Can a Titanium native module callback fire after its JavaScript Proxy is garbage collected?

Direct answer

Yes. A pending Titanium native module callback can fire after its JavaScript Proxy has been garbage collected. The Kroll bridge does not automatically keep the Proxy object alive for the lifetime of an asynchronous native call. It roots the JavaScript callback function through a native-side KrollCallback, but that root does not extend to the Proxy representing the native instance.

Likely explanation versus confirmed facts

Likely explanation: when JavaScript releases all references to the Proxy, the JavaScript engine may collect it while the native operation is still pending. The native side can still hold the KrollCallback and attempt to invoke it later. At that point the Proxy may already be finalized, producing an invalid-reference condition, a silent drop, or undefined behavior depending on the platform and SDK version.

Confirmed facts are limited until verified against your build: the bridge roots the callback, not the Proxy; iOS and Android manage the JavaScript engine and native heap separately; older Titanium SDKs tended toward more aggressive Proxy cleanup, while newer SDKs add more defensive callback checks. Exact behavior varies by SDK version and target platform.

Steps for this case

1. Retain a strong JavaScript reference to the Proxy and the callback until the native operation completes, fails, or is explicitly cancelled.
2. Release that reference in the completion or cancellation handler so both sides can reclaim the objects.
3. Ensure the native module clears its stored KrollCallback after invocation to avoid native-side leaks.
4. Confirm your Titanium SDK version and target platform, because callback lifetime handling differs between iOS JavaScriptCore and Android V8 and across SDK releases.

Missing diagnostic detail

Which Titanium SDK version and target platform are you using? This detail changes the recommendation because iOS may surface an error while Android may silently drop the invocation, and older SDKs behave differently from newer ones.

Verification

Create a minimal native module that accepts a callback, delays invocation, and logs whether the callback is still valid. Drop all JavaScript references to the Proxy in between and force garbage collection. Inspect native logs and the JavaScript console for errors, silent drops, or unhandled exceptions. Do not rely on this behavior in production until it is confirmed against your SDK version and platform.

This is a conservative draft for human review because current verification against the specific Titanium SDK and platform is required.