An indicator repaints when a value already shown for a closed bar later changes. The test is to record values on closed bars and check whether they are identical after more bars arrive. An indicator that moves only while the current bar is still forming is behaving like live price, not rewriting history.
Note the indicator's value, line position or marker on a recently closed bar. Wait for one or more new bars to close, then look at the same bar again. If anything about it has changed, history was rewritten. Reloading the chart and comparing is the same test run faster. A screenshot taken at the time is the cleanest record.
Three further comparisons catch most cases:
A change of settings recomputes the whole chart. That is a new calculation, not repainting.
A repainted history looks more accurate than the live indicator ever was, so any result measured on it flatters the tool. Repainting is separate from whether a tool is calibrated, which is a different test described in how to backtest a band indicator and how to compare band indicators.
Closed bars on the Behavioral Transform Model do not change, and the band for each bar is built from information available at the prior close only. The live bar's marker can update until it closes. The repaint article has the details, and why Oisigma publishes its methodology explains why the construction is open to this kind of check.
Passing the repaint check does not show that an indicator is accurate, calibrated, or profitable. It only shows the history is honest. The paper validates calibration, not the profitability of any use.
Is a repainting indicator always a problem?
Not by definition. Many indicators legitimately update on the live bar. The concern is closed-bar history being rewritten, especially when a backtest or screenshot was taken from the rewritten version.
Can alerts repaint?
An alert evaluated while a bar is forming can fire on a value that later changes, while one evaluated at the bar close cannot. The alerts article describes the notification layer.
Does a closed-bar-only indicator lag?
It uses completed data, so it cannot react before a bar closes. That is the trade for stable history; why closing prices matter covers it.
Details are in the working paper. The 30-day free trial lets you run this check on your own charts: start free, cancel anytime.
Oisigma provides descriptive market analytics for educational use. It is not investment advice, does not predict prices, and does not provide buy or sell signals. Statistics referenced are historical and were measured in our working paper (not peer-reviewed); past behavior is not a guarantee of future results. Trading and investing involve substantial risk of loss, including the possible loss of all capital invested. Leveraged products (futures, options, margin) carry additional risk and can result in losses that exceed your initial investment. Bollinger Bands® is a registered trademark of John Bollinger; Oisigma is not affiliated with or endorsed by Mr. Bollinger. RiskMetrics® is a registered trademark of MSCI Inc.; Oisigma is not affiliated with or endorsed by MSCI Inc. Nothing in this article is a recommendation to use any particular strategy. Read the full Disclaimer →
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