`summarize_background_review_actions` was structured on the assumption
that every parsed tool response is a fully-typed dict-of-fields. In
practice the memory/skill tools — and their wrappers over Mem0 OSS and
the skill_manage MCP server — sometimes serialize `_change` as a list
or scalar, and clamp `operations` to a single string when the field
came in via a partial JSON bridge.
The original code did the equivalent of:
change = data.get("_change", {})
change.get("description", "")
so when `_change` was a list the inner .get crashed with
`AttributeError: 'list' object has no attribute 'get'`, every ~10
turns the user saw the entire background review collapse.
Three defensive guards in summarize_background_review_actions:
- `call_details.get(tcid, {})` → `call_details.get(tcid) or {}` plus
`isinstance(detail, dict)` coercion. Catches stale scalar/None
values when a fork inherits partial state from a stale tool_call_id.
- `operations = detail.get("operations") or []` → `isinstance(ops_raw, list)`
coerce, then per-entry isinstance check before `.get()`. Skips
non-dict items without raising; an entire surrounding review no
longer goes down because one entry was malformed.
- `change = data.get("_change", {})` → `isinstance(change_raw, dict)`
coerce. The originally-reported crash class for skill_manage with
list-shaped _change now falls through to the generic summary path.
And the caller in `_run_review_in_thread` is wrapped in a try/except
that maps any residual summarize exception to `actions = []` and
emits a 'partial results' warning, so even an entirely unanticipated
shape won't take down the outer review — the user only sees
'Background memory/skill review failed' instead of the prior hard
crash that lost every successful action the fork had completed.
Tests: tests/test_background_review_list_shapes.py — standalone
pytest-free runner, 7/7 PASS:
a_change_as_list_does_not_crash (originally-reported shape)
a_change_as_int_does_not_crash (scalar fallback)
b_operations_as_string_treated_as_empty
b_operations_as_none_treated_as_empty
c_operations_contains_non_dict_entries (verbose-mode per-entry filter)
d_detail_non_dict_replaced_with_empty
e_call_defends_via_try_except (structural anchor)
Refs NousResearch/hermes-agent#59437
