## Two architectural cleanups, both surfaced by the wgdc8 experiment
### Part 1: volume_bar_size in cache key
Mirrors the imbalance_bar_threshold/ewma_alpha fix from `f7718b376`. The
volume bar size constant (100 contracts/bar) was previously hardcoded and
not in the fxcache key. Tuning it would have hit the same fossilization
bug as imbalance_bar_threshold did pre-fix.
Changes:
- `Hyperparams.volume_bar_size: u64` field added (default 100, matches
`DEFAULT_VOLUME_BAR_SIZE` for backwards compat).
- TrainingProfile loader reads `volume_bar_size` TOML key.
- `calculate_dbn_cache_key_full` signature 7 → 8 args. Hashed via
`to_le_bytes()`. Test `test_cache_key_includes_volume_bar_size`
added; passes alongside the 5 existing tests.
- 4 callers updated atomically (per `feedback_no_partial_refactor`):
`discover_and_load`, `data_loading.rs:146`, `train_baseline_rl.rs:599`,
`precompute_features.rs:259,720`.
- `data_loading.rs:279` now passes `self.hyperparams.volume_bar_size`
to `build_volume_bars` instead of the hardcoded `DEFAULT_VOLUME_BAR_SIZE`.
- New `--volume-bar-size` CLI arg on both binaries (default 100).
- New Argo workflow params `volume-bar-size` (default "100") and
`data-source` (default "mbp10") on both `train-template.yaml` and
`train-multi-seed-template.yaml`. Threaded into precompute + trainer
invocations.
- `scripts/argo-train.sh` exposes `--volume-bar-size <n>` and
`--data-source <s>` for ad-hoc overrides.
### Part 2: OFI front-month filter (latent bug fix)
`crates/ml/examples/precompute_features.rs:539-557` (the OFI/VPIN/Kyle's
Lambda computation branch when MBP-10 + trades data is available) was
loading trades unfiltered for per-bar microstructure feature computation.
The volume bar formation path filters front-month per-file (line 354), but
the OFI path did not.
Effect pre-fix: during contract rollover windows (e.g., ESZ24 → ESH25),
OFI per-bar microstructure features included trades from BOTH contracts
simultaneously, distorting VPIN, Kyle's Lambda, and trade imbalance
signals. Severity in production: small (front-month dominates ES.FUT
volume by 10-100×) but real and present in every prior MBP-10+trades
production run.
Fix: mirror the per-file `filter_front_month` call from the volume bar
path. Volume bar formation and OFI computation now both see the same
in-month trade tape. Added log line shows raw vs filtered count per file
for transparency.
## Why bundled
Both fixes touch trade-data plumbing in `precompute_features.rs` and the
fxcache key contract. Per `feedback_no_partial_refactor`, related
architectural cleanups land atomically. Both surfaced from the same
wgdc8 audit; bundling avoids two cache-key-invalidating commits in
sequence (each would force full fxcache regen).
## Compatibility
- `volume_bar_size` defaults to 100 → existing wgdc7-equivalent runs
reproduce, but with a *new* fxcache key (the f7718b376-era cache file
is unreachable; harmless, can GC manually).
- OFI fix is strictly more correct; no opt-out needed. Existing models
trained on contaminated OFI features may show slight feature
distribution drift on first cache regen — expected, not a regression.
- `data_source = "ohlcv"` Argo param now possible; routes precompute
through volume bar branch directly. wgdc8 experiment uses this to test
bar resolution sensitivity at volume_bar_size=500 (5× DEFAULT).
Tests: 6/6 feature_cache tests pass. Workspace + examples compile clean.
Audit-doc: `docs/dqn-wire-up-audit.md` updated.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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