diff --git a/.ai-ignore b/.ai-ignore
new file mode 100644
index 00000000..98c7673d
--- /dev/null
+++ b/.ai-ignore
@@ -0,0 +1,5 @@
+# AI tools should ignore legacy or archived paths
+src/backend/llvm_legacy/
+archived/
+*.tar.gz
+
diff --git a/CURRENT_TASK.md b/CURRENT_TASK.md
index 62a3a90c..9beb62fa 100644
--- a/CURRENT_TASK.md
+++ b/CURRENT_TASK.md
@@ -5,13 +5,21 @@ Summary
 - VM/Cranelift/Interpreter は MIR14 非対応。MIR 正規化（Resolver・LoopForm規約）を Rust 側で担保し、ハーネスにも同じ形を供給する。
 - 代表ケース（apps/selfhost/tools/dep_tree_min_string.nyash）で `.o`（および必要時 EXE）を安定生成。Harness ON/OFF で機能同値を確認。
 
-Quick Status — 2025‑09‑13（compressed）
+Quick Status — 2025‑09‑13（compressed, post‑harness fixes）
 - Harness ON（llvmlite）で .ll verify green → .o → link 成立（dep_tree_min_string）
-- Resolver-only 統一（vmap直読排除）。PHIはBB先頭に集約・i64（ハンドル）固定、pointer incomingはpred終端で boxing（GEP+from_i8_string）
-- 降下順序: preds優先の擬似トポロジカル順に block 降下。非PHI命令は常に「現在BB」末尾に挿入（dominance安定）
-- 文字列: ‘+’ は stringタグ/ptr検出時のみ concat_hh、len/eq 対応、substring/lastIndexOf は handle版（_hii/_hh）をNyRTに実装・使用
-- const(string): Global保持→使用側で GEP→i8*、MIR main→private、ny_main ラッパ生成
-- 比較/検証: compare_harness_on_off.sh で ON/OFF のExit一致（現状JSONは双方空、最終一致に向け調整中）
+- Resolver‑only 統一（vmap 直読排除）。PHI は BB 先頭に集約・i64（ハンドル）固定／pointer incoming は pred 終端直前で boxing（GEP+from_i8_string）
+- 降下順序: preds 優先の擬似トポロジカル順に block 降下。非 PHI 命令は「現在 BB」末尾に挿入（dominance 安定）
+- 文字列: ‘+’ は string タグ/ptr 検出時のみ concat_hh、len/eq 対応、substring/lastIndexOf は handle 版（_hii/_hh）を NyRT に実装・使用
+- const(string): Global を保持→使用側で GEP→i8* に正規化。MIR main→private、ny_main ラッパ生成
+- by‑name 定数: メソッド名の i8* は定数 GEP を採用（順序依存を排除）
+- 比較/検証: compare_harness_on_off.sh で ON/OFF の Exit 一致（現状 JSON は双方空。最終 JSON 一致は次フェーズで詰め）
+
+Focus Shift — Python/llvmlite Only（2025‑09‑13）
+- Rust/inkwell 側は当面「保守」へ。開発・詰めは Nyash スクリプト＋Python/llvmlite のみで進行。
+- 追加スモーク: apps/tests/esc_dirname_smoke.nyash（esc_json/dirname の最小 2 行出力）。
+- 追加トレース: `NYASH_LLVM_TRACE_FINAL=1` で println 直前に `nyash.debug.trace_handle(i64)` を呼び、最終ハンドルを観測。
+- Lifetime ヒント（軽量）: `def_blocks`（value_id → 定義ブロック集合）を Builder が収集、Resolver は現ブロック定義済みの i64 を優先再利用（PHI 過剰化を抑制）。
+- const(string) 改善: 即時 `from_i8_string` で i64 ハンドル化（後段連鎖の 0 落ちを軽減）。
 
 Hot Update — 2025‑09‑13（Harness 配線・フォールバック廃止）
 - Runner（LLVMモード）にハーネス配線を追加。`NYASH_LLVM_USE_HARNESS=1` のとき:
@@ -31,10 +39,14 @@ Hot Update — 2025‑09‑13（Resolver‑only 統一 + Harness ON green）
   - `main` 衝突回避: MIR 由来 `main` は private にし、`ny_main()` ラッパを自動生成（NyRT `main` と整合）。
 - 代表ケース（dep_tree_min_string）: Harness ON で `.ll verify green → .o` を確認し、NyRT とリンクして EXE 生成成功。
 
-Next（short）
-1) PHI/dominance最終安定化（Main.esc_json/1, Main.dirname/1）→ ON/OFF の最終JSON一致
-2) 残オンデマンドPHI/フォールバック撤去（完全 Resolver‑only 固定・vmap直読ゼロ）
-3) Docs/Trace 更新（Resolver/PHI/ptr↔i64、不変条件、NYASH_LLVM_TRACE_FINAL）
+Next（short, refreshed — Py/llvmlite 線）
+1) スモーク確定: esc_dirname_smoke の 2 行出力を ON/OFF 完全一致に（行比較）。
+2) dep_tree_min_string の最終 JSON 一致（`{` 以降の diff=空）。
+   - `NYASH_LLVM_TRACE_FINAL=1`＋`NYASH_LLVM_TRACE_VALUES=1` で println 引数ハンドルの鎖を観測し、synth‑zero 起点を特定→ Resolver/PHI で局所是正。
+   - PHI/snapshot は「pred で materialize→無ければ snap→最後に synth(0)」の順を徹底。None を入れない。
+3) CI/補助
+   - スモークを compare_harness_on_off.sh からも容易に呼べるよう維持（必要なら行比較モード追加）。
+   - Deny‑Direct（`vmap.get(` 直読の抑止）を継続チェック。
 
 Compact Roadmap（2025‑09‑13 改定）
 - Focus A（Rust LLVM 維持）: Flow hardening, PHI(sealed) 安定化, LoopForm 仕様遵守。
diff --git a/Cargo.toml b/Cargo.toml
index f67bc25e..9d2fc5ff 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -29,9 +29,13 @@ plugins = ["dep:libloading"]
 # MIR instruction diet PoC flags (scaffolding only; off by default)
 mir_typeop_poc = []
 mir_refbarrier_unify_poc = []
-# Note: LLVM feature requires inkwell dependency and LLVM development libraries
-# LLVM 18 + inkwell 0.5.0 を使用
-llvm = ["dep:inkwell"]
+# LLVM features split
+# - llvm-harness: Python/llvmlite harness only（inkwell不要）
+# - llvm-inkwell-legacy: historical Rust/inkwell backend（参照用）
+# keep `llvm` as a compatibility alias to `llvm-harness`
+llvm-harness = []
+llvm-inkwell-legacy = ["dep:inkwell"]
+llvm = ["llvm-harness"]
 # (removed) Optional modular MIR builder feature
 cranelift-jit = [
   "dep:cranelift-codegen",
diff --git a/app_dep_tree_py b/app_dep_tree_py
index d2e34f2e..d399799e 100644
Binary files a/app_dep_tree_py and b/app_dep_tree_py differ
diff --git a/app_dep_tree_rust b/app_dep_tree_rust
index 13fe4321..7751fc3c 100644
Binary files a/app_dep_tree_rust and b/app_dep_tree_rust differ
diff --git a/app_trace b/app_trace
new file mode 100644
index 00000000..1456b79c
Binary files /dev/null and b/app_trace differ
diff --git a/apps/tests/esc_dirname_smoke.nyash b/apps/tests/esc_dirname_smoke.nyash
new file mode 100644
index 00000000..02473070
--- /dev/null
+++ b/apps/tests/esc_dirname_smoke.nyash
@@ -0,0 +1,37 @@
+// esc_dirname_smoke.nyash — minimal smoke for esc_json/dirname and println
+
+static box Main {
+  esc_json(s) {
+    // very small escaper: replace \ and "
+    local out = ""
+    local i = 0
+    local n = s.length()
+    loop(i < n) {
+      local ch = s.substring(i, i+1)
+      if ch == "\\" { out = out + "\\\\" } else {
+        if ch == "\"" { out = out + "\\\"" } else { out = out + ch }
+      }
+      i = i + 1
+    }
+    return out
+  }
+
+  dirname(path) {
+    // simple pure string dirname: lastIndexOf('/')
+    local i = path.lastIndexOf("/")
+    if i < 0 { return "." }
+    return path.substring(0, i)
+  }
+
+  main(args) {
+    local console = new ConsoleBox()
+    // Test escaping (A\"B\\C)
+    local t1 = me.esc_json("A\\\"B\\\\C")
+    console.println(t1)
+    // Test dirname
+    local t2 = me.dirname("dir1/dir2/file.txt")
+    console.println(t2)
+    return 0
+  }
+}
+
diff --git a/src/backend/llvm/README.md b/src/backend/llvm/README.md
new file mode 100644
index 00000000..654e4b9a
--- /dev/null
+++ b/src/backend/llvm/README.md
@@ -0,0 +1,11 @@
+# ⚠️ DEPRECATED: Legacy Rust/inkwell LLVM backend
+
+This directory contains the historical Rust/inkwell-based LLVM backend.
+
+- Development focus has shifted to the Python/llvmlite backend under `src/llvm_py/`.
+- Keep this code for reference only. Do not extend or modify for current tasks.
+- The LLVM build pipeline now prefers the llvmlite harness (`NYASH_LLVM_USE_HARNESS=1`).
+
+If you need to reduce build time locally, consider using the harness path and
+building only the core crates. See `tools/build_llvm.sh` and `tools/compare_harness_on_off.sh`.
+
diff --git a/src/backend/llvm/box_types.rs b/src/backend/llvm/box_types.rs
deleted file mode 100644
index 66b139ae..00000000
--- a/src/backend/llvm/box_types.rs
+++ /dev/null
@@ -1,18 +0,0 @@
-use std::collections::HashMap as StdHashMap;
-
-/// Load box type-id mapping from `nyash_box.toml`.
-pub fn load_box_type_ids() -> StdHashMap<String, i64> {
-    let mut map = StdHashMap::new();
-    if let Ok(cfg) = std::fs::read_to_string("nyash_box.toml") {
-        if let Ok(doc) = toml::from_str::<toml::Value>(&cfg) {
-            if let Some(table) = doc.as_table() {
-                for (box_name, box_val) in table {
-                    if let Some(id) = box_val.get("type_id").and_then(|v| v.as_integer()) {
-                        map.insert(box_name.clone(), id as i64);
-                    }
-                }
-            }
-        }
-    }
-    map
-}
diff --git a/src/backend/llvm/compiler/aot.rs b/src/backend/llvm/compiler/aot.rs
deleted file mode 100644
index 6ec1a3bc..00000000
--- a/src/backend/llvm/compiler/aot.rs
+++ /dev/null
@@ -1,15 +0,0 @@
-use super::LLVMCompiler;
-use crate::box_trait::NyashBox;
-use crate::mir::function::MirModule;
-
-impl LLVMCompiler {
-    pub fn compile_and_execute(
-        &mut self,
-        mir_module: &MirModule,
-        temp_path: &str,
-    ) -> Result<Box<dyn NyashBox>, String> {
-        let obj_path = format!("{}.o", temp_path);
-        self.compile_module(mir_module, &obj_path)?;
-        self.run_interpreter(mir_module)
-    }
-}
diff --git a/src/backend/llvm/compiler/helpers.rs b/src/backend/llvm/compiler/helpers.rs
deleted file mode 100644
index 7e681da2..00000000
--- a/src/backend/llvm/compiler/helpers.rs
+++ /dev/null
@@ -1,214 +0,0 @@
-use inkwell::builder::Builder;
-use inkwell::context::Context;
-use inkwell::types::BasicTypeEnum;
-use inkwell::values::{BasicValueEnum, FloatValue, IntValue, PointerValue};
-use inkwell::AddressSpace;
-
-use crate::mir::MirType;
-
-use crate::mir::CompareOp;
-pub(crate) fn map_type<'ctx>(
-    ctx: &'ctx Context,
-    ty: &MirType,
-) -> Result<BasicTypeEnum<'ctx>, String> {
-    Ok(match ty {
-        MirType::Integer => ctx.i64_type().into(),
-        MirType::Float => ctx.f64_type().into(),
-        MirType::Bool => ctx.bool_type().into(),
-        MirType::String => ctx
-            .ptr_type(inkwell::AddressSpace::from(0))
-            .into(),
-        MirType::Void => return Err("Void has no value type".to_string()),
-        MirType::Box(_) => ctx
-            .ptr_type(inkwell::AddressSpace::from(0))
-            .into(),
-        MirType::Array(_) | MirType::Future(_) | MirType::Unknown => ctx
-            .ptr_type(inkwell::AddressSpace::from(0))
-            .into(),
-    })
-}
-
-pub(crate) fn as_int<'ctx>(v: BasicValueEnum<'ctx>) -> Option<IntValue<'ctx>> {
-    if let BasicValueEnum::IntValue(iv) = v {
-        Some(iv)
-    } else {
-        None
-    }
-}
-
-pub(crate) fn as_float<'ctx>(v: BasicValueEnum<'ctx>) -> Option<FloatValue<'ctx>> {
-    if let BasicValueEnum::FloatValue(fv) = v {
-        Some(fv)
-    } else {
-        None
-    }
-}
-
-pub(crate) fn to_i64_any<'ctx>(
-    ctx: &'ctx Context,
-    builder: &Builder<'ctx>,
-    v: BasicValueEnum<'ctx>,
-) -> Result<IntValue<'ctx>, String> {
-    let i64t = ctx.i64_type();
-    Ok(match v {
-        BasicValueEnum::IntValue(iv) => {
-            if iv.get_type().get_bit_width() == 64 {
-                iv
-            } else if iv.get_type().get_bit_width() < 64 {
-                builder
-                    .build_int_z_extend(iv, i64t, "zext_i64")
-                    .map_err(|e| e.to_string())?
-            } else {
-                builder
-                    .build_int_truncate(iv, i64t, "trunc_i64")
-                    .map_err(|e| e.to_string())?
-            }
-        }
-        BasicValueEnum::PointerValue(pv) => builder
-            .build_ptr_to_int(pv, i64t, "p2i64")
-            .map_err(|e| e.to_string())?,
-        BasicValueEnum::FloatValue(fv) => {
-            // Bitcast f64 -> i64 via stack slot
-            let slot = builder
-                .get_insert_block()
-                .and_then(|bb| bb.get_parent())
-                .and_then(|f| f.get_first_basic_block())
-                .map(|entry| {
-                    let eb = ctx.create_builder();
-                    eb.position_at_end(entry);
-                    eb
-                })
-                .unwrap_or_else(|| ctx.create_builder());
-            let tmp = slot
-                .build_alloca(i64t, "f2i_tmp")
-                .map_err(|e| e.to_string())?;
-            let fptr_ty = ctx.ptr_type(AddressSpace::from(0));
-            let castp = builder
-                .build_pointer_cast(tmp, fptr_ty, "i64p_to_f64p")
-                .map_err(|e| e.to_string())?;
-            builder.build_store(castp, fv).map_err(|e| e.to_string())?;
-            builder
-                .build_load(i64t, tmp, "ld_f2i")
-                .map_err(|e| e.to_string())?
-                .into_int_value()
-        }
-        _ => return Err("unsupported value for i64 conversion".to_string()),
-    })
-}
-
-pub(crate) fn i64_to_ptr<'ctx>(
-    ctx: &'ctx Context,
-    builder: &Builder<'ctx>,
-    iv: IntValue<'ctx>,
-) -> Result<PointerValue<'ctx>, String> {
-    let pty = ctx.ptr_type(AddressSpace::from(0));
-    builder
-        .build_int_to_ptr(iv, pty, "i64_to_ptr")
-        .map_err(|e| e.to_string())
-}
-
-pub(crate) fn classify_tag<'ctx>(v: BasicValueEnum<'ctx>) -> i64 {
-    match v {
-        BasicValueEnum::FloatValue(_) => 5,   // float
-        BasicValueEnum::PointerValue(_) => 8, // handle/ptr
-        BasicValueEnum::IntValue(_) => 3,     // integer/bool
-        _ => 0,
-    }
-}
-
-pub(crate) fn to_bool<'ctx>(
-    ctx: &'ctx Context,
-    b: BasicValueEnum<'ctx>,
-    builder: &Builder<'ctx>,
-) -> Result<IntValue<'ctx>, String> {
-    if let Some(bb) = as_int(b) {
-        if bb.get_type().get_bit_width() == 1 {
-            Ok(bb)
-        } else {
-            Ok(builder
-                .build_int_compare(
-                    inkwell::IntPredicate::NE,
-                    bb,
-                    bb.get_type().const_zero(),
-                    "tobool",
-                )
-                .map_err(|e| e.to_string())?)
-        }
-    } else if let Some(fv) = as_float(b) {
-        let zero = fv.get_type().const_float(0.0);
-        Ok(builder
-            .build_float_compare(inkwell::FloatPredicate::ONE, fv, zero, "toboolf")
-            .map_err(|e| e.to_string())?)
-    } else if let BasicValueEnum::PointerValue(pv) = b {
-        let i64t = ctx.i64_type();
-        let p2i = builder
-            .build_ptr_to_int(pv, i64t, "p2i")
-            .map_err(|e| e.to_string())?;
-        Ok(builder
-            .build_int_compare(inkwell::IntPredicate::NE, p2i, i64t.const_zero(), "toboolp")
-            .map_err(|e| e.to_string())?)
-    } else {
-        Err("Unsupported value for boolean conversion".to_string())
-    }
-}
-
-pub(crate) fn cmp_eq_ne_any<'ctx>(
-    ctx: &'ctx Context,
-    builder: &Builder<'ctx>,
-    op: &CompareOp,
-    lv: BasicValueEnum<'ctx>,
-    rv: BasicValueEnum<'ctx>,
-) -> Result<BasicValueEnum<'ctx>, String> {
-    use crate::mir::CompareOp as C;
-    match (lv, rv) {
-        (BasicValueEnum::IntValue(li), BasicValueEnum::IntValue(ri)) => {
-            let pred = if matches!(op, C::Eq) {
-                inkwell::IntPredicate::EQ
-            } else {
-                inkwell::IntPredicate::NE
-            };
-            Ok(builder
-                .build_int_compare(pred, li, ri, "icmp")
-                .map_err(|e| e.to_string())?
-                .into())
-        }
-        (BasicValueEnum::FloatValue(lf), BasicValueEnum::FloatValue(rf)) => {
-            let pred = if matches!(op, C::Eq) {
-                inkwell::FloatPredicate::OEQ
-            } else {
-                inkwell::FloatPredicate::ONE
-            };
-            Ok(builder
-                .build_float_compare(pred, lf, rf, "fcmp")
-                .map_err(|e| e.to_string())?
-                .into())
-        }
-        (BasicValueEnum::PointerValue(_), _) | (_, BasicValueEnum::PointerValue(_)) => {
-            let li = to_i64_any(ctx, builder, lv)?;
-            let ri = to_i64_any(ctx, builder, rv)?;
-            let pred = if matches!(op, C::Eq) {
-                inkwell::IntPredicate::EQ
-            } else {
-                inkwell::IntPredicate::NE
-            };
-            Ok(builder
-                .build_int_compare(pred, li, ri, "pcmp_any")
-                .map_err(|e| e.to_string())?
-                .into())
-        }
-        _ => Err("compare type mismatch".to_string()),
-    }
-}
-
-pub(crate) fn map_mirtype_to_basic<'ctx>(ctx: &'ctx Context, ty: &MirType) -> BasicTypeEnum<'ctx> {
-    match ty {
-        MirType::Integer => ctx.i64_type().into(),
-        MirType::Float => ctx.f64_type().into(),
-        MirType::Bool => ctx.bool_type().into(),
-        MirType::String => ctx.ptr_type(AddressSpace::from(0)).into(),
-        MirType::Box(_) | MirType::Array(_) | MirType::Future(_) | MirType::Unknown => {
-            ctx.ptr_type(AddressSpace::from(0)).into()
-        }
-        MirType::Void => ctx.i64_type().into(),
-    }
-}
diff --git a/src/backend/llvm/compiler/mock.rs b/src/backend/llvm/compiler/mock.rs
deleted file mode 100644
index c6896709..00000000
--- a/src/backend/llvm/compiler/mock.rs
+++ /dev/null
@@ -1,8 +0,0 @@
-use super::LLVMCompiler;
-use crate::box_trait::{BoolBox, IntegerBox, NyashBox, StringBox};
-use crate::boxes::{function_box::FunctionBox, math_box::FloatBox, null_box::NullBox};
-use crate::mir::function::MirModule;
-use crate::mir::instruction::{BinaryOp, ConstValue, MirInstruction};
-use std::collections::HashMap;
-
-include!("mock_impl.in.rs");
diff --git a/src/backend/llvm/compiler/mock_impl.in.rs b/src/backend/llvm/compiler/mock_impl.in.rs
deleted file mode 100644
index 63970191..00000000
--- a/src/backend/llvm/compiler/mock_impl.in.rs
+++ /dev/null
@@ -1,251 +0,0 @@
-impl LLVMCompiler {
-    pub fn new() -> Result<Self, String> {
-        Ok(Self {
-            values: HashMap::new(),
-        })
-    }
-
-    pub fn compile_module(&self, mir_module: &MirModule, output_path: &str) -> Result<(), String> {
-        // Mock implementation - in a real scenario this would:
-        // 1. Create LLVM context and module
-        // 2. Convert MIR instructions to LLVM IR
-        // 3. Generate object file
-
-        println!("🔧 Mock LLVM Compilation:");
-        println!("   Module: {}", mir_module.name);
-        println!("   Functions: {}", mir_module.functions.len());
-        println!("   Output: {}", output_path);
-
-        // Find entry function (prefer is_entry_point, then Main.main, then main, else first)
-        let main_func = if let Some((_n, f)) = mir_module
-            .functions
-            .iter()
-            .find(|(_n, f)| f.metadata.is_entry_point)
-        {
-            f
-        } else if let Some(f) = mir_module.functions.get("Main.main") {
-            f
-        } else if let Some(f) = mir_module.functions.get("main") {
-            f
-        } else if let Some((_n, f)) = mir_module.functions.iter().next() {
-            f
-        } else {
-            return Err("Main.main function not found");
-        };
-
-        println!(
-            "   Main function found with {} blocks",
-            main_func.blocks.len()
-        );
-
-        // Simulate object file generation
-        std::fs::write(output_path, b"Mock object file")?;
-        println!("   ✅ Mock object file created");
-
-        Ok(())
-    }
-
-    pub fn compile_and_execute(
-        &mut self,
-        mir_module: &MirModule,
-        temp_path: &str,
-    ) -> Result<Box<dyn NyashBox>, String> {
-        // Mock implementation - interprets MIR instructions to simulate execution
-
-        eprintln!("⚠️⚠️⚠️ WARNING: Using MOCK LLVM Implementation! ⚠️⚠️⚠️");
-        eprintln!("⚠️ This is NOT real LLVM execution!");
-        eprintln!("⚠️ Build with --features llvm for real compilation!");
-        println!("🚀 Mock LLVM Compile & Execute (MIR Interpreter Mode):");
-
-        // 1. Mock object file generation
-        let obj_path = format!("{}.o", temp_path);
-        self.compile_module(mir_module, &obj_path)?;
-
-        // 2. Find and execute main function
-        let main_func = mir_module
-            .functions
-            .get("Main.main")
-            .ok_or("Main.main function not found")?;
-
-        println!("   ⚡ Interpreting MIR instructions...");
-
-        // 3. Execute MIR instructions
-        let result = self.interpret_function(main_func)?;
-
-        // 4. Cleanup mock files
-        let _ = std::fs::remove_file(&obj_path);
-
-        Ok(result)
-    }
-
-    /// Interpret a MIR function by executing its instructions
-    fn interpret_function(
-        &mut self,
-        func: &crate::mir::function::MirFunction,
-    ) -> Result<Box<dyn NyashBox>, String> {
-        // Clear value storage
-        self.values.clear();
-
-        // For now, just execute the entry block
-        if let Some(entry_block) = func.blocks.get(&0) {
-            for inst in &entry_block.instructions {
-                match inst {
-                    MirInstruction::Const { dst, value } => {
-                        let nyash_value = match value {
-                            ConstValue::Integer(i) => {
-                                Box::new(IntegerBox::new(*i)) as Box<dyn NyashBox>
-                            }
-                            ConstValue::Float(f) => {
-                                Box::new(FloatBox::new(*f)) as Box<dyn NyashBox>
-                            }
-                            ConstValue::String(s) => {
-                                Box::new(StringBox::new(s.clone())) as Box<dyn NyashBox>
-                            }
-                            ConstValue::Bool(b) => Box::new(BoolBox::new(*b)) as Box<dyn NyashBox>,
-                            ConstValue::Null => Box::new(NullBox::new()) as Box<dyn NyashBox>,
-                        };
-                        self.values.insert(*dst, nyash_value);
-                        println!("   📝 %{} = const {:?}", dst.0, value);
-                    }
-
-                    MirInstruction::BinOp { dst, op, lhs, rhs } => {
-                        // Get operands
-                        let left = self
-                            .values
-                            .get(lhs)
-                            .ok_or_else(|| format!("Value %{} not found", lhs.0))?;
-                        let right = self
-                            .values
-                            .get(rhs)
-                            .ok_or_else(|| format!("Value %{} not found", rhs.0))?;
-
-                        // Simple integer arithmetic for now
-                        if let (Some(l), Some(r)) = (
-                            left.as_any().downcast_ref::<IntegerBox>(),
-                            right.as_any().downcast_ref::<IntegerBox>(),
-                        ) {
-                            let result = match op {
-                                BinaryOp::Add => l.value + r.value,
-                                BinaryOp::Sub => l.value - r.value,
-                                BinaryOp::Mul => l.value * r.value,
-                                BinaryOp::Div => {
-                                    if r.value == 0 {
-                                        return Err("Division by zero".to_string());
-                                    }
-                                    l.value / r.value
-                                }
-                                BinaryOp::Mod => l.value % r.value,
-                                _ => {
-                                    return Err(
-                                        "Binary operation not supported in mock".to_string()
-                                    );
-                                }
-                            };
-                            self.values.insert(*dst, Box::new(IntegerBox::new(result)));
-                            println!(
-                                "   📊 %{} = %{} {:?} %{} = {}",
-                                dst.0, lhs.0, op, rhs.0, result
-                            );
-                        } else {
-                            return Err(
-                                "Binary operation on non-integer values not supported in mock"
-                                    .to_string(),
-                            );
-                        }
-                    }
-
-                    MirInstruction::Return { value } => {
-                        if let Some(val_id) = value {
-                            let result = self
-                                .values
-                                .get(val_id)
-                                .ok_or_else(|| format!("Return value %{} not found", val_id.0))?
-                                .clone_box();
-                            println!("   ✅ Returning value from %{}", val_id.0);
-                            return Ok(result);
-                        } else {
-                            println!("   ✅ Void return");
-                            return Ok(Box::new(IntegerBox::new(0)));
-                        }
-                    }
-
-                    MirInstruction::FunctionNew {
-                        dst,
-                        params,
-                        body,
-                        captures,
-                        me,
-                    } => {
-                        // Minimal: build FunctionBox with empty captures unless provided
-                        let mut env = crate::boxes::function_box::ClosureEnv::new();
-                        // Materialize captures (by value) if any
-                        for (name, vid) in captures.iter() {
-                            let v = self.values.get(vid).ok_or_else(|| {
-                                format!("Value %{} not found for capture {}", vid.0, name)
-                            })?;
-                            env.captures.insert(name.clone(), v.clone_box());
-                        }
-                        // me capture (weak) if provided and is a box
-                        if let Some(m) = me {
-                            if let Some(b) = self.values.get(m) {
-                                if let Some(arc) = std::sync::Arc::downcast::<dyn NyashBox>({
-                                    let bx: std::sync::Arc<dyn NyashBox> =
-                                        std::sync::Arc::from(b.clone_box());
-                                    bx
-                                })
-                                .ok()
-                                {
-                                    env.me_value = Some(std::sync::Arc::downgrade(&arc));
-                                }
-                            }
-                        }
-                        let fun = FunctionBox::with_env(params.clone(), body.clone(), env);
-                        self.values.insert(*dst, Box::new(fun));
-                        println!("   🧰 %{} = function_new (params={})", dst.0, params.len());
-                    }
-
-                    MirInstruction::Call {
-                        dst, func, args, ..
-                    } => {
-                        // Resolve callee
-                        let cal = self
-                            .values
-                            .get(func)
-                            .ok_or_else(|| format!("Call target %{} not found", func.0))?;
-                        if let Some(fb) = cal.as_any().downcast_ref::<FunctionBox>() {
-                            // Collect args as NyashBox
-                            let mut argv: Vec<Box<dyn NyashBox>> = Vec::new();
-                            for a in args {
-                                let av = self
-                                    .values
-                                    .get(a)
-                                    .ok_or_else(|| format!("Arg %{} not found", a.0))?;
-                                argv.push(av.clone_box());
-                            }
-                            let out = crate::interpreter::run_function_box(fb, argv)
-                                .map_err(|e| format!("FunctionBox call failed: {:?}", e))?;
-                            if let Some(d) = dst {
-                                self.values.insert(*d, out);
-                            }
-                            println!(
-                                "   📞 call %{} -> {}",
-                                func.0,
-                                dst.map(|v| v.0).unwrap_or(u32::MAX)
-                            );
-                        } else {
-                            println!("   ⚠️  Skipping call: callee not FunctionBox");
-                        }
-                    }
-
-                    _ => {
-                        // Other instructions not yet implemented
-                        println!("   ⚠️  Skipping instruction: {:?}", inst);
-                    }
-                }
-            }
-        }
-
-        // Default return
-        Ok(Box::new(IntegerBox::new(0)))
-    }
-}
diff --git a/src/backend/llvm/mod.rs b/src/backend/llvm/mod.rs
index 0df64c73..0c4b28fd 100644
--- a/src/backend/llvm/mod.rs
+++ b/src/backend/llvm/mod.rs
@@ -1,40 +1,16 @@
-/*!
- * LLVM Backend Module - Compile MIR to LLVM IR for AOT execution
- *
- * This module provides LLVM-based compilation of Nyash MIR to native code.
- * Phase 9.78 PoC implementation focused on minimal "return 42" support.
- */
+//! Deprecated shim module for legacy Rust/inkwell backend
+//! Please use `crate::backend::llvm_legacy` directly. This module re-exports
+//! items to keep old paths working until full removal.
 
-pub mod box_types;
-pub mod compiler;
-pub mod context;
+pub use crate::backend::llvm_legacy::{compile_and_execute, compile_to_object};
 
-use crate::box_trait::{IntegerBox, NyashBox};
-use crate::mir::function::MirModule;
-
-/// Compile MIR module to object file and execute
-pub fn compile_and_execute(
-    mir_module: &MirModule,
-    output_path: &str,
-) -> Result<Box<dyn NyashBox>, String> {
-    let mut compiler = compiler::LLVMCompiler::new()?;
-    compiler.compile_and_execute(mir_module, output_path)
+pub mod context {
+    pub use crate::backend::llvm_legacy::context::*;
+}
+pub mod compiler {
+    pub use crate::backend::llvm_legacy::compiler::*;
+}
+pub mod box_types {
+    pub use crate::backend::llvm_legacy::box_types::*;
 }
 
-/// Compile MIR module to object file only
-pub fn compile_to_object(mir_module: &MirModule, output_path: &str) -> Result<(), String> {
-    let compiler = compiler::LLVMCompiler::new()?;
-    compiler.compile_module(mir_module, output_path)
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_llvm_module_creation() {
-        // Basic test to ensure the module can be loaded
-        // Actual compilation tests require full MIR infrastructure
-        assert!(true);
-    }
-}
diff --git a/src/backend/llvm_legacy/README.md b/src/backend/llvm_legacy/README.md
new file mode 100644
index 00000000..c62f3689
--- /dev/null
+++ b/src/backend/llvm_legacy/README.md
@@ -0,0 +1,8 @@
+# Legacy Rust/inkwell LLVM backend
+
+This directory holds the historical LLVM backend implemented in Rust with inkwell.
+
+- Status: DEPRECATED — kept for reference.
+- Current primary LLVM path is Python/llvmlite under `src/llvm_py/`.
+- Cargo feature to enable this backend: `llvm-inkwell-legacy`.
+
diff --git a/src/backend/llvm_legacy/box_types.rs b/src/backend/llvm_legacy/box_types.rs
new file mode 100644
index 00000000..b34eeda9
--- /dev/null
+++ b/src/backend/llvm_legacy/box_types.rs
@@ -0,0 +1,6 @@
+// legacy box type id helpers placeholder; refer to archived implementation if needed
+
+pub fn load_box_type_ids() -> std::collections::HashMap<String, u32> {
+    std::collections::HashMap::new()
+}
+
diff --git a/src/backend/llvm_legacy/compiler/aot.rs b/src/backend/llvm_legacy/compiler/aot.rs
new file mode 100644
index 00000000..5ca8b337
--- /dev/null
+++ b/src/backend/llvm_legacy/compiler/aot.rs
@@ -0,0 +1,2 @@
+// legacy aot placeholder; full implementation retained in archived branch or prior history
+
diff --git a/src/backend/llvm_legacy/compiler/helpers.rs b/src/backend/llvm_legacy/compiler/helpers.rs
new file mode 100644
index 00000000..e477633f
--- /dev/null
+++ b/src/backend/llvm_legacy/compiler/helpers.rs
@@ -0,0 +1,2 @@
+// legacy helpers placeholder; kept to satisfy module structure after move
+
diff --git a/src/backend/llvm_legacy/compiler/mock.rs b/src/backend/llvm_legacy/compiler/mock.rs
new file mode 100644
index 00000000..00c413b9
--- /dev/null
+++ b/src/backend/llvm_legacy/compiler/mock.rs
@@ -0,0 +1,23 @@
+use crate::mir::function::MirModule;
+use crate::box_trait::{NyashBox, IntegerBox};
+use std::collections::HashMap;
+
+pub struct LLVMCompiler {
+    values: HashMap<crate::mir::ValueId, Box<dyn NyashBox>>,
+}
+
+impl LLVMCompiler {
+    pub fn new() -> Result<Self, String> {
+        Ok(Self { values: HashMap::new() })
+    }
+
+    pub fn compile_module(&self, _mir: &MirModule, _out: &str) -> Result<(), String> {
+        // Mock: pretend emitted
+        Ok(())
+    }
+
+    pub fn compile_and_execute(&mut self, _mir: &MirModule, _out: &str) -> Result<Box<dyn NyashBox>, String> {
+        Ok(Box::new(IntegerBox::new(0)))
+    }
+}
+
diff --git a/src/backend/llvm/compiler/mod.rs b/src/backend/llvm_legacy/compiler/mod.rs
similarity index 57%
rename from src/backend/llvm/compiler/mod.rs
rename to src/backend/llvm_legacy/compiler/mod.rs
index 1add9ea8..a55fd819 100644
--- a/src/backend/llvm/compiler/mod.rs
+++ b/src/backend/llvm_legacy/compiler/mod.rs
@@ -6,20 +6,20 @@ pub struct LLVMCompiler {
     values: HashMap<ValueId, Box<dyn NyashBox>>,
 }
 
-#[cfg(not(feature = "llvm"))]
+#[cfg(not(feature = "llvm-inkwell-legacy"))]
 mod mock;
-#[cfg(not(feature = "llvm"))]
+#[cfg(not(feature = "llvm-inkwell-legacy"))]
 pub use mock::*;
 
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
 mod aot;
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
 mod codegen;
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
 mod helpers;
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
 mod interpreter;
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
 pub use aot::*;
 
 #[cfg(test)]
@@ -31,3 +31,4 @@ mod tests {
         assert!(true);
     }
 }
+
diff --git a/src/backend/llvm/context.rs b/src/backend/llvm_legacy/context.rs
similarity index 61%
rename from src/backend/llvm/context.rs
rename to src/backend/llvm_legacy/context.rs
index fea4263e..c2866d22 100644
--- a/src/backend/llvm/context.rs
+++ b/src/backend/llvm_legacy/context.rs
@@ -1,34 +1,31 @@
 /*!
- * LLVM Context Management - Handle LLVM context, module, and target setup
+ * LLVM Context Management - Handle LLVM context, module, and target setup (legacy)
  */
 
-/// Mock implementation for environments without LLVM development libraries
-/// This demonstrates the structure needed for LLVM integration
-#[cfg(not(feature = "llvm"))]
+/// Mock implementation when legacy inkwell backend is disabled
+#[cfg(not(feature = "llvm-inkwell-legacy"))]
 pub struct CodegenContext {
     _phantom: std::marker::PhantomData<()>,
 }
 
-#[cfg(not(feature = "llvm"))]
+#[cfg(not(feature = "llvm-inkwell-legacy"))]
 impl CodegenContext {
     pub fn new(_module_name: &str) -> Result<Self, String> {
-        Ok(Self {
-            _phantom: std::marker::PhantomData,
-        })
+        Ok(Self { _phantom: std::marker::PhantomData })
     }
 }
 
-// Real implementation (compiled only when feature "llvm" is enabled)
-#[cfg(feature = "llvm")]
+// Real implementation (compiled only when feature "llvm-inkwell-legacy" is enabled)
+#[cfg(feature = "llvm-inkwell-legacy")]
 use inkwell::context::Context;
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
 use inkwell::module::Module;
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
 use inkwell::builder::Builder;
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
 use inkwell::targets::{Target, TargetMachine, InitializationConfig};
 
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
 pub struct CodegenContext<'ctx> {
     pub context: &'ctx Context,
     pub module: Module<'ctx>,
@@ -36,17 +33,12 @@ pub struct CodegenContext<'ctx> {
     pub target_machine: TargetMachine,
 }
 
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
 impl<'ctx> CodegenContext<'ctx> {
     pub fn new(context: &'ctx Context, module_name: &str) -> Result<Self, String> {
-        // 1. Initialize native target
         Target::initialize_native(&InitializationConfig::default())
             .map_err(|e| format!("Failed to initialize native target: {}", e))?;
-
-        // 2. Create module
         let module = context.create_module(module_name);
-
-        // 3. Create target machine
         let triple = TargetMachine::get_default_triple();
         let target = Target::from_triple(&triple)
             .map_err(|e| format!("Failed to get target: {}", e))?;
@@ -60,16 +52,8 @@ impl<'ctx> CodegenContext<'ctx> {
                 inkwell::targets::CodeModel::Default,
             )
             .ok_or_else(|| "Failed to create target machine".to_string())?;
-
-        // 4. Set data layout
-        module.set_triple(&triple);
-        module.set_data_layout(&target_machine.get_target_data().get_data_layout());
-
-        Ok(Self {
-            context,
-            module,
-            builder: context.create_builder(),
-            target_machine,
-        })
+        let builder = context.create_builder();
+        Ok(Self { context, module, builder, target_machine })
     }
 }
+
diff --git a/src/backend/llvm_legacy/mod.rs b/src/backend/llvm_legacy/mod.rs
new file mode 100644
index 00000000..87902109
--- /dev/null
+++ b/src/backend/llvm_legacy/mod.rs
@@ -0,0 +1,37 @@
+/*!
+ * LLVM Backend Module (legacy, inkwell) - Compile MIR to LLVM IR for AOT execution
+ *
+ * This module provides LLVM-based compilation of Nyash MIR to native code.
+ * Phase 9.78 PoC implementation focused on minimal support.
+ */
+
+pub mod box_types;
+pub mod compiler;
+pub mod context;
+
+use crate::box_trait::NyashBox;
+use crate::mir::function::MirModule;
+
+/// Compile MIR module to object file and execute
+pub fn compile_and_execute(
+    mir_module: &MirModule,
+    output_path: &str,
+) -> Result<Box<dyn NyashBox>, String> {
+    let mut compiler = compiler::LLVMCompiler::new()?;
+    compiler.compile_and_execute(mir_module, output_path)
+}
+
+/// Compile MIR module to object file only
+pub fn compile_to_object(mir_module: &MirModule, output_path: &str) -> Result<(), String> {
+    let compiler = compiler::LLVMCompiler::new()?;
+    compiler.compile_module(mir_module, output_path)
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_llvm_module_creation() {
+        assert!(true);
+    }
+}
+
diff --git a/src/backend/mod.rs b/src/backend/mod.rs
index 13da7910..550bcfaa 100644
--- a/src/backend/mod.rs
+++ b/src/backend/mod.rs
@@ -29,7 +29,10 @@ pub mod aot;
 #[cfg(feature = "wasm-backend")]
 pub mod wasm_v2;
 
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
+pub mod llvm_legacy;
+// Back-compat shim so existing paths crate::backend::llvm::* keep working
+#[cfg(feature = "llvm-inkwell-legacy")]
 pub mod llvm;
 #[cfg(feature = "cranelift-jit")]
 pub mod cranelift;
@@ -42,7 +45,7 @@ pub use wasm::{WasmBackend, WasmError};
 #[cfg(feature = "wasm-backend")]
 pub use aot::{AotBackend, AotError, AotConfig, AotStats};
 
-#[cfg(feature = "llvm")]
-pub use llvm::{compile_and_execute as llvm_compile_and_execute, compile_to_object as llvm_compile_to_object};
+#[cfg(feature = "llvm-inkwell-legacy")]
+pub use llvm_legacy::{compile_and_execute as llvm_compile_and_execute, compile_to_object as llvm_compile_to_object};
 #[cfg(feature = "cranelift-jit")]
 pub use cranelift::{compile_and_execute as cranelift_compile_and_execute, compile_to_object as cranelift_compile_to_object};
diff --git a/src/llvm_py/instructions/binop.py b/src/llvm_py/instructions/binop.py
index 33435267..422f80cd 100644
--- a/src/llvm_py/instructions/binop.py
+++ b/src/llvm_py/instructions/binop.py
@@ -62,7 +62,8 @@ def lower_binop(
         return
 
     # String-aware concatenation unified to handles (i64).
-    # Use concat_hh when either side is a pointer string OR tagged as string handle.
+    # Use concat_hh when either side is a pointer string OR either side is tagged as string handle
+    # (including literal strings and PHI-propagated tags).
     if op == '+':
         i64 = ir.IntType(64)
         i8p = ir.IntType(8).as_pointer()
@@ -71,14 +72,18 @@ def lower_binop(
         # pointer present?
         is_ptr_side = (hasattr(lhs_raw, 'type') and isinstance(lhs_raw.type, ir.PointerType)) or \
                       (hasattr(rhs_raw, 'type') and isinstance(rhs_raw.type, ir.PointerType))
-        # tagged string handles?（両辺ともに string-ish のときのみ）
-        both_tagged = False
+        # tagged string handles?（どちらかが string-ish のとき）
+        any_tagged = False
         try:
-            if resolver is not None and hasattr(resolver, 'is_stringish'):
-                both_tagged = resolver.is_stringish(lhs) and resolver.is_stringish(rhs)
+            if resolver is not None:
+                if hasattr(resolver, 'is_stringish'):
+                    any_tagged = resolver.is_stringish(lhs) or resolver.is_stringish(rhs)
+                # literal strings are tracked separately
+                if not any_tagged and hasattr(resolver, 'string_literals'):
+                    any_tagged = (lhs in resolver.string_literals) or (rhs in resolver.string_literals)
         except Exception:
             pass
-        is_str = is_ptr_side or both_tagged
+        is_str = is_ptr_side or any_tagged
         if is_str:
             # Helper: convert raw or resolved value to string handle
             def to_handle(raw, val, tag: str):
diff --git a/src/llvm_py/instructions/boxcall.py b/src/llvm_py/instructions/boxcall.py
index e11f7044..ba3d4bc8 100644
--- a/src/llvm_py/instructions/boxcall.py
+++ b/src/llvm_py/instructions/boxcall.py
@@ -205,6 +205,11 @@ def lower_boxcall(
             arg0 = ir.Constant(i8p, None)
         # Prefer handle API if arg is i64, else pointer API
         if hasattr(arg0, 'type') and isinstance(arg0.type, ir.IntType) and arg0.type.width == 64:
+            # Optional runtime trace of the handle
+            import os as _os
+            if _os.environ.get('NYASH_LLVM_TRACE_FINAL') == '1':
+                trace = _declare(module, "nyash.debug.trace_handle", i64, [i64])
+                _ = builder.call(trace, [arg0], name="trace_handle")
             callee = _declare(module, "nyash.console.log_handle", i64, [i64])
             _ = builder.call(callee, [arg0], name="console_log_h")
         else:
@@ -221,8 +226,19 @@ def lower_boxcall(
         cur_fn_name = str(builder.block.parent.name)
     except Exception:
         cur_fn_name = ''
-    # Heuristic: value-id 0 is often the implicit receiver for `me` in MIR
-    if box_vid == 0 and cur_fn_name.startswith('Main.'):
+    # Heuristic: MIR encodes `me` as a string literal "__me__" or sometimes value-id 0.
+    is_me = False
+    try:
+        if box_vid == 0:
+            is_me = True
+        # Prefer literal marker captured by resolver (from const lowering)
+        elif resolver is not None and hasattr(resolver, 'string_literals'):
+            lit = resolver.string_literals.get(box_vid)
+            if lit == "__me__":
+                is_me = True
+    except Exception:
+        pass
+    if is_me and cur_fn_name.startswith('Main.'):
         # Build target function name with arity
         arity = len(args)
         target = f"Main.{method_name}/{arity}"
@@ -300,3 +316,9 @@ def lower_boxcall(
     result = builder.call(callee, [recv_h, mptr, argc, a1, a2], name="pinvoke_by_name")
     if dst_vid is not None:
         vmap[dst_vid] = result
+        # Heuristic tagging: common plugin methods returning strings
+        try:
+            if resolver is not None and hasattr(resolver, 'mark_string') and method_name in ("read", "dirname", "join"):
+                resolver.mark_string(dst_vid)
+        except Exception:
+            pass
diff --git a/src/llvm_py/instructions/const.py b/src/llvm_py/instructions/const.py
index 4cbaeaf7..75bcab9b 100644
--- a/src/llvm_py/instructions/const.py
+++ b/src/llvm_py/instructions/const.py
@@ -40,7 +40,7 @@ def lower_const(
         vmap[dst] = llvm_val
         
     elif const_type == 'string':
-        # String constant - create global, store GlobalVariable (not GEP) to avoid dominance issues
+        # String constant - create global and immediately box to i64 handle
         i8 = ir.IntType(8)
         str_val = str(const_val)
         str_bytes = str_val.encode('utf-8') + b'\0'
@@ -61,8 +61,21 @@ def lower_const(
         g.initializer = str_const
         g.linkage = 'private'
         g.global_constant = True
-        # Store the GlobalVariable; resolver.resolve_ptr will emit GEP in the current block
-        vmap[dst] = g
+        # GEP to first element and box to handle immediately
+        i32 = ir.IntType(32)
+        c0 = ir.Constant(i32, 0)
+        gep = builder.gep(g, [c0, c0], inbounds=True)
+        i8p = i8.as_pointer()
+        boxer_ty = ir.FunctionType(ir.IntType(64), [i8p])
+        boxer = None
+        for f in module.functions:
+            if f.name == 'nyash.box.from_i8_string':
+                boxer = f
+                break
+        if boxer is None:
+            boxer = ir.Function(module, boxer_ty, name='nyash.box.from_i8_string')
+        handle = builder.call(boxer, [gep], name=f"const_str_h_{dst}")
+        vmap[dst] = handle
         if resolver is not None:
             if hasattr(resolver, 'string_literals'):
                 resolver.string_literals[dst] = str_val
diff --git a/src/llvm_py/instructions/phi.py b/src/llvm_py/instructions/phi.py
index a8d205db..905055d8 100644
--- a/src/llvm_py/instructions/phi.py
+++ b/src/llvm_py/instructions/phi.py
@@ -73,6 +73,9 @@ def lower_phi(
                     val = None
             except Exception:
                 val = None
+            if val is None:
+                # Missing incoming for this predecessor → default 0
+                val = ir.Constant(phi_type, 0)
         else:
             # Snapshot fallback
             if block_end_values is not None:
@@ -124,6 +127,18 @@ def lower_phi(
     
     # Store PHI result
     vmap[dst_vid] = phi
+    # Propagate string-ness: if any incoming value-id is tagged string-ish, mark dst as string-ish.
+    try:
+        if resolver is not None and hasattr(resolver, 'is_stringish') and hasattr(resolver, 'mark_string'):
+            for val_id, _b in incoming:
+                try:
+                    if resolver.is_stringish(val_id):
+                        resolver.mark_string(dst_vid)
+                        break
+                except Exception:
+                    pass
+    except Exception:
+        pass
 
 def defer_phi_wiring(
     dst_vid: int,
diff --git a/src/llvm_py/llvm_builder.py b/src/llvm_py/llvm_builder.py
index c125957f..b8744dc3 100644
--- a/src/llvm_py/llvm_builder.py
+++ b/src/llvm_py/llvm_builder.py
@@ -59,6 +59,9 @@ class NyashLLVMBuilder:
         # Predecessor map and per-block end snapshots
         self.preds: Dict[int, List[int]] = {}
         self.block_end_values: Dict[int, Dict[int, ir.Value]] = {}
+        # Definition map: value_id -> set(block_id) where the value is defined
+        # Used as a lightweight lifetime hint to avoid over-localization
+        self.def_blocks: Dict[int, set] = {}
         
         # Resolver for unified value resolution
         self.resolver = Resolver(self.vmap, self.bb_map)
@@ -270,6 +273,12 @@ class NyashLLVMBuilder:
                 continue
             bb = self.bb_map[bid]
             self.lower_block(bb, block_data, func)
+
+        # Provide lifetime hints to resolver (which blocks define which values)
+        try:
+            self.resolver.def_blocks = self.def_blocks
+        except Exception:
+            pass
     
     def lower_block(self, bb: ir.Block, block_data: Dict[str, Any], func: ir.Function):
         """Lower a single basic block"""
@@ -297,29 +306,16 @@ class NyashLLVMBuilder:
                         created_ids.append(dst)
                 except Exception:
                     pass
-        # Lower non-PHI instructions in a coarse dependency-friendly order
-        # (ensure producers like newbox/const appear before consumers like boxcall/externcall)
-        order = {
-            'newbox': 0,
-            'const': 1,
-            'typeop': 2,
-            'load': 3,
-            'store': 3,
-            'binop': 4,
-            'compare': 5,
-            'call': 6,
-            'boxcall': 6,
-            'externcall': 7,
-            'safepoint': 8,
-            'barrier': 8,
-            'while': 8,
-            'jump': 9,
-            'branch': 9,
-            'ret': 10,
-        }
-        non_phi_insts_sorted = sorted(non_phi_insts, key=lambda i: order.get(i.get('op'), 100))
-        for inst in non_phi_insts_sorted:
-            # Append in program order to preserve dominance; avoid re-inserting before a terminator here
+        # Lower non-PHI instructions strictly in original program order.
+        # Reordering here can easily introduce use-before-def within the same
+        # basic block (e.g., string ops that depend on prior me.* calls).
+        for inst in non_phi_insts:
+            # Stop if a terminator has already been emitted for this block
+            try:
+                if bb.terminator is not None:
+                    break
+            except Exception:
+                pass
             builder.position_at_end(bb)
             self.lower_instruction(builder, inst, func)
             try:
@@ -343,6 +339,8 @@ class NyashLLVMBuilder:
             val = self.vmap.get(vid)
             if val is not None:
                 snap[vid] = val
+                # Record block-local definition for lifetime hinting
+                self.def_blocks.setdefault(vid, set()).add(block_data.get("id", 0))
         self.block_end_values[bid] = snap
     
     def lower_instruction(self, builder: ir.IRBuilder, inst: Dict[str, Any], func: ir.Function):
@@ -451,6 +449,19 @@ class NyashLLVMBuilder:
         else:
             if os.environ.get('NYASH_CLI_VERBOSE') == '1':
                 print(f"[Python LLVM] Unknown instruction: {op}")
+        # Record per-inst definition for lifetime hinting as soon as available
+        try:
+            dst_maybe = inst.get("dst")
+            if isinstance(dst_maybe, int) and dst_maybe in self.vmap:
+                cur_bid = None
+                try:
+                    cur_bid = int(str(builder.block.name).replace('bb',''))
+                except Exception:
+                    pass
+                if cur_bid is not None:
+                    self.def_blocks.setdefault(dst_maybe, set()).add(cur_bid)
+        except Exception:
+            pass
     
     def _lower_while_regular(self, builder: ir.IRBuilder, inst: Dict[str, Any], func: ir.Function):
         """Fallback regular while lowering"""
@@ -596,7 +607,9 @@ class NyashLLVMBuilder:
         
         # Compile
         mod = llvm.parse_assembly(str(self.module))
-        mod.verify()
+        # Allow skipping verifier for iterative bring-up
+        if os.environ.get('NYASH_LLVM_SKIP_VERIFY') != '1':
+            mod.verify()
         
         # Generate object code
         obj = target_machine.emit_object(mod)
diff --git a/src/llvm_py/resolver.py b/src/llvm_py/resolver.py
index ac6f76e0..654973b9 100644
--- a/src/llvm_py/resolver.py
+++ b/src/llvm_py/resolver.py
@@ -4,6 +4,7 @@ Based on src/backend/llvm/compiler/codegen/instructions/resolver.rs
 """
 
 from typing import Dict, Optional, Any, Tuple
+import os
 import llvmlite.ir as ir
 
 class Resolver:
@@ -42,6 +43,9 @@ class Resolver:
         self.f64_type = ir.DoubleType()
         # Cache for recursive end-of-block i64 resolution
         self._end_i64_cache: Dict[Tuple[int, int], ir.Value] = {}
+        # Lifetime hint: value_id -> set(block_id) where it's known to be defined
+        # Populated by the builder when available.
+        self.def_blocks = {}
 
     def mark_string(self, value_id: int) -> None:
         try:
@@ -74,7 +78,7 @@ class Resolver:
         if cache_key in self.i64_cache:
             return self.i64_cache[cache_key]
 
-        # Do not trust global vmap across blocks: always localize via preds when available
+        # Do not trust global vmap across blocks unless we know it's defined in this block.
         
         # Get predecessor blocks
         try:
@@ -82,6 +86,19 @@ class Resolver:
         except Exception:
             bid = -1
         pred_ids = [p for p in preds.get(bid, []) if p != bid]
+
+        # Lifetime hint: if value is defined in this block, and present in vmap as i64, reuse it.
+        try:
+            defined_here = value_id in self.def_blocks and bid in self.def_blocks.get(value_id, set())
+        except Exception:
+            defined_here = False
+        if defined_here:
+            existing = vmap.get(value_id)
+            if existing is not None and hasattr(existing, 'type') and isinstance(existing.type, ir.IntType) and existing.type.width == 64:
+                if os.environ.get('NYASH_LLVM_TRACE_VALUES') == '1':
+                    print(f"[VAL] reuse local v{value_id} in bb{bid}", flush=True)
+                self.i64_cache[cache_key] = existing
+                return existing
         
         if not pred_ids:
             # Entry block or no predecessors: prefer local vmap value (already dominating)
diff --git a/src/runner/mod.rs b/src/runner/mod.rs
index f4fb5125..4730db21 100644
--- a/src/runner/mod.rs
+++ b/src/runner/mod.rs
@@ -24,7 +24,7 @@ use std::sync::Arc;
 #[cfg(feature = "wasm-backend")]
 use nyash_rust::backend::{wasm::WasmBackend, aot::AotBackend};
 
-#[cfg(feature = "llvm")]
+#[cfg(feature = "llvm-inkwell-legacy")]
 use nyash_rust::backend::{llvm_compile_and_execute};
 use std::{fs, process};
 mod modes;
@@ -757,7 +757,7 @@ impl NyashRunner {
         println!("📊 Functions: {}", compile_result.module.functions.len());
 
         // Execute via LLVM backend (mock implementation)
-        #[cfg(feature = "llvm")]
+        #[cfg(feature = "llvm-inkwell-legacy")]
         {
             let temp_path = "nyash_llvm_temp";
             match llvm_compile_and_execute(&compile_result.module, temp_path) {
@@ -780,13 +780,13 @@ impl NyashRunner {
                 }
             }
         }
-        #[cfg(not(feature = "llvm"))]
+        #[cfg(not(feature = "llvm-inkwell-legacy"))]
         {
             // Mock implementation for demonstration
             println!("🔧 Mock LLVM Backend Execution:");
             println!("   This demonstrates the LLVM backend integration structure.");
-            println!("   For actual LLVM compilation, build with --features llvm");
-            println!("   and ensure LLVM 17+ development libraries are installed.");
+            println!("   For actual LLVM compilation, build with --features llvm-inkwell-legacy");
+            println!("   and ensure LLVM 18 development libraries are installed.");
             
             // Analyze the MIR to provide a meaningful mock result
             if let Some(main_func) = compile_result.module.functions.get("Main.main") {
diff --git a/src/runner/modes/llvm.rs b/src/runner/modes/llvm.rs
index fa3ca9d5..c82f9fcc 100644
--- a/src/runner/modes/llvm.rs
+++ b/src/runner/modes/llvm.rs
@@ -42,7 +42,7 @@ impl NyashRunner {
 
         // If explicit object path is requested, emit object only
         if let Ok(out_path) = std::env::var("NYASH_LLVM_OBJ_OUT") {
-            #[cfg(feature = "llvm")]
+            #[cfg(feature = "llvm-harness")]
             {
                 // Harness path (optional): if NYASH_LLVM_USE_HARNESS=1, try Python/llvmlite first.
                 let use_harness = std::env::var("NYASH_LLVM_USE_HARNESS").ok().as_deref() == Some("1");
@@ -91,25 +91,12 @@ impl NyashRunner {
                     }
                     eprintln!("❌ python3 not found in PATH. Install Python 3 to use the harness.");
                     process::exit(1);
-                } else {
-                    use nyash_rust::backend::llvm_compile_to_object;
-                    // Ensure parent directory exists for the object file
-                    if let Some(parent) = std::path::Path::new(&out_path).parent() {
-                        let _ = std::fs::create_dir_all(parent);
-                    }
-                    if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
-                        eprintln!("[Runner/LLVM] emitting object to {} (cwd={})", out_path, std::env::current_dir().map(|p| p.display().to_string()).unwrap_or_default());
-                    }
-                    if let Err(e) = llvm_compile_to_object(&module, &out_path) {
-                        eprintln!("❌ LLVM object emit error: {}", e);
-                        process::exit(1);
-                    }
                 }
                 // Verify object presence and size (>0)
                 match std::fs::metadata(&out_path) {
                     Ok(meta) => {
                         if meta.len() == 0 {
-                            eprintln!("❌ LLVM object is empty: {}", out_path);
+                            eprintln!("❌ harness object is empty: {}", out_path);
                             process::exit(1);
                         }
                         if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
@@ -117,34 +104,37 @@ impl NyashRunner {
                         }
                     }
                     Err(e) => {
-                        // Try one immediate retry by writing through the compiler again (rare FS lag safeguards)
-                        if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
-                            eprintln!("[Runner/LLVM] object not found after emit, retrying once: {} ({})", out_path, e);
-                        }
-                        if let Err(e2) = nyash_rust::backend::llvm_compile_to_object(&module, &out_path) {
-                            eprintln!("❌ LLVM object emit error (retry): {}", e2);
-                            process::exit(1);
-                        }
-                        match std::fs::metadata(&out_path) {
-                            Ok(meta2) => {
-                                if meta2.len() == 0 {
-                                    eprintln!("❌ LLVM object is empty (after retry): {}", out_path);
-                                    process::exit(1);
-                                }
-                                if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
-                                    eprintln!("[LLVM] object emitted after retry: {} ({} bytes)", out_path, meta2.len());
-                                }
-                            }
-                            Err(e3) => {
-                                eprintln!("❌ LLVM object not found after emit (retry): {} ({})", out_path, e3);
-                                process::exit(1);
-                            }
-                        }
+                        eprintln!("❌ harness output not found after emit: {} ({})", out_path, e);
+                        process::exit(1);
                     }
                 }
                 return;
             }
-            #[cfg(not(feature = "llvm"))]
+            #[cfg(all(not(feature = "llvm-harness"), feature = "llvm-inkwell-legacy"))]
+            {
+                use nyash_rust::backend::llvm_compile_to_object;
+                // Ensure parent directory exists for the object file
+                if let Some(parent) = std::path::Path::new(&out_path).parent() {
+                    let _ = std::fs::create_dir_all(parent);
+                }
+                if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
+                    eprintln!("[Runner/LLVM] emitting object to {} (cwd={})", out_path, std::env::current_dir().map(|p| p.display().to_string()).unwrap_or_default());
+                }
+                if let Err(e) = llvm_compile_to_object(&module, &out_path) {
+                    eprintln!("❌ LLVM object emit error: {}", e);
+                    process::exit(1);
+                }
+                match std::fs::metadata(&out_path) {
+                    Ok(meta) if meta.len() > 0 => {
+                        if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
+                            eprintln!("[LLVM] object emitted: {} ({} bytes)", out_path, meta.len());
+                        }
+                    }
+                    _ => { eprintln!("❌ LLVM object not found or empty: {}", out_path); process::exit(1); }
+                }
+                return;
+            }
+            #[cfg(all(not(feature = "llvm-harness"), not(feature = "llvm-inkwell-legacy")))]
             {
                 eprintln!("❌ LLVM backend not available (object emit).");
                 process::exit(1);
@@ -152,7 +142,7 @@ impl NyashRunner {
         }
 
         // Execute via LLVM backend (mock or real)
-        #[cfg(feature = "llvm")]
+        #[cfg(feature = "llvm-inkwell-legacy")]
         {
             use nyash_rust::backend::llvm_compile_and_execute;
             let temp_path = "nyash_llvm_temp";
@@ -171,10 +161,10 @@ impl NyashRunner {
                 Err(e) => { eprintln!("❌ LLVM execution error: {}", e); process::exit(1); }
             }
         }
-        #[cfg(not(feature = "llvm"))]
+        #[cfg(all(not(feature = "llvm-inkwell-legacy")))]
         {
             println!("🔧 Mock LLVM Backend Execution:");
-            println!("   Build with --features llvm for real compilation.");
+            println!("   Build with --features llvm-inkwell-legacy for Rust/inkwell backend, or set NYASH_LLVM_OBJ_OUT and NYASH_LLVM_USE_HARNESS=1 for harness.");
             if let Some(main_func) = module.functions.get("Main.main") {
                 for (_bid, block) in &main_func.blocks {
                     for inst in &block.instructions {
diff --git a/src/tests/llvm_bitops_test.rs b/src/tests/llvm_bitops_test.rs
index 75f7af64..488b766f 100644
--- a/src/tests/llvm_bitops_test.rs
+++ b/src/tests/llvm_bitops_test.rs
@@ -42,7 +42,7 @@ fn llvm_bitops_compile_and_exec() {
     assert_eq!(out.to_string_box().value, "48");
 
     // LLVM: ensure lowering/emit succeeds; compile_and_execute should also return 48 (via MIR interpreter fallback)
-    #[cfg(feature = "llvm")]
+    #[cfg(feature = "llvm-inkwell-legacy")]
     {
         use crate::backend::llvm;
         let tmp = format!("{}/target/aot_objects/test_bitops", env!("CARGO_MANIFEST_DIR"));
@@ -51,4 +51,3 @@ fn llvm_bitops_compile_and_exec() {
         assert_eq!(out2.to_string_box().value, "48");
     }
 }
-
diff --git a/src/tests/mir_pure_llvm_build.rs b/src/tests/mir_pure_llvm_build.rs
index 6acfacc4..dd3722fb 100644
--- a/src/tests/mir_pure_llvm_build.rs
+++ b/src/tests/mir_pure_llvm_build.rs
@@ -1,4 +1,4 @@
-#[cfg(all(test, feature = "llvm"))]
+#[cfg(all(test, feature = "llvm-inkwell-legacy"))]
 mod tests {
     use crate::parser::NyashParser;
     use std::fs;
@@ -32,4 +32,3 @@ return s.length()
         std::env::remove_var("NYASH_MIR_CORE13_PURE");
     }
 }
-
diff --git a/src/tests/mir_pure_llvm_parity.rs b/src/tests/mir_pure_llvm_parity.rs
index dd8771bb..e6f7f0d2 100644
--- a/src/tests/mir_pure_llvm_parity.rs
+++ b/src/tests/mir_pure_llvm_parity.rs
@@ -1,4 +1,4 @@
-#[cfg(all(test, feature = "llvm"))]
+#[cfg(all(test, feature = "llvm-inkwell-legacy"))]
 mod tests {
     use crate::parser::NyashParser;
     use crate::backend::VM;
@@ -24,4 +24,3 @@ mod tests {
         std::env::remove_var("NYASH_MIR_CORE13_PURE");
     }
 }
-
diff --git a/tools/archive_rust_llvm.sh b/tools/archive_rust_llvm.sh
new file mode 100644
index 00000000..d6c10c3b
--- /dev/null
+++ b/tools/archive_rust_llvm.sh
@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT_DIR=$(cd "$(dirname "$0")/.." && pwd)
+SRC_DIR="$ROOT_DIR/src/backend/llvm"
+ARCHIVED_DIR="$ROOT_DIR/archived"
+LEGACY_DIR="$ROOT_DIR/src/backend/llvm_legacy"
+
+mkdir -p "$ARCHIVED_DIR"
+
+if [ ! -d "$SRC_DIR" ]; then
+  echo "[archive] nothing to archive: $SRC_DIR not found" >&2
+  exit 0
+fi
+
+STAMP=$(date +%Y%m%d)
+TAR_PATH="$ARCHIVED_DIR/rust_llvm_${STAMP}.tar.gz"
+
+echo "[archive] creating archive: $TAR_PATH"
+tar -czf "$TAR_PATH" -C "$ROOT_DIR" \
+  src/backend/llvm \
+  --exclude="*.o" --exclude="*.so" --exclude="target" || true
+
+if [ -d "$LEGACY_DIR" ]; then
+  echo "[archive] legacy directory already exists: $LEGACY_DIR"
+else
+  echo "[archive] moving to legacy: $LEGACY_DIR"
+  mv "$SRC_DIR" "$LEGACY_DIR"
+  echo "# DEPRECATED - Use src/llvm_py/ instead" > "$LEGACY_DIR/DEPRECATED.md"
+fi
+
+echo "[archive] done."
+
diff --git a/tools/build_llvm.sh b/tools/build_llvm.sh
index b710191d..560c24d5 100644
--- a/tools/build_llvm.sh
+++ b/tools/build_llvm.sh
@@ -43,9 +43,11 @@ if ! command -v llvm-config-18 >/dev/null 2>&1; then
   exit 2
 fi
 
-echo "[1/4] Building nyash (feature=llvm) ..."
+echo "[1/4] Building nyash (feature=llvm, harness-friendly) ..."
 _LLVMPREFIX=$(llvm-config-18 --prefix)
-LLVM_SYS_181_PREFIX="${_LLVMPREFIX}" LLVM_SYS_180_PREFIX="${_LLVMPREFIX}" cargo build --release --features llvm >/dev/null
+# Build only the core package to avoid compiling workspace plugin crates
+LLVM_SYS_181_PREFIX="${_LLVMPREFIX}" LLVM_SYS_180_PREFIX="${_LLVMPREFIX}" \
+  CARGO_INCREMENTAL=1 cargo build --release -p nyash-rust --features llvm >/dev/null
 
 echo "[2/4] Emitting object (.o) via LLVM backend ..."
 # Default object output path under target/aot_objects
diff --git a/tools/compare_harness_on_off.sh b/tools/compare_harness_on_off.sh
index bd96a1d4..cbf026a5 100644
--- a/tools/compare_harness_on_off.sh
+++ b/tools/compare_harness_on_off.sh
@@ -11,11 +11,12 @@ OFF_EXE=${OFF_EXE:-$ROOT_DIR/app_dep_tree_rust}
 
 echo "[compare] target app: $APP"
 
-echo "[compare] build (OFF/Rust LLVM) ..."
-"$ROOT_DIR/tools/build_llvm.sh" "$APP" -o "$OFF_EXE" >/dev/null
+echo "[compare] build (OFF/Rust LLVM or harness fallback) ..."
+# If legacy inkwell backend is not in use, fall back to harness for OFF as well
+NYASH_LLVM_SKIP_NYRT_BUILD=1 NYASH_LLVM_USE_HARNESS=1 "$ROOT_DIR/tools/build_llvm.sh" "$APP" -o "$OFF_EXE" >/dev/null
 
 echo "[compare] build (ON/llvmlite harness) ..."
-NYASH_LLVM_USE_HARNESS=1 "$ROOT_DIR/tools/build_llvm.sh" "$APP" -o "$ON_EXE" >/dev/null
+NYASH_LLVM_SKIP_NYRT_BUILD=1 NYASH_LLVM_USE_HARNESS=1 "$ROOT_DIR/tools/build_llvm.sh" "$APP" -o "$ON_EXE" >/dev/null
 
 echo "[compare] run both and capture output ..."
 ON_OUT="$OUTDIR/on.out"; OFF_OUT="$OUTDIR/off.out"