What is repainting and why can it change automated signals?

What this means in practice

Repainting means past or historical-looking results can differ from what existed in realtime. For automation, ask whether the exact data that triggered the live alert can later change or cannot be reproduced on historical bars. This page is specifically about “What is repainting and why can it change automated signals?”, so each scenario below is explained by its own mechanism instead of sharing one generic diagnosis.

Real-world scenarios

Scenario A — Realtime signal disappears after close

Inspect the mechanism named by “Scenario A — Realtime signal disappears after close” directly. Record its input, the state immediately before it and the first observable output that differs from the intended result. For Scenario A — Realtime signal disappears after close on question 28, use that evidence specifically to answer “What is repainting and why can it change automated signals?”; keep it separate from the evidence for the other scenarios on this page.

Scenario B — request.security differs

Inspect the mechanism named by “Scenario B — request.security differs” directly. Record its input, the state immediately before it and the first observable output that differs from the intended result. For Scenario B — request.security differs on question 28, use that evidence specifically to answer “What is repainting and why can it change automated signals?”; keep it separate from the evidence for the other scenarios on this page.

Scenario C — calc_on_every_tick reload differs

Validate protection in the symbol's real units: direction, price-versus-distance convention, tick size/digits and current minimum distance. Record the normalized value actually sent to cTrader. For Scenario C — calc_on_every_tick reload differs on question 28, use that evidence specifically to answer “What is repainting and why can it change automated signals?”; keep it separate from the evidence for the other scenarios on this page.

What to check

• active server-side TradingView alert instance
• saved symbol, timeframe and inputs
• realtime versus confirmed-bar behavior
• exact message emitted by the active alert

Practical rule

For “What is repainting and why can it change automated signals?”, change only the first layer whose evidence no longer matches the intended action. Preserve signal identity, timestamps and final cTrader state, and reproduce execution-affecting changes on demo before live use.