A Range Period Interrupted by a Halt
Halts do one thing to the tape. They stop it, and the auction that restarts trading afterwards is a separate auction with its own price discovery rather than a continuation of the one that was interrupted. Every teardown orb trading setups beekeeping for beginners has logged of a halted opening range period reaches the same conclusion, that a range measured across a halt is two partial ranges added together, usually with a large gap in volume between them, and the boundaries it produces belong to two different states of the market.
What a Halt Actually Is
On equities it is usually a volatility interruption triggered by a move outside a band in a short window, or a news pending halt requested by the company. The first is mechanical and short. The second can last a long time and reopens at a price with no relationship to the pre halt levels. Which type it is determines whether anything from before is still usable.
The Reopening Auction Sets a New Reference
Price discovery at the reopen concentrates a great deal of activity into a few seconds, and the level it settles at is what participants work from afterwards. That level, rather than either boundary of the interrupted range, is the meaningful reference for the rest of the first hour. Marking it immediately is the single most useful thing to do.
Volume at the reopen is also enormous relative to the rest of the period, which distorts any relative volume figure computed across the whole range.
Restart the Measurement
The defensible response is to discard the pre halt range and begin a fresh period from the reopening print, using the same length as normal. That produces a boundary formed under a single set of conditions. Stitching the two halves together produces a rectangle no participant is looking at, which is the opposite of what a range is for.
Sizing After a Halt
Spreads are wide at the reopen and stay wide for several minutes, and the instrument frequently moves further per minute than it did before. A position size derived from the pre halt range is too large for the post halt market. Recomputing it from the new range, once that range exists, is the only version of the arithmetic that reflects what is actually being traded.
The Simplest Rule Is to Stand Down
Halted sessions are rare, the conditions are unlike anything in the sample size the rules were built on, and the spreads alone remove most of a small edge. Skipping the instrument for the rest of the day costs one session and avoids trading a setup that has never been measured. Log it, note the halt type and the reopening price, and let the record decide over a few years whether that default is too conservative.