Found live 2026-07-04 while verifying #2435 (bti_data persistence): a real Cian
offer page (200 OK, 595KB) parsed fine via extract_state() (which already tries
.concat() first, .push() as fallback per the #639 2026-05 format drift), but
extract_all_states() returned {} — it only ever scanned the legacy .push()
pattern via _RE_CIAN_PUSH, never updated when .concat() became the live format.
This silently starved both of its consumers of real data on every current-format
page: cian/detail.py's bti sister-state (the exact gap #2435 built persistence
for, which could never receive data) and cian/newbuilding.py's sister-state
extraction. Confirmed via live re-fetch after the fix: extract_all_states() now
returns 6 real MFE containers instead of an empty dict.
No test file previously existed for cian_state_parser.py (a stale .pyc from a
pre-scraper_kit-migration test was the only trace) — added tests/test_cian_state_parser.py
covering concat discovery, legacy push fallback, mixed-format precedence, and the
extract_state()/extract_all_states() consistency invariant that the bug violated.
Full backend suite: 2345 passed, 6 skipped, 1 pre-existing unrelated failure
(test_search_cache_hit, verified via git stash against clean main).
Refs #2435
