Yahoo's 2026 event-feed change (capitalGain events dropped for some
funds; no events at all for terminated tickers) can wipe good event
history on re-download. Defense in depth:
- overrides/event-backup/: last-known-good copy of every dividend/
capitalGain file (8,192 files, 58 MB); refresh with
scripts/backup_events.py after each dump update
- data.py event_file(): frozen > data-root (while populated) > backup;
used by panel reads, verify_official, and the double-listing scanner
- README: capital-gain files are mutual-fund-only in this dump; Yahoo
has no LT/ST split (tax.py taxes capg at lt_rate; the per-fund split
would come from fund-company annual tax statements or commercial feeds)
- tests: exact Timestamp .loc keys (pandas 3.x string matching returns a
Series on large DatetimeIndex)
Yahoo changed the shape of its event feed between downloads: a 2026-08
re-download of CVIX/JLPSX shows it no longer returns capitalGain events at
all (the dividend stream still carries the year-end rows), while stale
tickers now return no events at all. File-specific remove ops therefore
break silently on the next re-download, so the double-listing fix is now
expressed as layout-agnostic invariants applied at bundle assembly
(idempotent, hold for full and incremental builds):
dedup: [[date, amount]] keep at most one copy of a same-date/
same-amount cross-file pair (the capitalGain copy when both present)
drop_capg_copy: [date] the capitalGain row on that date is the
spurious copy of the dividend row
- data.py: apply_invariants() at bundle assembly + pure dedupe_event_rows()
shared with verify_official and tests (8 new test cases, 22 passing)
- JLPSX/CVSIX corrections rewritten with the invariants (2019-08-08 now
keeps the dividend amount per the verified same-date pattern)
- scripts/scan_double_listing.py: whole-dump sweep -> reports/double_listing/
6,421 symbols scanned: 1,218 with same-amount pairs (6,589), 1,631 with
differing-amount pairs (12,366, reported only - not distinguishable from
legitimate same-day div+capg without per-fund official data), 83 with
repeated within-file rows (ingest keep-last already collapses them)
- scripts/apply_dedup_corrections.py: bulk 'dedup' corrections for the
1,218 same-amount symbols (1,212 new files; the 6 verified funds keep
their explicit, official-verified corrections)
- scripts/check_corrections.py: integrity check for every correction op
against the actual (frozen) files - caught a mis-filed CVSIX entry
