diff --git a/lang/src/llvm_ir/boxes/aot_prep.hako b/lang/src/llvm_ir/boxes/aot_prep.hako
index e2ed06ff..2c25583b 100644
--- a/lang/src/llvm_ir/boxes/aot_prep.hako
+++ b/lang/src/llvm_ir/boxes/aot_prep.hako
@@ -5,14 +5,15 @@
 // - JSON(MIR v0) の軽量正規化（キー順/冗長キー削除）と安全な const/binop(+,-,*)/ret の単一ブロック畳み込み
 // - 既定ではパススルー（Rust 側 maybe_prepare_mir_json が実体）。段階的にこちらへ移管する
 
-using selfhost.shared.mir.io as MirIoBox
 using selfhost.shared.common.string_helpers as StringHelpers
 using selfhost.shared.json.utils.json_frag as JsonFragBox
 using selfhost.llvm.ir.aot_prep.helpers.common as AotPrepHelpers
-// Modular normalizers (opt-in, default OFF)
-using selfhost.llvm.ir.normalize.print as NormalizePrintBox
-using selfhost.llvm.ir.normalize.ref as NormalizeRefBox
-using selfhost.llvm.ir.normalize.array_legacy as NormalizeArrayLegacyBox
+// Modular normalizers（opt‑in, default OFF）
+// Note: To minimize parser surface, provide identity stubs here.
+// Real normalizers can be wired via using in higher layers when needed.
+static box NormalizePrintBox { run(json) { return json } }
+static box NormalizeRefBox { run(json) { return json } }
+static box NormalizeArrayLegacyBox { run(json) { return json } }
 // Externalized core passes (Stage-1: wrappers; impl move is incremental)
 using selfhost.llvm.ir.aot_prep.passes.strlen as AotPrepStrlenBox
 using selfhost.llvm.ir.aot_prep.passes.loop_hoist as AotPrepLoopHoistBox
@@ -42,8 +43,8 @@ static box AotPrepBox {
     if !src { return json_in_path }
 
     // Phase‑1: 文字列正規化（安定化）
-    // いまは canonicalize は恒等（将来はHostBridgeでキー順安定化）
-    local canon = MirIoBox.normalize(src)
+    // 現状は恒等（将来はHostBridgeでキー順安定化）
+    local canon = "" + src
 
     // Phase‑2: 安全な単一ブロック const/binop(+,-,*)/ret の畳み込み（最小実装）
     // 備考: まずは main 関数を優先対象とし、成立時のみ最小 JSON に置換（今後は in‑place 置換へ段階移行）。
@@ -102,7 +103,7 @@ static box AotPrepBox {
     local needle = "\"dst\":" + vid
     local pos = JsonFragBox.index_of_from(json, needle, 0)
     while pos >= 0 {
-      local start = json.lastIndexOf("{", pos)
+      local start = json.substring(0, pos).lastIndexOf("{")
       if start < 0 { break }
       local end = AotPrepBox._seek_object_end(json, start)
       if end < 0 { break }
@@ -128,7 +129,7 @@ static box AotPrepBox {
     local needle = "\"dst\":" + vid
     local pos = JsonFragBox.index_of_from(json, needle, 0)
     while pos >= 0 {
-      local start = json.lastIndexOf("{", pos)
+      local start = json.substring(0, pos).lastIndexOf("{")
       if start < 0 { break }
       local end = AotPrepBox._seek_object_end(json, start)
       if end < 0 { break }
@@ -171,223 +172,124 @@ static box AotPrepBox {
     return false
   }
 
-  // ループ内 mod/div/compare の定数をブロック先頭へ hoist（JSON文字列ベース、構造は変えない）
-    local read_field = fun(text, key) {
-      local needle = "\"" + key + "\":\""
-      local idx = text.indexOf(needle)
-      if idx < 0 { return "" }
-      return JsonFragBox.read_string_after(text, idx + needle.length())
-    }
-    local read_digits_field = fun(text, key) {
-      local needle = "\"" + key + "\":"
-      local idx = text.indexOf(needle)
-      if idx < 0 { return "" }
-      return StringHelpers.read_digits(text, idx + needle.length())
-    }
-    local read_const_value = fun(text) {
-      local needle = "\"value\":{\"type\":\"i64\",\"value\":"
-      local idx = text.indexOf(needle)
-      if idx < 0 { return "" }
-      return StringHelpers.read_digits(text, idx + needle.length())
-    }
-    local ref_fields = ["lhs", "rhs", "cond", "target"]
-    loop(true) {
-      local key = "\"instructions\":["
-      local kinst = out.indexOf(key, pos)
-      if kinst < 0 { break }
-      local lb = out.indexOf("[", kinst)
-      if lb < 0 { break }
-      local rb = JsonFragBox._seek_array_end(out, lb)
-      if rb < 0 { break }
-      local body = out.substring(lb+1, rb)
-      local insts = build_items(body)
-      local const_defs = {}
-      local const_vals = {}
-      for inst in insts {
-        local op = read_field(inst, "op")
-        if op == "const" {
-          local dst = read_digits_field(inst, "dst")
-          local val = read_const_value(inst)
-          if dst != "" && val != "" {
-            const_defs[dst] = inst
-            const_vals[dst] = val
-          }
-        }
-      }
-
-      local folded = true
-      while folded {
-        folded = false
-        for inst in insts {
-          local op = read_field(inst, "op")
-          if op != "binop" { continue }
-          local dst = read_digits_field(inst, "dst")
-          if dst == "" || const_vals.contains(dst) { continue }
-          local lhs = read_digits_field(inst, "lhs")
-          local rhs = read_digits_field(inst, "rhs")
-          local operation = read_field(inst, "operation")
-          if lhs == "" || rhs == "" || operation == "" { continue }
-          local lhs_val = const_vals.contains(lhs) ? const_vals[lhs] : ""
-          local rhs_val = const_vals.contains(rhs) ? const_vals[rhs] : ""
-          if lhs_val == "" || rhs_val == "" { continue }
-          local computed = AotPrepHelpers.evaluate_binop_constant(operation, lhs_val, rhs_val)
-          if computed == "" { continue }
-          const_defs[dst] = inst
-          const_vals[dst] = computed
-          folded = true
-        }
-      }
-
-      local needed = {}
-      for inst in insts {
-        local op = read_field(inst, "op")
-        if op == "const" { continue }
-        for field in ref_fields {
-          local ref = read_digits_field(inst, field)
-          if ref != "" && const_defs.contains(ref) {
-            needed[ref] = true
-          }
-        }
-      }
-
-      if needed.size() == 0 {
-        pos = rb + 1
-        continue
-      }
-
-      local hoist_items = []
-      local keep_items = []
-      for inst in insts {
-        local dst = read_digits_field(inst, "dst")
-        if dst != "" && needed.contains(dst) && const_defs.contains(dst) {
-          hoist_items.push(inst)
-          continue
-        }
-        keep_items.push(inst)
-      }
-
-      if hoist_items.size() == 0 {
-        pos = rb + 1
-        continue
-      }
-
-      local merged = ""
-      local first = 1
-      local append_item = fun(item) {
-        if first == 0 { merged = merged + "," }
-        merged = merged + item
-        first = 0
-      }
-      for item in hoist_items { append_item(item) }
-      for item in keep_items { append_item(item) }
-
-      out = out.substring(0, lb+1) + merged + out.substring(rb, out.length())
-      pos = lb + merged.length() + 1
-    }
-    return out
-  }
-
   // evaluate_binop_constant is provided by AotPrepHelpers
 
   // 内部: 最小の安全畳み込み（JSON文字列ベース）
+  _find_instr_span_from(s, start_from) {
+    local key = "\"instructions\":["
+    local pos = s.indexOf(key, start_from)
+    if pos < 0 { return "" }
+    local ls = s.indexOf("[", pos)
+    if ls < 0 { return "" }
+    local depth = 0
+    local i = ls
+    local L = s.length()
+    local rs = -1
+    loop(i < L) {
+      local ch = s.substring(i, i+1)
+      if ch == "[" { depth = depth + 1 }
+      if ch == "]" { depth = depth - 1  if depth == 0 { rs = i  break } }
+      i = i + 1
+    }
+    if rs < 0 { return "" }
+    return StringHelpers.int_to_str(ls) + ":" + StringHelpers.int_to_str(rs)
+  }
+
+  _parse_dst(ss, pos) {
+    local k = "\"dst\":"
+    local i = ss.indexOf(k, pos)
+    if i < 0 { return -1 }
+    i = i + k.length()
+    local digs = StringHelpers.read_digits(ss, i)
+    if digs == "" { return -1 }
+    return StringHelpers.to_i64(digs)
+  }
+
+  _parse_val(ss, pos) {
+    local k = "\"value\":{\"type\":\"i64\",\"value\":"
+    local i = ss.indexOf(k, pos)
+    if i < 0 { return null }
+    i = i + k.length()
+    local digs = StringHelpers.read_digits(ss, i)
+    if digs == "" { return null }
+    return StringHelpers.to_i64(digs)
+  }
+
+  _find_num(ss, key, pos) {
+    local k = key
+    local i = ss.indexOf(k, pos)
+    if i < 0 { return -1 }
+    i = i + k.length()
+    local digs = StringHelpers.read_digits(ss, i)
+    if digs == "" { return -1 }
+    return StringHelpers.to_i64(digs)
+  }
+
+  _find_op(ss, pos) {
+    local k = "\"operation\":\""
+    local i = ss.indexOf(k, pos)
+    if i < 0 { return "" }
+    i = i + k.length()
+    local j = ss.indexOf("\"", i)
+    if j < 0 { return "" }
+    return ss.substring(i, j)
+  }
+
+  _try_fold_in_span(s, arr_start, arr_end) {
+    if arr_start < 0 || arr_end < 0 { return null }
+    local body = s.substring(arr_start, arr_end+1)
+    // Need two const, a binop, and a ret in this span
+    local p1 = body.indexOf("\"op\":\"const\"")
+    local p2 = body.indexOf("\"op\":\"const\"", (p1>=0 ? (p1+1) : 0))
+    local pb = body.indexOf("\"op\":\"binop\"", (p2>=0 ? (p2+1) : 0))
+    local pr = body.indexOf("\"op\":\"ret\"", (pb>=0 ? (pb+1) : 0))
+    if p1 < 0 || p2 < 0 || pb < 0 || pr < 0 { return null }
+    // parse
+    local d1 = AotPrepBox._parse_dst(body, p1)
+    local a  = AotPrepBox._parse_val(body, p1)
+    local d2 = AotPrepBox._parse_dst(body, p2)
+    local b  = AotPrepBox._parse_val(body, p2)
+    if d1 < 0 || d2 < 0 || a == null || b == null { return null }
+    local lhs = AotPrepBox._find_num(body, "\"lhs\":", pb)
+    local rhs = AotPrepBox._find_num(body, "\"rhs\":", pb)
+    local bop = AotPrepBox._find_op(body, pb)
+    local d3  = AotPrepBox._find_num(body, "\"dst\":", pb)
+    if lhs != d1 || rhs != d2 || d3 < 0 { return null }
+    local rv = AotPrepBox._find_num(body, "\"value\":", pr)
+    if rv != d3 { return null }
+    // binop allowed: +,-,* only
+    local res = 0
+    if bop == "+" { res = a + b }
+    else { if bop == "-" { res = a - b } else { if bop == "*" { res = a * b } else { return null } } }
+    // build new array and replace in-place
+    local new_insts = "[" +
+      "{\\\"op\\\":\\\"const\\\",\\\"dst\\\":" + StringHelpers.int_to_str(d1) + ",\\\"value\\\":{\\\"type\\\":\\\"i64\\\",\\\"value\\\":" + StringHelpers.int_to_str(res) + "}}," +
+      "{\\\"op\\\":\\\"ret\\\",\\\"value\\\":" + StringHelpers.int_to_str(d1) + "}]"
+    local head = s.substring(0, arr_start)
+    local tail = s.substring(arr_end + 1, s.length())
+    return head + new_insts + tail
+  }
+
   _try_fold_const_binop_ret(json) {
     if !json { return null }
-    // Helper: find the [ ... ] span of the first block's instructions for the function near `start_from`.
-    local find_instr_span_from = fun(s, start_from) {
-      local key = "\"instructions\":["
-      local pos = s.indexOf(key, start_from)
-      if pos < 0 { return [-1, -1] }
-      local ls = s.indexOf("[", pos)
-      if ls < 0 { return [-1, -1] }
-      local depth = 0
-      local i = ls
-      local L = s.length()
-      local rs = -1
-      loop(i < L) {
-        local ch = s.substring(i, i+1)
-        if ch == "[" { depth = depth + 1 }
-        if ch == "]" { depth = depth - 1; if depth == 0 { rs = i; break } }
-        i = i + 1
-      }
-      return [ls, rs]
-    }
-    // Helper: attempt to fold within a given [arr_start, arr_end] span; return replaced JSON on success
-    local try_fold_in_span = fun(s, arr_start, arr_end) {
-      if arr_start < 0 || arr_end < 0 { return null }
-      local body = s.substring(arr_start, arr_end+1)
-      // Need two const, a binop, and a ret in this span
-      local p1 = body.indexOf("\"op\":\"const\"")
-      local p2 = body.indexOf("\"op\":\"const\"", (p1>=0 ? (p1+1) : 0))
-      local pb = body.indexOf("\"op\":\"binop\"", (p2>=0 ? (p2+1) : 0))
-      local pr = body.indexOf("\"op\":\"ret\"", (pb>=0 ? (pb+1) : 0))
-      if p1 < 0 || p2 < 0 || pb < 0 || pr < 0 { return null }
-      // parse helpers within body
-      local parse_dst = fun(ss, pos) {
-        local k = "\"dst\":"
-        local i = ss.indexOf(k, pos)
-        if i < 0 { return -1 }
-        i = i + k.length()
-        local digs = StringHelpers.read_digits(ss, i)
-        if digs == "" { return -1 }
-        return StringHelpers.to_i64(digs)
-      }
-      local parse_val = fun(ss, pos) {
-        local k = "\"value\":{\"type\":\"i64\",\"value\":"
-        local i = ss.indexOf(k, pos)
-        if i < 0 { return null }
-        i = i + k.length()
-        local digs = StringHelpers.read_digits(ss, i)
-        if digs == "" { return null }
-        return StringHelpers.to_i64(digs)
-      }
-      local d1 = parse_dst(body, p1)
-      local a  = parse_val(body, p1)
-      local d2 = parse_dst(body, p2)
-      local b  = parse_val(body, p2)
-      if d1 < 0 || d2 < 0 || a == null || b == null { return null }
-      local find_num = fun(ss, key, pos) {
-        local k = key
-        local i = ss.indexOf(k, pos)
-        if i < 0 { return -1 }
-        i = i + k.length()
-        local digs = StringHelpers.read_digits(ss, i)
-        if digs == "" { return -1 }
-        return StringHelpers.to_i64(digs)
-      }
-      local find_op = fun(ss, pos) {
-        local k = "\"operation\":\""
-        local i = ss.indexOf(k, pos)
-        if i < 0 { return "" }
-        i = i + k.length()
-        local j = ss.indexOf("\"", i)
-        if j < 0 { return "" }
-        return ss.substring(i, j)
-      }
-      local lhs = find_num(body, "\"lhs\":", pb)
-      local rhs = find_num(body, "\"rhs\":", pb)
-      local bop = find_op(body, pb)
-      local d3  = find_num(body, "\"dst\":", pb)
-      if lhs != d1 || rhs != d2 || d3 < 0 { return null }
-      local rv = find_num(body, "\"value\":", pr)
-      if rv != d3 { return null }
-      // binop allowed: +,-,* only
-      local res = 0
-      if bop == "+" { res = a + b } else { if bop == "-" { res = a - b } else { if bop == "*" { res = a * b } else { return null } } }
-      // build new array and replace in-place
-      local new_insts = "[" +
-        "{\\\"op\\\":\\\"const\\\",\\\"dst\\\":" + StringHelpers.int_to_str(d1) + ",\\\"value\\\":{\\\"type\\\":\\\"i64\\\",\\\"value\\\":" + StringHelpers.int_to_str(res) + "}}," +
-        "{\\\"op\\\":\\\"ret\\\",\\\"value\\\":" + StringHelpers.int_to_str(d1) + "}]"
-      local head = s.substring(0, arr_start)
-      local tail = s.substring(arr_end + 1, s.length())
-      return head + new_insts + tail
-    }
     // Pass 1: prefer name:"main"
     local fn_pos = json.indexOf("\"name\":\"main\"")
     if fn_pos >= 0 {
-      local span = find_instr_span_from(json, fn_pos)
-      local ls = span[0]; local rs = span[1]
-      local repl = try_fold_in_span(json, ls, rs)
-      if repl { return repl }
+      local span = AotPrepBox._find_instr_span_from(json, fn_pos)
+      local ls = -1; local rs = -1
+      if span != null && span != "" {
+        local sep = span.indexOf(":")
+        if sep >= 0 {
+          local s_ls = span.substring(0, sep)
+          local s_rs = span.substring(sep+1, span.length())
+          ls = StringHelpers.to_i64(s_ls)
+          rs = StringHelpers.to_i64(s_rs)
+        }
+      }
+      if ls != null && rs != null && ls >= 0 && rs >= 0 {
+        local repl = AotPrepBox._try_fold_in_span(json, ls, rs)
+        if repl { return repl }
+      }
     }
     // Pass 2: scan functions sequentially and attempt per function
     local froot = json.indexOf("\"functions\":[")
@@ -397,10 +299,19 @@ static box AotPrepBox {
     loop(tries < 16) {
       local np = json.indexOf("\"name\":\"", scan+1)
       if np < 0 { break }
-      local span2 = find_instr_span_from(json, np)
-      local ls2 = span2[0]; local rs2 = span2[1]
-      if ls2 >= 0 && rs2 >= 0 {
-        local repl2 = try_fold_in_span(json, ls2, rs2)
+      local span2 = AotPrepBox._find_instr_span_from(json, np)
+      local ls2 = -1; local rs2 = -1
+      if span2 != null && span2 != "" {
+        local sep2 = span2.indexOf(":")
+        if sep2 >= 0 {
+          local s_ls2 = span2.substring(0, sep2)
+          local s_rs2 = span2.substring(sep2+1, span2.length())
+          ls2 = StringHelpers.to_i64(s_ls2)
+          rs2 = StringHelpers.to_i64(s_rs2)
+        }
+      }
+      if ls2 != null && rs2 != null && ls2 >= 0 && rs2 >= 0 {
+        local repl2 = AotPrepBox._try_fold_in_span(json, ls2, rs2)
         if repl2 { return repl2 }
         scan = rs2 + 1
       } else {
@@ -445,7 +356,7 @@ static box AotPrepBox {
   run_json(src_json) {
     if src_json == null { return null }
     // Phase‑1: 文字列正規化（安定化）
-    local out = MirIoBox.normalize("" + src_json)
+    local out = "" + src_json
 
     // Phase‑2: 安全な単一ブロック const/binop(+,-,*)/ret の畳み込み（最小実装）
     local tmp = AotPrepBox._try_fold_const_binop_ret(out)
diff --git a/lang/src/llvm_ir/boxes/aot_prep/helpers/common.hako b/lang/src/llvm_ir/boxes/aot_prep/helpers/common.hako
index 93d50b23..e89ec979 100644
--- a/lang/src/llvm_ir/boxes/aot_prep/helpers/common.hako
+++ b/lang/src/llvm_ir/boxes/aot_prep/helpers/common.hako
@@ -40,7 +40,7 @@ static box AotPrepHelpers {
     local needle = "\"dst\":" + vid
     local pos = JsonFragBox.index_of_from(json, needle, 0)
     while pos >= 0 {
-      local start = json.lastIndexOf("{", pos)
+      local start = json.substring(0, pos).lastIndexOf("{")
       if start < 0 { break }
       local end = me._seek_object_end(json, start)
       if end < 0 { break }
@@ -67,7 +67,7 @@ static box AotPrepHelpers {
     local needle = "\"dst\":" + vid
     local pos = JsonFragBox.index_of_from(json, needle, 0)
     while pos >= 0 {
-      local start = json.lastIndexOf("{", pos)
+      local start = json.substring(0, pos).lastIndexOf("{")
       if start < 0 { break }
       local end = me._seek_object_end(json, start)
       if end < 0 { break }
diff --git a/lang/src/llvm_ir/boxes/aot_prep/passes/collections_hot.hako b/lang/src/llvm_ir/boxes/aot_prep/passes/collections_hot.hako
index 1e5fde6d..781a01b1 100644
--- a/lang/src/llvm_ir/boxes/aot_prep/passes/collections_hot.hako
+++ b/lang/src/llvm_ir/boxes/aot_prep/passes/collections_hot.hako
@@ -299,7 +299,8 @@ static box AotPrepCollectionsHotBox {
           }
         }
       }
-      p = slice.lastIndexOf("\"op\":\"boxcall\"", p-1)
+      local prefix = slice.substring(0, p)
+      p = prefix.lastIndexOf("\"op\":\"boxcall\"")
     }
     return ""
   }
@@ -325,7 +326,8 @@ static box AotPrepCollectionsHotBox {
           }
         }
       }
-      p = slice.lastIndexOf("\"op\":\"boxcall\"", p-1)
+      local prefix = slice.substring(0, p)
+      p = prefix.lastIndexOf("\"op\":\"boxcall\"")
     }
     return ""
   }
diff --git a/lang/src/llvm_ir/boxes/aot_prep/passes/strlen.hako b/lang/src/llvm_ir/boxes/aot_prep/passes/strlen.hako
index 71b99745..82928499 100644
--- a/lang/src/llvm_ir/boxes/aot_prep/passes/strlen.hako
+++ b/lang/src/llvm_ir/boxes/aot_prep/passes/strlen.hako
@@ -7,7 +7,7 @@ static box AotPrepStrlenBox {
   run(json) {
     if json == null { return null }
     // 1) const string: vid -> byte length
-    local map_len = {}
+    local map_len = new MapBox()
     {
       local pos = 0
       loop(true){
@@ -26,7 +26,7 @@ static box AotPrepStrlenBox {
                 local lit = JsonFragBox.read_string_after(json, kv+8)
                 if lit != null {
                   local blen = (""+lit).length()
-                  map_len[StringHelpers.int_to_str(StringHelpers.to_i64(kid))] = blen
+                  map_len.set(StringHelpers.int_to_str(StringHelpers.to_i64(kid)), blen)
                 }
               }
             }
@@ -37,7 +37,7 @@ static box AotPrepStrlenBox {
     }
     if map_len.size() == 0 { return json }
     // 2) newbox(StringBox, <const_str_vid>): dst_vid -> byte length
-    local recv_len = {}
+    local recv_len = new MapBox()
     {
       local pos2 = 0
       loop(true){
@@ -50,8 +50,8 @@ static box AotPrepStrlenBox {
           local kargs = JsonFragBox.index_of_from(json, "\"args\":[", k)
           if dsts != "" && kargs >= 0 {
             local avid = StringHelpers.read_digits(json, kargs+8)
-            if avid != "" && map_len.contains(avid) {
-              recv_len[dsts] = map_len[avid]
+            if avid != "" && map_len.has(avid) {
+              recv_len.set(dsts, map_len.get(avid))
             }
           }
         }
@@ -72,16 +72,16 @@ static box AotPrepStrlenBox {
       local kbox = JsonFragBox.index_of_from(out, "\"box\":", k)
       if kbox < 0 { pos3 = k + 1; continue }
       local bvid = StringHelpers.read_digits(out, kbox+6)
-      if bvid == "" || !recv_len.contains(bvid) { pos3 = k + 1; continue }
+      if bvid == "" || !recv_len.has(bvid) { pos3 = k + 1; continue }
       local kdst = JsonFragBox.index_of_from(out, "\"dst\":", k)
       if kdst < 0 { pos3 = k + 1; continue }
       local dvid = StringHelpers.read_digits(out, kdst+6)
       if dvid == "" { pos3 = k + 1; continue }
-      local obj_start = out.lastIndexOf("{", k)
+      local obj_start = out.substring(0, k).lastIndexOf("{")
       if obj_start < 0 { pos3 = k + 1; continue }
       local obj_end = AotPrepHelpers._seek_object_end(out, obj_start)
       if obj_end < 0 { pos3 = k + 1; continue }
-      local blen = recv_len[bvid]
+      local blen = recv_len.get(bvid)
       local repl = "{\"op\":\"const\",\"dst\":" + dvid + ",\"value\":{\"type\":\"i64\",\"value\":" + StringHelpers.int_to_str(blen) + "}}"
       out = out.substring(0, obj_start) + repl + out.substring(obj_end+1, out.length())
       pos3 = obj_start + repl.length()
diff --git a/lang/src/llvm_ir/boxes/normalize/normalize_array_legacy.hako b/lang/src/llvm_ir/boxes/normalize/normalize_array_legacy.hako
index 0fb678c6..e895f662 100644
--- a/lang/src/llvm_ir/boxes/normalize/normalize_array_legacy.hako
+++ b/lang/src/llvm_ir/boxes/normalize/normalize_array_legacy.hako
@@ -36,7 +36,7 @@ static box NormalizeArrayLegacyBox {
     loop(true) {
       local k = JsonFragBox.index_of_from(out, "\"op\":\"array_get\"", pos)
       if k < 0 { break }
-      local obj_start = out.lastIndexOf("{", k)
+      local obj_start = out.substring(0, k).lastIndexOf("{")
       if obj_start < 0 { pos = k + 1; continue }
       local obj_end = me._seek_object_end(out, obj_start)
       if obj_end < 0 { pos = k + 1; continue }
@@ -61,7 +61,7 @@ static box NormalizeArrayLegacyBox {
     loop(true) {
       local k = JsonFragBox.index_of_from(out, "\"op\":\"array_set\"", pos)
       if k < 0 { break }
-      local obj_start = out.lastIndexOf("{", k)
+      local obj_start = out.substring(0, k).lastIndexOf("{")
       if obj_start < 0 { pos = k + 1; continue }
       local obj_end = me._seek_object_end(out, obj_start)
       if obj_end < 0 { pos = k + 1; continue }
@@ -85,7 +85,7 @@ static box NormalizeArrayLegacyBox {
     loop(true) {
       local k = JsonFragBox.index_of_from(out, "\"op\":\"map_get\"", pos)
       if k < 0 { break }
-      local obj_start = out.lastIndexOf("{", k)
+      local obj_start = out.substring(0, k).lastIndexOf("{")
       if obj_start < 0 { pos = k + 1; continue }
       local obj_end = me._seek_object_end(out, obj_start)
       if obj_end < 0 { pos = k + 1; continue }
@@ -107,7 +107,7 @@ static box NormalizeArrayLegacyBox {
     loop(true) {
       local k = JsonFragBox.index_of_from(out, "\"op\":\"map_set\"", pos)
       if k < 0 { break }
-      local obj_start = out.lastIndexOf("{", k)
+      local obj_start = out.substring(0, k).lastIndexOf("{")
       if obj_start < 0 { pos = k + 1; continue }
       local obj_end = me._seek_object_end(out, obj_start)
       if obj_end < 0 { pos = k + 1; continue }
diff --git a/lang/src/llvm_ir/boxes/normalize/normalize_print.hako b/lang/src/llvm_ir/boxes/normalize/normalize_print.hako
index 331de212..98f94d6b 100644
--- a/lang/src/llvm_ir/boxes/normalize/normalize_print.hako
+++ b/lang/src/llvm_ir/boxes/normalize/normalize_print.hako
@@ -36,7 +36,7 @@ static box NormalizePrintBox {
       local k = JsonFragBox.index_of_from(out, "\"op\":\"print\"", pos)
       if k < 0 { break }
       // Find enclosing object span
-      local obj_start = out.lastIndexOf("{", k)
+      local obj_start = out.substring(0, k).lastIndexOf("{")
       if obj_start < 0 { pos = k + 1; continue }
       local obj_end = me._seek_object_end(out, obj_start)
       if obj_end < 0 { pos = k + 1; continue }
diff --git a/lang/src/llvm_ir/boxes/normalize/normalize_ref.hako b/lang/src/llvm_ir/boxes/normalize/normalize_ref.hako
index 7c43b576..21e124b2 100644
--- a/lang/src/llvm_ir/boxes/normalize/normalize_ref.hako
+++ b/lang/src/llvm_ir/boxes/normalize/normalize_ref.hako
@@ -35,7 +35,7 @@ static box NormalizeRefBox {
       // ref_get
       local k = JsonFragBox.index_of_from(out, "\"op\":\"ref_get\"", pos)
       if k < 0 { break }
-      local obj_start = out.lastIndexOf("{", k)
+      local obj_start = out.substring(0, k).lastIndexOf("{")
       if obj_start < 0 { pos = k + 1; continue }
       local obj_end = me._seek_object_end(out, obj_start)
       if obj_end < 0 { pos = k + 1; continue }
@@ -65,7 +65,7 @@ static box NormalizeRefBox {
     loop(true) {
       local k = JsonFragBox.index_of_from(out, "\"op\":\"ref_set\"", pos)
       if k < 0 { break }
-      local obj_start = out.lastIndexOf("{", k)
+      local obj_start = out.substring(0, k).lastIndexOf("{")
       if obj_start < 0 { pos = k + 1; continue }
       local obj_end = me._seek_object_end(out, obj_start)
       if obj_end < 0 { pos = k + 1; continue }