1. Safe Rust by default. unsafe only in storage hot paths: mmap, SIMD intrinsics, arena internals. Every unsafe block gets a // SAFETY: comment explaining the invariant.
2. Zero-copy where possible. mmap'd segments, &str/&[u8] references into pages, SIMD on contiguous arrays. Never copy data between storage and execution without reason.
3. Narrow on disk, wide in execution. Store the tightest encoding. Widen to uniform register-sized types (I64, F64) for SIMD and branch-free processing.
4. Trait-based abstraction. Pluggable backends, storage providers, distance metrics — all behind traits. Concrete types for hot paths, dyn Trait only at configuration boundaries.
5. Error types per crate. thiserror enums. Never anyhow in library crates — only in binaries and tests. Never unwrap() in production code paths.
6. Async with tokio. All I/O is async. CPU-bound work (SIMD, compression, hashing) runs on spawn_blocking or dedicated threads. Never block the tokio runtime.
7. Property tests for invariants. proptest for serialization round-trips, type coercion, binary format parsing. Unit tests for logic. Integration tests for cross-crate behavior.
8. Workspace crate structure. One crate per subsystem. Depend downward — never circular. Storage at the bottom, server at the top.</EXTREMELY-IMPORTANT>

Rust Systems Programming

MANDATORY FIRST RESPONSE PROTOCOL

Before writing any Rust code:

1. Identify which subsystem the task touches
2. Read the matching reference file(s) from the routing table
3. Check crate dependencies — is this a library crate (thiserror) or binary (anyhow)?
4. State the approach before implementing

Routing Table

Multiple tasks? Read multiple files.

Quick Rules

1. cargo fmt before commit. cargo clippy -- -D warnings must pass.
2. Explicit use imports — no glob imports except in test modules.
3. #[must_use] on functions returning Result or computed values.
4. #[inline] only on small functions called in hot loops — never on public API.
5. Feature flags for optional crate dependencies — #[cfg(feature = "tantivy")].
6. Send + Sync bounds on all trait objects that cross async boundaries.
7. Prefer &[u8] over Vec<u8> in function signatures. Own data at boundaries, borrow inside.
8. #[derive(Debug)] on all public types. #[derive(Clone)] only when cheap.
9. Document all public items. //! module docs. /// item docs with examples.
10. Integration tests in tests/ directory. Unit tests in #[cfg(test)] mod tests.