fix(blob): scale multipart part size for uploads above 80 GiB

[Diwak4r]

Summary

Multipart uploads fail for files larger than 80 GiB because the part size is hardcoded to 8 MiB, and the Vercel Blob API enforces a maximum of 10,000 parts per upload (8 MiB × 10,000 = 80 GiB). This contradicts the advertised 5 TB support for multipart uploads.

The fix scales the part size up for bodies with a known size above 80 GiB so the part count always stays at or under 10,000, e.g. a 100 GiB body now uploads with ~10.2 MiB parts instead of failing at part 10,001.

Changes

• packages/blob/src/multipart/upload.ts
  • Added getPartSizeInBytes(totalToLoad): returns the 8 MiB default for bodies at or under 80 GiB, otherwise Math.ceil(totalToLoad / 10_000).
  • uploadAllParts now derives the part size from totalToLoad instead of the module-level constant.
  • Decoupled the read-ahead memory bound (maxBytesInMemory) from the part size. It previously scaled with the part size (2 parts × concurrency), which would buffer gigabytes for the larger part sizes now used on big uploads; it stays at the previous 128 MiB ceiling.
• packages/blob/src/index.node.test.ts — new tests:
  • getPartSizeInBytes keeps 8 MiB at/under the 80 GiB ceiling.
  • Part size scales above 80 GiB and keeps the part count ≤ 10,000 (including for a 5 TiB body).
  • An upload above 80 GiB produces one scaled part instead of many 8 MiB parts.
  • Small bodies still split into 8 MiB parts (no regression).

Bodies with an unknown size (streams) keep the 8 MiB default, since the total length isn't known upfront.

Tests

• test:node — 6 suites, 176 tests, 20 snapshots ✅
• test:edge — 1 suite, 1 test, 2 snapshots ✅
• test:browser — 3 suites, 19 tests, 3 snapshots ✅

Fixes #1067

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