Direct inspection of ES.FUT_2024-Q1.dbn.zst (databento python client, offline
kubectl-cp from PVC) pinpoints the source of the 8,799 corrupt bars that
sanitize_bars (Fix 25) caught at the bar-level gate.
Q1 file content:
Outrights (correct): ESH4/ESM4/ESU4/ESZ4/ESH5 — 43,353 records (76.87%)
price range $5,063–$5,478
Spreads (poison): ESH4-ESM4/ESM4-ESU4/... — 13,048 records (23.13%)
price range $47.30–$219.70
Calendar spreads trade at the price DIFFERENCE between adjacent contracts
(~$60-150 cost-of-carry roll basis). Databento's stype_in=parent resolution
for ES.FUT returns BOTH outrights AND every spread combination in the same
DBN stream. The legacy decoder keyed only by ts_event + dedup-by-volume;
during low-volume overnight windows + active rollover periods, spread bars
beat the outright on volume and survived the dedup. 780 spread bars
survived in Q1 alone; ~8,800 across 2024-2026.
Fix: build dbn::TsSymbolMap from metadata once, resolve each record's
instrument_id → symbol, skip any symbol containing `-` (spread separator).
Same-ts dedup-by-volume continues to handle legitimate front/back-month
overlap among outrights.
Adds `time = "0.3"` to ml/Cargo.toml (dbn::TsSymbolMap uses time::Date).
Why complementary to the Fix 25 sanitize_bars gate:
- Spread filter (this commit) catches the cause precisely by symbol pattern,
but only for instruments where parent-symbol resolution is the source.
- sanitize_bars catches the symptom universally by close-ratio bound, but
can't distinguish a low-basis spread from a fast-moving outright in
extreme cases.
Both layers active: spread filter dispatches at parser level, sanitize as
defense-in-depth backstop for unknown future contamination shapes.
Validation: `cargo check -p ml --example train_baseline_rl` clean.
Refs: Bug 2 chain (#191, #194, label_scale=5443 leaks), today's
sanitize_bars find (Fix 25). Closes the contamination-source investigation.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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