- The cargo target folder is <cache>/cargo-target, next to Wasmtime's
cache, which moves to <cache>/wasmtime: Wasmtime's cleanup worker
deletes unknown entries in its folder, also Cargo's artifacts.
- Builds use the SDK at <cache>/sdk/<content hash>/, so cargo reuses
the compiled SDK in every world. /plugins/cargo/sdk/ stays for agents.
- Tests run in the release profile and share compiled crates with the
release build.
- The cargo and cli tests use a persistent cache in CARGO_TARGET_TMPDIR:
warm, the cargo suite takes 11 s (was 235 s) and the cli suite 6 s
(was 149 s).
- nix flake check runs ignored stress tests. AGENTS.md: rules for fast
tests.