What happened
CME reported that triggered sell-dollar options have sped up the yen's advance, with the currency pair dropping 2.1% to 155.34, the lowest since August 3.
The most actively traded instrument on Thursday was an overnight dollar put option with a strike price of 155.0, reflecting growing all-day demand for protection at that level.
Why it matters
A break below 155.23 would push dollar-yen under the level seen during Japan's latest yen-buying intervention, potentially inviting further dollar selling.
Many traders view 155 as a pivotal resistance threshold for the yen, as Japan's April intervention failed to move the currency past it, making this a closely watched trigger zone.
Key facts
CME said demand for options at the 155.0 yen strike price increased throughout the day.
USD/JPY fell 2.1% to 155.34, its lowest level since August 3.
If 155.23 is broken, the pair would fall below the level reached during the last yen-buying intervention.
Japan's April intervention did not push the yen beyond the 155 level, which is seen as key resistance.
What to watch next
Whether dollar-yen tests the 155.0 strike area and whether a decisive break triggers a fresh wave of dollar selling from options-related flows.
How Japanese authorities respond if the pair moves below the intervention-related level of 155.23.