Sweep the R:R floor; fix a holdout metric artifact

min_rr = 2.0 was hand-set in Admin (2026-06-24) and never swept — the gate
ablation only tested the floor on-vs-off, never its level. It was the last
un-swept knob in the live gate.

Swept against portfolio Sharpe under the real exit, with a parity self-check
(reproduces_production_gate: the row at the live floor must rebuild production's
exact 1,089-setup qualified set — it does).

  min_rr   qualified   in-sample Sh/CAGR   OOS Sh/CAGR (entries >= 2024-07)
  0.0        6636      1.98 / 58.5%        2.02 / 66.2%
  1.2        3897      1.34 / 33.9%        1.12 / 28.8%
  1.5        3127      1.20 / 29.6%        1.12 / 28.8%
  1.75       1974      1.64 / 44.5%        1.15 / 27.4%
  2.0 (live) 1089      2.04 / 50.4%        2.78 / 73.3%
  2.25        577      1.64 / 31.8%        1.71 / 31.9%
  2.5         286      1.67 / 29.0%        0.68 /  8.7%

KEEP 2.0. It is the optimum in both windows, and a peak that reproduces in data
it was never fitted to is real evidence. But treat it as fragile: unlike the ATR
trail (a plateau), this is a spike with a trough beside it — +/-0.25 costs ~0.4
Sharpe in-sample and ~1.6 out-of-sample — and the curve is bimodal (floor-off is
good, 1.2-1.75 is bad, 2.0 is good). The hand-set value landed on the peak by
luck, not by tuning. Do not nudge it.

Worth knowing: turning the floor OFF entirely is the second-best row in both
windows, with substantially higher CAGR (58.5% / 66.2%) and more trades. If CAGR
ever outranks Sharpe here, "no R:R floor" is a live option — and it would sever
the gate's last dependency on the weak S/R detector.

Also fixes a metric artifact in the holdout harness. The train book's equity curve
ran to the end of the data while its entries stopped at the split, so it sat in
flat cash for two years and deflated its own CAGR/Sharpe (reported 0.95 / 14.6%;
actually 1.31 / 29.6%). _simulate_portfolio now truncates the calendar to
hold_days after the last entry when end_date is set — it only triggers on the
holdout train window, so no other number moves. The clear-air OOS verdict is
unaffected: it rests on the test row, whose entries and curve both start at the
split and were always clean. Both holdout reports regenerated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -429,6 +429,7 @@ Research-only flags, all off by default (the default report is byte-identical to
 | Flag | What it does |
 |---|---|
 | `BACKTEST_HOLDOUT_SPLIT=YYYY-MM-DD` | Adds a `holdout` section: train (entries before) vs test (entries on/after), as disjoint books |
+| `BACKTEST_MIN_RR_SWEEP=1` | Sweeps the activation R:R floor against portfolio Sharpe. Combine with `BACKTEST_HOLDOUT_SPLIT` to sweep out-of-sample |
 | `BACKTEST_RESEARCH_EXITS=1` | Adds the rejected take-profit exit rows to the exit comparison |
 | `BACKTEST_ATR_TARGET_FALLBACK=k` | Synthesizes a k×ATR target where S/R offers none |
 | `BACKTEST_FALLBACK_CLEAR_AIR_ONLY=1` | Restricts that fallback to setups with genuinely no structure ahead |