audioOS 9.9.18.4 (build 22L255) is an official Apple over-the-air update for the HomePod (2nd generation), released on 2025-03-31T17:29:47Z. The update package is 1.44 GB. This is a delta (partial) update that requires 16.6 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 4a27cd55d54357d1d88587ef8bedd44c1951c567454a2d27ad3b0eb2a2094fa7.aea.