The case-mismatch EPUB fixture builds an archive with @zip.js/zip.js' BlobWriter and then wraps the resulting Blob into a File:
const blob = await writer.close();
new File([blob], 'case-mismatch.epub', ...);
Under vitest's happy-dom/jsdom, the File/Blob polyfill does not correctly pull bytes out of a nested Blob part produced by zip.js. The outer File reports a non-zero size, but the bytes BlobReader sees in DocumentLoader (libs/document.ts: 'new BlobReader(this.file)') are not a valid ZIP — getEntries() yields nothing, open() falls through with book = null, and the test crashes at:
TypeError: Cannot read properties of null (reading 'sections')
Materialize the zip bytes into a plain ArrayBuffer first, then construct the File from that. ArrayBuffer parts go through the polyfill cleanly because they don't require recursive Blob unwrapping, so zip.js reads a real archive and the test passes:
const arrayBuffer = await blob.arrayBuffer();
new File([arrayBuffer], 'case-mismatch.epub', ...);
This brings the fixture in line with the rest of the test suite (paginator-expand, page-progress-epub, toc-cfi-mapping, ...) which already use ArrayBuffer-based File construction. No production code is affected: real browsers handle nested-Blob File construction correctly.
Try an exact ZIP entry match first, then fall back to a case-insensitive lookup for EPUB resources when archive entry casing differs from manifest paths.
Keep ambiguous case-only duplicates exact-match only, and add a regression test that opens a real EPUB through DocumentLoader.
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