HomePod firmware code (labeled AudioAccessory1,1) shows that the smart speaker runs the full iOS stack like an iPhone without a screen and relies on a shell app called SoundBoard (presumably like SpringBoard on iOS).
Like Apple’s other products, HomePod will support accessibility features including VoiceOver according to the firmware code.
The top surface area is also limited to the Siri design and plus or minus symbols as press saw when viewing demo HomePods in June. This touch surface area will be used to optionally activate Siri with a long press or interact with music and volume control and timers.
Based on the firmware code, Troughton-Smith believes the illuminated part of the HomePod top surface is an LED matrix versus a few large LEDs which could support more than just plus and minus symbols and the Siri animation in the future.
Despite running iOS code, however, it doesn’t appear that the HomePod OS will support third party apps or extensions in its current shape. Apple could always add more developer opportunities to HomePod in the future after shipping the core experience, of course.
HomePod is scheduled to ship sometime in December for $349 each.