• Firmus has agreed to invest about US$300m for up to 150Tbps of capacity on SUBCO's planned APX East cable
  • The 25-year agreement gives Firmus a future Australia-US route for its AI infrastructure, with APX East targeting service in Q4 2028

The fact

Firmus has agreed to become a cornerstone customer on SUBCO’s planned APX East submarine cable, committing about US$300 million for up to 150Tbps of dedicated capacity over 25 years. The cable is being developed as a direct route between Australia and the mainland United States and is expected to enter service in the fourth quarter of 2028. Firmus plans to use the capacity to connect its Australian AI Factory network with the US and other international markets, making APX East part of the network supporting its wider AI infrastructure build.

For now, the agreement secures future capacity rather than a live connection. APX East is still under development, and Firmus will only be able to use the route once the cable, landing infrastructure, testing and commissioning are complete.

The assessment

By committing before APX East is built, Firmus can design parts of its network around a known block of future trans-Pacific capacity rather than waiting for the cable to enter service. For a company adding AI sites in Australia, that means international connectivity can be planned alongside campus links and terrestrial backhaul instead of being dealt with later. The trade-off is that part of that plan now depends on SUBCO meeting its 2028 delivery schedule.

Firmus has not said when it expects to activate the full 150Tbps, which sites will connect first or how those sites will reach the cable landing points. It has also not detailed what alternative routes would carry traffic if APX East is delayed. For BTW readers, those details will show whether this remains a large capacity reservation or becomes a network plan that is being built in step with Firmus’s compute expansion.

What to watch

Watch whether SUBCO keeps APX East on track for its fourth-quarter 2028 service target and when Firmus begins connecting its Australian AI sites to the system. Marine construction, cable landings, system testing and customer activation will show whether the contracted capacity is becoming usable infrastructure on schedule.