Lock lookback and chart scale before you mark a flag or pennant

Start with the window, not the sketch

A flag is a compact, usually sloping coil that follows a sharp directional move and can be stated as a rectangular OHLC structure rather than a freehand sketch. A pennant is a tapering coil after a sharp move, constructed from converging swing highs and lows instead of a parallel channel.

Editorial reading: recognition is a construction problem. Lock the chart-scale and the historical window first. Only then treat the resulting shape as a hypothesis that can be marked, coded, or rejected.

Name the chart-scale

Flag-detection rules can be written for daily bars and for intraday bars, so construction must name the chart-scale being used. Chart-scale is the bar interval on which the same structural rules are evaluated, from intraday bars through multi-week daily sequences.

Flags and pennants appear among common chart patterns reviewed in a currency-charting discussion, so the construction is not treated as equity-only in this material.

Set lookback against the bar-reference-limit

Construction of the detector includes an explicit parameter for how many bars the study will reference. Lookback is the count of historical bars a detector must read before it can accept or reject a flag or pennant condition.

A flag-detection study cannot evaluate when it tries to read more historical bars than the platform lookback limit allows. That cap is the bar-reference-limit. If it is smaller than the detector lookback, the construction cannot run.

One construction adjustment for that failure is to raise the allowed lookback so the study can reference 150 bars.

Separate visual markup from a testable hypothesis

The same flag rules can be stored as a charting study and as a strategy, separating visual markup from a testable hypothesis. Flag identification can be rebuilt in a spreadsheet from price columns, so the pattern is a data rule rather than a drawing on one chart.