My 'Top Candidate' Backtest Flag Always Picked the Same 4 Coins

I've already written about the two ends of this pipeline: the full archive audit that found 9 pairs worth trusting out of 1,400 tested, and the 20 finalists that all failed my deepest walk-forward stage. This is the part in between — the flag I use to shortlist a config before it even gets to those later stages, and what happens when you actually look at what it shortlisted.

The flag is called is_top_candidate. It's a threshold pass on an earlier scoring run — net profit, win rate, profit factor, nothing fancier than that. Out of 12,331 scored configs spanning 176 different coins, exactly 50 ever earned it. I went looking at which coins those 50 belonged to, expecting some spread. There wasn't one.

50 flags, 4 coins

Every backtest_results row with is_top_candidate=1, grouped by coin. 12,331 total scored configs, 176 distinct coins tested.

One coin was 60% of the entire flag

MEGAUSDT alone accounts for 30 of the 50 flags — every one of them the same range_bottom_reclaim strategy family with minor parameter variation. The single best run: 95.0% win rate, profit factor 3.09, net $668.08 over 1,600 trades, entry within a 1.10% take-profit and a -0.81% first DCA level. That's not 30 independent edges. It's one coin's specific price history, scored 30 slightly different ways, and the flag couldn't tell the difference between that and 30 real ideas.

LIGHTUSDT is the odd one out and worth a second look on its own: 35.1% average win rate, less than half of MEGAUSDT's, and it still cleared the flag on net profit and profit factor (1.87) alone. A coin can lose more often than it wins and still pass a threshold built around net and profit factor. That's a real, defensible way for a strategy to make money — until you remember the flag's job was supposed to be picking out the safest bets, not the highest-variance ones.

I retested all 4 through the stricter pipeline. All 4 failed

Since writing about the 20 finalists, I've been running coins through a newer broad-screening stage that scores on more than net and win rate — it also checks how P&L clusters across trading days. I went back and pulled these same 4 coins from that pipeline's results.

Same 4 coins, scored again through the newer 2,331-config broad-screening batch used in the 20-finalists piece.

BILLUSDT and ARIAUSDT scored negative on every single retested run — not just on average, their best run was still negative. MEGAUSDT, the coin with 95.6% average win rate under the old flag, barely cleared zero on its single best of 12 retested runs and averaged -33.71. LIGHTUSDT wasn't in the retest batch at all — it didn't survive whatever upstream filtering happens before a coin even gets scored again. None of the 4 made it into the 20 finalists I wrote about last week either. Two completely separate scoring passes over the same market data agreed on exactly nothing.

What I'm changing about how I read the flag

The flag isn't wrong on its own math — every one of those 50 configs really did clear its net/win-rate/profit-factor threshold on the data it was scored against. The problem is what the concentration hides. When 60% of a flag's entire output is one coin, it isn't telling you "this is a good strategy." It's telling you "this coin's specific 1,600-trade history happened to produce good numbers under these particular parameters." I can't tell those two things apart from inside the flag. I can only tell them apart by checking how many different coins produced a pass, and by that measure this flag was overfit before I ever got to walk-forward testing.

Going forward I'm treating any flag or filter that clears fewer than a handful of distinct coins the same way I'd treat a single backtest with a suspiciously high profit factor — not disqualifying on its own, but a reason to check the concentration before trusting the number.

Before you trust a "top candidate" flag

1. Count the distinct coins, not just the pass rate. 50 of 12,331 configs (0.4%) cleared my flag, but they came from only 4 of 176 coins tested. A low pass rate on a small handful of symbols is concentration risk, not selectivity.
2. Watch for one symbol dominating the winners. 30 of 50 flags — 60% — were the same coin run with minor parameter changes. That's one price history scored many ways, not many independent edges.
3. Re-score with a second, stricter pipeline before trusting a flag. All 4 coins that passed my original flag scored negative on average — or didn't survive to be retested at all — under a newer broad-screening pass.
4. A high win rate on one symbol doesn't transfer. MEGAUSDT's 95.6% average win rate under the old flag became a -33.71 average score under the new one.

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