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Chaser

A chaser is a passive limit order that re-pegs to the top of the book every time the best bid (for buys) or ask (for sells) moves. It earns the maker rebate and rarely crosses — at the cost of fills being uncertain when the market walks away. Use it for size you want filled cheaply but don't need filled instantly. Each chaser runs as a background task in the safe-cex worker; list them with chasers and kill via kill <id> or chase cancel.

Minimum viable​

chase buy $100

Posts a limit at the best bid, re-pegs on every bid update, no termination guard — runs until filled, killed, or the exchange rejects.

Variations​

chase sell 50% reduce

Reduce-only chaser that closes 50% of the focused position. Side gets auto-inverted relative to the position when used with %all% or loop.

chase buy $500 to 1%

Terminate-at guard. If the price drifts more than 1% from the chaser's starting price, the chaser cancels itself. Accepted forms for to <length>: absolute (to 49500), percent (to 1%), dollar (to $50 or to 50$).

chase buy WIFUSDT,ENAUSDT $100

Multi-symbol fan-out — each symbol spawns its own chaser instance with its own $100 notional.

chase sell %all% 20% reduce

The %all% token (only valid with chase … reduce) expands to every position on the implied side. With sell it picks longs; with buy it picks shorts. 20% partial close per position.

chase cancel

Stop the newest active chaser and cancel its resting order. Use chase cancel keep to stop the chaser but leave the order resting in the book.

loop longs: chase sell 50% reduce

Spawn one reduce-only chaser per long position. See loop for the loop variants.

Gotchas​

  • Chasers run in the safe-cex worker — the REPL doesn't block, the chaser keeps re-pegging even if you walk away. tasks and chasers both list them; kill <id> and chase cancel both stop them.
  • chase cancel always targets the newest chaser, not all of them. For bulk cancel use chasers cancel all or kill all.
  • %all% only resolves under chase reduce. chase buy %all% without reduce is rejected — there's no sensible expansion for opening.
  • The chaser's "starting price" for to <length> is the first peg, not the price at which you typed the command. Latency between the two is usually tiny but worth knowing if the book is fast.
  • Stops aren't chased — only limits. To trail a stop, see Trailing stop.
  • The chaser keeps a single resting order at a time. It cancels-and-replaces on every peg — busy markets burn through cancel quota faster than a static limit. If you hit rate limits, raise to <length> or use twap.