Hey man, love this toolbox angle-it’s a breath of fresh air from the usual “one true strategy” echo chamber. I’ve been tinkering with something similar for a couple years on futures (mostly /ES and /NQ), and your setup resonates because it forces you to think modular instead of monolithic. The meta-selector flipping tools based on regime prints is smart; I’ve seen single edges crumble when vol regimes shift, and yours sounds like it dodges that nicely. Quick thoughts on your questions, pulling from what worked (and bombed) in my backtests and a bit of live paper trading.
On regime fingerprints: Vol percentile and spread/vol are solid baselines-they’re cheap and real-time friendly-but I’ve leaned on the VIX futures curve slope (front minus back month) as a killer add-on for spotting compression/expansion early. It’s a proxy for fear greed without needing options data, and it clusters well with your cross-asset corrs (ES/ZN/DXY). For robustness, I filter it through a 5-min rolling EMA to cut noise, and pair it with order flow imbalance (bid/ask volume ratio over the last 100 prints). Anything fancier like microstructure entropy (e.g., quote update frequency normalized by vol) can lag in HFT-heavy tapes, so I embargo it unless you’re co-lo’d.
Data-mining the selector: Brutal problem-I’ve nuked more playbooks than I can count from sneaky lookahead. Regime-level walk-forward is key: segment your data into vol/skew buckets first, then optimize tools within each without cross-contamination. For microstructure stuff like queue slopes or stuffing bursts, I use a “blindfold” test-backtest with lagged signals (e.g., 1-bar delay) and only unlag if it holds in embargoed periods (last 6 months OOS). Tool-level constraints help too: cap params per regime (say, max 3 vars per tool) and run sensitivity sweeps. If you’re scripting this, Python’s backtrader or Zipline with regime partitioning has saved me from overfitting hell.
PnL attribution: Counterfactual replay is gold for isolating the selector-I’ve done it by simming “what if” paths where the selector picks randomly or sticks to one tool, then diff the drawdowns. Shapley values are overkill unless you’ve got a small toolset (under 5); they explode combinatorially. Simpler: decompose via contribution analysis-track selector hit rate (tools that outperformed baseline in that regime) vs. tool PnL, and weight by time spent in regime. In live, I A/B test by splitting position size: half selector-driven, half fixed-tool, over a month.
Execution wrappers: Your post-only vs. IOC toggle is spot-on; add ISO (immediate-or-cancel with post-only flag) for when fragility spikes-it’s a broker staple (Interactive Brokers handles it clean for retail) but watch for venue quirks on CME where dark pools eat liquidity during vol pops. Venue-aware rules are clutch: skip lit if dark ratio > 2:1 (track via free SIP feeds), and iceberg for range scalping to avoid telegraphing. Retail broker gotchas? TD Ameritrade (now Schwab) can be laggy on TWAP during auctions, so I fallback to manual POV if spreads > 1 tick. Discretionary offsets? Only if you’re algo-ing it-hardcode ’em based on historical fill stats to avoid bias.
News shock proxies: Unusual auction imbalance dispersion is clever and free via exchange APIs (CME’s got real-time MDP feeds if you parse ’em). Options IV/RV jumps work if you scrape free Yahoo/ CBOE data every 15 mins, but for edgier stuff, I hack Google Alerts RSS for EDGAR filings or use free Twitter API bursts (keyword spikes on “FOMC” or tickers). Not perfect, but correlates 70% with paid shock indices in my tests-pair with your bulletin pings for a no-cost kill-switch.
Failure modes from my setup: Selector overfitting to recent regimes was the big one- it chased 2022’s vol crush and got wrecked in the 2023 grind. Fix: decay weights on historical regimes (e.g., exponential with half-life of 3 months). Tool cannibalization happened with mean-rev and momentum overlapping in chop; I added a mutual exclusion rule (no co-activation if corrs > 0.6). And yeah, execution can mask edges-my wrappers ate 20% of PnL early on, so I baseline ’em separately with zero-edge trades.
The open tool spec schema? Hell yes, it’d be huge-standardizing inputs (e.g., min tick data reqs), outputs (PnL vectors per regime), and a plug-and-play backtester for selectors would cut dev time in half. If you’re serious, maybe mock one up in JSON and share? I’ve got a barebones YAML version for my tools that enforces risk budgets-could evolve into a community thing.
This meta approach has me rethinking my whole book; if you’ve got pseudocode for the selector logic or toy data, I’d love to sanity-check it against my /CL runs. Who’s else building kits like this?