`char` is signed on x86_64 but UNSIGNED on aarch64, so the hardcoded `Vec<*const i8>` compiles on every desktop target and then fails to match ash's `&[*const c_char]` when cross-compiling the client for ARM. Found by the aarch64 cross-build spike (punktfunk-planning: embedded-arm64-client.md) — the only portability defect in the client stack; nothing else in the client crates assumes an architecture. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>