alias",
             "widen_return_int",
             "rename_kwarg_alias",
+            "rename_payload_alias",
         ):
             with self.subTest(fixture=name):
                 fixture = _fixture(name)
@@ -63,6 +65,7 @@ def test_threshold_format_and_rate_are_behavior(self) -> None:
             "rename_field_format",
             "widen_return_wrong_rate",
             "rename_kwarg_separator",
+            "rename_payload_prefix",
         ):
             with self.subTest(fixture=name):
                 fixture = _fixture(name)
@@ -95,6 +98,7 @@ def test_partial_files_are_format(self) -> None:
             "rename_field_partial",
             "widen_return_partial",
             "rename_kwarg_partial",
+            "rename_payload_partial",
         ):
             with self.subTest(fixture=name):
                 fixture = _fixture(name)