Korea's 'sidecar' explained — and how it differs from a circuit breaker
A sidecar pauses only program trading for five minutes when futures move sharply
The three lines
- The sidecar halts program-trading orders for five minutes on sharp futures moves
- Unlike a circuit breaker, the market itself keeps trading throughout
- It fires on surges as well as crashes — and 2026 is setting activation records
Key questions
- What exactly is a sidecar
- A Korean market curb: when KOSPI 200 futures move 5% (KOSDAQ: futures 6% plus index 3%) for one sustained minute, automated program orders lose effect for five minutes. Manual orders keep executing — only the algorithmic feedback loop is interrupted.
- How is it different from a circuit breaker
- Severity. The sidecar is a preventive brake pausing only program orders for five minutes, both directions, once per day. The circuit breaker is the emergency brake — index drops of 8/15/20% halt the entire market for 20 minutes or the day. Korea used both in 2026: breakers in July's crash, sidecars in August's melt-up.
- Is frequent firing a bad sign
- It signals volatility, not direction. This week alone produced four activations — three on KOSDAQ's surge and one on KOSPI's 4.33% rebound — all on the BUY side. Count the brake taps and you learn the road is rough, not which way it bends.
Four times this week. Three days running on KOSDAQ, then Wednesday on the main KOSPI board — "buy sidecar activated" has become a routine Seoul headline that global readers of Korean markets keep encountering unexplained. This is the standing reference.
1. What it stops: only the machines, only five minutes
The sidecar targets program trading — automated basket orders. When futures move sharply (KOSPI 200 futures ±5%, or KOSDAQ 150 futures ±6% with the index ±3%, sustained one minute), program order quotes are suspended for five minutes, cutting the algorithmic feedback loop that amplifies sharp moves.
The market stays open throughout — manual orders execute normally. And it fires both directions: all four of this week's activations were buy-side sidecars, halting program buying stampedes during surges.
2. The two brakes compared
| Item | Sidecar | Circuit breaker |
|---|---|---|
| Trigger | futures move (5-6%) | index crash (8/15/20%) |
| Stops | program quotes only | all trading |
| Duration | 5 minutes | 20 min to full day |
| Direction | surge and crash | crash only |
| Frequency | once daily per market | once per stage |
| Character | preventive brake | emergency brake |
In sequence: the sidecar is the first buffer, the breaker the last resort. Korea's 2026 has needed both — breakers in July's crash (see that standing reference), sidecars through August's melt-up.
3. What is still open
The year's activation count keeps setting records, and this page gets re-linked each time the headline recurs. This week's live case is in the KOSPI rebound story; the crash-side mechanism in "Circuit breakers: the three stop-lines."