Child Machine States Not Updating in XState

[pixeliner]

Minimal Reproducible Example
I've created a minimal POC demonstrating the issue: CodeSandbox.

Background
I'm working on a larger system where I have multiple state machines managing different responsibilities. Each machine primarily holds states and performs simple calculations, while a coordinator machine orchestrates more complex behaviors like:

• Loading from storage
• Updating a timestamp using requestAnimationFrame
• Other asynchronous or coordinating tasks

So in general the coordinator machine acts as the central controller, managing multiple child state machines. On entry, it spawns the viewportMachine, storing a reference in its context. This allows it to forward events like SET_ZOOM directly to the viewportMachine without handling the logic itself. Each child machine is responsible for its own state updates and calculations, while the coordinator focuses on orchestrating high-level operations such as loading animations, playback control, and saving data.

Issue

• The events appear to be sent to the child machine (as per the logs).
• However, the child machine's state does not change in response.

Is there something I'm missing in terms of how child machines handle state transitions?
Or is there a better approach to structuring finite state transitions across multiple child machines?

Any guidance would be much appreciated!