BacktestHarness::new(cfg, &dev, trunk) constructs a MultiHorizonLoader
(inference_only=true), captures the trunk's perception Graph A using
loader.peek_first() as the template, then allocates a LobSimCuda.
run() walks the chronological snapshot stream, calls apply_snapshot on
every event, and at decision-stride boundaries:
trunk.update_input_buffers(raw)
→ trunk.perception_forward_captured() → (probs[N_HORIZONS], proj)
→ sim.broadcast_alpha(&probs)
→ sim.step_decision(ts, target_vol, ann_factor, max_lots)
Returns RunStats { events_processed, decisions_taken }. The harness
deliberately accepts an externally-built CfcTrunk (random-init in v1)
because a checkpoint format isn't pinned in ml-alpha yet; when one
lands, the binary CLI (C9) can switch from new_random to load_checkpoint.
trainer_parity.rs Ring 1b — two ignored tests:
peek_first_byte_equal_across_modes
Verifies the Mbp10RawInput produced by the loader path used by the
backtest harness (inference_only=true) is BYTE-EQUAL to what the
trainer's loader (inference_only=false) produces from the same
source. Guards against any future refactor accidentally diverging
the two paths (e.g. someone special-casing inference path to skip
regime feature computation). All 50 f32 fields + scalars compared
via .to_bits() equality.
inference_iteration_matches_chronological_snapshots
Verifies next_inference_input() yields monotone-ts snapshots with
correct cur==prev semantics on the first read and prev_ts==prior_ts
afterwards.
Both tests skip gracefully when FOXHUNT_TEST_DATA fixtures lack
populated sidecars (the placeholder-empty bins committed in the
test_data/ tree).
GPU-side inference parity (probs[N_HORIZONS] bit-equal across loader
modes) is deferred until ml-alpha pins a checkpoint format and we have
a small checkpoint fixture to gate it on FOXHUNT_TEST_CKPT.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
a4127935a8