NFT Curve Graduation After Sell-Back: Reserve Accounting and an Identifier Collision in PumpDrop

PumpDrop sells sequentially minted NFTs on a rising curve, permits sell-back before graduation and aims to move its reserve into a locked NFT-claim liquidity position when outstanding supply reaches a cap. An isolated build passed five existing selected tests, including a 256-run fuzz test of reserve accounting and one no-sell graduation. A new deterministic test shows a distinct liveness failure: after buying three of ten curve NFTs, selling two and buying the nine needed to reach the cap, the final buy reverts during graduation with an ERC-721 duplicate-identifier error. Curve IDs 11 and 12 already exist when graduation tries to mint fixed reserve IDs 11 through 16. The entire attempted buy rolls back. This is a conditional, reproducible source-version finding, not a claim that every launch is blocked or that any live user was harmed. It separates reserve solvency from the ability to complete the promised transition. Preparation of this report was assisted by Codex. The research programme is directed toward human agency, financial inclusion, and evidence-based accountability. Intended social benefits are distinguished from measured technical results in the manuscript. The manuscript and newly authored analysis are offered under CC BY 4.0. Any supplied source files retain the license terms stated in the supplement; the record license does not replace third-party source licenses.