Most systems do. At pastjob we had a few different levels: - halt - just stop trading - exit-only - only exit positions (but do so according to our alphas, no

Most systems do. At pastjob we had a few different levels: - halt - just stop trading - exit-only - only exit positions (but do so according to our alphas, no hurry) - flatten - exit in a hurry but obey certain limits (often if liquidity was thin we would just "journal" the shares - move them to a long-term-hold (meaning more than the current day) account to exit in the opening auction the next day - market exit - get the fuck out, now, no matter what the cost. I never saw us use that last one.