hakorune/docs/development/strategies/de-rust-roadmap.md

# De‑Rust Roadmap (Phase 21.9+)

Purpose: reduce Rust surface (non‑plugin) while keeping correctness and reversibility. Make Hakorune (Hako) the primary host for parsing/building/executing; keep Rust for kernel/ABI/thin wrappers.

## Phases

### Phase 0 — Archive (low risk)
- Target: Rust LLVM backend (src/backend/llvm) — deprecated in favor of Python llvmlite.
- Action: move to `archive/rust-llvm-backend/` with a clear RESTORE.md.
- Acceptance: `cargo build --release` (default features) remains green; quick smokes green.
- Revert: `git mv archive/rust-llvm-backend/llvm src/backend/`.

### Phase 1 — Quick Wins (1–2 months)
- hv1_inline → Hako parity (already functionally covered; keep as perf path).
- MIR interpreter parity check; route Primary to Hako VM.
- TLV codec → C shim (FFI) with thin Rust wrapper.
- LLVM wrapper → Hako/C harness (Python stays primary until Hako IR is ready).

Deliverables & Tests
- hv1_inline: parity canaries = phase2037/flow + phase2170/state; add `HAKO_VERIFY_DISABLE_INLINE` opt-out (optional).
- TLV C shim: round‑trip tests (encode→decode) on representative payloads; FFI error mapping spec.
- MIR interpreter: keep as diagnostic path; parity sample set (const/binop/compare/branch/jump/ret/phi/mir_call minimal).
- LLVM wrapper: unify CLI entry; ensure `NYASH_LLVM_USE_HARNESS=1` path stays green.

### Phase 2 — Core Thinning (2–4 months)
- Plugin loader thin C wrapper (dlopen/dlsym), unify host ABI.
- Basic boxes (Array/Map/File) small C core (handle‑based), keep Rust shim.
- Resolver/Using: SSOT in Hako; runner uses shared policy.

SSOT for Using/Resolver (summary)
- Resolution order: modules (nyash.toml) → relative path inference → not found (warn) with verbose details.
- Analyzer/HakoCheck follows the same order; runner shares policy helpers. No path‑literal using in strict profiles.

### Phase 3 — Long‑haul (3–6 months)
- Python llvmlite → Hako IR builder + C ABI.
- Parser/MIR builder fully Hako‑first; Rust becomes fallback.
- NyKernel minimal C runtime (BoxCall dispatcher + collections + file).

## Principles
- Guard everything by env/features; defaults unchanged.
- Keep changes reversible (small diffs, RESTORE docs, fallbacks).
- Test gates: quick smokes + representative hv1/hakovm parity.

## Today (suggested)
1) Stage Phase‑0 move as a script (not auto‑run) + RESTORE.md.
2) Add phase docs (docs/private/roadmap/phases/phase-21.9/PLAN.md).
3) Keep CI/dev instructions intact (no build break when features=none).

## Test Strategy (gates)
- Quick: tools/smokes/v2/profiles/quick/core/* (phase2037 flow, phase2170 state) — green.
- Verify routing: HAKO_VERIFY_PRIMARY=hakovm (default); hv1_inline perf path parity (env toggles only).
- Build: `cargo build --release` (default features); LLVM paths are opt‑in.
- Docs: keep RESTORE steps for any archived parts; small diffs, easy rollback.