fix(sp21): Return v3.1 — drop short-rollout guard for volume bars (atomic)

Single-file fix to `compute_epoch_financials`: remove the
`if n_returns_f >= bars_per_year` short-rollout fallback that
left v2 semantics in place for sub-year rollouts. For Foxhunt's
volume bars, `bars_per_day ≈ 34_496` → `bars_per_year ≈ 8.69M`,
while a training epoch produces `n_returns ≈ 4.10M`. The guard
fired on every production epoch, so the v3 CAGR fix was a no-op.

Diagnosis chain:
- v3 commit (2937da889) merged the n_returns >= bars_per_year guard
- Smoke v4 (commit 62b5a50e8, workflow train-frv8x) epoch 1 showed
  Return=+2.963e2% — bit-identical to v1's pre-fix output
- Hypothesis 1 (cache poisoning): ruled out — ensure-binary log
  shows "Cache MISS: compiling binaries for 62b5a50e8" and ml crate
  was recompiled fresh
- Hypothesis 2 (different commit): ruled out — workflow params confirm
  commit-sha = 62b5a50e8 = current HEAD
- Hypothesis 3 (bars_per_year mismatch): confirmed — v4 log emits
  "Bars per day (from data): 34496" which makes bars_per_year > n_returns
  and triggers the v2 fallback inside the v3 branch

Fix: unconditional CAGR. The log-space clamp [-23, +20] bounds
the display in all edge cases (tests with tiny n_returns
extrapolate aggressively; the clamp caps at exp(20) - 1 ≈ +4.85e8%).

Expected v5 epoch 1 Return: ~+1.770e3% (was +2.963e2% under v4).
The new value is the *actual annualized* projection: 1377% over
a 0.47-year rollout. Overfit cycles cap at +4.85e8% (was +e19%).

Tests:
- cargo test -p ml --lib financials → 7/7
- Sign-only assertions in test cases (all > 0.0) — no regressions

Files changed:
- crates/ml/src/trainers/dqn/financials.rs: 1 conditional removed,
  comment block updated with v3 → v3.1 history
- docs/dqn-wire-up-audit.md: diagnosis + fix entry for 2026-05-11

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/ml/src/trainers/dqn/financials.rs

@@ -80,13 +80,15 @@ pub(crate) fn compute_epoch_financials(
     // bars): annualized = exp(45.93 × 19_656 / 4_096_000) − 1 ≈ 24.7% —
     // a reasonable, interpretable number.
     //
-    // History (do not regress to either earlier form):
+    // History (do not regress to any earlier form):
     //   v1 (pre-2026-04): mean_per_bar × bars_per_year (arithmetic
     //       annualization) — produced -51,234% on negative per-bar means.
     //   v2 (2026-04..2026-05-11): log_growth.exp() − 1 (total compounded,
     //       no annualization) — produced +e19% on long rollouts.
-    //   v3 (this commit, 2026-05-11): annualized compounded — bounded by
-    //       construction and operationally meaningful.
+    //   v3 (2026-05-11): annualized compounded for n_returns >= bars_per_year,
+    //       fallback to v2 below it — but the fallback subsumed all production
+    //       runs on volume bars (bars_per_year ≈ 8.7M > n_returns ≈ 4.1M).
+    //   v3.1 (2026-05-11): unconditional CAGR — the clamp handles edge cases.
     //
     // Lower bound: -100% (log_growth.exp() − 1 ≥ -1 when log_growth ≥
     // log(1e-10) ≈ -23 per the per-bar clamp). Upper bound: practically
@@ -112,20 +114,25 @@ pub(crate) fn compute_epoch_financials(
         // annualization factor exceeds 1, which would extrapolate a
         // brief positive run to absurd annualized magnitudes (a 5-bar
         // test with 1.5% gain would annualize to e8% on 1-min bars).
-        // For sub-year rollouts, report TOTAL compounded growth
-        // instead — same `log_growth.exp() − 1` as the v2 formula,
-        // bounded by the per-bar floor to ±100% per the inflation
-        // audit's WR=46% honest meter discipline.
+        // **v3.1 (2026-05-11)**: dropped the `n_returns >= bars_per_year`
+        // short-rollout guard. The guard fell back to raw `log_growth`
+        // (= v2 formula) whenever the rollout was shorter than a trading
+        // year. For Foxhunt's volume bars the data extracts
+        // `bars_per_day ≈ 34_496` → `bars_per_year ≈ 8.7M`, but a single
+        // training epoch produces `n_returns ≈ 4.1M` step returns. Result:
+        // every production epoch took the v2 branch and the v3 fix was a
+        // no-op — smoke v4 epoch 1 (commit 62b5a50e8) reproduced v1's
+        // `Return=+2.963e2%` exactly.
+        //
+        // Unconditional CAGR is the correct invariant: "what annualized
+        // return is this policy producing?" works for any rollout length.
+        // Tests (very small n_returns) get extrapolated (a 5-bar +1.5%
+        // test extrapolates to e8% nominally) — the log-space clamp
+        // `[-23, +20]` bounds the display magnitude, and the test cases
+        // below assert ordering / sign, not exact magnitudes.
         let n_returns_f = n_returns as f64;
         if log_growth.is_finite() && n_returns_f > 0.0 && bars_per_year > 0.0 {
-            let log_scaled = if n_returns_f >= bars_per_year {
-                // Production rollout (typically ~4M bars vs ~20K bars/year)
-                // — annualize for CAGR semantics.
-                log_growth * bars_per_year / n_returns_f
-            } else {
-                // Short rollout (tests, warmup) — report total compounded.
-                log_growth
-            };
+            let log_scaled = log_growth * bars_per_year / n_returns_f;
             // Sanity bounds: lower at -23 (≈ -100% by construction
             // from per-bar `(1+r).max(1e-10)` floor), upper at +20
             // (≈ exp(20) − 1 ≈ +4.85e8% — beyond this magnitude the

docs/dqn-wire-up-audit.md

@@ -15349,3 +15349,84 @@ validate the full SP21 cascade end-to-end. Watch:
   (Phase 8 ISV-driven gains)
 - evaluate_baseline reproduces val_Sharpe / val_PF within 5%
   tolerance on the same checkpoint+window.
+
+## 2026-05-11 — Return v3.1: drop short-rollout guard, unconditional CAGR (atomic)
+
+### Scope (atomic single commit)
+
+One-file fix to `compute_epoch_financials`: drop the
+`if n_returns_f >= bars_per_year` short-rollout fallback. v3
+left the v2 formula in place for sub-year rollouts, but for
+Foxhunt's **volume bars** the data extracts
+`bars_per_day ≈ 34_496` → `bars_per_year ≈ 8.7M`, while a
+single training epoch produces `n_returns ≈ 4.1M`. Result: the
+v3 guard fired for *every* production epoch, so the v3 fix was
+a no-op. Smoke v4 (commit 62b5a50e8, workflow train-frv8x)
+epoch 1 reproduced v1's `Return=+2.963e2%` bit-identically.
+
+### Diagnosis
+
+- v1 epoch 1 stats: Sharpe=70.40, log_growth ≈ ln(3.963) ≈ 1.377
+- v3 expectation (assuming 5-min bars, bars_per_year=98_280):
+  `exp(1.377 × 98280/4.1M) - 1 ≈ +3.36% (= +3.359e0%)`
+- v4 actual: `Return=+2.963e2%` (same as v1)
+- Volume bar diagnostic in log:
+  `Bars per day (from data): 34496 (17835714 total bars)` →
+  `bars_per_year = 34_496 × 252 = 8.69M > n_returns = 4.1M` →
+  guard fires → v2 fallback path
+
+### Fix
+
+Replace:
+```rust
+let log_scaled = if n_returns_f >= bars_per_year {
+    log_growth * bars_per_year / n_returns_f
+} else {
+    log_growth
+};
+```
+with unconditional CAGR:
+```rust
+let log_scaled = log_growth * bars_per_year / n_returns_f;
+```
+
+The log-space clamp `[-23, +20]` still bounds the display.
+Tests (very small `n_returns`) extrapolate aggressively (a 5-bar
+test produces clamp-bounded ~e8% display) but all test
+assertions are sign-only (`> 0.0`), so no test regresses.
+
+### Expected v5 epoch 1 Return
+
+- log_growth ≈ 1.377 (same training-side stats as v1)
+- log_scaled = 1.377 × 8.69M / 4.1M = 2.92
+- exp(2.92) - 1 ≈ 17.7 → `Return=+1.770e3%` (≈ 1770% annualized)
+
+Higher baseline than 296% because the metric now actually
+extrapolates a 0.47-year rollout to a per-year CAGR. The clamp
+caps overfit overflow at ~`+4.852e8%` (was `+8.73e19%` under v2).
+
+### Files changed
+
+- `crates/ml/src/trainers/dqn/financials.rs`: drop guard, update
+  comment block (v3 → v3.1 history line)
+- `docs/dqn-wire-up-audit.md`: this entry
+
+### Pearls + invariants honoured
+
+- **feedback_no_quickfixes**: minimal scope, restores v3's original
+  CAGR intent without changing other semantics
+- **feedback_no_legacy_aliases**: removes the now-misnamed
+  "short-rollout guard" rather than renaming or wrapping it
+- **pearl_audit_first_caught_5_of_7_hypotheses_were_wrong**:
+  hypothesis-driven diagnosis (cache poisoning suspected →
+  ruled out by `git show` + workflow commit-sha check →
+  actual root cause: volume-bar `bars_per_year` mismatch)
+
+### Verification
+
+```
+cargo test -p ml --lib financials                      # 7/7
+```
+
+No CUDA build needed for this fix (financials.rs is CPU-only).
+Production validation deferred to v5 smoke dispatch.