The pair traded near 160 ahead of the release of US consumer price index data for July, which again drew attention to the possibility of intervention by Japanese and US authorities to curb further yen weakening.

BofA noted that a break of 160 without subsequent government action would be perceived as evidence of limited political resolve. In such a scenario, USD/JPY could approach 165 in August, and the Japanese government bond yield curve would likely assume a "bearish" shape, with long-term yields rising faster than short-term yields. Confidence in the authorities' actions increased after Japan and the US conducted a coordinated intervention on July 31.

However, analysts note that confidence has since been undermined: officials abandoned further intervention after weaker-than-expected US employment data pushed the USD/JPY below August 7. The pair subsequently returned to the 159 mark.

More decisive action by the authorities could restore confidence. An intervention that significantly lowers the USD/JPY after the release of strong US inflation data would indicate that officials were waiting for the risky event to pass before acting.

Authorities could also intervene after weak consumer price index data pushes the pair lower, cementing the move and thereby demonstrating an intention to strengthen the yen beyond a temporary correction.

A more limited response would leave confidence undermined. If officials prevent a break of 160 but fail to push the pair closer to 155, markets may conclude that the authorities are comfortable with the pair trading in the 155-160 range.

Repeated interventions to defend 160 could prove costly. In such a case, the Bank of Japan could face increasing pressure to accelerate interest rate hikes, shifting the primary burden of yen support from foreign exchange interventions to monetary policy.

BofA emphasized that accurately predicting the timing or trigger for intervention remains difficult, as authorities have little incentive to formulate a predictable response pattern.