diff --git a/CHANGELOG.md b/CHANGELOG.md
index 39f0b23e..5291f682 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,14 @@
 This changelog tracks high‑level milestones while Core MIR and Phase 12 evolve. For detailed per‑file history, see git log and docs under `docs/development/roadmap/`.
 
 ## 2025‑09‑06
+
+### Phase 22.3 (Kernel Minimal C Runtime — design wrap)
+- Added minimal C runtime crate (design-stage): `crates/nyash_kernel_min_c` (staticlib).
+- LLVM extern lowering: normalized `nyash.console.*` → `nyash_console_*` for C linkage.
+- Hako-first MIR emit stabilized via wrapper (`tools/hakorune_emit_mir.sh`): Stage‑B JSON is emitted with `NYASH_JSON_ONLY=1` and sanitized; builder falls back to Rust CLI on failure (defaults keep quick green).
+
+### Prep for Phase 21.10 (LLVM line — crate backend)
+- Backend selector and S3 canaries exist; print EXE canary currently SKIP pending small normalization. Next: enable print EXE PASS with env‑guarded normalization in ny‑llvmc (no default behavior changes).
 - Core‑13 flip complete: code/tests enforce Core‑13 minimal kernel. Normalizations (Array/Ref→BoxCall, TypeCheck/Cast/Barrier/WeakRef unification) are ON by default via env (NYASH_MIR_CORE13=1). New tests validate normalization.
 - Docs synced: step‑50 marked done; DEV quickstart points to Core‑13 reference.
 
diff --git a/CURRENT_TASK.md b/CURRENT_TASK.md
index 69095557..59ae4142 100644
--- a/CURRENT_TASK.md
+++ b/CURRENT_TASK.md
@@ -1,4 +1,26 @@
-# Current Task — Phase 21.4（Hako Parser → Analyzer / Self‑Host）
+# Current Task — Phase 21.10（LLVM line – crate backend print EXE）
+
+Status (22.3 wrap)
+- 22.3 締め: 最小Cランタイム（設計）/Cシンボル整合（nyash.console.*→nyash_console_*）を反映。
+- Hako-first MIR emit は wrapper 経由で安定（Stage‑B 出力の RC 混入を抑止、Hako→失敗時は Rust CLI にフォールバック）。
+- 緑条件は quick 代表セット + phase2231 canary（rc=42）で確認済み。
+
+Next (this phase) — 22.x continuation
+1) TLV配線（既定OFF）+ parityカナリア
+   - 既存の `nyash-tlv`（optional / feature `tlv-shim`）を `src/runtime/plugin_ffi_common.rs` に薄く配線。
+   - 制御: feature + `HAKO_TLV_SHIM=1`（トレース `HAKO_TLV_SHIM_TRACE{,_DETAIL}`）。
+   - 受け入れ: ON/OFF で実行/rc 同一（parity）+ トレース観測が可能。
+
+2) SSOTメッセージ・相対推定の整形 + 代表カナリアの常時化
+   - 曖昧時のメッセージ統一（件数+先頭N、legacy委譲の明記）。
+   - cwd vs using_paths 優先の明文化・軽量canaryを quick 常時化。
+
+3) ビルダーの JsonFragBox / PatternUtilBox 採用（差分小さい箇所から）
+   - 手書きスキャンの置換を段階導入。If/Compare VarInt / Return BinOp VarVar 周辺を優先。
+
+4) C‑core 一点通し（Map.set）+ parity維持（既定OFF）
+   - feature+ENV で no‑op 経路を通し、ON/OFF parity をカナリアで検証。
+
 
 目的（このフェーズで到達するゴール）
 - Hako Parser（MVP）で AST JSON v0 を出力し、Analyzer の一次入力に採用（text は fallback 維持）。
@@ -41,6 +63,10 @@ Toggles quicklist
 - EXE‑first: `SMOKES_ENABLE_SELFHOST=1`（既定OFF）
 - TLV: `--features tlv-shim` + `HAKO_TLV_SHIM=1`（既定OFF/配線は無害な identity）
 - Using SSOT: `HAKO_USING_SSOT=1`（MVP は現行解決ロジックを経由しつつタグ出力）
+- ENV consolidation（既定不変）
+  - NY compiler: 主 `NYASH_USE_NY_COMPILER`、alias `NYASH_DISABLE_NY_COMPILER`/`HAKO_DISABLE_NY_COMPILER`（受理＋警告、一度だけ）
+  - LLVM opt: 主 `NYASH_LLVM_OPT_LEVEL`、alias `HAKO_LLVM_OPT_LEVEL`（受理＋警告、一度だけ）
+  - Gate‑C: 主 `NYASH_GATE_C_CORE`、alias `HAKO_GATE_C_CORE`（受理＋警告、一度だけ）
 
 22.1 progress (today)
 - TLV配線（最小導線・既定OFF）
diff --git a/README.md b/README.md
index bdc156dc..c24a09cb 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,18 @@
 **A Seriously-Crafted Hobby Language**  
 **From Zero to Native Binary in 20 Days - The AI-Powered Language Revolution**
 
+Quick — Emit MIR (Hako‑first helper)
+- Generate MIR(JSON) from a Hako file using the Stage‑B parser + MirBuilder (wrapper falls back to the Rust CLI builder on failure to keep runs green):
+
+```
+tools/hakorune_emit_mir.sh path/to/program.hako /tmp/program.mir.json
+target/release/hakorune --mir-json-file /tmp/program.mir.json
+```
+
+Notes
+- The wrapper runs Stage‑B with `NYASH_JSON_ONLY=1` to keep the output clean (no `RC:` lines).
+- When the Hako MirBuilder fails (e.g., under development), it automatically falls back to `--program-json-to-mir` (no behavior change by default).
+
 *[🇯🇵 日本語版はこちら / Japanese Version](README.ja.md)*
 
 [![Selfhost Minimal](https://github.com/moe-charm/nyash/actions/workflows/selfhost-minimal.yml/badge.svg?branch=selfhosting-dev)](https://github.com/moe-charm/nyash/actions/workflows/selfhost-minimal.yml)
diff --git a/crates/nyash-llvm-compiler/src/main.rs b/crates/nyash-llvm-compiler/src/main.rs
index 550291ac..ae0c9649 100644
--- a/crates/nyash-llvm-compiler/src/main.rs
+++ b/crates/nyash-llvm-compiler/src/main.rs
@@ -6,6 +6,7 @@ use std::process::Command;
 
 use anyhow::{bail, Context, Result};
 use clap::{ArgAction, Parser};
+use serde_json::Value as JsonValue;
 
 #[derive(Parser, Debug)]
 #[command(
@@ -86,29 +87,59 @@ fn main() -> Result<()> {
         return Ok(());
     }
 
-    // Prepare input JSON path: either from file or stdin -> temp file
+    // Prepare input JSON path: either from file or stdin -> temp file.
+    // Optionally normalize canary JSON into the shape expected by the Python builder
+    // when HAKO_LLVM_CANARY_NORMALIZE=1 (no default behavior change).
     let mut temp_path: Option<PathBuf> = None;
+    let canary_norm = env::var("HAKO_LLVM_CANARY_NORMALIZE").ok().as_deref() == Some("1");
     let input_path = if args.infile == "-" {
         let mut buf = String::new();
         std::io::stdin()
             .read_to_string(&mut buf)
             .context("reading MIR JSON from stdin")?;
-        // Basic sanity check that it's JSON
-        let _: serde_json::Value =
+        let mut val: serde_json::Value =
             serde_json::from_str(&buf).context("stdin does not contain valid JSON")?;
+        if canary_norm {
+            val = normalize_canary_json(val);
+        }
         let tmp = std::env::temp_dir().join("ny_llvmc_stdin.json");
         let mut f = File::create(&tmp).context("create temp json file")?;
-        f.write_all(buf.as_bytes()).context("write temp json")?;
+        let out = serde_json::to_vec(&val).context("serialize normalized json")?;
+        f.write_all(&out).context("write temp json")?;
         temp_path = Some(tmp.clone());
         tmp
     } else {
-        PathBuf::from(&args.infile)
+        let p = PathBuf::from(&args.infile);
+        if canary_norm {
+            // Read file, normalize, and write to a temp path
+            let mut buf = String::new();
+            File::open(&p).and_then(|mut f| f.read_to_string(&mut buf)).context("read input json")?;
+            let mut val: serde_json::Value = serde_json::from_str(&buf).context("input is not valid JSON")?;
+            val = normalize_canary_json(val);
+            let tmp = std::env::temp_dir().join("ny_llvmc_in.json");
+            let mut f = File::create(&tmp).context("create temp json file")?;
+            let out = serde_json::to_vec(&val).context("serialize normalized json")?;
+            f.write_all(&out).context("write temp json")?;
+            temp_path = Some(tmp.clone());
+            tmp
+        } else {
+            p
+        }
     };
 
     if !input_path.exists() {
         bail!("input JSON not found: {}", input_path.display());
     }
 
+    // Optional: preflight shape/hints (best-effort; no behavior change)
+    if let Ok(s) = std::fs::read_to_string(&input_path) {
+        if let Ok(val) = serde_json::from_str::<JsonValue>(&s) {
+            if let Some(hint) = shape_hint(&val) {
+                eprintln!("[ny-llvmc/hint] {}", hint);
+            }
+        }
+    }
+
     // Produce object first
     let obj_path = if emit_exe {
         let mut p = args.out.clone();
@@ -118,6 +149,20 @@ fn main() -> Result<()> {
         args.out.clone()
     };
 
+    // Optional: print concise shape hint in verbose mode when not normalizing
+    if env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") && env::var("HAKO_LLVM_CANARY_NORMALIZE").ok().as_deref() != Some("1") {
+        if let Ok(mut f) = File::open(&input_path) {
+            let mut buf = String::new();
+            if f.read_to_string(&mut buf).is_ok() {
+                if let Ok(val) = serde_json::from_str::<serde_json::Value>(&buf) {
+                    if let Some(h) = shape_hint(&val) {
+                        eprintln!("[ny-llvmc/hint] {}", h);
+                    }
+                }
+            }
+        }
+    }
+
     run_harness_in(&harness_path, &input_path, &obj_path).with_context(|| {
         format!(
             "failed to compile MIR JSON via harness: {}",
@@ -144,6 +189,93 @@ fn main() -> Result<()> {
     Ok(())
 }
 
+/// Return a concise hint if the MIR JSON likely has a schema/shape mismatch for the Python harness.
+fn shape_hint(v: &JsonValue) -> Option<String> {
+    // Accept both v0/v1 tolerant; only emit hint on common canary shapes
+    // 1) schema_version numeric 1 rather than string "1.0"
+    if let Some(sv) = v.get("schema_version") {
+        if sv.is_number() {
+            if sv.as_i64() == Some(1) {
+                return Some("schema_version=1 detected; set to \"1.0\" or enable HAKO_LLVM_CANARY_NORMALIZE=1".into());
+            }
+        } else if sv.as_str() == Some("1") {
+            return Some("schema_version=\"1\" detected; prefer \"1.0\" or enable HAKO_LLVM_CANARY_NORMALIZE=1".into());
+        }
+    }
+    // 2) blocks use 'inst' instead of 'instructions'
+    if let Some(funcs) = v.get("functions") {
+        if let Some(arr) = funcs.as_array() {
+            for f in arr {
+                if let Some(blocks) = f.get("blocks").and_then(|b| b.as_array()) {
+                    for b in blocks {
+                        if b.get("inst").is_some() && b.get("instructions").is_none() {
+                            return Some("block key 'inst' found; rename to 'instructions' or enable HAKO_LLVM_CANARY_NORMALIZE=1".into());
+                        }
+                    }
+                }
+            }
+        }
+    }
+    None
+}
+
+/// Normalize a very small canary JSON into the shape expected by the Python harness.
+/// - Accepts schema_version as number or string; coerces to "1.0" when 1.
+/// - Renames block key 'inst' -> 'instructions'.
+/// - Converts const {"ty":"i64","value":N} into {"value":{"type":"i64","value":N}}
+fn normalize_canary_json(mut v: serde_json::Value) -> serde_json::Value {
+    use serde_json::{Map, Value};
+    // schema_version: number 1 -> string "1.0"
+    match v.get_mut("schema_version") {
+        Some(Value::Number(n)) if n.as_i64() == Some(1) => {
+            *v.get_mut("schema_version").unwrap() = Value::String("1.0".to_string());
+        }
+        Some(Value::String(s)) if s == "1" => {
+            *v.get_mut("schema_version").unwrap() = Value::String("1.0".to_string());
+        }
+        _ => {}
+    }
+    // functions as array
+    if let Some(funcs) = v.get_mut("functions") {
+        if let Value::Array(ref mut arr) = funcs {
+            for func in arr.iter_mut() {
+                if let Value::Object(ref mut fm) = func {
+                    if let Some(blocks_v) = fm.get_mut("blocks") {
+                        if let Value::Array(ref mut blks) = blocks_v {
+                            for blk in blks.iter_mut() {
+                                if let Value::Object(ref mut bm) = blk {
+                                    // Rename 'inst' -> 'instructions'
+                                    if let Some(insts) = bm.remove("inst") {
+                                        bm.insert("instructions".to_string(), insts);
+                                    }
+                                    // Normalize instructions
+                                    if let Some(Value::Array(ref mut ins_arr)) = bm.get_mut("instructions") {
+                                        for ins in ins_arr.iter_mut() {
+                                            if let Value::Object(ref mut im) = ins {
+                                                if im.get("op").and_then(|x| x.as_str()) == Some("const") {
+                                                    // if 'ty' and flat 'value' exist, wrap into typed value
+                                                    if let (Some(ty), Some(val)) = (im.remove("ty"), im.remove("value")) {
+                                                        let mut val_obj = Map::new();
+                                                        if let Value::String(ts) = ty { val_obj.insert("type".to_string(), Value::String(ts)); }
+                                                        else { val_obj.insert("type".to_string(), ty); }
+                                                        val_obj.insert("value".to_string(), val);
+                                                        im.insert("value".to_string(), Value::Object(val_obj));
+                                                    }
+                                                }
+                                            }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+    v
+}
+
 fn run_harness_dummy(harness: &Path, out: &Path) -> Result<()> {
     ensure_python()?;
     let mut cmd = Command::new("python3");
@@ -182,10 +314,13 @@ fn ensure_python() -> Result<()> {
 }
 
 fn propagate_opt_level(cmd: &mut Command) {
-    let level = env::var("HAKO_LLVM_OPT_LEVEL")
-        .ok()
-        .or_else(|| env::var("NYASH_LLVM_OPT_LEVEL").ok());
+    let hako = env::var("HAKO_LLVM_OPT_LEVEL").ok();
+    let nyash = env::var("NYASH_LLVM_OPT_LEVEL").ok();
+    let level = nyash.clone().or(hako.clone());
     if let Some(level) = level {
+        if hako.is_some() && nyash.is_none() {
+            eprintln!("[deprecate/env] 'HAKO_LLVM_OPT_LEVEL' is deprecated; use 'NYASH_LLVM_OPT_LEVEL'");
+        }
         cmd.env("HAKO_LLVM_OPT_LEVEL", &level);
         cmd.env("NYASH_LLVM_OPT_LEVEL", &level);
     }
diff --git a/crates/nyash_kernel_min_c/src/kernel_min.c b/crates/nyash_kernel_min_c/src/kernel_min.c
index 298f1c09..2d344659 100644
--- a/crates/nyash_kernel_min_c/src/kernel_min.c
+++ b/crates/nyash_kernel_min_c/src/kernel_min.c
@@ -17,8 +17,6 @@ long nyash_box_from_i8_string(char* p) {
     return 0;
 }
 
-// Optional minimal stubs (not used by default; reserved for future reps)
-long nyash_array_birth_h(void) { return 1; }
-long nyash_array_length_h(long handle) { (void)handle; return 0; }
-long nyash_map_birth_h(void) { return 1; }
-long nyash_map_size_h(long handle) { (void)handle; return 0; }
+// Note: Additional array/map stubs intentionally omitted to avoid symbol
+// clashes with the full NyKernel when linked together. Keep this file minimal
+// (console only) for print canaries.
diff --git a/docs/ENV_VARS.md b/docs/ENV_VARS.md
index 147e9668..c6682996 100644
--- a/docs/ENV_VARS.md
+++ b/docs/ENV_VARS.md
@@ -2,6 +2,10 @@
 
 This document lists the environment flags introduced or used by the Phase 22.1 work. Defaults are OFF and behavior remains unchanged unless noted.
 
+- NYASH_JSON_ONLY=0|1
+  - Quiet JSON pipelines: suppresses `RC:` and routine logs on stdout (diagnostics still go to stderr).
+  - Used by Stage‑B → Program(JSON) emit to keep the output clean for downstream processing.
+
 - HAKO_USING_SSOT=0|1
   - Enables the SSOT resolver gate in the runner pipeline.
   - When ON, resolution first consults the SSOT bridge (modules-only MVP). If not resolved, it falls back to the existing resolver.
@@ -91,13 +95,34 @@ LLVM backend selector (builder wrapper)
   - `crate`: uses `./target/release/ny-llvmc` (build with `cargo build -p nyash-llvm-compiler --release`).
   - `native`: reserved for future Hako-native builder.
   - Linking extras for `--emit exe`: pass via `HAKO_AOT_LDFLAGS` (e.g., `-static`), `ny-llvmc` consumes `--libs`.
+  - Note: crate 経路では ny_main の戻り値（i64）がプロセスの終了コードに反映されます（rc mapping）。
+
+- HAKO_LLVM_CANARY_NORMALIZE=0|1
+  - 開発/カナリア専用の正規化スイッチ。`1` のとき、最小の JSON 形状差（`schema_version=1` → `"1.0"`、`blocks.inst` → `instructions`、`const` の `ty/value` 包装）を自動補正してからビルドします。
+  - 既定は `0`（無効）。既存ツールの挙動は変わりません。`NYASH_CLI_VERBOSE=1` のとき形状ヒントを `[ny-llvmc/hint]` で出力します。
 
 Name mapping note (EXE link convenience)
 - nyash.console.* は C リンク時にシンボル名 `nyash_console_*` に正規化される（ドット→アンダースコア）。
   - 例: `externcall nyash.console.log(i8*)` → C シンボル `nyash_console_log`。
   - 最小 C ランタイム（Phase 22.3）の `nyash-kernel-min-c` は `nyash_console_log(char*)` を提供（設計段階）。
-
+  
 Kernel Minimal C Runtime (Phase 22.3 — design)
 - NYASH_KERNEL_C_MIN=0|1
   - Reserved toggle for enabling the minimal C runtime shims（design‑stage; defaults OFF）
   - Build: `cargo build --release -p nyash-kernel-min-c`（not linked by default）
+
+ENV consolidation (aliases)
+- NY compiler path
+  - Primary: `NYASH_USE_NY_COMPILER=0|1`
+  - Accepted aliases (deprecated; prints a one‑time warning):
+    - `NYASH_DISABLE_NY_COMPILER=1` → equivalent to `NYASH_USE_NY_COMPILER=0`
+    - `HAKO_DISABLE_NY_COMPILER=1` → equivalent to `NYASH_USE_NY_COMPILER=0`
+- LLVM opt level
+  - Primary: `NYASH_LLVM_OPT_LEVEL`
+  - Accepted alias (deprecated; one‑time warning): `HAKO_LLVM_OPT_LEVEL`
+- Gate‑C (Core direct route)
+  - Primary: `NYASH_GATE_C_CORE`
+  - Accepted alias (deprecated; one‑time warning): `HAKO_GATE_C_CORE`
+
+Notes
+- Primary keys are preferred and will be kept. Aliases remain accepted for a grace period and emit a concise deprecation line once per process.
diff --git a/lang/src/mir/builder/internal/lower_if_compare_box.hako b/lang/src/mir/builder/internal/lower_if_compare_box.hako
index c9f1425d..cf5d032d 100644
--- a/lang/src/mir/builder/internal/lower_if_compare_box.hako
+++ b/lang/src/mir/builder/internal/lower_if_compare_box.hako
@@ -5,51 +5,51 @@ using selfhost.shared.json.utils.json_frag as JsonFragBox
 static box LowerIfCompareBox {
   try_lower(program_json) {
     local s = "" + program_json
-    local k_if = s.indexOf("\"type\":\"If\"")
+    local k_if = JsonFragBox.index_of_from(s, "\"type\":\"If\"", 0)
     if k_if < 0 { return null }
     // cond Compare
-    local k_cmp = s.indexOf("\"type\":\"Compare\"", k_if)
+    local k_cmp = JsonFragBox.index_of_from(s, "\"type\":\"Compare\"", k_if)
     if k_cmp < 0 { return null }
-    local k_op = s.indexOf("\"op\":", k_cmp)
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_cmp)
     if k_op < 0 { return null }
     local op = JsonFragBox.read_string_after(s, k_op + 5)
     if op == null { return null }
     if !(op == "<" || op == ">" || op == "<=" || op == ">=" || op == "==" || op == "!=") { return null }
     // lhs/rhs ints
-    local klhs = s.indexOf("\"lhs\":{", k_cmp)
+    local klhs = JsonFragBox.index_of_from(s, "\"lhs\":{", k_cmp)
     if klhs < 0 { return null }
-    local ti = s.indexOf("\"type\":\"Int\"", klhs)
+    local ti = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", klhs)
     if ti < 0 { return null }
-    local kv_lhs = s.indexOf("\"value\":", ti)
+    local kv_lhs = JsonFragBox.index_of_from(s, "\"value\":", ti)
     if kv_lhs < 0 { return null }
     local lhs_val = JsonFragBox.read_int_after(s, kv_lhs + 8)
     if lhs_val == null { return null }
-    local krhs = s.indexOf("\"rhs\":{", k_cmp)
+    local krhs = JsonFragBox.index_of_from(s, "\"rhs\":{", k_cmp)
     if krhs < 0 { return null }
-    local ti2 = s.indexOf("\"type\":\"Int\"", krhs)
+    local ti2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", krhs)
     if ti2 < 0 { return null }
-    local kv_rhs = s.indexOf("\"value\":", ti2)
+    local kv_rhs = JsonFragBox.index_of_from(s, "\"value\":", ti2)
     if kv_rhs < 0 { return null }
     local rhs_val = JsonFragBox.read_int_after(s, kv_rhs + 8)
     if rhs_val == null { return null }
     // then/else return ints
-    local kth = s.indexOf("\"then\":", k_if)
+    local kth = JsonFragBox.index_of_from(s, "\"then\":", k_if)
     if kth < 0 { return null }
-    local rt = s.indexOf("\"type\":\"Return\"", kth)
+    local rt = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kth)
     if rt < 0 { return null }
-    local ti3 = s.indexOf("\"type\":\"Int\"", rt)
+    local ti3 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt)
     if ti3 < 0 { return null }
-    local kv_then = s.indexOf("\"value\":", ti3)
+    local kv_then = JsonFragBox.index_of_from(s, "\"value\":", ti3)
     if kv_then < 0 { return null }
     local then_val = JsonFragBox.read_int_after(s, kv_then + 8)
     if then_val == null { return null }
-    local kel = s.indexOf("\"else\":", k_if)
+    local kel = JsonFragBox.index_of_from(s, "\"else\":", k_if)
     if kel < 0 { return null }
-    local rt2 = s.indexOf("\"type\":\"Return\"", kel)
+    local rt2 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kel)
     if rt2 < 0 { return null }
-    local ti4 = s.indexOf("\"type\":\"Int\"", rt2)
+    local ti4 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt2)
     if ti4 < 0 { return null }
-    local kv_else = s.indexOf("\"value\":", ti4)
+    local kv_else = JsonFragBox.index_of_from(s, "\"value\":", ti4)
     if kv_else < 0 { return null }
     local else_val = JsonFragBox.read_int_after(s, kv_else + 8)
     if else_val == null { return null }
diff --git a/lang/src/mir/builder/internal/lower_if_compare_fold_binints_box.hako b/lang/src/mir/builder/internal/lower_if_compare_fold_binints_box.hako
index cd8321bf..d9dbc81d 100644
--- a/lang/src/mir/builder/internal/lower_if_compare_fold_binints_box.hako
+++ b/lang/src/mir/builder/internal/lower_if_compare_fold_binints_box.hako
@@ -7,15 +7,15 @@ using selfhost.shared.mir.schema as MirSchemaBox
 static box LowerIfCompareFoldBinIntsBox {
   _fold_bin_ints(s, k_bin_start) {
     // expects: {"type":"Binary","op":"+|-|*|/","lhs":{"type":"Int","value":L},"rhs":{"type":"Int","value":R}}
-    local kop = s.indexOf("\"op\":\"", k_bin_start); if kop < 0 { return null }
+    local kop = JsonFragBox.index_of_from(s, "\"op\":\"", k_bin_start); if kop < 0 { return null }
     local iop = kop + 6; local op = s.substring(iop, iop+1)
     if !(op == "+" || op == "-" || op == "*" || op == "/") { return null }
-    local kli = s.indexOf("\"type\":\"Int\"", k_bin_start); if kli < 0 { return null }
-    local kvl = s.indexOf("\"value\":", kli); if kvl < 0 { return null }
+    local kli = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_bin_start); if kli < 0 { return null }
+    local kvl = JsonFragBox.index_of_from(s, "\"value\":", kli); if kvl < 0 { return null }
     local l = JsonFragBox.read_int_after(s, kvl + 8); if l == null { return null }
     // rhs int
-    local kri = s.indexOf("\"type\":\"Int\"", kli + 1); if kri < 0 { return null }
-    local kv2 = s.indexOf("\"value\":", kri); if kv2 < 0 { return null }
+    local kri = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", kli + 1); if kri < 0 { return null }
+    local kv2 = JsonFragBox.index_of_from(s, "\"value\":", kri); if kv2 < 0 { return null }
     local r = JsonFragBox.read_int_after(s, kv2 + 8); if r == null { return null }
     // compute
     local li = 0; local ri = 0; // string to int by simple parse (assume i64 fits)
@@ -32,17 +32,17 @@ static box LowerIfCompareFoldBinIntsBox {
     // node may be Int, Binary(Int,Int), or Var with Local Int before if_pos
     if node_pos < 0 { return null }
     // Int
-    if s.indexOf("\"type\":\"Int\"", node_pos) == node_pos { // best-effort
-      local kv = s.indexOf("\"value\":", node_pos); if kv < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"type\":\"Int\"", node_pos) == node_pos { // best-effort
+      local kv = JsonFragBox.index_of_from(s, "\"value\":", node_pos); if kv < 0 { return null }
       return JsonFragBox.read_int_after(s, kv + 8)
     }
     // Binary
-    if s.indexOf("\"type\":\"Binary\"", node_pos) == node_pos {
+    if JsonFragBox.index_of_from(s, "\"type\":\"Binary\"", node_pos) == node_pos {
       return me._fold_bin_ints(s, node_pos)
     }
     // Var(name)
-    if s.indexOf("\"type\":\"Var\"", node_pos) == node_pos {
-      local kn = s.indexOf("\"name\":\"", node_pos); if kn < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"type\":\"Var\"", node_pos) == node_pos {
+      local kn = JsonFragBox.index_of_from(s, "\"name\":\"", node_pos); if kn < 0 { return null }
       local name = JsonFragBox.read_string_after(s, kn + 5); if name == null { return null }
       // find last matching Local Int before if_pos via util
       return PatternUtilBox.find_local_int_before(s, name, if_pos)
@@ -51,29 +51,29 @@ static box LowerIfCompareFoldBinIntsBox {
   }
   try_lower(program_json){
     local s = "" + program_json
-    local k_if = s.indexOf("\"type\":\"If\""); if k_if < 0 { return null }
-    local k_cmp = s.indexOf("\"type\":\"Compare\"", k_if); if k_cmp < 0 { return null }
-    local k_op = s.indexOf("\"op\":", k_cmp); if k_op < 0 { return null }
+    local k_if = JsonFragBox.index_of_from(s, "\"type\":\"If\"", 0); if k_if < 0 { return null }
+    local k_cmp = JsonFragBox.index_of_from(s, "\"type\":\"Compare\"", k_if); if k_cmp < 0 { return null }
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_cmp); if k_op < 0 { return null }
     local sym = JsonFragBox.read_string_after(s, k_op + 5); if sym == null { return null }
     local op = PatternUtilBox.map_cmp(sym); if op == null { return null }
     // locate lhs/rhs node starts (Var/Int/Binary)
-    local klhs = s.indexOf("\"lhs\":{", k_cmp); if klhs < 0 { return null }
-    local krhs = s.indexOf("\"rhs\":{", k_cmp); if krhs < 0 { return null }
+    local klhs = JsonFragBox.index_of_from(s, "\"lhs\":{", k_cmp); if klhs < 0 { return null }
+    local krhs = JsonFragBox.index_of_from(s, "\"rhs\":{", k_cmp); if krhs < 0 { return null }
     local lhs_pos = klhs + 6
     local rhs_pos = krhs + 6
     local lhs_val = me._resolve_side_int(s, lhs_pos, k_if)
     local rhs_val = me._resolve_side_int(s, rhs_pos, k_if)
     if lhs_val == null || rhs_val == null { return null }
     // then/else Return(Int)
-    local kth = s.indexOf("\"then\":", k_if); if kth < 0 { return null }
-    local rt1 = s.indexOf("\"type\":\"Return\"", kth); if rt1 < 0 { return null }
-    local ti1 = s.indexOf("\"type\":\"Int\"", rt1); if ti1 < 0 { return null }
-    local kv1 = s.indexOf("\"value\":", ti1); if kv1 < 0 { return null }
+    local kth = JsonFragBox.index_of_from(s, "\"then\":", k_if); if kth < 0 { return null }
+    local rt1 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kth); if rt1 < 0 { return null }
+    local ti1 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt1); if ti1 < 0 { return null }
+    local kv1 = JsonFragBox.index_of_from(s, "\"value\":", ti1); if kv1 < 0 { return null }
     local then_v = JsonFragBox.read_int_after(s, kv1 + 8); if then_v == null { return null }
-    local kel = s.indexOf("\"else\":", k_if); if kel < 0 { return null }
-    local rt2 = s.indexOf("\"type\":\"Return\"", kel); if rt2 < 0 { return null }
-    local ti2 = s.indexOf("\"type\":\"Int\"", rt2); if ti2 < 0 { return null }
-    local kv2b = s.indexOf("\"value\":", ti2); if kv2b < 0 { return null }
+    local kel = JsonFragBox.index_of_from(s, "\"else\":", k_if); if kel < 0 { return null }
+    local rt2 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kel); if rt2 < 0 { return null }
+    local ti2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt2); if ti2 < 0 { return null }
+    local kv2b = JsonFragBox.index_of_from(s, "\"value\":", ti2); if kv2b < 0 { return null }
     local else_v = JsonFragBox.read_int_after(s, kv2b + 8); if else_v == null { return null }
     // Build MIR
     local b0 = new ArrayBox(); b0.push(MirSchemaBox.inst_const(1, lhs_val)); b0.push(MirSchemaBox.inst_const(2, rhs_val)); b0.push(MirSchemaBox.inst_compare(op,1,2,3)); b0.push(MirSchemaBox.inst_branch(3,1,2))
diff --git a/lang/src/mir/builder/internal/lower_if_compare_fold_varint_box.hako b/lang/src/mir/builder/internal/lower_if_compare_fold_varint_box.hako
index fd15222c..041365f0 100644
--- a/lang/src/mir/builder/internal/lower_if_compare_fold_varint_box.hako
+++ b/lang/src/mir/builder/internal/lower_if_compare_fold_varint_box.hako
@@ -7,24 +7,24 @@ using selfhost.shared.json.utils.json_frag as JsonFragBox
 static box LowerIfCompareFoldVarIntBox {
   _fold_bin_varint(s, k_bin, if_pos) {
     // Binary with one Var and one Int; resolve Var via Local and compute result
-    local kop = s.indexOf("\"op\":\"", k_bin); if kop < 0 { return null }
+    local kop = JsonFragBox.index_of_from(s, "\"op\":\"", k_bin); if kop < 0 { return null }
     local op = JsonFragBox.read_string_after(s, kop + 5)
     if !(op=="+"||op=="-"||op=="*"||op=="/") { return null }
-    local klv = s.indexOf("\"lhs\":{\"type\":\"Var\"", k_bin)
-    local kli = s.indexOf("\"lhs\":{\"type\":\"Int\"", k_bin)
-    local krv = s.indexOf("\"rhs\":{\"type\":\"Var\"", k_bin)
-    local kri = s.indexOf("\"rhs\":{\"type\":\"Int\"", k_bin)
+    local klv = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Var\"", k_bin)
+    local kli = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Int\"", k_bin)
+    local krv = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Var\"", k_bin)
+    local kri = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Int\"", k_bin)
     local vval = null; local ival = null
     if klv >= 0 && kri >= 0 {
-      local kn = s.indexOf("\"name\":", klv); if kn < 0 { return null }
+      local kn = JsonFragBox.index_of_from(s, "\"name\":", klv); if kn < 0 { return null }
       local name = JsonFragBox.read_string_after(s, kn + 7)
       vval = PatternUtilBox.find_local_int_before(s, name, if_pos)
-      local kv = s.indexOf("\"value\":", kri); if kv < 0 { return null }
+      local kv = JsonFragBox.index_of_from(s, "\"value\":", kri); if kv < 0 { return null }
       ival = JsonFragBox.read_int_after(s, kv + 8)
     } else if kli >= 0 && krv >= 0 {
-      local kv2 = s.indexOf("\"value\":", kli); if kv2 < 0 { return null }
+      local kv2 = JsonFragBox.index_of_from(s, "\"value\":", kli); if kv2 < 0 { return null }
       ival = JsonFragBox.read_int_after(s, kv2 + 8)
-      local kn2 = s.indexOf("\"name\":", krv); if kn2 < 0 { return null }
+      local kn2 = JsonFragBox.index_of_from(s, "\"name\":", krv); if kn2 < 0 { return null }
       local name2 = JsonFragBox.read_string_after(s, kn2 + 7)
       vval = PatternUtilBox.find_local_int_before(s, name2, if_pos)
     }
@@ -36,17 +36,17 @@ static box LowerIfCompareFoldVarIntBox {
   }
   _resolve_side(s, node_pos, if_pos) {
     // Try Int
-    if s.indexOf("\"type\":\"Int\"", node_pos) == node_pos {
-      local kv = s.indexOf("\"value\":", node_pos); if kv < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"type\":\"Int\"", node_pos) == node_pos {
+      local kv = JsonFragBox.index_of_from(s, "\"value\":", node_pos); if kv < 0 { return null }
       return JsonFragBox.read_int_after(s, kv + 8)
     }
     // Binary(Var,Int) or (Int,Var)
-    if s.indexOf("\"type\":\"Binary\"", node_pos) == node_pos {
+    if JsonFragBox.index_of_from(s, "\"type\":\"Binary\"", node_pos) == node_pos {
       return me._fold_bin_varint(s, node_pos, if_pos)
     }
     // Var → Local Int
-    if s.indexOf("\"type\":\"Var\"", node_pos) == node_pos {
-      local kn = s.indexOf("\"name\":", node_pos); if kn < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"type\":\"Var\"", node_pos) == node_pos {
+      local kn = JsonFragBox.index_of_from(s, "\"name\":", node_pos); if kn < 0 { return null }
       local name = JsonFragBox.read_string_after(s, kn + 7)
       return PatternUtilBox.find_local_int_before(s, name, if_pos)
     }
@@ -54,26 +54,26 @@ static box LowerIfCompareFoldVarIntBox {
   }
   try_lower(program_json){
     local s = "" + program_json
-    local k_if = s.indexOf("\"type\":\"If\""); if k_if < 0 { return null }
-    local k_cmp = s.indexOf("\"type\":\"Compare\"", k_if); if k_cmp < 0 { return null }
-    local k_op = s.indexOf("\"op\":", k_cmp); if k_op < 0 { return null }
+    local k_if = JsonFragBox.index_of_from(s, "\"type\":\"If\"", 0); if k_if < 0 { return null }
+    local k_cmp = JsonFragBox.index_of_from(s, "\"type\":\"Compare\"", k_if); if k_cmp < 0 { return null }
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_cmp); if k_op < 0 { return null }
     local op_sym = JsonFragBox.read_string_after(s, k_op + 5)
     local op = PatternUtilBox.map_cmp(op_sym); if op == null { return null }
-    local klhs = s.indexOf("\"lhs\":{", k_cmp); if klhs < 0 { return null }
-    local krhs = s.indexOf("\"rhs\":{", k_cmp); if krhs < 0 { return null }
+    local klhs = JsonFragBox.index_of_from(s, "\"lhs\":{", k_cmp); if klhs < 0 { return null }
+    local krhs = JsonFragBox.index_of_from(s, "\"rhs\":{", k_cmp); if krhs < 0 { return null }
     local lhs = me._resolve_side(s, klhs+6, k_if)
     local rhs = me._resolve_side(s, krhs+6, k_if)
     if lhs == null || rhs == null { return null }
     // then/else Return(Int)
-    local kth = s.indexOf("\"then\":", k_if); if kth < 0 { return null }
-    local rt1 = s.indexOf("\"type\":\"Return\"", kth); if rt1 < 0 { return null }
-    local ti1 = s.indexOf("\"type\":\"Int\"", rt1); if ti1 < 0 { return null }
-    local kv1 = s.indexOf("\"value\":", ti1); if kv1 < 0 { return null }
+    local kth = JsonFragBox.index_of_from(s, "\"then\":", k_if); if kth < 0 { return null }
+    local rt1 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kth); if rt1 < 0 { return null }
+    local ti1 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt1); if ti1 < 0 { return null }
+    local kv1 = JsonFragBox.index_of_from(s, "\"value\":", ti1); if kv1 < 0 { return null }
     local tv = JsonFragBox.read_int_after(s, kv1 + 8); if tv == null { return null }
-    local kel = s.indexOf("\"else\":", k_if); if kel < 0 { return null }
-    local rt2 = s.indexOf("\"type\":\"Return\"", kel); if rt2 < 0 { return null }
-    local ti2 = s.indexOf("\"type\":\"Int\"", rt2); if ti2 < 0 { return null }
-    local kv2b = s.indexOf("\"value\":", ti2); if kv2b < 0 { return null }
+    local kel = JsonFragBox.index_of_from(s, "\"else\":", k_if); if kel < 0 { return null }
+    local rt2 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kel); if rt2 < 0 { return null }
+    local ti2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt2); if ti2 < 0 { return null }
+    local kv2b = JsonFragBox.index_of_from(s, "\"value\":", ti2); if kv2b < 0 { return null }
     local ev = JsonFragBox.read_int_after(s, kv2b + 8); if ev == null { return null }
     // Build
     local b0=new ArrayBox(); b0.push(MirSchemaBox.inst_const(1,lhs)); b0.push(MirSchemaBox.inst_const(2,rhs)); b0.push(MirSchemaBox.inst_compare(op,1,2,3)); b0.push(MirSchemaBox.inst_branch(3,1,2))
diff --git a/lang/src/mir/builder/internal/lower_if_compare_varint_box.hako b/lang/src/mir/builder/internal/lower_if_compare_varint_box.hako
index 15ad820a..7f357047 100644
--- a/lang/src/mir/builder/internal/lower_if_compare_varint_box.hako
+++ b/lang/src/mir/builder/internal/lower_if_compare_varint_box.hako
@@ -7,50 +7,51 @@ using selfhost.shared.json.utils.json_frag as JsonFragBox
 static box LowerIfCompareVarIntBox {
   try_lower(program_json){
     local s = "" + program_json
-    local k_if = s.indexOf("\"type\":\"If\""); if k_if < 0 { return null }
-    local k_cmp = s.indexOf("\"type\":\"Compare\"", k_if); if k_cmp < 0 { return null }
-    local k_op = s.indexOf("\"op\":", k_cmp); if k_op < 0 { return null }
+    // Locate If → Compare → op using robust index_of_from helpers
+    local k_if = JsonFragBox.index_of_from(s, "\"type\":\"If\"", 0); if k_if < 0 { return null }
+    local k_cmp = JsonFragBox.index_of_from(s, "\"type\":\"Compare\"", k_if); if k_cmp < 0 { return null }
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_cmp); if k_op < 0 { return null }
     local op_sym = JsonFragBox.read_string_after(s, k_op + 5)
     local op = PatternUtilBox.map_cmp(op_sym); if op == null { return null }
     // Var vs Int
-    local klhs_var = s.indexOf("\"lhs\":{\"type\":\"Var\"", k_cmp)
-    local krhs_int = s.indexOf("\"rhs\":{\"type\":\"Int\"", k_cmp)
+    local klhs_var = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Var\"", k_cmp)
+    local krhs_int = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Int\"", k_cmp)
     local aval=null; local bval=null
     if klhs_var >= 0 && krhs_int >= 0 {
-      local k_name = s.indexOf("\"name\":", klhs_var); if k_name < 0 { return null }
+      local k_name = JsonFragBox.index_of_from(s, "\"name\":", klhs_var); if k_name < 0 { return null }
       local name = JsonFragBox.read_string_after(s, k_name + 7)
       aval = PatternUtilBox.find_local_int_before(s, name, k_if)
-      local ki = s.indexOf("\"type\":\"Int\"", krhs_int)
+      local ki = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", krhs_int)
       if ki >= 0 {
-        local kv = s.indexOf("\"value\":", ki); if kv < 0 { return null }
+        local kv = JsonFragBox.index_of_from(s, "\"value\":", ki); if kv < 0 { return null }
         bval = JsonFragBox.read_int_after(s, kv + 8)
       }
     } else {
       // Int vs Var
-      local klhs_int = s.indexOf("\"lhs\":{\"type\":\"Int\"", k_cmp)
-      local krhs_var = s.indexOf("\"rhs\":{\"type\":\"Var\"", k_cmp)
+      local klhs_int = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Int\"", k_cmp)
+      local krhs_var = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Var\"", k_cmp)
       if klhs_int >= 0 && krhs_var >= 0 {
-        local ki2 = s.indexOf("\"type\":\"Int\"", klhs_int)
+        local ki2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", klhs_int)
         if ki2 >= 0 {
-          local kv2 = s.indexOf("\"value\":", ki2); if kv2 < 0 { return null }
+          local kv2 = JsonFragBox.index_of_from(s, "\"value\":", ki2); if kv2 < 0 { return null }
           aval = JsonFragBox.read_int_after(s, kv2 + 8)
         }
-        local k_name2 = s.indexOf("\"name\":", krhs_var); if k_name2 < 0 { return null }
+        local k_name2 = JsonFragBox.index_of_from(s, "\"name\":", krhs_var); if k_name2 < 0 { return null }
         local name2 = JsonFragBox.read_string_after(s, k_name2 + 7)
         if name2 != null { bval = PatternUtilBox.find_local_int_before(s, name2, k_if) }
       }
     }
     if aval == null || bval == null { return null }
     // then/else Return(Int)
-    local kth = s.indexOf("\"then\":", k_if); if kth < 0 { return null }
-    local rt1 = s.indexOf("\"type\":\"Return\"", kth); if rt1 < 0 { return null }
-    local ti1 = s.indexOf("\"type\":\"Int\"", rt1); if ti1 < 0 { return null }
-    local kv_then = s.indexOf("\"value\":", ti1); if kv_then < 0 { return null }
+    local kth = JsonFragBox.index_of_from(s, "\"then\":", k_if); if kth < 0 { return null }
+    local rt1 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kth); if rt1 < 0 { return null }
+    local ti1 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt1); if ti1 < 0 { return null }
+    local kv_then = JsonFragBox.index_of_from(s, "\"value\":", ti1); if kv_then < 0 { return null }
     local then_v = JsonFragBox.read_int_after(s, kv_then + 8); if then_v == null { return null }
-    local kel = s.indexOf("\"else\":", k_if); if kel < 0 { return null }
-    local rt2 = s.indexOf("\"type\":\"Return\"", kel); if rt2 < 0 { return null }
-    local ti2 = s.indexOf("\"type\":\"Int\"", rt2); if ti2 < 0 { return null }
-    local kv_else = s.indexOf("\"value\":", ti2); if kv_else < 0 { return null }
+    local kel = JsonFragBox.index_of_from(s, "\"else\":", k_if); if kel < 0 { return null }
+    local rt2 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kel); if rt2 < 0 { return null }
+    local ti2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt2); if ti2 < 0 { return null }
+    local kv_else = JsonFragBox.index_of_from(s, "\"value\":", ti2); if kv_else < 0 { return null }
     local else_v = JsonFragBox.read_int_after(s, kv_else + 8); if else_v == null { return null }
     // Build MIR
     local b0=new ArrayBox(); b0.push(MirSchemaBox.inst_const(1,aval)); b0.push(MirSchemaBox.inst_const(2,bval)); b0.push(MirSchemaBox.inst_compare(op,1,2,3)); b0.push(MirSchemaBox.inst_branch(3,1,2))
diff --git a/lang/src/mir/builder/internal/lower_if_compare_varvar_box.hako b/lang/src/mir/builder/internal/lower_if_compare_varvar_box.hako
index c4c2c3d6..e8d17344 100644
--- a/lang/src/mir/builder/internal/lower_if_compare_varvar_box.hako
+++ b/lang/src/mir/builder/internal/lower_if_compare_varvar_box.hako
@@ -11,21 +11,21 @@ using selfhost.shared.json.utils.json_frag as JsonFragBox
 static box LowerIfCompareVarVarBox {
   try_lower(program_json) {
     local s = "" + program_json
-    local k_if = s.indexOf("\"type\":\"If\"")
+    local k_if = JsonFragBox.index_of_from(s, "\"type\":\"If\"", 0)
     if k_if < 0 { return null }
-    local k_cmp = s.indexOf("\"type\":\"Compare\"", k_if)
+    local k_cmp = JsonFragBox.index_of_from(s, "\"type\":\"Compare\"", k_if)
     if k_cmp < 0 { return null }
     // LHS/RHS Var names
     local lhs_name = null
-    local klhs = s.indexOf("\"lhs\":{\"type\":\"Var\"", k_cmp)
+    local klhs = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Var\"", k_cmp)
     if klhs >= 0 {
-      local k_name_lhs = s.indexOf("\"name\":", klhs); if k_name_lhs < 0 { return null }
+      local k_name_lhs = JsonFragBox.index_of_from(s, "\"name\":", klhs); if k_name_lhs < 0 { return null }
       lhs_name = JsonFragBox.read_string_after(s, k_name_lhs + 7)
     }
     local rhs_name = null
-    local krhs = s.indexOf("\"rhs\":{\"type\":\"Var\"", k_cmp)
+    local krhs = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Var\"", k_cmp)
     if krhs >= 0 {
-      local k_name_rhs = s.indexOf("\"name\":", krhs); if k_name_rhs < 0 { return null }
+      local k_name_rhs = JsonFragBox.index_of_from(s, "\"name\":", krhs); if k_name_rhs < 0 { return null }
       rhs_name = JsonFragBox.read_string_after(s, k_name_rhs + 7)
     }
     if lhs_name == null || rhs_name == null { return null }
@@ -34,21 +34,21 @@ static box LowerIfCompareVarVarBox {
     local bval = PatternUtilBox.find_local_int_before(s, rhs_name, k_if)
     if aval == null || bval == null { return null }
     // op map
-    local k_op = s.indexOf("\"op\":", k_cmp); if k_op < 0 { return null }
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_cmp); if k_op < 0 { return null }
     local sym = JsonFragBox.read_string_after(s, k_op + 5)
     if sym == null { return null }
     local op = PatternUtilBox.map_cmp(sym)
     if op == null { return null }
     // then/else Return(Int)
-    local kth = s.indexOf("\"then\":", k_if); if kth < 0 { return null }
-    local rt1 = s.indexOf("\"type\":\"Return\"", kth); if rt1 < 0 { return null }
-    local ti1 = s.indexOf("\"type\":\"Int\"", rt1); if ti1 < 0 { return null }
-    local kv_then = s.indexOf("\"value\":", ti1); if kv_then < 0 { return null }
+    local kth = JsonFragBox.index_of_from(s, "\"then\":", k_if); if kth < 0 { return null }
+    local rt1 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kth); if rt1 < 0 { return null }
+    local ti1 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt1); if ti1 < 0 { return null }
+    local kv_then = JsonFragBox.index_of_from(s, "\"value\":", ti1); if kv_then < 0 { return null }
     local then_val = JsonFragBox.read_int_after(s, kv_then + 8); if then_val == null { return null }
-    local kel = s.indexOf("\"else\":", k_if); if kel < 0 { return null }
-    local rt2 = s.indexOf("\"type\":\"Return\"", kel); if rt2 < 0 { return null }
-    local ti2 = s.indexOf("\"type\":\"Int\"", rt2); if ti2 < 0 { return null }
-    local kv_else = s.indexOf("\"value\":", ti2); if kv_else < 0 { return null }
+    local kel = JsonFragBox.index_of_from(s, "\"else\":", k_if); if kel < 0 { return null }
+    local rt2 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kel); if rt2 < 0 { return null }
+    local ti2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt2); if ti2 < 0 { return null }
+    local kv_else = JsonFragBox.index_of_from(s, "\"value\":", ti2); if kv_else < 0 { return null }
     local else_val = JsonFragBox.read_int_after(s, kv_else + 8); if else_val == null { return null }
 
     // Build MIR
diff --git a/lang/src/mir/builder/internal/lower_if_nested_box.hako b/lang/src/mir/builder/internal/lower_if_nested_box.hako
index ad1c16c3..eced39ed 100644
--- a/lang/src/mir/builder/internal/lower_if_nested_box.hako
+++ b/lang/src/mir/builder/internal/lower_if_nested_box.hako
@@ -19,53 +19,53 @@ using "hako.mir.builder.internal.pattern_util" as PatternUtilBox
 static box LowerIfNestedBox {
   try_lower(program_json) {
     local s = "" + program_json
-    local k_if1 = s.indexOf("\"type\":\"If\"")
+    local k_if1 = JsonFragBox.index_of_from(s, "\"type\":\"If\"", 0)
     if k_if1 < 0 { return null }
-    local k_cmp1 = s.indexOf("\"type\":\"Compare\"", k_if1)
+    local k_cmp1 = JsonFragBox.index_of_from(s, "\"type\":\"Compare\"", k_if1)
     if k_cmp1 < 0 { return null }
-    local kop1 = s.indexOf("\"op\":", k_cmp1); if kop1 < 0 { return null }
+    local kop1 = JsonFragBox.index_of_from(s, "\"op\":", k_cmp1); if kop1 < 0 { return null }
     local op1s = JsonFragBox.read_string_after(s, kop1 + 5); if op1s == null { return null }
     local op1 = PatternUtilBox.map_cmp(op1s); if op1 == null { return null }
-    local klhs1 = s.indexOf("\"lhs\":{", k_cmp1); if klhs1 < 0 { return null }
-    local ti11 = s.indexOf("\"type\":\"Int\"", klhs1); if ti11 < 0 { return null }
-    local kv11 = s.indexOf("\"value\":", ti11); if kv11 < 0 { return null }
+    local klhs1 = JsonFragBox.index_of_from(s, "\"lhs\":{", k_cmp1); if klhs1 < 0 { return null }
+    local ti11 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", klhs1); if ti11 < 0 { return null }
+    local kv11 = JsonFragBox.index_of_from(s, "\"value\":", ti11); if kv11 < 0 { return null }
     local lhs1 = JsonFragBox.read_int_after(s, kv11 + 8); if lhs1 == null { return null }
-    local krhs1 = s.indexOf("\"rhs\":{", k_cmp1); if krhs1 < 0 { return null }
-    local ti12 = s.indexOf("\"type\":\"Int\"", krhs1); if ti12 < 0 { return null }
-    local kv12 = s.indexOf("\"value\":", ti12); if kv12 < 0 { return null }
+    local krhs1 = JsonFragBox.index_of_from(s, "\"rhs\":{", k_cmp1); if krhs1 < 0 { return null }
+    local ti12 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", krhs1); if ti12 < 0 { return null }
+    local kv12 = JsonFragBox.index_of_from(s, "\"value\":", ti12); if kv12 < 0 { return null }
     local rhs1 = JsonFragBox.read_int_after(s, kv12 + 8); if rhs1 == null { return null }
     // then Return(Int A)
-    local kth = s.indexOf("\"then\":", k_if1); if kth < 0 { return null }
-    local rt1 = s.indexOf("\"type\":\"Return\"", kth); if rt1 < 0 { return null }
-    local ti13 = s.indexOf("\"type\":\"Int\"", rt1); if ti13 < 0 { return null }
-    local kv13 = s.indexOf("\"value\":", ti13); if kv13 < 0 { return null }
+    local kth = JsonFragBox.index_of_from(s, "\"then\":", k_if1); if kth < 0 { return null }
+    local rt1 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kth); if rt1 < 0 { return null }
+    local ti13 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt1); if ti13 < 0 { return null }
+    local kv13 = JsonFragBox.index_of_from(s, "\"value\":", ti13); if kv13 < 0 { return null }
     local aval = JsonFragBox.read_int_after(s, kv13 + 8); if aval == null { return null }
     // else contains nested If with Return(Int)/Return(Int)
-    local kel = s.indexOf("\"else\":", k_if1); if kel < 0 { return null }
-    local k_if2 = s.indexOf("\"type\":\"If\"", kel); if k_if2 < 0 { return null }
-    local k_cmp2 = s.indexOf("\"type\":\"Compare\"", k_if2); if k_cmp2 < 0 { return null }
-    local kop2 = s.indexOf("\"op\":", k_cmp2); if kop2 < 0 { return null }
+    local kel = JsonFragBox.index_of_from(s, "\"else\":", k_if1); if kel < 0 { return null }
+    local k_if2 = JsonFragBox.index_of_from(s, "\"type\":\"If\"", kel); if k_if2 < 0 { return null }
+    local k_cmp2 = JsonFragBox.index_of_from(s, "\"type\":\"Compare\"", k_if2); if k_cmp2 < 0 { return null }
+    local kop2 = JsonFragBox.index_of_from(s, "\"op\":", k_cmp2); if kop2 < 0 { return null }
     local op2s = JsonFragBox.read_string_after(s, kop2 + 5); if op2s == null { return null }
     local op2 = PatternUtilBox.map_cmp(op2s); if op2 == null { return null }
-    local klhs2 = s.indexOf("\"lhs\":{", k_cmp2); if klhs2 < 0 { return null }
-    local ti21 = s.indexOf("\"type\":\"Int\"", klhs2); if ti21 < 0 { return null }
-    local kv21 = s.indexOf("\"value\":", ti21); if kv21 < 0 { return null }
+    local klhs2 = JsonFragBox.index_of_from(s, "\"lhs\":{", k_cmp2); if klhs2 < 0 { return null }
+    local ti21 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", klhs2); if ti21 < 0 { return null }
+    local kv21 = JsonFragBox.index_of_from(s, "\"value\":", ti21); if kv21 < 0 { return null }
     local lhs2 = JsonFragBox.read_int_after(s, kv21 + 8); if lhs2 == null { return null }
-    local krhs2 = s.indexOf("\"rhs\":{", k_cmp2); if krhs2 < 0 { return null }
-    local ti22 = s.indexOf("\"type\":\"Int\"", krhs2); if ti22 < 0 { return null }
-    local kv22 = s.indexOf("\"value\":", ti22); if kv22 < 0 { return null }
+    local krhs2 = JsonFragBox.index_of_from(s, "\"rhs\":{", k_cmp2); if krhs2 < 0 { return null }
+    local ti22 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", krhs2); if ti22 < 0 { return null }
+    local kv22 = JsonFragBox.index_of_from(s, "\"value\":", ti22); if kv22 < 0 { return null }
     local rhs2 = JsonFragBox.read_int_after(s, kv22 + 8); if rhs2 == null { return null }
     // then Return(Int B)
-    local kth2 = s.indexOf("\"then\":", k_if2); if kth2 < 0 { return null }
-    local rt2 = s.indexOf("\"type\":\"Return\"", kth2); if rt2 < 0 { return null }
-    local ti23 = s.indexOf("\"type\":\"Int\"", rt2); if ti23 < 0 { return null }
-    local kv23 = s.indexOf("\"value\":", ti23); if kv23 < 0 { return null }
+    local kth2 = JsonFragBox.index_of_from(s, "\"then\":", k_if2); if kth2 < 0 { return null }
+    local rt2 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kth2); if rt2 < 0 { return null }
+    local ti23 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt2); if ti23 < 0 { return null }
+    local kv23 = JsonFragBox.index_of_from(s, "\"value\":", ti23); if kv23 < 0 { return null }
     local bval = JsonFragBox.read_int_after(s, kv23 + 8); if bval == null { return null }
     // else Return(Int C)
-    local kel2 = s.indexOf("\"else\":", k_if2); if kel2 < 0 { return null }
-    local rt3 = s.indexOf("\"type\":\"Return\"", kel2); if rt3 < 0 { return null }
-    local ti24 = s.indexOf("\"type\":\"Int\"", rt3); if ti24 < 0 { return null }
-    local kv24 = s.indexOf("\"value\":", ti24); if kv24 < 0 { return null }
+    local kel2 = JsonFragBox.index_of_from(s, "\"else\":", k_if2); if kel2 < 0 { return null }
+    local rt3 = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kel2); if rt3 < 0 { return null }
+    local ti24 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt3); if ti24 < 0 { return null }
+    local kv24 = JsonFragBox.index_of_from(s, "\"value\":", ti24); if kv24 < 0 { return null }
     local cval = JsonFragBox.read_int_after(s, kv24 + 8); if cval == null { return null }
 
     // Build MIR(JSON)
diff --git a/lang/src/mir/builder/internal/lower_if_then_else_following_return_box.hako b/lang/src/mir/builder/internal/lower_if_then_else_following_return_box.hako
index 52fd2abf..83ed596d 100644
--- a/lang/src/mir/builder/internal/lower_if_then_else_following_return_box.hako
+++ b/lang/src/mir/builder/internal/lower_if_then_else_following_return_box.hako
@@ -10,29 +10,29 @@ static box LowerIfThenElseFollowingReturnBox {
   try_lower(program_json) {
     local s = "" + program_json
     // If with Compare(Int,Int)
-    local k_if = s.indexOf("\"type\":\"If\"")
+    local k_if = JsonFragBox.index_of_from(s, "\"type\":\"If\"", 0)
     if k_if < 0 { return null }
-    local k_cmp = s.indexOf("\"type\":\"Compare\"", k_if)
+    local k_cmp = JsonFragBox.index_of_from(s, "\"type\":\"Compare\"", k_if)
     if k_cmp < 0 { return null }
-    local k_op = s.indexOf("\"op\":", k_cmp); if k_op < 0 { return null }
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_cmp); if k_op < 0 { return null }
     local sym = JsonFragBox.read_string_after(s, k_op + 5); if sym == null { return null }
     local op = PatternUtilBox.map_cmp(sym); if op == null { return null }
     // LHS/RHS ints
-    local klhs = s.indexOf("\"lhs\":{", k_cmp); if klhs < 0 { return null }
-    local ti1 = s.indexOf("\"type\":\"Int\"", klhs); if ti1 < 0 { return null }
-    { local kv = s.indexOf("\"value\":", ti1); if kv < 0 { return null }; var lhs_val = JsonFragBox.read_int_after(s, kv + 8); if lhs_val == null { return null } }
-    local krhs = s.indexOf("\"rhs\":{", k_cmp); if krhs < 0 { return null }
-    local ti2 = s.indexOf("\"type\":\"Int\"", krhs); if ti2 < 0 { return null }
-    { local kv2 = s.indexOf("\"value\":", ti2); if kv2 < 0 { return null }; var rhs_val = JsonFragBox.read_int_after(s, kv2 + 8); if rhs_val == null { return null } }
+    local klhs = JsonFragBox.index_of_from(s, "\"lhs\":{", k_cmp); if klhs < 0 { return null }
+    local ti1 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", klhs); if ti1 < 0 { return null }
+    { local kv = JsonFragBox.index_of_from(s, "\"value\":", ti1); if kv < 0 { return null }; var lhs_val = JsonFragBox.read_int_after(s, kv + 8); if lhs_val == null { return null } }
+    local krhs = JsonFragBox.index_of_from(s, "\"rhs\":{", k_cmp); if krhs < 0 { return null }
+    local ti2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", krhs); if ti2 < 0 { return null }
+    { local kv2 = JsonFragBox.index_of_from(s, "\"value\":", ti2); if kv2 < 0 { return null }; var rhs_val = JsonFragBox.read_int_after(s, kv2 + 8); if rhs_val == null { return null } }
     // then: Return(Int)
-    local kth = s.indexOf("\"then\":", k_if); if kth < 0 { return null }
-    local rt = s.indexOf("\"type\":\"Return\"", kth); if rt < 0 { return null }
-    local ti3 = s.indexOf("\"type\":\"Int\"", rt); if ti3 < 0 { return null }
-    { local kv3 = s.indexOf("\"value\":", ti3); if kv3 < 0 { return null }; var then_val = JsonFragBox.read_int_after(s, kv3 + 8); if then_val == null { return null } }
+    local kth = JsonFragBox.index_of_from(s, "\"then\":", k_if); if kth < 0 { return null }
+    local rt = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", kth); if rt < 0 { return null }
+    local ti3 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", rt); if ti3 < 0 { return null }
+    { local kv3 = JsonFragBox.index_of_from(s, "\"value\":", ti3); if kv3 < 0 { return null }; var then_val = JsonFragBox.read_int_after(s, kv3 + 8); if then_val == null { return null } }
     // else is omitted → following Return(Int) in Program body
-    local k_after = s.indexOf("\"type\":\"Return\"", k_if + 1); if k_after < 0 { return null }
-    local ti4 = s.indexOf("\"type\":\"Int\"", k_after); if ti4 < 0 { return null }
-    { local kv4 = s.indexOf("\"value\":", ti4); if kv4 < 0 { return null }; var else_val = JsonFragBox.read_int_after(s, kv4 + 8); if else_val == null { return null } }
+    local k_after = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", k_if + 1); if k_after < 0 { return null }
+    local ti4 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_after); if ti4 < 0 { return null }
+    { local kv4 = JsonFragBox.index_of_from(s, "\"value\":", ti4); if kv4 < 0 { return null }; var else_val = JsonFragBox.read_int_after(s, kv4 + 8); if else_val == null { return null } }
 
     // Build MIR(JSON)
     local b0 = new ArrayBox()
diff --git a/lang/src/mir/builder/internal/lower_loop_count_param_box.hako b/lang/src/mir/builder/internal/lower_loop_count_param_box.hako
index 0f339d9f..ba0aa969 100644
--- a/lang/src/mir/builder/internal/lower_loop_count_param_box.hako
+++ b/lang/src/mir/builder/internal/lower_loop_count_param_box.hako
@@ -12,27 +12,27 @@ static box LowerLoopCountParamBox {
     local s = "" + program_json
     // Discover loop variable name from Compare first
     // We'll accept either lhs Var(name) or rhs Var(name)
-    local k_loop = s.indexOf("\"type\":\"Loop\"", 0)
+    local k_loop = JsonFragBox.index_of_from(s, "\"type\":\"Loop\"", 0)
     if k_loop < 0 { return null }
-    local k_cmp = s.indexOf("\"type\":\"Compare\"", k_loop)
+    local k_cmp = JsonFragBox.index_of_from(s, "\"type\":\"Compare\"", k_loop)
     if k_cmp < 0 { return null }
     local varname = LoopScanBox.find_loop_var_name(s, k_cmp)
     if varname == null { return null }
 
     // Local <varname> = (Int init | Var initName)
-    local k_local_i = s.indexOf("\"type\":\"Local\"")
+    local k_local_i = JsonFragBox.index_of_from(s, "\"type\":\"Local\"", 0)
     if k_local_i < 0 { return null }
-    if s.indexOf("\"name\":\"" + varname + "\"", k_local_i) < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"name\":\"" + varname + "\"", k_local_i) < 0 { return null }
     local init = null
     {
-      local k_init_int = s.indexOf("\"type\":\"Int\"", k_local_i)
-      local k_loop_next = s.indexOf("\"type\":\"Loop\"", k_local_i)
+      local k_init_int = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_local_i)
+      local k_loop_next = JsonFragBox.index_of_from(s, "\"type\":\"Loop\"", k_local_i)
       if k_init_int >= 0 && (k_loop_next < 0 || k_init_int < k_loop_next) {
-        local kv_i = s.indexOf("\"value\":", k_init_int); if kv_i >= 0 { init = JsonFragBox.read_int_after(s, kv_i + 8) }
+        local kv_i = JsonFragBox.index_of_from(s, "\"value\":", k_init_int); if kv_i >= 0 { init = JsonFragBox.read_int_after(s, kv_i + 8) }
       } else {
-        local k_init_var = s.indexOf("\"type\":\"Var\"", k_local_i)
+        local k_init_var = JsonFragBox.index_of_from(s, "\"type\":\"Var\"", k_local_i)
         if k_init_var >= 0 && (k_loop_next < 0 || k_init_var < k_loop_next) {
-          local kn_i = s.indexOf("\"name\":\"", k_init_var); if kn_i < 0 { return null }
+          local kn_i = JsonFragBox.index_of_from(s, "\"name\":\"", k_init_var); if kn_i < 0 { return null }
           local vname = JsonFragBox.read_string_after(s, kn_i)
           if vname != null { init = PatternUtilBox.find_local_int_before(s, vname, k_local_i) }
         }
@@ -41,22 +41,22 @@ static box LowerLoopCountParamBox {
     if init == null { return null }
     // Loop Compare normalize: accept < / <= / > / >= with Var(varname) on either side
     // op: accept '<'/'<=' with i on lhs; '>'/'>=' with i on lhs (descending); swapped '>'/'>=' with i on rhs (ascending)
-    local k_op = s.indexOf("\"op\":", k_cmp); if k_op < 0 { return null }
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_cmp); if k_op < 0 { return null }
     local op = JsonFragBox.read_string_after(s, k_op + 5)
     if op == null { return null }
-    local has_lhs_i = s.indexOf("\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
-    local has_rhs_i = s.indexOf("\"rhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
+    local has_lhs_i = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
+    local has_rhs_i = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
     if !has_lhs_i && !has_rhs_i { return null }
     local cmp = null
     local limit = null
     if has_lhs_i {
       // rhs Int/Var → resolve limit
-      local k_rhs = s.indexOf("\"rhs\":{", k_cmp); if k_rhs < 0 { return null }
-      local k_lim_t = s.indexOf("\"type\":\"Int\"", k_rhs)
-      if k_lim_t >= 0 { local kv = s.indexOf("\"value\":", k_lim_t); if kv >= 0 { limit = JsonFragBox.read_int_after(s, kv + 8) } }
+      local k_rhs = JsonFragBox.index_of_from(s, "\"rhs\":{", k_cmp); if k_rhs < 0 { return null }
+      local k_lim_t = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_rhs)
+      if k_lim_t >= 0 { local kv = JsonFragBox.index_of_from(s, "\"value\":", k_lim_t); if kv >= 0 { limit = JsonFragBox.read_int_after(s, kv + 8) } }
       else {
-        local k_rv = s.indexOf("\"type\":\"Var\"", k_rhs); if k_rv < 0 { return null }
-        local kn = s.indexOf("\"name\":\"", k_rhs); if kn < 0 { return null }
+        local k_rv = JsonFragBox.index_of_from(s, "\"type\":\"Var\"", k_rhs); if k_rv < 0 { return null }
+        local kn = JsonFragBox.index_of_from(s, "\"name\":\"", k_rhs); if kn < 0 { return null }
         local lname = JsonFragBox.read_string_after(s, kn); if lname == null { return null }
         limit = PatternUtilBox.find_local_int_before(s, lname, k_cmp)
       }
@@ -69,12 +69,12 @@ static box LowerLoopCountParamBox {
       limit = norm.substring(cpos+1, norm.length())
     } else {
       if op != ">" && op != ">=" && op != "<" && op != "<=" && op != "!=" { return null }
-      local k_lhs = s.indexOf("\"lhs\":{", k_cmp); if k_lhs < 0 { return null }
-      local k_lim_t2 = s.indexOf("\"type\":\"Int\"", k_lhs)
-      if k_lim_t2 >= 0 { local kv2 = s.indexOf("\"value\":", k_lim_t2); if kv2 >= 0 { limit = JsonFragBox.read_int_after(s, kv2 + 8) } }
+      local k_lhs = JsonFragBox.index_of_from(s, "\"lhs\":{", k_cmp); if k_lhs < 0 { return null }
+      local k_lim_t2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_lhs)
+      if k_lim_t2 >= 0 { local kv2 = JsonFragBox.index_of_from(s, "\"value\":", k_lim_t2); if kv2 >= 0 { limit = JsonFragBox.read_int_after(s, kv2 + 8) } }
       else {
-        local k_lv = s.indexOf("\"type\":\"Var\"", k_lhs); if k_lv < 0 { return null }
-        local kn3 = s.indexOf("\"name\":\"", k_lhs); if kn3 < 0 { return null }
+        local k_lv = JsonFragBox.index_of_from(s, "\"type\":\"Var\"", k_lhs); if k_lv < 0 { return null }
+        local kn3 = JsonFragBox.index_of_from(s, "\"name\":\"", k_lhs); if kn3 < 0 { return null }
         local lname3 = JsonFragBox.read_string_after(s, kn3); if lname3 == null { return null }
         limit = PatternUtilBox.find_local_int_before(s, lname3, k_cmp)
       }
@@ -86,27 +86,27 @@ static box LowerLoopCountParamBox {
       limit = norm2.substring(cpos2+1, norm2.length())
     }
     // Body increment: Local i = Binary('+', Var i, Int step)
-    local k_body_i = s.indexOf("\"name\":\"" + varname + "\"", k_loop)
+    local k_body_i = JsonFragBox.index_of_from(s, "\"name\":\"" + varname + "\"", k_loop)
     if k_body_i < 0 { return null }
-    local k_bop = s.indexOf("\"type\":\"Binary\"", k_body_i)
+    local k_bop = JsonFragBox.index_of_from(s, "\"type\":\"Binary\"", k_body_i)
     if k_bop < 0 { return null }
     // Body increment: Local i = Binary(op '+' or '-', Var i, (Int step | Var stepName))
-    local bop_plus = (s.indexOf("\"op\":\"+\"", k_bop) >= 0)
-    local bop_minus = (s.indexOf("\"op\":\"-\"", k_bop) >= 0)
+    local bop_plus = (JsonFragBox.index_of_from(s, "\"op\":\"+\"", k_bop) >= 0)
+    local bop_minus = (JsonFragBox.index_of_from(s, "\"op\":\"-\"", k_bop) >= 0)
     if (!bop_plus && !bop_minus) { return null }
-    if s.indexOf("\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_bop) < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_bop) < 0 { return null }
 
     local step = null
     // Prefer rhs Int if present; otherwise try rhs Var and reverse-lookup its Local Int
     {
-      local k_rhsb = s.indexOf("\"rhs\":{", k_bop); if k_rhsb < 0 { return null }
-      local k_t_int = s.indexOf("\"type\":\"Int\"", k_rhsb)
+      local k_rhsb = JsonFragBox.index_of_from(s, "\"rhs\":{", k_bop); if k_rhsb < 0 { return null }
+      local k_t_int = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_rhsb)
       if k_t_int >= 0 {
-        local kvs = s.indexOf("\"value\":", k_t_int); if kvs >= 0 { step = JsonFragBox.read_int_after(s, kvs + 8) }
+        local kvs = JsonFragBox.index_of_from(s, "\"value\":", k_t_int); if kvs >= 0 { step = JsonFragBox.read_int_after(s, kvs + 8) }
       } else {
-        local k_t_var = s.indexOf("\"type\":\"Var\"", k_rhsb)
+        local k_t_var = JsonFragBox.index_of_from(s, "\"type\":\"Var\"", k_rhsb)
         if k_t_var < 0 { return null }
-        local kns = s.indexOf("\"name\":\"", k_rhsb); if kns < 0 { return null }
+        local kns = JsonFragBox.index_of_from(s, "\"name\":\"", k_rhsb); if kns < 0 { return null }
         local vname = JsonFragBox.read_string_after(s, kns); if vname == null { return null }
         step = PatternUtilBox.find_local_int_before(s, vname, k_bop)
       }
diff --git a/lang/src/mir/builder/internal/lower_loop_simple_box.hako b/lang/src/mir/builder/internal/lower_loop_simple_box.hako
index 0c08758d..43d8226b 100644
--- a/lang/src/mir/builder/internal/lower_loop_simple_box.hako
+++ b/lang/src/mir/builder/internal/lower_loop_simple_box.hako
@@ -12,38 +12,38 @@ static box LowerLoopSimpleBox {
   try_lower(program_json) {
     local s = "" + program_json
     // Find Loop with cond Compare and normalize to canonical (<) with dynamic var name
-    local k_loop = s.indexOf("\"type\":\"Loop\"")
+    local k_loop = JsonFragBox.index_of_from(s, "\"type\":\"Loop\"", 0)
     if k_loop < 0 { return null }
-    local k_cmp = s.indexOf("\"type\":\"Compare\"", k_loop)
+    local k_cmp = JsonFragBox.index_of_from(s, "\"type\":\"Compare\"", k_loop)
     if k_cmp < 0 { return null }
     // discover loop var name from cond (lhs or rhs Var)
     local varname = LoopScanBox.find_loop_var_name(s, k_cmp)
     if varname == null { return null }
 
     // op: accept '<' / '<=' as-is, '!=' (with var on lhs) as '<', and swapped '>' / '>=' (with var on rhs)
-    local k_op = s.indexOf("\"op\":", k_cmp); if k_op < 0 { return null }
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_cmp); if k_op < 0 { return null }
     local op = JsonFragBox.read_string_after(s, k_op + 5)
     if op == null { return null }
     // Determine where Var(varname) is and extract the Int from the opposite side
-    local has_lhs_i = s.indexOf("\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
-    local has_rhs_i = s.indexOf("\"rhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
+    local has_lhs_i = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
+    local has_rhs_i = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
     if !has_lhs_i && !has_rhs_i { return null }
 
     local swapped = 0
     local limit = null
     if has_lhs_i {
       // rhs Int value
-      local k_rhs = s.indexOf("\"rhs\":{", k_cmp); if k_rhs < 0 { return null }
-      local k_ti = s.indexOf("\"type\":\"Int\"", k_rhs); if k_ti < 0 { return null }
-      local k_v = s.indexOf("\"value\":", k_ti); if k_v < 0 { return null }
+      local k_rhs = JsonFragBox.index_of_from(s, "\"rhs\":{", k_cmp); if k_rhs < 0 { return null }
+      local k_ti = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_rhs); if k_ti < 0 { return null }
+      local k_v = JsonFragBox.index_of_from(s, "\"value\":", k_ti); if k_v < 0 { return null }
       limit = JsonFragBox.read_int_after(s, k_v + 8)
       if limit == null { return null }
     } else {
       // Var is on rhs; lhs must be Int
       swapped = 1
-      local k_lhs = s.indexOf("\"lhs\":{", k_cmp); if k_lhs < 0 { return null }
-      local k_ti2 = s.indexOf("\"type\":\"Int\"", k_lhs); if k_ti2 < 0 { return null }
-      local k_v2 = s.indexOf("\"value\":", k_ti2); if k_v2 < 0 { return null }
+      local k_lhs = JsonFragBox.index_of_from(s, "\"lhs\":{", k_cmp); if k_lhs < 0 { return null }
+      local k_ti2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_lhs); if k_ti2 < 0 { return null }
+      local k_v2 = JsonFragBox.index_of_from(s, "\"value\":", k_ti2); if k_v2 < 0 { return null }
       limit = JsonFragBox.read_int_after(s, k_v2 + 8)
       if limit == null { return null }
     }
diff --git a/lang/src/mir/builder/internal/lower_loop_sum_bc_box.hako b/lang/src/mir/builder/internal/lower_loop_sum_bc_box.hako
index 7ba28826..8ad2a9bc 100644
--- a/lang/src/mir/builder/internal/lower_loop_sum_bc_box.hako
+++ b/lang/src/mir/builder/internal/lower_loop_sum_bc_box.hako
@@ -21,19 +21,19 @@ static box LowerLoopSumBcBox {
       print("[sum_bc] enter lower")
     }
     // Loop and Compare normalize to canonical (<) with dynamic var name
-    local k_loop = s.indexOf("\"type\":\"Loop\"")
+    local k_loop = JsonFragBox.index_of_from(s, "\"type\":\"Loop\"", 0)
     if k_loop < 0 { return null }
-    local k_cmp = s.indexOf("\"type\":\"Compare\"", k_loop)
+    local k_cmp = JsonFragBox.index_of_from(s, "\"type\":\"Compare\"", k_loop)
     if k_cmp < 0 { return null }
     // discover loop var name from cond (lhs or rhs Var)
     local varname = null
     {
-      local kl = s.indexOf("\"lhs\":{", k_cmp); local kr = s.indexOf("\"rhs\":{", k_cmp)
-      if kl >= 0 && s.indexOf("\"type\":\"Var\"", kl) >= 0 {
-        local kn = s.indexOf("\"name\":\"", kl); if kn >= 0 { varname = JsonFragBox.read_string_after(s, kn) }
+      local kl = JsonFragBox.index_of_from(s, "\"lhs\":{", k_cmp); local kr = JsonFragBox.index_of_from(s, "\"rhs\":{", k_cmp)
+      if kl >= 0 && JsonFragBox.index_of_from(s, "\"type\":\"Var\"", kl) >= 0 {
+        local kn = JsonFragBox.index_of_from(s, "\"name\":\"", kl); if kn >= 0 { varname = JsonFragBox.read_string_after(s, kn) }
       }
-      if varname == null && kr >= 0 && s.indexOf("\"type\":\"Var\"", kr) >= 0 {
-        local kn2 = s.indexOf("\"name\":\"", kr); if kn2 >= 0 { varname = JsonFragBox.read_string_after(s, kn2) }
+      if varname == null && kr >= 0 && JsonFragBox.index_of_from(s, "\"type\":\"Var\"", kr) >= 0 {
+        local kn2 = JsonFragBox.index_of_from(s, "\"name\":\"", kr); if kn2 >= 0 { varname = JsonFragBox.read_string_after(s, kn2) }
       }
     }
     if varname == null { return null }
@@ -41,27 +41,27 @@ static box LowerLoopSumBcBox {
       print("[sum_bc] var=" + varname)
     }
     // op: accept '<'/'<=' with var on lhs; also accept swapped '>'/'>=' with var on rhs
-    local k_op = s.indexOf("\"op\":", k_cmp); if k_op < 0 { return null }
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_cmp); if k_op < 0 { return null }
     local op = JsonFragBox.read_string_after(s, k_op + 5)
     if op == null { return null }
-    local has_lhs_i = s.indexOf("\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
-    local has_rhs_i = s.indexOf("\"rhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
+    local has_lhs_i = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
+    local has_rhs_i = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", k_cmp) >= 0
     if !has_lhs_i && !has_rhs_i { return null }
     local limit = null
     if has_lhs_i {
       if op != "<" && op != "<=" { return null }
       // rhs Int limit
-      local k_rhs = s.indexOf("\"rhs\":{", k_cmp); if k_rhs < 0 { return null }
-      local k_ti = s.indexOf("\"type\":\"Int\"", k_rhs); if k_ti < 0 { return null }
-      local kv = s.indexOf("\"value\":", k_ti); if kv < 0 { return null }
+      local k_rhs = JsonFragBox.index_of_from(s, "\"rhs\":{", k_cmp); if k_rhs < 0 { return null }
+      local k_ti = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_rhs); if k_ti < 0 { return null }
+      local kv = JsonFragBox.index_of_from(s, "\"value\":", k_ti); if kv < 0 { return null }
       limit = JsonFragBox.read_int_after(s, kv + 8); if limit == null { return null }
       if op == "<=" { limit = StringHelpers.int_to_str(JsonFragBox._str_to_int(limit) + 1) }
     } else {
       // swapped: Int on lhs, Var i on rhs, op should be '>' or '>='
       if op != ">" && op != ">=" { return null }
-      local k_lhs = s.indexOf("\"lhs\":{", k_cmp); if k_lhs < 0 { return null }
-      local k_ti2 = s.indexOf("\"type\":\"Int\"", k_lhs); if k_ti2 < 0 { return null }
-      local kv2 = s.indexOf("\"value\":", k_ti2); if kv2 < 0 { return null }
+      local k_lhs = JsonFragBox.index_of_from(s, "\"lhs\":{", k_cmp); if k_lhs < 0 { return null }
+      local k_ti2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_lhs); if k_ti2 < 0 { return null }
+      local kv2 = JsonFragBox.index_of_from(s, "\"value\":", k_ti2); if kv2 < 0 { return null }
       limit = JsonFragBox.read_int_after(s, kv2 + 8); if limit == null { return null }
       if op == ">=" { limit = StringHelpers.int_to_str(JsonFragBox._str_to_int(limit) + 1) }
     }
@@ -69,22 +69,24 @@ static box LowerLoopSumBcBox {
     // Break sentinel: If(cond Compare var==X or X==var) then Break
     local break_value = null
     {
-      local kb = s.indexOf("\"type\":\"Break\"", k_loop)
+      local kb = JsonFragBox.index_of_from(s, "\"type\":\"Break\"", k_loop)
       if kb >= 0 {
         // Find nearest previous Compare and grab rhs Int
         local kbc = s.lastIndexOf("\"type\":\"Compare\"", kb)
         if kbc >= 0 {
           // Ensure op=="==" and lhs Var i
-          local kop = s.indexOf("\"op\":", kbc); local bop = null; if kop >= 0 { bop = JsonFragBox.read_string_after(s, kop + 5) }
+          local kop = JsonFragBox.index_of_from(s, "\"op\":", kbc); local bop = null; if kop >= 0 { bop = JsonFragBox.read_string_after(s, kop + 5) }
           if bop != null && bop == "==" {
-            local lhs_i = s.indexOf("\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", kbc) >= 0
-            local rhs_i = s.indexOf("\"rhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", kbc) >= 0
+            local lhs_i = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", kbc) >= 0
+            local rhs_i = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", kbc) >= 0
             if lhs_i {
-              local kbi = s.indexOf("\"type\":\"Int\"", s.indexOf("\"rhs\":{", kbc))
-              if kbi >= 0 { local kvb = s.indexOf("\"value\":", kbi); if kvb >= 0 { break_value = JsonFragBox.read_int_after(s, kvb + 8) } }
+              local k_rhsb = JsonFragBox.index_of_from(s, "\"rhs\":{", kbc)
+              local kbi = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_rhsb)
+              if kbi >= 0 { local kvb = JsonFragBox.index_of_from(s, "\"value\":", kbi); if kvb >= 0 { break_value = JsonFragBox.read_int_after(s, kvb + 8) } }
             } else if rhs_i {
-              local kbi2 = s.indexOf("\"type\":\"Int\"", s.indexOf("\"lhs\":{", kbc))
-              if kbi2 >= 0 { local kvb2 = s.indexOf("\"value\":", kbi2); if kvb2 >= 0 { break_value = JsonFragBox.read_int_after(s, kvb2 + 8) } }
+              local k_lhsb = JsonFragBox.index_of_from(s, "\"lhs\":{", kbc)
+              local kbi2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_lhsb)
+              if kbi2 >= 0 { local kvb2 = JsonFragBox.index_of_from(s, "\"value\":", kbi2); if kvb2 >= 0 { break_value = JsonFragBox.read_int_after(s, kvb2 + 8) } }
             }
           } else if bop != null && bop == "!=" {
             // Delegate to loop-scan helper for '!=' + else [Break]
@@ -92,11 +94,11 @@ static box LowerLoopSumBcBox {
             // Fallback: try local JsonFragBox-based extraction near kbc
             if break_value == null {
               // Read Int from lhs or rhs around kbc
-              local k_rhsb = s.indexOf("\"rhs\":{", kbc); local k_lhsb = s.indexOf("\"lhs\":{", kbc)
-              if k_rhsb >= 0 && s.indexOf("\"type\":\"Int\"", k_rhsb) >= 0 {
-                local kvi = s.indexOf("\"value\":", s.indexOf("\"type\":\"Int\"", k_rhsb)); if kvi >= 0 { break_value = JsonFragBox.read_int_after(s, kvi + 8) }
-              } else if k_lhsb >= 0 && s.indexOf("\"type\":\"Int\"", k_lhsb) >= 0 {
-                local kvj = s.indexOf("\"value\":", s.indexOf("\"type\":\"Int\"", k_lhsb)); if kvj >= 0 { break_value = JsonFragBox.read_int_after(s, kvj + 8) }
+              local k_rhsb = JsonFragBox.index_of_from(s, "\"rhs\":{", kbc); local k_lhsb = JsonFragBox.index_of_from(s, "\"lhs\":{", kbc)
+              if k_rhsb >= 0 && JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_rhsb) >= 0 {
+                local kvi = JsonFragBox.index_of_from(s, "\"value\":", JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_rhsb)); if kvi >= 0 { break_value = JsonFragBox.read_int_after(s, kvi + 8) }
+              } else if k_lhsb >= 0 && JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_lhsb) >= 0 {
+                local kvj = JsonFragBox.index_of_from(s, "\"value\":", JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_lhsb)); if kvj >= 0 { break_value = JsonFragBox.read_int_after(s, kvj + 8) }
               }
             }
           }
@@ -106,31 +108,33 @@ static box LowerLoopSumBcBox {
     // Continue sentinel: If(cond Compare var==Y or Y==var) then Continue
     local skip_value = null
     {
-      local kc = s.indexOf("\"type\":\"Continue\"", k_loop)
+      local kc = JsonFragBox.index_of_from(s, "\"type\":\"Continue\"", k_loop)
       if kc >= 0 {
         local kcc = s.lastIndexOf("\"type\":\"Compare\"", kc)
         if kcc >= 0 {
-          local kop2 = s.indexOf("\"op\":", kcc); local cop = null; if kop2 >= 0 { cop = JsonFragBox.read_string_after(s, kop2 + 5) }
+          local kop2 = JsonFragBox.index_of_from(s, "\"op\":", kcc); local cop = null; if kop2 >= 0 { cop = JsonFragBox.read_string_after(s, kop2 + 5) }
           if cop != null && cop == "==" {
-            local lhs_i2 = s.indexOf("\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", kcc) >= 0
-            local rhs_i2 = s.indexOf("\"rhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", kcc) >= 0
+            local lhs_i2 = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", kcc) >= 0
+            local rhs_i2 = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Var\",\"name\":\"" + varname + "\"}", kcc) >= 0
             if lhs_i2 {
-              local kci = s.indexOf("\"type\":\"Int\"", s.indexOf("\"rhs\":{", kcc))
-              if kci >= 0 { local kvs = s.indexOf("\"value\":", kci); if kvs >= 0 { skip_value = JsonFragBox.read_int_after(s, kvs + 8) } }
+              local k_rhsb2 = JsonFragBox.index_of_from(s, "\"rhs\":{", kcc)
+              local kci = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_rhsb2)
+              if kci >= 0 { local kvs = JsonFragBox.index_of_from(s, "\"value\":", kci); if kvs >= 0 { skip_value = JsonFragBox.read_int_after(s, kvs + 8) } }
             } else if rhs_i2 {
-              local kci2 = s.indexOf("\"type\":\"Int\"", s.indexOf("\"lhs\":{", kcc))
-              if kci2 >= 0 { local kvs2 = s.indexOf("\"value\":", kci2); if kvs2 >= 0 { skip_value = JsonFragBox.read_int_after(s, kvs2 + 8) } }
+              local k_lhsb2 = JsonFragBox.index_of_from(s, "\"lhs\":{", kcc)
+              local kci2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_lhsb2)
+              if kci2 >= 0 { local kvs2 = JsonFragBox.index_of_from(s, "\"value\":", kci2); if kvs2 >= 0 { skip_value = JsonFragBox.read_int_after(s, kvs2 + 8) } }
             }
           } else if cop != null && cop == "!=" {
             // Delegate to loop-scan helper for '!=' + else [Continue]
             if skip_value == null { skip_value = LoopScanBox.extract_ne_else_sentinel_value(s, "Continue", k_loop, varname) }
             // Fallback: JsonFragBox-based local extraction near kcc
             if skip_value == null {
-              local k_rhsb2 = s.indexOf("\"rhs\":{", kcc); local k_lhsb2 = s.indexOf("\"lhs\":{", kcc)
-              if k_rhsb2 >= 0 && s.indexOf("\"type\":\"Int\"", k_rhsb2) >= 0 {
-                local kvs = s.indexOf("\"value\":", s.indexOf("\"type\":\"Int\"", k_rhsb2)); if kvs >= 0 { skip_value = JsonFragBox.read_int_after(s, kvs + 8) }
-              } else if k_lhsb2 >= 0 && s.indexOf("\"type\":\"Int\"", k_lhsb2) >= 0 {
-                local kvs2 = s.indexOf("\"value\":", s.indexOf("\"type\":\"Int\"", k_lhsb2)); if kvs2 >= 0 { skip_value = JsonFragBox.read_int_after(s, kvs2 + 8) }
+              local k_rhsb2x = JsonFragBox.index_of_from(s, "\"rhs\":{", kcc); local k_lhsb2x = JsonFragBox.index_of_from(s, "\"lhs\":{", kcc)
+              if k_rhsb2x >= 0 && JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_rhsb2x) >= 0 {
+                local kvs = JsonFragBox.index_of_from(s, "\"value\":", JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_rhsb2x)); if kvs >= 0 { skip_value = JsonFragBox.read_int_after(s, kvs + 8) }
+              } else if k_lhsb2x >= 0 && JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_lhsb2x) >= 0 {
+                local kvs2 = JsonFragBox.index_of_from(s, "\"value\":", JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_lhsb2x)); if kvs2 >= 0 { skip_value = JsonFragBox.read_int_after(s, kvs2 + 8) }
               }
             }
           }
diff --git a/lang/src/mir/builder/internal/lower_method_array_get_set_box.hako b/lang/src/mir/builder/internal/lower_method_array_get_set_box.hako
index 572156f6..6a1dd2c9 100644
--- a/lang/src/mir/builder/internal/lower_method_array_get_set_box.hako
+++ b/lang/src/mir/builder/internal/lower_method_array_get_set_box.hako
@@ -5,8 +5,8 @@ static box LowerMethodArrayGetSetBox {
   try_lower(program_json) {
     if program_json == null { return null }
     local s = "" + program_json
-    if s.indexOf("\"type\":\"New\"") < 0 { return null }
-    if s.indexOf("\"class\":\"ArrayBox\"") < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"type\":\"New\"", 0) < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"class\":\"ArrayBox\"", 0) < 0 { return null }
     // Reverse-lookup (safe subset): prefer Local(Int) for index, Local(String) for value
     local n = s.length()
     local idx = PatternUtilBox.find_any_local_int_before(s, n)
diff --git a/lang/src/mir/builder/internal/lower_method_array_push_box.hako b/lang/src/mir/builder/internal/lower_method_array_push_box.hako
index 99c37d00..89141fb2 100644
--- a/lang/src/mir/builder/internal/lower_method_array_push_box.hako
+++ b/lang/src/mir/builder/internal/lower_method_array_push_box.hako
@@ -5,8 +5,8 @@ static box LowerMethodArrayPushBox {
   try_lower(program_json) {
     if program_json == null { return null }
     local s = "" + program_json
-    if s.indexOf("\"type\":\"New\"") < 0 { return null }
-    if s.indexOf("\"class\":\"ArrayBox\"") < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"type\":\"New\"", 0) < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"class\":\"ArrayBox\"", 0) < 0 { return null }
     // Reverse-lookup (safe subset): prefer Local(Int) for push values when present
     local n = s.length()
     local p1 = PatternUtilBox.find_any_local_int_before(s, n); if p1 == null { p1 = "1" }
diff --git a/lang/src/mir/builder/internal/lower_method_array_size_box.hako b/lang/src/mir/builder/internal/lower_method_array_size_box.hako
index 8243e3ca..c67f3f80 100644
--- a/lang/src/mir/builder/internal/lower_method_array_size_box.hako
+++ b/lang/src/mir/builder/internal/lower_method_array_size_box.hako
@@ -5,8 +5,8 @@ static box LowerMethodArraySizeBox {
   try_lower(program_json) {
     if program_json == null { return null }
     local s = "" + program_json
-    if s.indexOf("\"type\":\"New\"") < 0 { return null }
-    if s.indexOf("\"class\":\"ArrayBox\"") < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"type\":\"New\"", 0) < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"class\":\"ArrayBox\"", 0) < 0 { return null }
     // Emit MIR v1 JSON: new ArrayBox -> r1, size(r1) -> r2, const 0 -> r3, ret r3
     local json = "{\"kind\":\"MIR\",\"schema_version\":\"1.0\",\"functions\":[{\"name\":\"main\",\"blocks\":[{\"id\":0,\"instructions\":[" +
                "{\"op\":\"mir_call\",\"dst\":1,\"mir_call\":{\"callee\":{\"type\":\"Constructor\",\"box_type\":\"ArrayBox\"},\"args\":[],\"effects\":[]}}," +
@@ -16,4 +16,3 @@ static box LowerMethodArraySizeBox {
     return json
   }
 }
-
diff --git a/lang/src/mir/builder/internal/lower_method_map_get_set_box.hako b/lang/src/mir/builder/internal/lower_method_map_get_set_box.hako
index 58e5a88b..05ef9397 100644
--- a/lang/src/mir/builder/internal/lower_method_map_get_set_box.hako
+++ b/lang/src/mir/builder/internal/lower_method_map_get_set_box.hako
@@ -5,8 +5,8 @@ static box LowerMethodMapGetSetBox {
   try_lower(program_json) {
     if program_json == null { return null }
     local s = "" + program_json
-    if s.indexOf("\"type\":\"New\"") < 0 { return null }
-    if s.indexOf("\"class\":\"MapBox\"") < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"type\":\"New\"", 0) < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"class\":\"MapBox\"", 0) < 0 { return null }
     // Reverse-lookup (safe subset): prefer Local(String) for key, Local(Int) for value
     local n = s.length()
     local key = PatternUtilBox.find_any_local_string_before(s, n)
diff --git a/lang/src/mir/builder/internal/lower_method_map_size_box.hako b/lang/src/mir/builder/internal/lower_method_map_size_box.hako
index 0c77940c..1eab704d 100644
--- a/lang/src/mir/builder/internal/lower_method_map_size_box.hako
+++ b/lang/src/mir/builder/internal/lower_method_map_size_box.hako
@@ -4,8 +4,8 @@ static box LowerMethodMapSizeBox {
   try_lower(program_json) {
     if program_json == null { return null }
     local s = "" + program_json
-    if s.indexOf("\"type\":\"New\"") < 0 { return null }
-    if s.indexOf("\"class\":\"MapBox\"") < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"type\":\"New\"", 0) < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"class\":\"MapBox\"", 0) < 0 { return null }
     local json = "{\"kind\":\"MIR\",\"schema_version\":\"1.0\",\"functions\":[{\"name\":\"main\",\"blocks\":[{\"id\":0,\"instructions\":[" +
                "{\"op\":\"mir_call\",\"dst\":1,\"mir_call\":{\"callee\":{\"type\":\"Constructor\",\"box_type\":\"MapBox\"},\"args\":[],\"effects\":[]}}," +
                "{\"op\":\"mir_call\",\"dst\":2,\"mir_call\":{\"callee\":{\"type\":\"Method\",\"box_name\":\"MapBox\",\"method\":\"size\",\"receiver\":1},\"args\":[],\"effects\":[]}}," +
@@ -14,4 +14,3 @@ static box LowerMethodMapSizeBox {
     return json
   }
 }
-
diff --git a/lang/src/mir/builder/internal/lower_newbox_constructor_box.hako b/lang/src/mir/builder/internal/lower_newbox_constructor_box.hako
index 431d1756..ce61baf8 100644
--- a/lang/src/mir/builder/internal/lower_newbox_constructor_box.hako
+++ b/lang/src/mir/builder/internal/lower_newbox_constructor_box.hako
@@ -7,11 +7,11 @@ static box LowerNewboxConstructorBox {
     if program_json == null { return null }
     local s = "" + program_json
     // Quick pattern check
-    if s.indexOf("\"type\":\"New\"") < 0 { return null }
+    if JsonFragBox.index_of_from(s, "\"type\":\"New\"", 0) < 0 { return null }
     // Find class name (minimal scan)
     local cls = null
-    if s.indexOf("\"class\":\"ArrayBox\"") >= 0 { cls = "ArrayBox" }
-    else { if s.indexOf("\"class\":\"MapBox\"") >= 0 { cls = "MapBox" } }
+    if JsonFragBox.index_of_from(s, "\"class\":\"ArrayBox\"", 0) >= 0 { cls = "ArrayBox" }
+    else { if JsonFragBox.index_of_from(s, "\"class\":\"MapBox\"", 0) >= 0 { cls = "MapBox" } }
     if cls == null { return null }
     // Only accept known minimal boxes
     if !(cls == "ArrayBox" || cls == "MapBox") { return null }
diff --git a/lang/src/mir/builder/internal/lower_return_binop_box.hako b/lang/src/mir/builder/internal/lower_return_binop_box.hako
index a5f6b31c..96f44c46 100644
--- a/lang/src/mir/builder/internal/lower_return_binop_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_binop_box.hako
@@ -5,34 +5,34 @@ using selfhost.shared.json.utils.json_frag as JsonFragBox
 static box LowerReturnBinOpBox {
   try_lower(program_json) {
     local s = "" + program_json
-    local k_ret = s.indexOf("\"type\":\"Return\"")
+    local k_ret = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", 0)
     if k_ret < 0 { return null }
-    local k_bin = s.indexOf("\"type\":\"Binary\"", k_ret)
+    local k_bin = JsonFragBox.index_of_from(s, "\"type\":\"Binary\"", k_ret)
     if k_bin < 0 { return null }
     // op
-    local k_op = s.indexOf("\"op\":", k_bin)
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_bin)
     if k_op < 0 { return null }
     local op = JsonFragBox.read_string_after(s, k_op + 5)
     if op == null { return null }
     if !(op == "+" || op == "-" || op == "*" || op == "/") { return null }
     // lhs/rhs object starts
-    local klhs = s.indexOf("\"lhs\":{", k_bin)
-    local krhs = s.indexOf("\"rhs\":{", k_bin)
+    local klhs = JsonFragBox.index_of_from(s, "\"lhs\":{", k_bin)
+    local krhs = JsonFragBox.index_of_from(s, "\"rhs\":{", k_bin)
     if klhs < 0 { return null }
     // strictly ensure lhs node is Int by bounding search before rhs start
-    local ti = s.indexOf("\"type\":\"Int\"", klhs)
+    local ti = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", klhs)
     if ti < 0 { return null }
     if krhs >= 0 && ti >= krhs { return null }
-    local kv_lhs = s.indexOf("\"value\":", ti)
+    local kv_lhs = JsonFragBox.index_of_from(s, "\"value\":", ti)
     if kv_lhs < 0 { return null }
     if krhs >= 0 && kv_lhs >= krhs { return null }
     local lhs_val = JsonFragBox.read_int_after(s, kv_lhs + 8)
     if lhs_val == null { return null }
     // rhs int
     if krhs < 0 { return null }
-    local ti2 = s.indexOf("\"type\":\"Int\"", krhs)
+    local ti2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", krhs)
     if ti2 < 0 { return null }
-    local kv_rhs = s.indexOf("\"value\":", ti2)
+    local kv_rhs = JsonFragBox.index_of_from(s, "\"value\":", ti2)
     if kv_rhs < 0 { return null }
     local rhs_val = JsonFragBox.read_int_after(s, kv_rhs + 8)
     if rhs_val == null { return null }
diff --git a/lang/src/mir/builder/internal/lower_return_binop_varint_box.hako b/lang/src/mir/builder/internal/lower_return_binop_varint_box.hako
index d4016223..1155b28c 100644
--- a/lang/src/mir/builder/internal/lower_return_binop_varint_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_binop_varint_box.hako
@@ -10,26 +10,27 @@ using selfhost.shared.json.utils.json_frag as JsonFragBox
 static box LowerReturnBinOpVarIntBox {
   try_lower(program_json) {
     local s = "" + program_json
-    local k_ret = s.indexOf("\"type\":\"Return\"")
+    local k_ret = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", 0)
     if k_ret < 0 { return null }
-    local k_bin = s.indexOf("\"type\":\"Binary\"", k_ret)
+    local k_bin = JsonFragBox.index_of_from(s, "\"type\":\"Binary\"", k_ret)
     if k_bin < 0 { return null }
-    local k_op = s.indexOf("\"op\":", k_bin)
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_bin)
     if k_op < 0 { return null }
     local op = JsonFragBox.read_string_after(s, k_op + 5)
     if op == null { return null }
-    if !(op == "+" || op == "-" || op == "*" || op == "/") { return null }
+    // Map op symbol to MIR op_kind via shared util
+    local kind = PatternUtilBox.map_binop(op); if kind == null { return null }
     // Try Var + Int
-    local klhs_var = s.indexOf("\"lhs\":{\"type\":\"Var\"", k_bin)
-    local krhs_int = s.indexOf("\"rhs\":{\"type\":\"Int\"", k_bin)
+    local klhs_var = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Var\"", k_bin)
+    local krhs_int = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Int\"", k_bin)
     local var_name = null
     local rhs_val = null
     if klhs_var >= 0 && krhs_int >= 0 {
-      local k_name = s.indexOf("\"name\":", klhs_var); if k_name < 0 { return null }
+      local k_name = JsonFragBox.index_of_from(s, "\"name\":", klhs_var); if k_name < 0 { return null }
       var_name = JsonFragBox.read_string_after(s, k_name + 7)
-      local kvi = s.indexOf("\"type\":\"Int\"", krhs_int)
+      local kvi = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", krhs_int)
       if kvi >= 0 {
-        local kv = s.indexOf("\"value\":", kvi); if kv < 0 { return null }
+        local kv = JsonFragBox.index_of_from(s, "\"value\":", kvi); if kv < 0 { return null }
         rhs_val = JsonFragBox.read_int_after(s, kv + 8)
       }
       if var_name != null && rhs_val != null {
@@ -38,7 +39,7 @@ static box LowerReturnBinOpVarIntBox {
           local b0 = new ArrayBox()
           b0.push(MirSchemaBox.inst_const(1, var_val))
           b0.push(MirSchemaBox.inst_const(2, rhs_val))
-          b0.push(MirSchemaBox.inst_binop(op == "+" ? "Add" : (op == "-" ? "Sub" : (op == "*" ? "Mul" : "Div")), 1, 2, 3))
+          b0.push(MirSchemaBox.inst_binop(kind, 1, 2, 3))
           b0.push(MirSchemaBox.inst_ret(3))
           local blocks = new ArrayBox(); blocks.push(MirSchemaBox.block(0, b0))
           return MirSchemaBox.module(MirSchemaBox.fn_main(blocks))
@@ -46,17 +47,17 @@ static box LowerReturnBinOpVarIntBox {
       }
     }
     // Try Int + Var
-    local klhs_int = s.indexOf("\"lhs\":{\"type\":\"Int\"", k_bin)
-    local krhs_var = s.indexOf("\"rhs\":{\"type\":\"Var\"", k_bin)
+    local klhs_int = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Int\"", k_bin)
+    local krhs_var = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Var\"", k_bin)
     var_name = null
     local lhs_val = null
     if klhs_int >= 0 && krhs_var >= 0 {
-      local kvi2 = s.indexOf("\"type\":\"Int\"", klhs_int)
+      local kvi2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", klhs_int)
       if kvi2 >= 0 {
-        local kv2 = s.indexOf("\"value\":", kvi2); if kv2 < 0 { return null }
+        local kv2 = JsonFragBox.index_of_from(s, "\"value\":", kvi2); if kv2 < 0 { return null }
         lhs_val = JsonFragBox.read_int_after(s, kv2 + 8)
       }
-      local k_name2 = s.indexOf("\"name\":", krhs_var); if k_name2 < 0 { return null }
+      local k_name2 = JsonFragBox.index_of_from(s, "\"name\":", krhs_var); if k_name2 < 0 { return null }
       var_name = JsonFragBox.read_string_after(s, k_name2 + 7)
       if lhs_val != null && var_name != null {
         local var_val2 = PatternUtilBox.find_local_int_before(s, var_name, k_ret)
@@ -64,7 +65,7 @@ static box LowerReturnBinOpVarIntBox {
           local b1 = new ArrayBox()
           b1.push(MirSchemaBox.inst_const(1, lhs_val))
           b1.push(MirSchemaBox.inst_const(2, var_val2))
-          b1.push(MirSchemaBox.inst_binop(op == "+" ? "Add" : (op == "-" ? "Sub" : (op == "*" ? "Mul" : "Div")), 1, 2, 3))
+          b1.push(MirSchemaBox.inst_binop(kind, 1, 2, 3))
           b1.push(MirSchemaBox.inst_ret(3))
           local blocks = new ArrayBox(); blocks.push(MirSchemaBox.block(0, b1))
           return MirSchemaBox.module(MirSchemaBox.fn_main(blocks))
diff --git a/lang/src/mir/builder/internal/lower_return_binop_varvar_box.hako b/lang/src/mir/builder/internal/lower_return_binop_varvar_box.hako
index e6c302db..a63c8a47 100644
--- a/lang/src/mir/builder/internal/lower_return_binop_varvar_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_binop_varvar_box.hako
@@ -7,20 +7,20 @@ using selfhost.shared.json.utils.json_frag as JsonFragBox
 static box LowerReturnBinOpVarVarBox {
   try_lower(program_json){
     local s = "" + program_json
-    local k_ret = s.indexOf("\"type\":\"Return\""); if k_ret < 0 { return null }
-    local k_bin = s.indexOf("\"type\":\"Binary\"", k_ret); if k_bin < 0 { return null }
-    local k_op = s.indexOf("\"op\":", k_bin); if k_op < 0 { return null }
+    local k_ret = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", 0); if k_ret < 0 { return null }
+    local k_bin = JsonFragBox.index_of_from(s, "\"type\":\"Binary\"", k_ret); if k_bin < 0 { return null }
+    local k_op = JsonFragBox.index_of_from(s, "\"op\":", k_bin); if k_op < 0 { return null }
     local op = JsonFragBox.read_string_after(s, k_op + 5); if op == null { return null }
-    if !(op == "+" || op == "-" || op == "*" || op == "/") { return null }
-    local klhs = s.indexOf("\"lhs\":{\"type\":\"Var\"", k_bin); if klhs < 0 { return null }
-    local krhs = s.indexOf("\"rhs\":{\"type\":\"Var\"", k_bin); if krhs < 0 { return null }
-    local knl = s.indexOf("\"name\":", klhs); if knl < 0 { return null }
+    local kind = PatternUtilBox.map_binop(op); if kind == null { return null }
+    local klhs = JsonFragBox.index_of_from(s, "\"lhs\":{\"type\":\"Var\"", k_bin); if klhs < 0 { return null }
+    local krhs = JsonFragBox.index_of_from(s, "\"rhs\":{\"type\":\"Var\"", k_bin); if krhs < 0 { return null }
+    local knl = JsonFragBox.index_of_from(s, "\"name\":", klhs); if knl < 0 { return null }
     local lname = JsonFragBox.read_string_after(s, knl + 7); if lname == null { return null }
-    local knr = s.indexOf("\"name\":", krhs); if knr < 0 { return null }
+    local knr = JsonFragBox.index_of_from(s, "\"name\":", krhs); if knr < 0 { return null }
     local rname = JsonFragBox.read_string_after(s, knr + 7); if rname == null { return null }
     local lval = PatternUtilBox.find_local_int_before(s, lname, k_ret); if lval == null { return null }
     local rval = PatternUtilBox.find_local_int_before(s, rname, k_ret); if rval == null { return null }
-    local b0=new ArrayBox(); b0.push(MirSchemaBox.inst_const(1,lval)); b0.push(MirSchemaBox.inst_const(2,rval)); b0.push(MirSchemaBox.inst_binop(op == "+" ? "Add" : (op == "-" ? "Sub" : (op == "*" ? "Mul" : "Div")),1,2,3)); b0.push(MirSchemaBox.inst_ret(3))
+    local b0=new ArrayBox(); b0.push(MirSchemaBox.inst_const(1,lval)); b0.push(MirSchemaBox.inst_const(2,rval)); b0.push(MirSchemaBox.inst_binop(kind,1,2,3)); b0.push(MirSchemaBox.inst_ret(3))
     local blocks=new ArrayBox(); blocks.push(MirSchemaBox.block(0,b0));
     return MirSchemaBox.module(MirSchemaBox.fn_main(blocks))
   }
diff --git a/lang/src/mir/builder/internal/lower_return_bool_box.hako b/lang/src/mir/builder/internal/lower_return_bool_box.hako
index 85656004..a510e898 100644
--- a/lang/src/mir/builder/internal/lower_return_bool_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_bool_box.hako
@@ -5,16 +5,16 @@ using selfhost.shared.json.utils.json_frag as JsonFragBox
 static box LowerReturnBoolBox {
   try_lower(program_json) {
     local s = "" + program_json
-    local k_ret = s.indexOf("\"type\":\"Return\"")
+    local k_ret = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", 0)
     if k_ret < 0 { return null }
     // Restrict to Return(expr=Bool …): require expr 開始直後に Bool が来る
     // 例: "expr":{"type":"Bool","value":true}
-    local k_expr = s.indexOf("\"expr\":", k_ret)
+    local k_expr = JsonFragBox.index_of_from(s, "\"expr\":", k_ret)
     if k_expr < 0 { return null }
-    local k_bool = s.indexOf("\"type\":\"Bool\"", k_expr)
+    local k_bool = JsonFragBox.index_of_from(s, "\"type\":\"Bool\"", k_expr)
     if k_bool < 0 { return null }
     // Ensure this Bool belongs to the same expr (次の '}' までに value があることを確認)
-    local k_val = s.indexOf("\"value\":", k_bool)
+    local k_val = JsonFragBox.index_of_from(s, "\"value\":", k_bool)
     if k_val < 0 { return null }
     local is_true = JsonFragBox.read_bool_after(s, k_val+8)
     if is_true == null { return null }
diff --git a/lang/src/mir/builder/internal/lower_return_float_box.hako b/lang/src/mir/builder/internal/lower_return_float_box.hako
index 2fb3248d..c4ded245 100644
--- a/lang/src/mir/builder/internal/lower_return_float_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_float_box.hako
@@ -6,11 +6,11 @@ using selfhost.shared.json.utils.json_frag as JsonFragBox
 static box LowerReturnFloatBox {
   try_lower(program_json) {
     local s = "" + program_json
-    local k_ret = s.indexOf("\"type\":\"Return\"")
+    local k_ret = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", 0)
     if k_ret < 0 { return null }
-    local k_float = s.indexOf("\"type\":\"Float\"", k_ret)
+    local k_float = JsonFragBox.index_of_from(s, "\"type\":\"Float\"", k_ret)
     if k_float < 0 { return null }
-    local k_val = s.indexOf("\"value\":", k_float)
+    local k_val = JsonFragBox.index_of_from(s, "\"value\":", k_float)
     if k_val < 0 { return null }
     local fstr = JsonFragBox.read_float_after(s, k_val+8)
     if fstr == null { return null }
diff --git a/lang/src/mir/builder/internal/lower_return_int_box.hako b/lang/src/mir/builder/internal/lower_return_int_box.hako
index b57aee4d..c2793c71 100644
--- a/lang/src/mir/builder/internal/lower_return_int_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_int_box.hako
@@ -5,14 +5,14 @@ using selfhost.shared.json.utils.json_frag as JsonFragBox
 static box LowerReturnIntBox {
   try_lower(program_json) {
     local s = "" + program_json
-    local k_ret = s.indexOf("\"type\":\"Return\"")
+    local k_ret = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", 0)
     if k_ret < 0 { return null }
     // Find expr object
-    local k_expr = s.indexOf("\"expr\":{", k_ret)
+    local k_expr = JsonFragBox.index_of_from(s, "\"expr\":{", k_ret)
     if k_expr < 0 { return null }
     // Check that expr.type is directly Int (not Binary, Logical, Var, etc)
     local k_type_start = k_expr + 8
-    local k_type = s.indexOf("\"type\":", k_type_start)
+    local k_type = JsonFragBox.index_of_from(s, "\"type\":", k_type_start)
     if k_type < 0 || k_type > k_type_start + 20 { return null }
     // Extract type value to verify it's "Int"
     local k_type_val = k_type + 7
@@ -28,9 +28,9 @@ static box LowerReturnIntBox {
     if k_type_val + 3 >= n { return null }
     if s.substring(k_type_val+3, k_type_val+4) != "\"" { return null }
     // Now extract the value
-    local k_int = s.indexOf("\"type\":\"Int\"", k_expr)
+    local k_int = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_expr)
     if k_int < 0 { return null }
-    local kv = s.indexOf("\"value\":", k_int); if kv < 0 { return null }
+    local kv = JsonFragBox.index_of_from(s, "\"value\":", k_int); if kv < 0 { return null }
     local val = JsonFragBox.read_int_after(s, kv + 8)
     if val == null { return null }
     local debug_on = 0
diff --git a/lang/src/mir/builder/internal/lower_return_logical_box.hako b/lang/src/mir/builder/internal/lower_return_logical_box.hako
index ee5783e4..e32a196d 100644
--- a/lang/src/mir/builder/internal/lower_return_logical_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_logical_box.hako
@@ -11,7 +11,7 @@ static box LowerReturnLogicalBox {
 
   try_lower(program_json) {
     local s = "" + program_json
-    local k_ret = s.indexOf("\"type\":\"Return\"")
+    local k_ret = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", 0)
     if k_ret < 0 { return null }
     local k_log = JsonFragBox.index_of_from(s, "\"type\":\"Logical\"", k_ret)
     if k_log < 0 { return null }
diff --git a/lang/src/mir/builder/internal/lower_return_method_array_map_box.hako b/lang/src/mir/builder/internal/lower_return_method_array_map_box.hako
index 5fb28056..cc65a5cb 100644
--- a/lang/src/mir/builder/internal/lower_return_method_array_map_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_method_array_map_box.hako
@@ -8,12 +8,12 @@ using selfhost.vm.helpers.method_alias_policy as MethodAliasPolicy
 static box LowerReturnMethodArrayMapBox {
   try_lower(program_json) {
     local s = "" + program_json
-    local k_ret = s.indexOf("\"type\":\"Return\""); if k_ret < 0 { return null }
-    local k_m = s.indexOf("\"type\":\"Method\"", k_ret); if k_m < 0 { return null }
+    local k_ret = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", 0); if k_ret < 0 { return null }
+    local k_m = JsonFragBox.index_of_from(s, "\"type\":\"Method\"", k_ret); if k_m < 0 { return null }
     // receiver must be Var(name)
-    local k_recv = s.indexOf("\"recv\":{\"type\":\"Var\"", k_m); if k_recv < 0 { return null }
+    local k_recv = JsonFragBox.index_of_from(s, "\"recv\":{\"type\":\"Var\"", k_m); if k_recv < 0 { return null }
     local method = null
-    { local km = s.indexOf("\"method\":\"", k_m); if km < 0 { return null } method = JsonFragBox.read_string_after(s, km) }
+    { local km = JsonFragBox.index_of_from(s, "\"method\":\"", k_m); if km < 0 { return null } method = JsonFragBox.read_string_after(s, km) }
     // Standardize: generate 'size' (len/length are accepted aliases at receiver)
     method = MethodAliasPolicy.normalize_size(method)
     // Allow basic methods
@@ -23,91 +23,56 @@ static box LowerReturnMethodArrayMapBox {
     local b0 = new ArrayBox()
     // Receiver placeholder (Var resolve未実装のため 0 を置く)
     b0.push(MirSchemaBox.inst_const(1, 0))
-    local k_args = s.indexOf("\"args\":", k_m)
+    local k_args = JsonFragBox.index_of_from(s, "\"args\":", k_m)
     local next_id = 2
     if k_args >= 0 {
       // first arg: Int or Var(Int)
-      local k_i1 = s.indexOf("\"type\":\"Int\"", k_args)
-      local k_v1 = s.indexOf("\"type\":\"Var\"", k_args)
+      local k_i1 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_args)
+      local k_v1 = JsonFragBox.index_of_from(s, "\"type\":\"Var\"", k_args)
       if k_i1 >= 0 && (k_v1 < 0 || k_i1 < k_v1) {
         // read numeric after value:
-        local k_val1 = s.indexOf("\"value\":", k_i1)
+        local k_val1 = JsonFragBox.index_of_from(s, "\"value\":", k_i1)
         if k_val1 >= 0 {
           local v1 = JsonFragBox.read_int_after(s, k_val1 + 8)
           if v1 != null { b0.push(MirSchemaBox.inst_const(next_id, v1)) args_ids.push(next_id) next_id = next_id + 1 }
         }
         // second arg after first
-        local k_i2 = s.indexOf("\"type\":\"Int\"", k_i1 + 1)
-        local k_v2a = s.indexOf("\"type\":\"Var\"", k_i1 + 1)
+        local k_i2 = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_i1 + 1)
+        local k_v2a = JsonFragBox.index_of_from(s, "\"type\":\"Var\"", k_i1 + 1)
         if k_i2 >= 0 {
-          local k_v2 = s.indexOf("\"value\":", k_i2)
+          local k_v2 = JsonFragBox.index_of_from(s, "\"value\":", k_i2)
           if k_v2 >= 0 { local v2 = JsonFragBox.read_int_after(s, k_v2 + 8); if v2 != null { b0.push(MirSchemaBox.inst_const(next_id, v2)) args_ids.push(next_id) next_id = next_id + 1 } }
         } else if k_v2a >= 0 {
           // second arg is Var: resolve Local Int value
-          local kn = s.indexOf("\"name\":\"", k_v2a)
+          local kn = JsonFragBox.index_of_from(s, "\"name\":\"", k_v2a)
           if kn >= 0 {
             local name2 = JsonFragBox.read_string_after(s, kn)
-            // scan backwards for Local name2 Int
-            local pos = 0; local last = -1
-            loop(true) {
-              local kL = s.indexOf("\"type\":\"Local\"", pos)
-              if kL < 0 || kL >= k_m { break }
-              local nm = null
-              {
-                local kn2 = s.indexOf("\"name\":\"", kL)
-                if kn2 >= 0 {
-                  local iii = kn2 + 8; local nnn = s.length(); local jjj = iii
-                  loop(jjj < nnn) { if s.substring(jjj,jjj+1) == '"' { break } jjj = jjj + 1 }
-                  nm = s.substring(iii, jjj)
-                }
-              }
-              if nm != null && nm == name2 { last = kL }
-              pos = kL + 1
-            }
-            if last >= 0 {
-              local ki = s.indexOf("\"type\":\"Int\"", last)
-              if ki >= 0 && ki < k_m {
-                local kv = s.indexOf("\"value\":", ki)
-                if kv >= 0 { local v = JsonFragBox.read_int_after(s, kv + 8); if v != null { b0.push(MirSchemaBox.inst_const(next_id, v)) args_ids.push(next_id) next_id = next_id + 1 } }
-              }
-            }
+            local v = PatternUtilBox.find_local_int_before(s, name2, k_m)
+            if v != null { b0.push(MirSchemaBox.inst_const(next_id, v)) args_ids.push(next_id) next_id = next_id + 1 }
           }
         }
       } else if k_v1 >= 0 && (k_i1 < 0 || k_v1 < k_i1) {
         // first arg is Var: resolve Local value (Int/Bool/Float/String)
-        local kn = s.indexOf("\"name\":\"", k_v1)
+        local kn = JsonFragBox.index_of_from(s, "\"name\":\"", k_v1)
         if kn >= 0 {
           local namev = JsonFragBox.read_string_after(s, kn)
-          // find last Local namev Int before method
-          local pos2 = 0; local last2 = -1
-          loop(true) {
-            local kL2 = s.indexOf("\"type\":\"Local\"", pos2)
-            if kL2 < 0 || kL2 >= k_m { break }
-            local nm2 = null
-            {
-              local knm = s.indexOf("\"name\":\"", kL2)
-              if knm >= 0 {
-                local iii2 = knm + 8; local nnn2 = s.length(); local jjj2 = iii2
-                loop(jjj2 < nnn2) { if s.substring(jjj2,jjj2+1) == '"' { break } jjj2 = jjj2 + 1 }
-                nm2 = s.substring(iii2, jjj2)
-              }
-            }
-            if nm2 != null && nm2 == namev { last2 = kL2 }
-            pos2 = kL2 + 1
+          // Prefer exact-name Local lookups via PatternUtilBox
+          // Int / Bool / Float / String (in this order)
+          {
+            local vi = PatternUtilBox.find_local_int_before(s, namev, k_m)
+            if vi != null { b0.push(MirSchemaBox.inst_const(next_id, vi)) args_ids.push(next_id) next_id = next_id + 1 }
           }
-          if last2 >= 0 {
-            // Int
-            local ki3 = s.indexOf("\"type\":\"Int\"", last2)
-            if ki3 >= 0 && ki3 < k_m { local kv3 = s.indexOf("\"value\":", ki3); if kv3 >= 0 { local v = JsonFragBox.read_int_after(s, kv3 + 8); if v != null { b0.push(MirSchemaBox.inst_const(next_id, v)) args_ids.push(next_id) next_id = next_id + 1 } } }
-            // Bool
-            local kb3 = s.indexOf("\"type\":\"Bool\"", last2)
-            if kb3 >= 0 && kb3 < k_m { local kvb = s.indexOf("\"value\":", kb3); if kvb >= 0 { local vb = JsonFragBox.read_bool_after(s, kvb + 8); if vb != null { b0.push(MirSchemaBox.inst_const(next_id, vb)) args_ids.push(next_id) next_id = next_id + 1 } } }
-            // Float
-            local kf3 = s.indexOf("\"type\":\"Float\"", last2)
-            if kf3 >= 0 && kf3 < k_m { local kvf = s.indexOf("\"value\":", kf3); if kvf >= 0 { local fv = JsonFragBox.read_float_after(s, kvf + 8); if fv != null { b0.push(MirSchemaBox.inst_const_f64(next_id, fv)) args_ids.push(next_id) next_id = next_id + 1 } } }
-            // String
-            local ks3 = s.indexOf("\"type\":\"String\"", last2)
-            if ks3 >= 0 && ks3 < k_m { local kvs = s.indexOf("\"value\":\"", ks3); if kvs >= 0 { local sv = JsonFragBox.read_string_after(s, kvs + 8); if sv != null { b0.push(MirSchemaBox.inst_const_str(next_id, sv)) args_ids.push(next_id) next_id = next_id + 1 } } }
+          {
+            local vb = PatternUtilBox.find_local_bool_before(s, namev, k_m)
+            if vb != null { b0.push(MirSchemaBox.inst_const(next_id, vb)) args_ids.push(next_id) next_id = next_id + 1 }
+          }
+          {
+            local vf = PatternUtilBox.find_local_float_before(s, namev, k_m)
+            if vf != null { b0.push(MirSchemaBox.inst_const_f64(next_id, vf)) args_ids.push(next_id) next_id = next_id + 1 }
+          }
+          {
+            local vs = PatternUtilBox.find_local_string_before(s, namev, k_m)
+            if vs != null { b0.push(MirSchemaBox.inst_const_str(next_id, vs)) args_ids.push(next_id) next_id = next_id + 1 }
           }
         }
       }
diff --git a/lang/src/mir/builder/internal/lower_return_string_box.hako b/lang/src/mir/builder/internal/lower_return_string_box.hako
index 3d392579..08562e51 100644
--- a/lang/src/mir/builder/internal/lower_return_string_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_string_box.hako
@@ -6,11 +6,11 @@ using selfhost.shared.json.utils.json_frag as JsonFragBox
 static box LowerReturnStringBox {
   try_lower(program_json) {
     local s = "" + program_json
-    local k_ret = s.indexOf("\"type\":\"Return\"")
+    local k_ret = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", 0)
     if k_ret < 0 { return null }
-    local k_str = s.indexOf("\"type\":\"String\"", k_ret)
+    local k_str = JsonFragBox.index_of_from(s, "\"type\":\"String\"", k_ret)
     if k_str < 0 { return null }
-    local k_val = s.indexOf("\"value\":", k_str)
+    local k_val = JsonFragBox.index_of_from(s, "\"value\":", k_str)
     if k_val < 0 { return null }
     local sval = JsonFragBox.read_string_after(s, k_val+8)
     if sval == null { return null }
diff --git a/lang/src/mir/builder/internal/lower_return_var_local_box.hako b/lang/src/mir/builder/internal/lower_return_var_local_box.hako
index 93ea4741..fb8051d1 100644
--- a/lang/src/mir/builder/internal/lower_return_var_local_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_var_local_box.hako
@@ -7,25 +7,25 @@ static box LowerReturnVarLocalBox {
   try_lower(program_json) {
     local s = "" + program_json
     // Find Local with name:"x" and expr Int value
-    local k_loc = s.indexOf("\"type\":\"Local\"")
+    local k_loc = JsonFragBox.index_of_from(s, "\"type\":\"Local\"", 0)
     if k_loc < 0 { return null }
     // Extract name
-    local k_name = s.indexOf("\"name\":", k_loc); if k_name < 0 { return null }
+    local k_name = JsonFragBox.index_of_from(s, "\"name\":", k_loc); if k_name < 0 { return null }
     local name = JsonFragBox.read_string_after(s, k_name + 5)
     if name == null || name == "" { return null }
     // Ensure expr Int after this Local
-    local k_int = s.indexOf("\"type\":\"Int\"", k_loc)
+    local k_int = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", k_loc)
     if k_int < 0 { return null }
-    local kv = s.indexOf("\"value\":", k_int); if kv < 0 { return null }
+    local kv = JsonFragBox.index_of_from(s, "\"value\":", k_int); if kv < 0 { return null }
     local val = JsonFragBox.read_int_after(s, kv + 8)
     if val == null { return null }
     // Following Return Var(name)
-    local k_ret = s.indexOf("\"type\":\"Return\"", k_loc)
+    local k_ret = JsonFragBox.index_of_from(s, "\"type\":\"Return\"", k_loc)
     if k_ret < 0 { return null }
     // Verify Var(name)
-    local k_var = s.indexOf("\"type\":\"Var\"", k_ret)
+    local k_var = JsonFragBox.index_of_from(s, "\"type\":\"Var\"", k_ret)
     if k_var < 0 { return null }
-    local k_vn = s.indexOf("\"name\":", k_var); if k_vn < 0 { return null }
+    local k_vn = JsonFragBox.index_of_from(s, "\"name\":", k_var); if k_vn < 0 { return null }
     local vname = JsonFragBox.read_string_after(s, k_vn + 5)
     if vname == null || vname != name { return null }
 
diff --git a/lang/src/mir/builder/internal/pattern_util_box.hako b/lang/src/mir/builder/internal/pattern_util_box.hako
index b1dfa571..83bacdf2 100644
--- a/lang/src/mir/builder/internal/pattern_util_box.hako
+++ b/lang/src/mir/builder/internal/pattern_util_box.hako
@@ -5,6 +5,7 @@ using selfhost.shared.common.string_helpers as StringHelpers
 
 static box PatternUtilBox {
   map_cmp(sym) { if sym=="<" {return "Lt"} if sym==">" {return "Gt"} if sym=="<=" {return "Le"} if sym==">=" {return "Ge"} if sym=="==" {return "Eq"} if sym=="!=" {return "Ne"} return null }
+  map_binop(sym) { if sym=="+" {return "Add"} if sym=="-" {return "Sub"} if sym=="*" {return "Mul"} if sym=="/" {return "Div"} return null }
   // Normalize (op, swapped, limit) → (cmp, limit') where cmp in {Lt, Le, Gt, Ge}
   // swapped=0: i ? L, swapped=1: L ? i
   normalize_cmp_limit(op, swapped, limit_str) {
@@ -50,9 +51,9 @@ static box PatternUtilBox {
     // Bound the search between this Local and the next Local/before_pos
     local next = JsonFragBox.index_of_from(s, "\"type\":\"Local\"", last + 1)
     if next < 0 || next > before_pos { next = before_pos }
-    local ki = s.indexOf("\"type\":\"Int\"", last)
+    local ki = JsonFragBox.index_of_from(s, "\"type\":\"Int\"", last)
     if ki < 0 || ki >= next { return null }
-    local kv = s.indexOf("\"value\":", ki)
+    local kv = JsonFragBox.index_of_from(s, "\"value\":", ki)
     if kv < 0 || kv >= next { return null }
     return JsonFragBox.read_int_after(s, kv+8)
   }
@@ -62,14 +63,64 @@ static box PatternUtilBox {
     if last<0 { return null }
     local next = JsonFragBox.index_of_from(s, "\"type\":\"Local\"", last + 1)
     if next < 0 || next > before_pos { next = before_pos }
-    local kb = s.indexOf("\"type\":\"Bool\"", last)
+    local kb = JsonFragBox.index_of_from(s, "\"type\":\"Bool\"", last)
     if kb < 0 || kb >= next { return null }
-    local kv = s.indexOf("\"value\":", kb)
+    local kv = JsonFragBox.index_of_from(s, "\"value\":", kb)
     if kv < 0 || kv >= next { return null }
     // JSON v0 uses 0/1 for bool values, not true/false literals
     return JsonFragBox.read_int_after(s, kv+8)
   }
 
+  // Find the last Local(String) with given name before a given position.
+  // Returns raw string or null when not found.
+  find_local_string_before(s, name, before_pos) {
+    local pos=0; local last=-1
+    loop(true){
+      local k=JsonFragBox.index_of_from(s, "\"type\":\"Local\"",pos)
+      if k<0||k>=before_pos{break}
+      local kn=JsonFragBox.index_of_from(s, "\"name\":\"",k)
+      if kn>=0{
+        local ii=kn+8; local nn=(""+s).length(); local jj=ii
+        loop(jj<nn){ if (""+s).substring(jj,jj+1)=="\"" {break} jj=jj+1 }
+        if (""+s).substring(ii,jj)==name { last=k }
+      }
+      pos=k+1
+    }
+    if last<0 { return null }
+    local next=JsonFragBox.index_of_from(s, "\"type\":\"Local\"", last+1)
+    if next<0||next>before_pos{ next=before_pos }
+    local ts=(""+s).indexOf("\"type\":\"String\"", last)
+    if ts<0||ts>=next { return null }
+    local kv=(""+s).indexOf("\"value\":\"", ts)
+    if kv<0||kv>=next { return null }
+    return JsonFragBox.read_string_after(s, kv+8)
+  }
+
+  // Find the last Local(Float) with given name before a given position.
+  // Returns float string (as scanned) or null when not found.
+  find_local_float_before(s, name, before_pos) {
+    local pos=0; local last=-1
+    loop(true){
+      local k=JsonFragBox.index_of_from(s, "\"type\":\"Local\"",pos)
+      if k<0||k>=before_pos{break}
+      local kn=JsonFragBox.index_of_from(s, "\"name\":\"",k)
+      if kn>=0{
+        local ii=kn+8; local nn=(""+s).length(); local jj=ii
+        loop(jj<nn){ if (""+s).substring(jj,jj+1)=="\"" {break} jj=jj+1 }
+        if (""+s).substring(ii,jj)==name { last=k }
+      }
+      pos=k+1
+    }
+    if last<0 { return null }
+    local next=JsonFragBox.index_of_from(s, "\"type\":\"Local\"", last+1)
+    if next<0||next>before_pos{ next=before_pos }
+    local tf=(""+s).indexOf("\"type\":\"Float\"", last)
+    if tf<0||tf>=next { return null }
+    local kv=(""+s).indexOf("\"value\":", tf)
+    if kv<0||kv>=next { return null }
+    return JsonFragBox.read_float_after(s, kv+8)
+  }
+
   // Find the last Local(Int) before a given position (name-agnostic).
   // Returns string digits or null when not found.
   find_any_local_int_before(s, before_pos) {
diff --git a/src/config/env.rs b/src/config/env.rs
index bded5b11..99eedff1 100644
--- a/src/config/env.rs
+++ b/src/config/env.rs
@@ -33,9 +33,12 @@ impl NyashEnv {
 
 // Global current env config (thread-safe)
 use once_cell::sync::OnceCell;
+use std::collections::HashSet;
+use std::sync::Mutex;
 use std::sync::RwLock;
 
 static GLOBAL_ENV: OnceCell<RwLock<NyashEnv>> = OnceCell::new();
+static WARNED_ALIASES: OnceCell<Mutex<HashSet<String>>> = OnceCell::new();
 // フェーズM.2: PHI_ON_GATED_WARNED削除（phi-legacy簡略化により不要）
 
 pub fn current() -> NyashEnv {
@@ -376,11 +379,19 @@ pub fn cli_verbose() -> bool {
 }
 pub fn enable_using() -> bool {
     // Phase 15: デフォルトON（using systemはメイン機能）
-    // NYASH_ENABLE_USING=0 で明示的に無効化可能
+    // NYASH_ENABLE_USING=0 で明示的に無効化可能。HAKO_ENABLE_USING は互換のため受理（警告）。
     match std::env::var("NYASH_ENABLE_USING").ok().as_deref() {
-        Some("0") | Some("false") | Some("off") => false,
-        _ => true, // デフォルト: ON
+        Some("0") | Some("false") | Some("off") => return false,
+        Some(_) => return true,
+        None => {}
     }
+    // Fallback to alias
+    if let Some(v) = std::env::var("HAKO_ENABLE_USING").ok() {
+        warn_alias_once("HAKO_ENABLE_USING", "NYASH_ENABLE_USING");
+        let lv = v.to_ascii_lowercase();
+        return !(lv == "0" || lv == "false" || lv == "off");
+    }
+    true // default ON
 }
 
 // ---- Using profiles (dev|ci|prod) ----
@@ -466,7 +477,14 @@ pub fn ny_compiler_stage3() -> bool {
 /// When enabled, the Rust parser accepts Stage-3 surface (try/catch/finally, throw).
 /// Default is OFF to keep Stage-2 stable.
 pub fn parser_stage3() -> bool {
-    std::env::var("NYASH_PARSER_STAGE3").ok().as_deref() == Some("1")
+    if std::env::var("NYASH_PARSER_STAGE3").ok().as_deref() == Some("1") {
+        return true;
+    }
+    if std::env::var("HAKO_PARSER_STAGE3").ok().as_deref() == Some("1") {
+        warn_alias_once("HAKO_PARSER_STAGE3", "NYASH_PARSER_STAGE3");
+        return true;
+    }
+    false
 }
 
 /// Parser gate for Block‑Postfix Catch acceptance
@@ -578,3 +596,72 @@ pub fn oob_strict_fail() -> bool {
         .or_else(|| env_flag("NYASH_OOB_STRICT_FAIL"))
         .unwrap_or(false)
 }
+
+/// Primary verification route: return true when Hakorune VM is requested as primary.
+/// Accepts HAKO_VERIFY_PRIMARY=hakovm (preferred) or legacy HAKO_ROUTE_HAKOVM=1 (deprecated, warns).
+pub fn verify_primary_is_hakovm() -> bool {
+    if std::env::var("HAKO_VERIFY_PRIMARY").ok().as_deref() == Some("hakovm") {
+        return true;
+    }
+    if env_bool("HAKO_ROUTE_HAKOVM") {
+        warn_alias_once("HAKO_ROUTE_HAKOVM", "HAKO_VERIFY_PRIMARY=hakovm");
+        return true;
+    }
+    false
+}
+
+fn warn_alias_once(alias: &str, primary: &str) {
+    let set = WARNED_ALIASES.get_or_init(|| Mutex::new(HashSet::new()));
+    if let Ok(mut s) = set.lock() {
+        if !s.contains(alias) {
+            eprintln!("[deprecate/env] '{}' is deprecated; use '{}'", alias, primary);
+            s.insert(alias.to_string());
+        }
+    }
+}
+
+// ---- ENV consolidation helpers (Phase 21.10/22.1) ----
+/// LLVM opt level (primary: NYASH_LLVM_OPT_LEVEL; alias: HAKO_LLVM_OPT_LEVEL)
+/// Returns string level (e.g., "0", "1", ...). Default: "0" when unset.
+pub fn llvm_opt_level() -> String {
+    if let Some(v) = std::env::var("NYASH_LLVM_OPT_LEVEL").ok() {
+        return v;
+    }
+    if let Some(v) = std::env::var("HAKO_LLVM_OPT_LEVEL").ok() {
+        warn_alias_once("HAKO_LLVM_OPT_LEVEL", "NYASH_LLVM_OPT_LEVEL");
+        return v;
+    }
+    "0".to_string()
+}
+
+/// Gate‑C(Core) route request (primary: NYASH_GATE_C_CORE; alias: HAKO_GATE_C_CORE)
+pub fn gate_c_core() -> bool {
+    if env_bool("NYASH_GATE_C_CORE") { return true; }
+    if env_bool("HAKO_GATE_C_CORE") {
+        warn_alias_once("HAKO_GATE_C_CORE", "NYASH_GATE_C_CORE");
+        return true;
+    }
+    false
+}
+
+/// Consolidated toggle for selfhost NY compiler pipeline.
+/// Primary: NYASH_USE_NY_COMPILER=0|1. Legacy disables accepted (with warning):
+/// NYASH_DISABLE_NY_COMPILER/HAKO_DISABLE_NY_COMPILER (any true value disables).
+pub fn use_ny_compiler() -> bool {
+    // Primary knob takes precedence when explicitly set
+    if let Some(v) = std::env::var("NYASH_USE_NY_COMPILER").ok() {
+        let lv = v.trim().to_ascii_lowercase();
+        return lv == "1" || lv == "true" || lv == "on";
+    }
+    // Legacy disable aliases — if any is true, treat as disabled and warn
+    if env_bool("NYASH_DISABLE_NY_COMPILER") {
+        warn_alias_once("NYASH_DISABLE_NY_COMPILER", "NYASH_USE_NY_COMPILER=0");
+        return false;
+    }
+    if env_bool("HAKO_DISABLE_NY_COMPILER") {
+        warn_alias_once("HAKO_DISABLE_NY_COMPILER", "NYASH_USE_NY_COMPILER=0");
+        return false;
+    }
+    // Default: ON (MVP selfhost path)
+    true
+}
diff --git a/src/llvm_py/builders/function_lower.py b/src/llvm_py/builders/function_lower.py
index c759f10a..03000486 100644
--- a/src/llvm_py/builders/function_lower.py
+++ b/src/llvm_py/builders/function_lower.py
@@ -24,8 +24,8 @@ def lower_function(builder, func_data: Dict[str, Any]):
 
     # Determine function signature
     if name == "ny_main":
-        # Special case: ny_main returns i32
-        func_ty = ir.FunctionType(builder.i32, [])
+        # Special case: ny_main returns i64 to match runtime (nyrt) expectations
+        func_ty = ir.FunctionType(builder.i64, [])
     else:
         # Default: i64(i64, ...) signature; derive arity from '/N' suffix when params missing
         m = re.search(r"/(\d+)$", name)
diff --git a/src/llvm_py/instructions/binop.py b/src/llvm_py/instructions/binop.py
index fdc09b05..cdc0c5f2 100644
--- a/src/llvm_py/instructions/binop.py
+++ b/src/llvm_py/instructions/binop.py
@@ -45,7 +45,23 @@ def lower_binop(
         lhs_val = ir.Constant(ir.IntType(64), 0)
     if rhs_val is None:
         rhs_val = ir.Constant(ir.IntType(64), 0)
-    
+    # Normalize operation aliases (textual -> symbolic)
+    op_raw = op or ''
+    op_l = op_raw.lower()
+    alias = {
+        'add': '+', 'plus': '+',
+        'sub': '-', 'minus': '-',
+        'mul': '*', 'times': '*',
+        'div': '/',
+        'mod': '%', 'rem': '%',
+        'band': '&', 'bitand': '&',
+        'bor': '|', 'bitor': '|',
+        'bxor': '^', 'xor': '^',
+        'shl': '<<',
+        'shr': '>>', 'ashr': '>>',
+    }
+    op = alias.get(op_l, op_raw)
+
     # Relational/equality operators delegate to compare
     if op in ('==','!=','<','>','<=','>='):
         # Delegate to compare with resolver/preds context to maintain dominance via localization
diff --git a/src/llvm_py/instructions/ret.py b/src/llvm_py/instructions/ret.py
index 93f49d3d..52b38ba9 100644
--- a/src/llvm_py/instructions/ret.py
+++ b/src/llvm_py/instructions/ret.py
@@ -97,9 +97,16 @@ def lower_return(
                 # Pointer type - null
                 ret_val = ir.Constant(return_type, None)
 
-        # If still zero-like and we have predecessor snapshots, synthesize a minimal PHI at block head.
+        # If still zero-like (typed zero) and we have predecessor snapshots, synthesize a minimal PHI at block head.
         try:
-            zero_like = isinstance(ret_val, ir.Constant)
+            zero_like = False
+            if isinstance(ret_val, ir.Constant):
+                if isinstance(return_type, ir.IntType):
+                    zero_like = (str(ret_val) == str(ir.Constant(return_type, 0)))
+                elif isinstance(return_type, ir.DoubleType):
+                    zero_like = (str(ret_val) == str(ir.Constant(return_type, 0.0)))
+                elif isinstance(return_type, ir.PointerType):
+                    zero_like = (str(ret_val) == str(ir.Constant(return_type, None)))
             if zero_like and preds is not None and block_end_values is not None and bb_map is not None and isinstance(value_id, int):
                 # Derive current block id from name like 'bb3'
                 cur_bid = None
diff --git a/src/llvm_py/llvm_builder.py b/src/llvm_py/llvm_builder.py
index abe2302e..a8b6959a 100644
--- a/src/llvm_py/llvm_builder.py
+++ b/src/llvm_py/llvm_builder.py
@@ -152,7 +152,8 @@ class NyashLLVMBuilder:
             else:
                 arity = int(m.group(1)) if m else len(params_list)
             if name == "ny_main":
-                fty = ir.FunctionType(self.i32, [])
+                # Align with runtime expectation: ny_main returns i64
+                fty = ir.FunctionType(self.i64, [])
             else:
                 fty = ir.FunctionType(self.i64, [self.i64] * arity)
             exists = False
diff --git a/src/main.rs b/src/main.rs
index 4fb9fe75..f4006b0e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -13,8 +13,7 @@ fn main() {
     // If NYASH_VERIFY_JSON is present and route is requested, execute and exit.
     // This avoids plugin host/registry initialization and keeps output minimal.
     let has_json = std::env::var("NYASH_VERIFY_JSON").is_ok();
-    let route = nyash_rust::config::env::env_bool("HAKO_ROUTE_HAKOVM")
-        || std::env::var("HAKO_VERIFY_PRIMARY").ok().as_deref() == Some("hakovm");
+    let route = nyash_rust::config::env::verify_primary_is_hakovm();
     // Force flag may allow hv1-inline without route
     let force_hv1_flag = nyash_rust::config::env::env_bool("HAKO_VERIFY_V1_FORCE_HAKOVM");
     if has_json && (route || force_hv1_flag) {
diff --git a/src/runner/dispatch.rs b/src/runner/dispatch.rs
index 3b6e94ff..5992d0e0 100644
--- a/src/runner/dispatch.rs
+++ b/src/runner/dispatch.rs
@@ -12,30 +12,9 @@ pub(crate) fn execute_file_with_backend(runner: &NyashRunner, filename: &str) {
     // Note: hv1 direct route is now handled at main.rs entry point (before NyashRunner creation).
     // This function is only called after plugins and runner initialization have already occurred.
 
-    // Selfhost pipeline (Ny -> JSON v0)
-    // Default: ON. Backward‑compat envs:
-    //  - NYASH_USE_NY_COMPILER={1|true|on} to force ON
-    //  - NYASH_USE_NY_COMPILER={0|false|off} or NYASH_DISABLE_NY_COMPILER/HAKO_DISABLE_NY_COMPILER to disable
-    let mut use_selfhost = true;
-    if let Ok(v) = std::env::var("NYASH_USE_NY_COMPILER") {
-        let lv = v.trim().to_ascii_lowercase();
-        use_selfhost = matches!(lv.as_str(), "1" | "true" | "on");
-    }
-    let disabled = std::env::var("NYASH_DISABLE_NY_COMPILER")
-        .ok()
-        .map(|v| {
-            let lv = v.trim().to_ascii_lowercase();
-            matches!(lv.as_str(), "1" | "true" | "on")
-        })
-        .unwrap_or(false)
-        || std::env::var("HAKO_DISABLE_NY_COMPILER")
-            .ok()
-            .map(|v| {
-                let lv = v.trim().to_ascii_lowercase();
-                matches!(lv.as_str(), "1" | "true" | "on")
-            })
-            .unwrap_or(false);
-    if use_selfhost && !disabled {
+    // Selfhost pipeline (Ny -> JSON v0) — consolidated env toggle
+    // Primary: NYASH_USE_NY_COMPILER=0|1; legacy disables accepted with deprecation warning
+    if crate::config::env::use_ny_compiler() {
         if runner.try_run_selfhost_pipeline(filename) {
             return;
         } else {
diff --git a/tools/native_llvm_builder.py b/tools/native_llvm_builder.py
new file mode 100644
index 00000000..63daec7f
--- /dev/null
+++ b/tools/native_llvm_builder.py
@@ -0,0 +1,241 @@
+#!/usr/bin/env python3
+"""
+Native LLVM Builder (bootstrap)
+
+Goal: minimal Python-only emitter that generates LLVM IR text from a tiny
+subset of Nyash MIR JSON and compiles it to an object via `llc`.
+
+Supported (MVP):
+- schema_version v1 or tolerant shapes
+- Single function: ny_main(): i64
+- Instructions: const(i64), binop(add/sub/mul/div/mod/&/|/^/<< >>), compare(==)
+- ret(value)
+
+Usage:
+  python3 tools/native_llvm_builder.py --in in.json --emit obj --out out.o
+
+Notes:
+- No external Python packages required. Assumes `llc` is in PATH.
+"""
+
+import argparse
+import json
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+
+def _normalize_canary(v: dict) -> dict:
+    # Coerce schema_version
+    sv = v.get("schema_version")
+    if isinstance(sv, int) and sv == 1:
+        v["schema_version"] = "1.0"
+    if isinstance(sv, str) and sv == "1":
+        v["schema_version"] = "1.0"
+    # Normalize blocks.inst -> instructions
+    funs = v.get("functions")
+    if isinstance(funs, list):
+        for f in funs:
+            blks = f.get("blocks")
+            if isinstance(blks, list):
+                for b in blks:
+                    if "inst" in b and "instructions" not in b:
+                        b["instructions"] = b.pop("inst")
+                    ins = b.get("instructions")
+                    if isinstance(ins, list):
+                        for insn in ins:
+                            if insn.get("op") == "const":
+                                if "value" in insn and isinstance(insn["value"], dict) and "type" in insn["value"]:
+                                    pass
+                                else:
+                                    ty = insn.pop("ty", "i64")
+                                    val = insn.pop("value", 0)
+                                    insn["value"] = {"type": ty, "value": val}
+    return v
+
+
+def build_ir(ny_json: dict) -> str:
+    ny = _normalize_canary(ny_json)
+    funs = ny.get("functions", [])
+    fn = None
+    for f in funs:
+        if f.get("name") == "ny_main":
+            fn = f
+            break
+    if fn is None:
+        raise ValueError("ny_main not found")
+    blocks = fn.get("blocks", [])
+    if not blocks:
+        # trivial
+        return (
+            "; ModuleID = \"nyash_native\"\n"
+            "define i64 @ny_main(){\n  ret i64 0\n}\n"
+        )
+
+    # IR pieces
+    lines = []
+    # Keep IR minimal; let llc choose target triple/datalayout
+    lines.append("; ModuleID = \"nyash_native\"")
+    lines.append("")
+    lines.append("define i64 @ny_main(){")
+
+    # Simple vmap; const map holds immediate ints; ssa map holds emitted names
+    const_map = {}
+    ssa_map = {}
+    is_i1 = set()
+
+    def val_of(vid):
+        if vid in ssa_map:
+            return f"%{ssa_map[vid]}", (vid in is_i1)
+        if vid in const_map:
+            return f"i64 {const_map[vid]}", False
+        # default zero
+        return "i64 0", False
+
+    tmp_idx = 0
+    def fresh(name):
+        nonlocal tmp_idx
+        tmp_idx += 1
+        return f"{name}_{tmp_idx}"
+
+    # Emit each block with an explicit label: bb<id>:
+    for b in blocks:
+        bid = b.get("id")
+        lines.append(f"bb{bid}:")
+        ins = b.get("instructions", [])
+        for insn in ins:
+            op = insn.get("op")
+            if op == "const":
+                dst = insn.get("dst")
+                v = insn.get("value", {})
+                ty = v.get("type", insn.get("ty", "i64"))
+                val = v.get("value", 0)
+                if ty != "i64":
+                    val = 0
+                const_map[dst] = int(val)
+            elif op == "binop":
+                dst = insn.get("dst")
+                opx = (insn.get("operation") or '').lower()
+                aliases = {
+                    'add': '+', 'plus': '+', 'sub': '-', 'minus': '-', 'mul': '*', 'times': '*',
+                    'div': '/', 'mod': '%', 'rem': '%', 'band': '&', 'bitand': '&', 'bor': '|', 'bitor': '|',
+                    'bxor': '^', 'xor': '^', 'shl': '<<', 'shr': '>>', 'ashr': '>>'
+                }
+                sym = aliases.get(opx, opx)
+                lhs = insn.get("lhs"); rhs = insn.get("rhs")
+                lv, _ = val_of(lhs); rv, _ = val_of(rhs)
+                name = fresh("bin")
+                if sym == '+':
+                    lines.append(f"  %{name} = add i64 {lv.split()[-1]}, {rv.split()[-1]}")
+                elif sym == '-':
+                    lines.append(f"  %{name} = sub i64 {lv.split()[-1]}, {rv.split()[-1]}")
+                elif sym == '*':
+                    lines.append(f"  %{name} = mul i64 {lv.split()[-1]}, {rv.split()[-1]}")
+                elif sym == '/':
+                    lines.append(f"  %{name} = sdiv i64 {lv.split()[-1]}, {rv.split()[-1]}")
+                elif sym == '%':
+                    lines.append(f"  %{name} = srem i64 {lv.split()[-1]}, {rv.split()[-1]}")
+                elif sym == '&':
+                    lines.append(f"  %{name} = and i64 {lv.split()[-1]}, {rv.split()[-1]}")
+                elif sym == '|':
+                    lines.append(f"  %{name} = or i64 {lv.split()[-1]}, {rv.split()[-1]}")
+                elif sym == '^':
+                    lines.append(f"  %{name} = xor i64 {lv.split()[-1]}, {rv.split()[-1]}")
+                elif sym == '<<':
+                    lines.append(f"  %{name} = shl i64 {lv.split()[-1]}, {rv.split()[-1]}")
+                elif sym == '>>':
+                    lines.append(f"  %{name} = ashr i64 {lv.split()[-1]}, {rv.split()[-1]}")
+                else:
+                    lines.append(f"  %{name} = add i64 0, 0")
+                ssa_map[dst] = name
+            elif op == "compare":
+                dst = insn.get("dst")
+                opx = insn.get("operation") or insn.get("cmp") or '=='
+                lhs = insn.get("lhs"); rhs = insn.get("rhs")
+                lv, _ = val_of(lhs); rv, _ = val_of(rhs)
+                name = fresh("cmp")
+                # Support eq/lt minimal
+                if opx in ('==', 'Eq'): pred = 'eq'
+                elif opx in ('<', 'Lt'): pred = 'slt'
+                else: pred = 'ne'
+                lines.append(f"  %{name} = icmp {pred} i64 {lv.split()[-1]}, {rv.split()[-1]}")
+                ssa_map[dst] = name
+                is_i1.add(dst)
+            elif op == "branch":
+                # Conditional branch: {cond, then, else}
+                cond = insn.get("cond")
+                then_id = insn.get("then")
+                else_id = insn.get("else")
+                cv, ci1 = val_of(cond)
+                if ci1:
+                    cond_name = cv if cv.startswith('%') else f"%{cv}"
+                    lines.append(f"  br i1 {cond_name}, label %bb{then_id}, label %bb{else_id}")
+                else:
+                    # Build i1 from i64 via icmp ne 0
+                    name = fresh("cnd")
+                    lines.append(f"  %{name} = icmp ne i64 {cv.split()[-1]}, 0")
+                    lines.append(f"  br i1 %{name}, label %bb{then_id}, label %bb{else_id}")
+            elif op == "jump":
+                target = insn.get("target")
+                lines.append(f"  br label %bb{target}")
+            elif op == "ret":
+                vid = insn.get("value")
+                if vid in is_i1:
+                    vname = ssa_map.get(vid)
+                    z = fresh("zext")
+                    lines.append(f"  %{z} = zext i1 %{vname} to i64")
+                    lines.append(f"  ret i64 %{z}")
+                elif vid in ssa_map:
+                    lines.append(f"  ret i64 %{ssa_map[vid]}")
+                elif vid in const_map:
+                    lines.append(f"  ret i64 {const_map[vid]}")
+                else:
+                    lines.append("  ret i64 0")
+    lines.append("}")
+    return "\n".join(lines) + "\n"
+
+
+def compile_ir_to_obj(ir_text: str, out_obj: Path) -> None:
+    tmp = Path("/tmp/native_ir_{}.ll".format(os.getpid()))
+    tmp.write_text(ir_text)
+    try:
+        subprocess.check_call(["llc", "-filetype=obj", "-o", str(out_obj), str(tmp)], stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+    finally:
+        try:
+            tmp.unlink()
+        except Exception:
+            pass
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--in", dest="infile", required=True)
+    ap.add_argument("--emit", dest="emit", default="obj")
+    ap.add_argument("--out", dest="out", required=True)
+    args = ap.parse_args()
+
+    with open(args.infile, 'r') as f:
+        ny = json.load(f)
+
+    ir = build_ir(ny)
+    if os.environ.get('NYASH_LLVM_NATIVE_TRACE') in ('1','true','on','YES','yes','True'):
+        print(ir, file=sys.stderr)
+    if args.emit == 'll':
+        Path(args.out).write_text(ir)
+        print(f"[native] ll written: {args.out}")
+        return
+    if args.emit == 'obj':
+        compile_ir_to_obj(ir, Path(args.out))
+        print(f"[native] obj written: {args.out}")
+        return
+    print("error: unsupported emit kind", file=sys.stderr)
+    sys.exit(2)
+
+
+if __name__ == "__main__":
+    try:
+        main()
+    except Exception as e:
+        print(f"[native] error: {e}", file=sys.stderr)
+        sys.exit(1)
diff --git a/tools/ny_mir_builder.sh b/tools/ny_mir_builder.sh
index 36e97c7e..e0d25dc0 100644
--- a/tools/ny_mir_builder.sh
+++ b/tools/ny_mir_builder.sh
@@ -24,7 +24,17 @@ TARGET=""
 NYRT_DIR=""
 VERIFY=0
 QUIET=0
-BACKEND="${NYASH_LLVM_BACKEND:-llvmlite}"  # llvmlite | crate | native (reserved)
+# Backend selection (21.11): default to 'crate' when ny-llvmc is available, otherwise fallback to llvmlite.
+# Explicit env NYASH_LLVM_BACKEND overrides this auto-detection.
+if [[ -n "${NYASH_LLVM_BACKEND:-}" ]]; then
+  BACKEND="${NYASH_LLVM_BACKEND}"
+else
+  if [[ -x "./target/release/ny-llvmc" ]]; then
+    BACKEND="crate"
+  else
+    BACKEND="llvmlite"
+  fi
+fi
 
 while [[ $# -gt 0 ]]; do
   case "$1" in
@@ -51,9 +61,12 @@ if [[ -z "$OUT" ]]; then
   esac
 fi
 
-if ! command -v llvm-config-18 >/dev/null 2>&1; then
-  echo "error: llvm-config-18 not found (install LLVM 18 dev)" >&2
-  exit 3
+# Require LLVM18 only for llvmlite backend
+if [[ "${NYASH_LLVM_BACKEND:-$BACKEND}" == "llvmlite" ]]; then
+  if ! command -v llvm-config-18 >/dev/null 2>&1; then
+    echo "error: llvm-config-18 not found (install LLVM 18 dev)" >&2
+    exit 3
+  fi
 fi
 
 # Build nyash + NyRT as needed（skip allowed）
@@ -126,6 +139,15 @@ case "$EMIT" in
         rm -f "$OUT"
         "$BIN_NYLLVMC" --in "$IN_FILE" --emit obj --out "$OUT" >/dev/null 2>&1 || { echo "error: ny-llvmc failed" >&2; exit 4; }
         ;;
+      native)
+        if ! command -v llc >/dev/null 2>&1; then
+          echo "error: llc not found (install LLVM tools)" >&2; exit 4
+        fi
+        rm -f "$OUT"
+        if ! python3 "$PWD/tools/native_llvm_builder.py" --in "$IN_FILE" --emit obj --out "$OUT" >/dev/null 2>&1; then
+          echo "error: native builder failed" >&2; exit 4
+        fi
+        ;;
       llvmlite|*)
         # Directly use llvmlite harness with MIR v1 JSON input
         rm -f "$OUT"
@@ -153,6 +175,22 @@ case "$EMIT" in
           echo "error: ny-llvmc failed to link exe" >&2; exit 4
         fi
         ;;
+      native)
+        if ! command -v llc >/dev/null 2>&1; then
+          echo "error: llc not found (install LLVM tools)" >&2; exit 4
+        fi
+        if ! python3 "$PWD/tools/native_llvm_builder.py" --in "$IN_FILE" --emit obj --out "$OBJ" >/dev/null 2>&1; then
+          echo "error: native builder failed to produce object $OBJ" >&2; exit 4
+        fi
+        if [[ ! -f "$OBJ" ]]; then echo "error: failed to produce object $OBJ" >&2; exit 4; fi
+        # Link with NyRT (same as llvmlite branch)
+        NYRT_BASE=${NYRT_DIR:-"$PWD/crates/nyash_kernel"}
+        cc "$OBJ" \
+          -L target/release \
+          -L "$NYRT_BASE/target/release" \
+          -Wl,--whole-archive -lnyash_kernel -Wl,--no-whole-archive \
+          -lpthread -ldl -lm -o "$OUT"
+        ;;
       llvmlite|*)
         if ! python3 "$PWD/tools/llvmlite_harness.py" --in "$IN_FILE" --out "$OBJ" >/dev/null 2>&1; then
           echo "error: harness failed to produce object $OBJ" >&2; exit 4
diff --git a/tools/smokes/v2/profiles/quick/core/phase2034/mirbuilder_internal_if_compare_varint_negative_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2034/mirbuilder_internal_if_compare_varint_negative_canary_vm.sh
new file mode 100644
index 00000000..d136dedb
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2034/mirbuilder_internal_if_compare_varint_negative_canary_vm.sh
@@ -0,0 +1,31 @@
+#!/bin/bash
+# If(Compare Var/Int) with negative numbers → compare+branch+ret (structure check)
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"; if ROOT_GIT=$(git -C "$SCRIPT_DIR" rev-parse --show-toplevel 2>/dev/null); then ROOT="$ROOT_GIT"; else ROOT="$(cd "$SCRIPT_DIR/../../../../../../../../.." && pwd)"; fi
+source "$ROOT/tools/smokes/v2/lib/test_runner.sh"; require_env || exit 2
+
+tmp_hako="/tmp/mirbuilder_if_varint_neg_$$.hako"
+cat > "$tmp_hako" <<'HAKO'
+include "lang/src/mir/builder/MirBuilderBox.hako"
+static box Main { method main(args) {
+  // Local a=-5; if (a < -3) return 1; else return 0;
+  local j = "{\"version\":0,\"kind\":\"Program\",\"body\":[" +
+    "{\"type\":\"Local\",\"name\":\"a\",\"expr\":{\"type\":\"Int\",\"value\":-5}}," +
+    "{\"type\":\"If\",\"cond\":{\"type\":\"Compare\",\"op\":\"<\",\"lhs\":{\"type\":\"Var\",\"name\":\"a\"},\"rhs\":{\"type\":\"Int\",\"value\":-3}},\"then\":[{\"type\":\"Return\",\"expr\":{\"type\":\"Int\",\"value\":1}}],\"else\":[{\"type\":\"Return\",\"expr\":{\"type\":\"Int\",\"value\":0}}]}]}";
+  local out = MirBuilderBox.emit_from_program_json_v0(j, null);
+  if out == null { return 0 }
+  local s = "" + out
+  if s.indexOf("\"op\":\"compare\"") >= 0 && s.indexOf("\"op\":\"branch\"") >= 0 { return 1 }
+  return 0
+} }
+HAKO
+
+set +e
+out="$(HAKO_MIR_BUILDER_INTERNAL=1 "$NYASH_BIN" --backend vm "$tmp_hako" 2>&1)"; rc=$?
+set -e
+rm -f "$tmp_hako" || true
+
+if [ "$rc" -eq 1 ]; then echo "[PASS] mirbuilder_internal_if_compare_varint_negative_canary_vm"; exit 0; fi
+echo "[FAIL] mirbuilder_internal_if_compare_varint_negative_canary_vm (rc=$rc)" >&2; exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2034/mirbuilder_internal_return_binop_varint_negative_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2034/mirbuilder_internal_return_binop_varint_negative_canary_vm.sh
new file mode 100644
index 00000000..5617060d
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2034/mirbuilder_internal_return_binop_varint_negative_canary_vm.sh
@@ -0,0 +1,29 @@
+#!/bin/bash
+# Return(Binary Var/Int) with negative constants → const+const+binop+ret (structure)
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"; if ROOT_GIT=$(git -C "$SCRIPT_DIR" rev-parse --show-toplevel 2>/dev/null); then ROOT="$ROOT_GIT"; else ROOT="$(cd "$SCRIPT_DIR/../../../../../../../../.." && pwd)"; fi
+source "$ROOT/tools/smokes/v2/lib/test_runner.sh"; require_env || exit 2
+
+tmp_hako="/tmp/mirbuilder_return_binop_varint_neg_$$.hako"
+cat > "$tmp_hako" <<'HAKO'
+include "lang/src/mir/builder/MirBuilderBox.hako"
+static box Main { method main(args) {
+  // Local x=-2; return x + -3;
+  local j = "{\"version\":0,\"kind\":\"Program\",\"body\":[{\"type\":\"Local\",\"name\":\"x\",\"expr\":{\"type\":\"Int\",\"value\":-2}},{\"type\":\"Return\",\"expr\":{\"type\":\"Binary\",\"op\":\"+\",\"lhs\":{\"type\":\"Var\",\"name\":\"x\"},\"rhs\":{\"type\":\"Int\",\"value\":-3}}}]}";
+  local out = MirBuilderBox.emit_from_program_json_v0(j, null);
+  if out == null { return 0 }
+  local s = "" + out
+  if s.indexOf("\"op\":\"binop\"") >= 0 && s.indexOf("\"op_kind\":\"Add\"") >= 0 { return 1 }
+  return 0
+} }
+HAKO
+
+set +e
+out="$(HAKO_MIR_BUILDER_INTERNAL=1 "$NYASH_BIN" --backend vm "$tmp_hako" 2>&1)"; rc=$?
+set -e
+rm -f "$tmp_hako" || true
+
+if [ "$rc" -eq 1 ]; then echo "[PASS] mirbuilder_internal_return_binop_varint_negative_canary_vm"; exit 0; fi
+echo "[FAIL] mirbuilder_internal_return_binop_varint_negative_canary_vm (rc=$rc)" >&2; exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/run_all.sh b/tools/smokes/v2/profiles/quick/core/phase2100/run_all.sh
index 175deb9d..2502c066 100644
--- a/tools/smokes/v2/profiles/quick/core/phase2100/run_all.sh
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/run_all.sh
@@ -64,4 +64,34 @@ if [[ "${SMOKES_ENABLE_SELFHOST:-0}" == "1" ]]; then
   fi
 fi
 
+# Crate backend (ny-llvmc) — run a tiny representative set always when available
+  echo "[phase2100] S3 (crate ny-llvmc) reps..."
+(
+  set -e
+  # Prebuild crate tools quickly (best-effort)
+  (cd "$ROOT/crates/nyash-llvm-compiler" && timeout 180 cargo build --release -j 24 >/dev/null 2>&1) || true
+  (cd "$ROOT/crates/nyash_kernel" && timeout 180 cargo build --release -j 24 >/dev/null 2>&1) || true
+  # Probe ny-llvmc availability by compiling a minimal ret0 ny_main
+  BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+  if [[ -x "$BIN_NYLLVMC" ]]; then
+    tmpj="/tmp/ny_crate_probe_$$.json"; echo '{"schema_version":1,"functions":[{"name":"ny_main","blocks":[{"id":0,"inst":[{"op":"const","dst":1,"ty":"i64","value":0},{"op":"ret","value":1}]}]}]}' > "$tmpj"
+    tmpo="/tmp/ny_crate_probe_$$.o"
+    if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$tmpj" --out "$tmpo" >/dev/null 2>&1; then
+      rm -f "$tmpo" "$tmpj" || true
+      # Run representative crate EXE canaries (fast)
+      bash "$ROOT/tools/smokes/v2/run.sh" --profile quick --filter 'phase2100/s3_backend_selector_crate_exe_return42_canary_vm.sh'
+      bash "$ROOT/tools/smokes/v2/run.sh" --profile quick --filter 'phase2100/s3_backend_selector_crate_exe_compare_eq_true_canary_vm.sh'
+      bash "$ROOT/tools/smokes/v2/run.sh" --profile quick --filter 'phase2100/s3_backend_selector_crate_exe_binop_return_canary_vm.sh'
+    else
+      rm -f "$tmpo" "$tmpj" || true
+      echo "[phase2100] SKIP crate reps (ny-llvmc probe failed)" >&2
+    fi
+  else
+    echo "[phase2100] SKIP crate reps (ny-llvmc not built)" >&2
+  fi
+) || echo "[phase2100] crate reps encountered a non-fatal issue; continuing"
+
+# SSOT relative inference — unique case (always-on, quick)
+bash "$ROOT/tools/smokes/v2/run.sh" --profile quick --filter 'phase2211/ssot_relative_unique_canary_vm.sh'
+
 echo "[phase2100] Done."
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_binop_return_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_binop_return_canary_vm.sh
new file mode 100644
index 00000000..ea24651f
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_binop_return_canary_vm.sh
@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+# Prebuild required tools/libraries
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+# Minimal MIR v1 JSON that computes 40+2 then returns 42.
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":40},
+        {"op":"const","dst":2,"ty":"i64","value":2},
+        {"op":"binop","operation":"add","lhs":1,"rhs":2,"dst":3},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_binop_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_binop_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 42 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_binop_return_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_binop_return_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_bitwise_and_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_bitwise_and_canary_vm.sh
new file mode 100644
index 00000000..382ec262
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_bitwise_and_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":5},
+        {"op":"const","dst":2,"ty":"i64","value":3},
+        {"op":"binop","operation":"&","lhs":1,"rhs":2,"dst":3},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_and_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_and_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 1 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_bitwise_and_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_bitwise_and_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_eq_true_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_eq_true_canary_vm.sh
new file mode 100644
index 00000000..dd3b3b60
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_eq_true_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":7},
+        {"op":"const","dst":2,"ty":"i64","value":7},
+        {"op":"compare","operation":"==","lhs":1,"rhs":2,"dst":3},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_cmp_eq_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_cmp_eq_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 1 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_compare_eq_true_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_compare_eq_true_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_ge_boundary_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_ge_boundary_canary_vm.sh
new file mode 100644
index 00000000..be6b4608
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_ge_boundary_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":0},
+        {"op":"const","dst":2,"ty":"i64","value":-1},
+        {"op":"compare","operation":">=","lhs":1,"rhs":2,"dst":3},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_cmp_ge_b_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_cmp_ge_b_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 1 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_compare_ge_boundary_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_compare_ge_boundary_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_le_boundary_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_le_boundary_canary_vm.sh
new file mode 100644
index 00000000..0c3e51f0
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_le_boundary_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":-1},
+        {"op":"const","dst":2,"ty":"i64","value":0},
+        {"op":"compare","operation":"<=","lhs":1,"rhs":2,"dst":3},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_cmp_le_b_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_cmp_le_b_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 1 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_compare_le_boundary_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_compare_le_boundary_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_lt_neg_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_lt_neg_canary_vm.sh
new file mode 100644
index 00000000..05e6a327
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_lt_neg_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":-5},
+        {"op":"const","dst":2,"ty":"i64","value":0},
+        {"op":"compare","operation":"<","lhs":1,"rhs":2,"dst":3},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_cmp_lt_neg_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_cmp_lt_neg_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 1 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_compare_lt_neg_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_compare_lt_neg_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_ne_true_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_ne_true_canary_vm.sh
new file mode 100644
index 00000000..1b1f2c66
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_compare_ne_true_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":7},
+        {"op":"const","dst":2,"ty":"i64","value":8},
+        {"op":"compare","operation":"!=","lhs":1,"rhs":2,"dst":3},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_cmp_ne_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_cmp_ne_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 1 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_compare_ne_true_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_compare_ne_true_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_div_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_div_canary_vm.sh
new file mode 100644
index 00000000..efa840c5
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_div_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":5},
+        {"op":"const","dst":2,"ty":"i64","value":2},
+        {"op":"binop","operation":"/","lhs":1,"rhs":2,"dst":3},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_div_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_div_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 2 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_div_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_div_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_phi_branch_return42_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_phi_branch_return42_canary_vm.sh
new file mode 100644
index 00000000..00a0fcdf
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_phi_branch_return42_canary_vm.sh
@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+# Branch: if (1 == 1) then return 42 else return 7 → expect rc=42
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":1},
+        {"op":"const","dst":2,"ty":"i64","value":1},
+        {"op":"compare","operation":"==","lhs":1,"rhs":2,"dst":3},
+        {"op":"branch","cond":3,"then":1,"else":2}
+      ]},
+      {"id":1,"inst":[
+        {"op":"const","dst":4,"ty":"i64","value":42},
+        {"op":"ret","value":4}
+      ]},
+      {"id":2,"inst":[
+        {"op":"const","dst":5,"ty":"i64","value":7},
+        {"op":"ret","value":5}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_phi_ret42_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_phi_ret42_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 42 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_phi_branch_return42_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_phi_branch_return42_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_print_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_print_canary_vm.sh
index 8d0b7c40..65723b43 100644
--- a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_print_canary_vm.sh
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_print_canary_vm.sh
@@ -29,10 +29,10 @@ APP="/tmp/ny_crate_backend_exe_print_$$"
 TMP_JSON="/tmp/ny_crate_backend_exe_print_$$.json"
 echo "$JSON" > "$TMP_JSON"
 
-LIBDIR_MIN="$ROOT/crates/nyash_kernel_min_c/target/release"
+LIBDIR_MIN="$ROOT/target/release"
 LIBS="-L $LIBDIR_MIN -lnyash_kernel_min_c"
 
-if "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --libs "$LIBS" --out "$APP" >/dev/null 2>&1; then
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --libs="$LIBS" --out "$APP" >/dev/null 2>&1; then
   if [[ -x "$APP" ]]; then
     set +e
     out="$($APP 2>/dev/null)"; rc=$?
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_rem_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_rem_canary_vm.sh
new file mode 100644
index 00000000..e8f56211
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_rem_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":5},
+        {"op":"const","dst":2,"ty":"i64","value":2},
+        {"op":"binop","operation":"%","lhs":1,"rhs":2,"dst":3},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_rem_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_rem_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 1 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_rem_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_rem_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_return42_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_return42_canary_vm.sh
new file mode 100644
index 00000000..2101a0d5
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_return42_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+# Prebuild required tools/libraries
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+# Minimal MIR v1 JSON that returns 42.
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":42},
+        {"op":"ret","value":1}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_ret42_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_ret42_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 42 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_return42_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[SKIP] s3_backend_selector_crate_exe_return42_canary_vm (rc mapping not active)" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 0
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_return_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_return_canary_vm.sh
new file mode 100644
index 00000000..7584c15d
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_return_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+# Prebuild required tools/libraries
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+# Minimal MIR v1 JSON that returns 0.
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":0},
+        {"op":"ret","value":1}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_ret_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_ret_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 0 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_return_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_return_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_shift_left_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_shift_left_canary_vm.sh
new file mode 100644
index 00000000..544db6ef
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_shift_left_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":4},
+        {"op":"const","dst":2,"ty":"i64","value":1},
+        {"op":"binop","operation":"<<","lhs":1,"rhs":2,"dst":3},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_shl_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_shl_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 8 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_shift_left_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_shift_left_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_shift_right_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_shift_right_canary_vm.sh
new file mode 100644
index 00000000..c7173530
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2100/s3_backend_selector_crate_exe_shift_right_canary_vm.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_NYLLVMC="$ROOT/target/release/ny-llvmc"
+
+(cd "$ROOT" && cargo build -q --release -p nyash-llvm-compiler >/dev/null) || true
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":8},
+        {"op":"const","dst":2,"ty":"i64","value":1},
+        {"op":"binop","operation":">>","lhs":1,"rhs":2,"dst":3},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+APP="/tmp/ny_crate_backend_exe_shr_$$"
+TMP_JSON="/tmp/ny_crate_backend_exe_shr_$$.json"
+echo "$JSON" > "$TMP_JSON"
+
+if HAKO_LLVM_CANARY_NORMALIZE=1 "$BIN_NYLLVMC" --in "$TMP_JSON" --emit exe --nyrt "$ROOT/target/release" --out "$APP" >/dev/null 2>&1; then
+  if [[ -x "$APP" ]]; then
+    set +e
+    "$APP" >/dev/null 2>&1; rc=$?
+    set -e
+    if [ "$rc" -eq 4 ]; then
+      echo "[PASS] s3_backend_selector_crate_exe_shift_right_canary_vm"
+      rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+      exit 0
+    fi
+  fi
+fi
+echo "[FAIL] s3_backend_selector_crate_exe_shift_right_canary_vm" >&2
+rm -f "$APP" "$TMP_JSON" 2>/dev/null || true
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_binop_add_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_binop_add_canary_vm.sh
new file mode 100644
index 00000000..e3383395
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_binop_add_canary_vm.sh
@@ -0,0 +1,51 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_BUILDER="$ROOT/tools/ny_mir_builder.sh"
+
+if ! command -v llc >/dev/null 2>&1; then
+  echo "[SKIP] native_backend_binop_add_canary_vm (llc not found)" >&2
+  exit 0
+fi
+
+# Build NyRT quietly (link step)
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":40},
+        {"op":"const","dst":2,"ty":"i64","value":2},
+        {"op":"binop","dst":3,"operation":"Add","lhs":1,"rhs":2},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+TMP_JSON="/tmp/native_binop_add_$$.json"; echo "$JSON" > "$TMP_JSON"
+APP="/tmp/native_binop_add_$$"
+
+set +e
+NYASH_LLVM_BACKEND=native NYASH_LLVM_SKIP_BUILD=1 bash "$BIN_BUILDER" --in "$TMP_JSON" --emit exe -o "$APP" >/dev/null 2>&1
+RC_BUILD=$?
+set -e
+if [ "$RC_BUILD" -ne 0 ]; then
+  echo "[SKIP] native_backend_binop_add_canary_vm (native builder failed)" >&2
+  rm -f "$TMP_JSON" "$APP"; exit 0
+fi
+
+set +e
+"$APP" >/dev/null 2>&1; rc=$?
+set -e
+rm -f "$TMP_JSON" "$APP" 2>/dev/null || true
+if [ "$rc" -eq 42 ]; then
+  echo "[PASS] native_backend_binop_add_canary_vm"
+  exit 0
+fi
+echo "[FAIL] native_backend_binop_add_canary_vm (rc=$rc)" >&2
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_branch_eq_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_branch_eq_canary_vm.sh
new file mode 100644
index 00000000..1cdeb334
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_branch_eq_canary_vm.sh
@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_BUILDER="$ROOT/tools/ny_mir_builder.sh"
+
+if ! command -v llc >/dev/null 2>&1; then
+  echo "[SKIP] native_backend_branch_eq_canary_vm (llc not found)" >&2
+  exit 0
+fi
+
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+# Compare false (5==6) -> branch to else (ret 42)
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":5},
+        {"op":"const","dst":2,"ty":"i64","value":42},
+        {"op":"compare","dst":3,"operation":"==","lhs":1,"rhs":2},
+        {"op":"branch","cond":3, "then":1, "else":2}
+      ]},
+      {"id":1,"inst":[
+        {"op":"ret","value":1}
+      ]},
+      {"id":2,"inst":[
+        {"op":"ret","value":2}
+      ]}
+    ]}
+  ]
+}'
+
+TMP_JSON="/tmp/native_branch_eq_$$.json"; echo "$JSON" > "$TMP_JSON"
+APP="/tmp/native_branch_eq_$$"
+
+set +e
+NYASH_LLVM_BACKEND=native NYASH_LLVM_SKIP_BUILD=1 bash "$BIN_BUILDER" --in "$TMP_JSON" --emit exe -o "$APP" >/dev/null 2>&1
+RC_BUILD=$?
+set -e
+if [ "$RC_BUILD" -ne 0 ]; then
+  echo "[SKIP] native_backend_branch_eq_canary_vm (native builder failed)" >&2
+  rm -f "$TMP_JSON" "$APP"; exit 0
+fi
+
+set +e
+"$APP" >/dev/null 2>&1; rc=$?
+set -e
+rm -f "$TMP_JSON" "$APP" 2>/dev/null || true
+if [ "$rc" -eq 42 ]; then
+  echo "[PASS] native_backend_branch_eq_canary_vm"
+  exit 0
+fi
+echo "[FAIL] native_backend_branch_eq_canary_vm (rc=$rc)" >&2
+exit 1
diff --git a/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_compare_eq_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_compare_eq_canary_vm.sh
new file mode 100644
index 00000000..5e38adf5
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_compare_eq_canary_vm.sh
@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_BUILDER="$ROOT/tools/ny_mir_builder.sh"
+
+if ! command -v llc >/dev/null 2>&1; then
+  echo "[SKIP] native_backend_compare_eq_canary_vm (llc not found)" >&2
+  exit 0
+fi
+
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":5},
+        {"op":"const","dst":2,"ty":"i64","value":5},
+        {"op":"compare","dst":3,"operation":"==","lhs":1,"rhs":2},
+        {"op":"ret","value":3}
+      ]}
+    ]}
+  ]
+}'
+
+TMP_JSON="/tmp/native_cmp_eq_$$.json"; echo "$JSON" > "$TMP_JSON"
+APP="/tmp/native_cmp_eq_$$"
+
+set +e
+NYASH_LLVM_BACKEND=native NYASH_LLVM_SKIP_BUILD=1 bash "$BIN_BUILDER" --in "$TMP_JSON" --emit exe -o "$APP" >/dev/null 2>&1
+RC_BUILD=$?
+set -e
+if [ "$RC_BUILD" -ne 0 ]; then
+  echo "[SKIP] native_backend_compare_eq_canary_vm (native builder failed)" >&2
+  rm -f "$TMP_JSON" "$APP"; exit 0
+fi
+
+set +e
+"$APP" >/dev/null 2>&1; rc=$?
+set -e
+rm -f "$TMP_JSON" "$APP" 2>/dev/null || true
+if [ "$rc" -eq 1 ]; then
+  echo "[PASS] native_backend_compare_eq_canary_vm"
+  exit 0
+fi
+echo "[FAIL] native_backend_compare_eq_canary_vm (rc=$rc)" >&2
+exit 1
+
diff --git a/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_return42_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_return42_canary_vm.sh
new file mode 100644
index 00000000..fb9f17c3
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2120/native_backend_return42_canary_vm.sh
@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/../../../../../../.." && pwd)"
+BIN_BUILDER="$ROOT/tools/ny_mir_builder.sh"
+
+# Require llc (native path)
+if ! command -v llc >/dev/null 2>&1; then
+  echo "[SKIP] native_backend_return42_canary_vm (llc not found)" >&2
+  exit 0
+fi
+
+# Prebuild NyRT (for linking)
+(cd "$ROOT/crates/nyash_kernel" && cargo build -q --release >/dev/null) || true
+
+JSON='{
+  "schema_version": 1,
+  "functions": [
+    {"name":"ny_main","blocks":[
+      {"id":0,"inst":[
+        {"op":"const","dst":1,"ty":"i64","value":42},
+        {"op":"ret","value":1}
+      ]}
+    ]}
+  ]
+}'
+
+TMP_JSON="/tmp/native_ret42_$$.json"; echo "$JSON" > "$TMP_JSON"
+APP="/tmp/native_ret42_$$"
+
+if ! NYASH_LLVM_BACKEND=native NYASH_LLVM_SKIP_BUILD=1 bash "$BIN_BUILDER" --in "$TMP_JSON" --emit exe -o "$APP" >/dev/null 2>&1; then
+  echo "[SKIP] native_backend_return42_canary_vm (native builder failed)" >&2
+  rm -f "$TMP_JSON" "$APP"; exit 0
+fi
+set +e
+"$APP" >/dev/null 2>&1; rc=$?
+set -e
+rm -f "$TMP_JSON" "$APP" 2>/dev/null || true
+if [ "$rc" -eq 42 ]; then
+  echo "[PASS] native_backend_return42_canary_vm"
+  exit 0
+fi
+echo "[FAIL] native_backend_return42_canary_vm" >&2
+exit 1
diff --git a/tools/smokes/v2/profiles/quick/core/phase2211/tlv_shim_parity_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2211/tlv_shim_parity_canary_vm.sh
new file mode 100644
index 00000000..abef9a66
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2211/tlv_shim_parity_canary_vm.sh
@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+source "$(dirname "$0")/../../../../lib/test_runner.sh"
+require_env >/dev/null || exit 2
+
+# Build nyash with tlv-shim feature (even if we run OFF for parity)
+( cd "$NYASH_ROOT" && cargo build -q --release -p nyash-rust --features tlv-shim )
+
+CODE='
+static box Main {
+  main() {
+    local m = new MapBox()
+    m.set("k", "v")
+    print(m.get("k"))
+    return 0
+  }
+}
+'
+
+o1=$(HAKO_TLV_SHIM=0 run_nyash_vm -c "$CODE" 2>&1 | tr -d '\r')
+o2=$(HAKO_TLV_SHIM=1 run_nyash_vm -c "$CODE" 2>&1 | tr -d '\r')
+
+# Strip shim trace if any to compare pure program output
+o1p=$(printf "%s\n" "$o1" | awk '!/^\[tlv\/shim:/')
+o2p=$(printf "%s\n" "$o2" | awk '!/^\[tlv\/shim:/')
+
+if diff -u <(printf "%s\n" "$o1p") <(printf "%s\n" "$o2p") >/dev/null; then
+  echo "[PASS] tlv_shim_parity_canary_vm"
+  exit 0
+fi
+echo "[FAIL] tlv_shim_parity_canary_vm" >&2
+echo "--- OFF ---" >&2; echo "$o1" >&2
+echo "--- ON ----" >&2; echo "$o2" >&2
+exit 1
+