Build a resumable upload contract that survives duplicate chunks, missing parts, and a timed-out finalize call.
A 12 MB artifact is split into three chunks. The client uploads chunk 2 twice, loses the response to finalize, and retries. A weak API creates two artifacts or assembles corrupted data.
Define the contract
type Chunk={sessionId:string,index:number,sha256:string,size:number};
type Finalize={sessionId:string,orderedHashes:string[],artifactSha256:string};
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