Interface PendingEntry

an entry whose upload is still in flight

The hash is a digest of the bytes, so the entry describes the upload before the server has it — you can splice it into a parent index immediately. Disposing waits for the upload to land, and throws if it failed, so scoping it keeps a root hash from being written against a file that never arrived:

let hash;
{
  await using entry = await raw.putFile(`${id}.pdf`, bytes);
  hash = entry.hash;
}
await raw.putRootHash(hash, generation);
Copy

Where the number of uploads isn't known until runtime, collect them in an AsyncDisposableStack with stack.use(entry); the scope holding the stack waits for all of them.