Microtask queue execution after Isolate::TerminateExecution() timeout

When an embedder enforces a script timeout by calling Isolate::TerminateExecution(), V8 sets an internal flag that causes the next interrupt check to throw a special Terminated exception. The embedder catches this exception via TryCatch and must call CancelTerminateExecution() to reset the isolate for reuse.

The documented behavior states that termination is "best effort" and does not guarantee immediate stop. A specific unresolved aspect is microtask queue handling: if termination occurs while a promise reaction is running, already-queued microtasks may continue to execute before the Terminated exception propagates. This can produce observable side effects—such as promise resolutions, global mutations, or additional async scheduling—after the logical timeout deadline has passed.

The V8 source indicates interrupt checks occur at specific points in generated code and certain runtime calls, but the exact placement varies by version and optimization tier. WebAssembly code without explicit interrupt checks and long-running native operations (regex, JSON.parse) can further delay termination delivery.

• Does the microtask queue drain completely before the Terminated exception unwinds the stack, or only microtasks already queued at the moment of the interrupt check?
• Is there a supported embedder hook to suppress or cancel pending microtasks as part of timeout handling, short of discarding the isolate?
• How does microtask execution after termination interact with CancelTerminateExecution() when the embedder attempts to reuse the isolate?