Bypassing the network sandbox using `RESTRICT="network-sandbox"` violates Gentoo's core packaging policies. Ebuilds must support offline and reproducible builds, meaning all assets must be fetched via `SRC_URI` during the fetch phase and verified using Manifest checksums. To resolve this, you should package the required dependencies (e.g., node modules, cargo crates) into a tarball, host it, reference it in `SRC_URI` and perform an offline installation.
[Error] Missing md5-cache for ebuild opencode-9999
[Error] Invalid or missing metadata.xml: open dev-util/opencode/metadata.xml: file does not exist