# ITHZ Limitations

ITHZ-CFC v0.1-alpha-rc1 is a release-candidate research tool, not a production archive replacement.

## No General Superiority Claim

ITHZ does not claim general superiority over ZIP, tar.gz, 7z, zstd, brotli, or other mature archive tools.

P7B/P9/P14 results show useful deterministic planning and some small-file ZIP/deflate niche signals, but tar.gz remains a strong solid-stream baseline and often produces smaller archives on the tested corpora.

## Guarded Data

Media and already-compressed formats are usually STORE/guarded:

```text
jpg/jpeg/png/webp/gif/mp4/mkv/mov/avi/zip/rar/7z/gz/pdf/docx/xlsx/pptx
```

The intended behavior is to avoid forced structure extraction on high-entropy or precompressed data.

P15B confirms this limitation on the negative mixed precompressed/random smoke
profile: it stayed guarded/store-like (`negative_guard_count=180`) and was
larger than ZIP/tar.gz. That is expected behavior for this class, not a
superiority signal.

## Metadata Overhead

P15A size attribution shows that the inspected aggregate is payload-dominated,
but metadata-heavy small-file profiles still expose future optimisation targets:
file tables and path tables are the largest non-payload components. P15A is a
diagnostic result only; it does not change the archive format.

P16A continues this as a gated estimate. It reports possible path/file/offset
metadata savings, but it does not write a physical p9-v4 or p7b-v3 manifest.
Until a version-bumped writer exists, P16A numbers should be read as P17 design
guidance rather than as a changed archive format.

P17A adds a physical `p9-v4-experimental` writer, but it is explicit-only and
not a default format. It captured only `4,878 B` of positive physical savings
across the tested rows, far less than the P16A estimate. This means metadata
compaction remains an experimental design area, especially for deeper
path/prefix and offset-table layout work.

P17B tested ordering/partition diagnostic variants and found no physical byte
win over the current canonical output in the reduced matrix. Those variants
are not default candidates from this evidence.

P20 adds an explicit `p9-v5-experimental` metadata writer candidate. It improves
the tested metadata matrices (`6,759 B` saved versus p9-v4 in P20C and `8,578 B`
positive savings in P20D beta smoke), but it remains experimental. The default
p9-v3/P7B writer is unchanged, and p9-v5 should not be presented as a production
format or general archive-ratio claim.

## Current Value

The current ITHZ value is:

- deterministic auto-mixed planning;
- schedule-stable semantic plan hashes;
- inspectable family and method decisions;
- `--why` explanations for files;
- safe verification without restored-tree writes;
- per-file restore and extract-file UX;
- explicit safety and compatibility gates.

Compression ratio work remains future profile-specific research.
