[psadi]

Nightly builds have failed every day since 2026-10-21. Two separate Zig 0.17.0 regressions are responsible; ZIG_VERSION is read dynamically from upstream build.zig.zon (minimum_zig_version), so both appeared without any change in this repo once tip moved to 0.17.0.

1. --global-cache-dir was removed from zig build

Zig 0.17.0 only accepts --global-cache-dir on build-exe/run, not zig build, so the build died seconds after starting:

+ zig build ... --global-cache-dir /tmp/offline-cache
error: unrecognized argument: --global-cache-dir

Fix: feed the pre-fetched offline cache through ZIG_GLOBAL_CACHE_DIR, which every Zig release honors (and which fetch-zig-cache.sh already required). No version-gated CLI flag is needed any more.

2. zig fetch caches tarballs in a layout zig build rejects

With the flag fixed, the build then failed with hash mismatches for all 37 dependencies:

pkg/zlib/build.zig.zon:10:21: error: hash mismatch: manifest declares N-V-__8AAB0eQwD-0Md...
but the fetched package has N-V-__8AAB0eQwDaat...

In 0.17.0, standalone zig fetch stores the package tarball with the upstream top-level directory still nested (<hash>/zlib-1.3.1/...), while zig build expects package-root-relative paths and therefore re-hashes it as a different package. Reproduced outside containers with a clean global cache; a plain zig build fetch produces the correct layout.

Fix: on Zig >= 0.17 pre-populate the cache with zig build --fetch=all (new in 0.17), which writes the layout the build expects and resolves lazy/transitive deps itself — the exact gap nix/build-support/fetch-zig-cache.sh used to work around.

Zig < 0.16 keeps the previous --system /tmp/offline-cache/p + fetch-script behaviour.

Verification

• 0.17.0: zig build --fetch=all on the tip source succeeds, and the following zig build no longer reports hash mismatches.
• shellcheck --severity=warning --shell=sh, shfmt, and the rest of pre-commit pass.
• Full pipeline (setup-env → build-ghostty → bundle-appimage → validate-appimage) running in the same Arch container CI uses; this PR run is the end-to-end check.

Note: transient 500s from deps.files.ghostty.org were seen while testing; unrelated to this change.