This appears to be Claude (et al) run amok on a problem, the solution is very creative and well detailed. I had my Claude take a crack at examining more character encodings, to see if it could be optimized for varying input URLs:

> The two-tier base32768/base91 dispatch is the right design because the output alphabet and the input character set are independent concerns — the encoding choice should be driven by the two metrics that actually matter (visible chars vs. wire bytes), and base32768 and base91 already represent the optimal endpoints of that tradeoff. Any intermediate alphabet would be dominated on both axes simultaneously. Meanwhile, input character distribution is already exploited implicitly by deflate’s Huffman stage, so there’s no compression signal left for an explicit tier system to capture. The architecture is both minimal and complete: two tiers, zero header bytes, and no complexity left on the table.