Conditions That Can Never Be True

A condition that can never be true does not crash anything. It makes its signal silent: the backtest shows zero trades, the live strategy never acts, and nothing points at the cause. RSI > 120 looks like a typo for 20, and RSI < 30 AND RSI > 70 usually meant OR. Both are easy to write and slow to find, so the engine refuses them when the strategy is parsed, with the JSON path of the condition or the AND group.

The same check runs in the browser (form, node and JSON editors) with the same messages and paths, so a problem shows on the condition row, the node or the JSON line before anything is saved or backtested.

{
  "valid": false,
  "errors": [{
    "path": "entry.signals[0].conditions",
    "message": "'RSI(14, close) < 30' and 'RSI(14, close) > 70' can never both be true"
  }]
}

Nested ANDs are checked as one group (RSI < 30 AND (RSI > 40) is caught). A contradiction inside one branch of an OR is reported at that branch's path, because that branch can never contribute.

• Edges of the range. RSI >= 100 and RSI crossesAbove 99 can happen, so they pass.
• Different bars or timeframes. EMA(20) > EMA(20)[1], High[1] < Low (a gap) and RSI < 30 AND 1h RSI > 70 compare different values.
• OR and NOT. RSI < 30 OR RSI > 70 is fine, and a NOT is never treated as a contradiction.
• Anything it cannot prove. Unbounded values (MACD, ROC, formulas, QuaScript series) have no declared range and are never rejected on range grounds. The check has no false positives: every rejection is a condition no market data could satisfy.

Every catalog output declares the values it can take: a range (RSI 0…100), a floor (ATR ≥ 0, prices > 0), a discrete set (events 0 / 1, directions ±1) or whole numbers (clock values). For one condition the checker asks whether any value in that range satisfies the operator; for a cross it needs a value on each side of the level. For an AND it collects, per series (and per pair of series), the bounds each condition demands and intersects them — a cross also bounds the previous bar. An empty intersection is a contradiction, and the message names the two conditions that clash.

The engine's check is apps/hft/dsl/src/dsl/satisfiability.cpp; the browser mirror is strategy-builder/dsl/satisfiability.ts. A test (scripts/verify-conditions.mts) generates thousands of random condition trees and confirms the two agree on every verdict and path, and that every condition rejected as never true is in fact false on every bar of several synthetic markets.

• Picking an indicator fills in a right-hand side that can be true: RSI < 30, Doji == 1, Close > EMA(20), Volume > VolumeSMA(20), TimeOfDay >= 930.
• Changing the operator or the output repairs a constant that would become impossible (Supertrend line → direction switches the value to 0 for a cross).
• Events and directions are chosen from a list of their possible values; numbers outside the range are pulled back when the field loses focus.
• Right-hand-side modes that cannot work are hidden — there is no “Field” option for RSI.
• Conflicting AND groups show an error on the group (form) or the logic node (node editor).