ADR-0008 — Repository and heavy artifacts on the external SSD

Status: Accepted · 2026-08-18

Context

Development machine: MacBook Air M4, 16 GB RAM, 256 GB internal SSD, 1 TB Samsung T7 external SSD. The internal disk cannot hold the repo, cargo target directories, benchmark corpora (10–15 real repositories at M08), Git mirrors and profiling data.

Decision

The repository, cargo build artifacts, benchmark corpora, Git mirrors and profiling output live on the external volume. Toolchains and the cargo registry stay on the internal disk. No machine-specific path is committed: the target-dir override lives in the developer's user-level ~/.cargo/config.toml, documented (not committed) in docs/development/external-storage.md.

Alternatives

• Everything internal — rejected: 256 GB minus OS and toolchains cannot hold the M08 corpus.
• Committed .cargo/config.toml with a /Volumes/... path — rejected: breaks every other machine, violates the no-machine-paths rule.

Consequences

The volume shipped exFAT: no hard links (cargo copies its incremental cache — harmless, slower), no xattrs (macOS writes AppleDouble ._* sidecars, including inside .git). Mitigations: ._* gitignored, make clean-sidecars, QG-001 fails if a sidecar is ever tracked. Reformatting to APFS is the recommended permanent fix and is documented as a user decision, not performed unilaterally.