Repository navigation
P2: Add Zstd-coded 7Z decoding after confirmed compatibility gap #316
Description
Verification result — 2026-11-06
Confirmed decoder gap; dedicated support is recommended. Stow's pinned stock 7-Zip 26.04 lists ordinary, Delta-filtered, encrypted, split and encrypted-split Zstd-coded 7Z archives, but payload test/read/extraction returns exit 2 with Unsupported Method. File-list success does not establish readable contents.
Fixtures were independently generated by py7zr 1.1.4 and 7-Zip-zstd commit bc1fb8a66d4ef549b6ac9bbc1bd660fecd2a572f, then extracted by their producing implementations with exact-byte comparison. The synthetic payload is 20,000 bytes; SHA-256 478007740bc18d4c4194865ad9944f46e82904030c69fda4a5e20a9ff145926a. Ordinary .zst/.tar.zst support is unrelated. The alternate engine was used only as a fixture producer and is not bundled.
PR #319 retains reproducible fixtures and safe-failure tests. All five cases were exercised through Stow’s sandboxed engine for selected and all-content extraction. Originals and destination contents were preserved on failure. Complete split archives initially misreported codec failure as missing volumes; #319 fixes that diagnostic. The final 740-test suite passes, including these explicit known-gap tests; this is not decoder support. Decoder implementation should be a dedicated P2 compatibility change, preserving sandbox, bounded resource/cancellation behavior, checksums, signing, Universal 2 and licensing. Validate solid/multi-file, corrupt input and passwords in addition to this corpus. Do not mark this issue closed on safe-failure test success.
Standalone Zstd/TAR.ZST support does not prove support for the Zstd coder in 7Z. Pinned 7-Zip 26.04 capability output lacks that coder.
- Produce independently generated ordinary, Delta, encrypted and split Zstd-in-7Z samples.
- Compare listing, reading/preview and extraction with exact-byte checks through Stow where practical.
- Record reproducible success/failure and decide whether a decoder change is warranted.
- Do not replace the official engine or weaken the sandbox without evaluating maintenance, licensing and signed distribution implications.
- This issue starts as validation, not an implementation or parity claim.
Ownership and validation
Codex / Grok Bot owns functional correctness, state, security, cancellation and tests. Claude Code owns visual design and motion; functional controls may be implemented now, with visual treatment pending review. No Claude Code assignment or acceptance is claimed. Preserve keyboard access and existing accessibility semantics; full VoiceOver acceptance remains deferred under AGENTS.md. Add Simplified Chinese for user-facing strings. Validate focused regressions and the full required build/test/localization checks.
Approved by the user on 2026-11-06 (Pacific/Honolulu), following the ArcZip 1.1.5–1.2.2 assessment. Parent roadmap: #39. Reference: https://arczip.app/changelog/?lang=zh
Activity
[-]P1 investigation: Verify Zstd-in-7Z compatibility and scope decoder support[/-][+]P2: Add Zstd-coded 7Z decoding after confirmed compatibility gap[/+]skyswordw commentedon Nov 8, 2026
Implementation is now in #342, based on the official 26.04 source with a small decoder-only registration of its existing Zstd decoder. It adds a 512 MiB per-window bound, known-property validation and full corresponding-source packaging/offline build; it does not import the full 7-Zip-zstd fork, add an encoder or weaken the sandbox.
Final local integration: 771 tests passed with zero failures/skips. Exact-byte verify/preview/selected/all extraction, encrypted/split/Delta, solid/non-solid inputs, staged Save mutations, corrupt inputs, wrong passwords and cancellation after intermediate progress passed. Both executable slices and an offline source rebuild were checked. Ad-hoc package structure/signatures/DMG checks passed with 12 universal binaries.
Keep this issue open until review and fresh CI complete. Local fresh-window smoke fails identically on the unchanged baseline and candidate; the strict gate remains enabled and the clean CI package/snapshot runs are pending. Developer ID/notarization and physical Finder installation remain separate release acceptance. This supersedes the gap as the current implementation status, while retaining #319's original reproduction evidence.
skyswordw commentedon Nov 8, 2026
Resolved by merged #342 after independent functional reviews and all four clean CI checks (build-test, Universal 2, snapshots and Release package). The package log explicitly records a fresh Welcome render and zero ad-hoc verification problems. Final local integration passed 771 tests with zero failures/skips.
Acceptance now includes exact-byte verification, preview, selected/all extraction, encrypted/split/Delta and solid/non-solid inputs, staged Save mutations, corruption/property/window rejection and active cancellation. The official-source patch adds only a decoder, caps each 7Z Zstd window at 512 MiB, preserves sandboxing and ships complete offline-rebuildable source. These documented limits replace the old safe-failure-only status; signed/notarized release acceptance remains separate. #317 is still open for FSKit exFAT publication.