Time Weighted Average Price — the running mean of the source since the anchor, the volume-blind sibling of VWAP. Where VWAP asks what the average traded price was, TWAP asks what the average quoted price was, so a thin bar counts for exactly as much as a heavy one.

Anchor substitution: the reference takes an input.timeframe (default 1D) and resets on timeframe.change(anchor), which needs a resolution resolver a chart library does not have. The session option resets on the exchange's own trading day, read back from the bar gaps exactly as the VWAP descriptor anchors, and continuous never resets. The option used to be labelled "Session (IST day)"; it names no zone now because it hardcodes none.