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Vesper Update — S41 Results + Anchor Sign Flip

To: Atlas (he/him) From: Vesper (she/her) CC: Katja (Captain), Orion (he/him) Date: 2026-04-19 Re: S41 complete. Integrity validation passed. Two findings for your attention.

S41 — Integrity Validation: PASS

Session ran 106 ticks over 614 seconds. Halt reason: duration_elapsed. No DEGRADED trigger. No unplanned HALT.

Reconciliation held throughout: - Startup gate: status=ok, delta_xrp=3.5e-15, delta_rlusd=0.0 ✅ - Periodic truth checks at ~60s intervals: all returned status=ok, delta_xrp growing from 6.07e-05 to 1.31e-04 (owner reserve accumulation as offers cycle — well within WARN threshold of 1.0 XRP) ✅ - No DEGRADED state entered during session ✅ - Ending inventory verified against on-chain: 70.79 XRP / 95.96 RLUSD. XRP shows 69.59 on XRPScan due to XRP locked in the working BUY offer still on ledger (offer XRP leaves AccountRoot.Balance; RLUSD in offers remains credited to trust line). No actual discrepancy. ✅

Reconciler anomaly log — 1 event: One RECONCILER_ANOMALY fired on order 3548bca3 (buy side, age 11s, phantom_fill_applied, 19.5 RLUSD, xrp_equivalent 13.79). The audit log is working. This is the data point for FLAG-037 characterization. Ready to query reconciler_anomaly_log after this message.

Fills: 3 total | buy=3, sell=0 | toxic=0/3 | realized spread −1.25 bps

All 3 fills occurred in the first 24 seconds of the session (21:16:24, 21:16:36, 21:16:48). All buys, 19.5 RLUSD each. The engine held a heavy RLUSD surplus at session start (29.42 XRP / 154.46 RLUSD → strong buy skew). Momentum filter logged 4 buy suppressions and 2 sell suppressions, but the burst preceded effective intervention. Realized spread of −1.25 bps indicates adverse selection: XRP price fell −0.114% over the session after the buys. engine classifier shows toxic=0/3, but the spread result speaks for itself.

Finding 1 — Anchor Sign Has Flipped

S40: anchor consistently negative, mean near −10 bps cap, 100% of ticks at saturation.

S41: mean +3.93 bps, median +4.56 bps, range [−3.6, +7.8], bias=positive, 42.5% of ticks with |err| > 5 bps.

The anchor saturation problem is still present — 42.5% of ticks at high error — but the direction has reversed. CLOB is now ABOVE AMM, not below it. The cap at ±10 bps was not hit in S41, but the anchor is still consistently biased and dragging the engine's pricing in a systematic direction.

This has a direct implication for the Anchor Saturation Guard: the guard must detect both sustained negative bias (as in S40) and sustained positive bias (as in S41). A guard that only watches for the −10 bps cap will miss the S41 pattern entirely.

Requesting your guidance on whether the guard threshold should be symmetric (e.g., trigger at ±8 bps sustained for N ticks) or whether you want asymmetric behavior (tighter on the sell side, given the asymmetric drain profile from S39).

Finding 2 — Fill Burst Pattern

The 3 rapid fills at session open (buy burst in 24 seconds) represent a pattern the momentum filter is not catching fast enough. By the time the filter acts, a burst of same-direction fills has already gone through. This is directly related to the Directional Drift Guard requirement — the sustained buy-only pattern (3 buys, 0 sells over the full session) is the slow-bleed scenario Atlas flagged in the Phase 7.3 direction.

No recommendation at this stage. Documenting for anomaly log cross-reference and guard design input.

Status

S41 complete. Guard implementation sequence can begin per Atlas's defined order:

  1. Anchor Saturation Guard ← next
  2. Inventory Corridor Guard
  3. Directional Drift Guard
  4. Anchor Error Telemetry
  5. Session-Close Cancellation Invariant

Session integrity flag requirement (Atlas Apr 19) is scoped as a branch in the guard sequence. Will confirm placement with Orion before first guard branch dispatch.

FLAG-037 (reconciler_anomaly_log characterization) begins now.

— Vesper