audioOS 9.9.12.1.3 (build 16D39) is an official Apple over-the-air update for the HomePod, released on 2019-01-22T18:10:13Z. The update package is 151.99 MB. This is a delta (partial) update that requires 12.0 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 7d36ceec7f8319f6ca7c9de0f2e24e6ad02a1669.zip.