# the TIBX prototype writer silently truncated files and replaced bad UUIDs - #402
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… UUIDs AcronisTibxWriter.Build stores each file in a single DATA page. Content longer than that page was cut to 4076 bytes with no error, and an archive UUID of the wrong length was quietly swapped for a random one. Build now checks its inputs first. A file larger than the new MaximumFileContentLength is refused with NotSupportedException, and so is a UUID that is not 16 bytes (ArgumentException). Accepted content is copied in full. Boundary tests cover exactly the maximum, one byte past it, and a 15-byte UUID. The writer is still an unadvertised structural prototype and CanCreate stays off. The earlier branch's REFERENCE.md regeneration deleted about 44k lines. It was dropped and the file regenerated from main's.
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What changed
The existing reader-inverting TIBX prototype stored file content in one DATA page but silently truncated content larger than that page. It also silently generated a replacement UUID when a caller supplied an invalid-length UUID.
This change validates file inputs up front, exposes the maximum supported single-page payload, rejects oversized files and malformed UUIDs, and copies the full content for all accepted sizes. Tests cover the exact payload boundary and both rejection cases.
Scope
Acronis documents TIBX as its version 12 backup-chain format, but does not publish the LSM writer format. The existing writer remains an unadvertised structural prototype; this PR does not claim vendor-restorable backup creation. Full multi-page data mapping and metadata-preserving creation require the proprietary LSM/index and extent structures.
References
acronis-tib-readerused only as a behavioral/format reference; no implementation code copied: https://github.com/TreadingTheTiber/acronis-tib-readerValidation
git diff --checkpassed.dotnetis not installed.