diff --git a/src/backend/mir_interpreter/handlers/boxes_map.rs b/src/backend/mir_interpreter/handlers/boxes_map.rs
index c5a0bf04..2557a0fb 100644
--- a/src/backend/mir_interpreter/handlers/boxes_map.rs
+++ b/src/backend/mir_interpreter/handlers/boxes_map.rs
@@ -30,7 +30,13 @@ pub(super) fn try_handle_map_box(
                             "MapBox.getField expects 1 arg".into(),
                         ));
                     }
-                    let k = this.reg_load(args[0])?.to_nyash_box();
+                    let k_vm = this.reg_load(args[0])?;
+                    // Field access expects a String key; otherwise return a stable tag.
+                    if !matches!(k_vm, VMValue::String(_)) {
+                        if let Some(d) = dst { this.regs.insert(d, VMValue::String("[map/bad-key] field name must be string".to_string())); }
+                        return Ok(true);
+                    }
+                    let k = k_vm.to_nyash_box();
                     let ret = mb.get(k);
                     if let Some(d) = dst {
                         this.regs.insert(d, VMValue::from_nyash_box(ret));
@@ -43,7 +49,12 @@ pub(super) fn try_handle_map_box(
                             "MapBox.setField expects 2 args".into(),
                         ));
                     }
-                    let k = this.reg_load(args[0])?.to_nyash_box();
+                    let k_vm = this.reg_load(args[0])?;
+                    if !matches!(k_vm, VMValue::String(_)) {
+                        if let Some(d) = dst { this.regs.insert(d, VMValue::String("[map/bad-key] field name must be string".to_string())); }
+                        return Ok(true);
+                    }
+                    let k = k_vm.to_nyash_box();
                     let v = this.reg_load(args[1])?.to_nyash_box();
                     let ret = mb.set(k, v);
                     if let Some(d) = dst {
diff --git a/src/backend/mir_interpreter/handlers/boxes_object_fields.rs b/src/backend/mir_interpreter/handlers/boxes_object_fields.rs
index c34a870d..27ec72ad 100644
--- a/src/backend/mir_interpreter/handlers/boxes_object_fields.rs
+++ b/src/backend/mir_interpreter/handlers/boxes_object_fields.rs
@@ -40,6 +40,24 @@ pub(super) fn try_handle_object_fields(
             if args.len() != 1 {
                 return Err(VMError::InvalidInstruction("getField expects 1 arg".into()));
             }
+            // MapBox special-case: bridge to MapBox.get, with string-only key
+            if let Ok(VMValue::BoxRef(bref)) = this.reg_load(box_val) {
+                if bref.as_any().downcast_ref::<crate::boxes::map_box::MapBox>().is_some() {
+                    let key_vm = this.reg_load(args[0])?;
+                    if let VMValue::String(_) = key_vm {
+                        let k = key_vm.to_nyash_box();
+                        let map = bref.share_box();
+                        if let Some(mb) = map.as_any().downcast_ref::<crate::boxes::map_box::MapBox>() {
+                            let ret = mb.get(k);
+                            if let Some(d) = dst { this.regs.insert(d, VMValue::from_nyash_box(ret)); }
+                            return Ok(true);
+                        }
+                    } else {
+                        if let Some(d) = dst { this.regs.insert(d, VMValue::String("[map/bad-key] field name must be string".to_string())); }
+                        return Ok(true);
+                    }
+                }
+            }
             if std::env::var("NYASH_VM_TRACE").ok().as_deref() == Some("1") {
                 let rk = match this.reg_load(box_val) {
                     Ok(VMValue::BoxRef(ref b)) => format!("BoxRef({})", b.type_name()),
@@ -282,6 +300,25 @@ pub(super) fn try_handle_object_fields(
                     "setField expects 2 args".into(),
                 ));
             }
+            // MapBox special-case: bridge to MapBox.set, with string-only key
+            if let Ok(VMValue::BoxRef(bref)) = this.reg_load(box_val) {
+                if bref.as_any().downcast_ref::<crate::boxes::map_box::MapBox>().is_some() {
+                    let key_vm = this.reg_load(args[0])?;
+                    if let VMValue::String(_) = key_vm {
+                        let k = key_vm.to_nyash_box();
+                        let v = this.reg_load(args[1])?.to_nyash_box();
+                        let map = bref.share_box();
+                        if let Some(mb) = map.as_any().downcast_ref::<crate::boxes::map_box::MapBox>() {
+                            let _ = mb.set(k, v);
+                            if let Some(d) = dst { this.regs.insert(d, VMValue::Void); }
+                            return Ok(true);
+                        }
+                    } else {
+                        if let Some(d) = dst { this.regs.insert(d, VMValue::String("[map/bad-key] field name must be string".to_string())); }
+                        return Ok(true);
+                    }
+                }
+            }
             let fname = match this.reg_load(args[0])? {
                 VMValue::String(s) => s,
                 v => v.to_string(),
diff --git a/tools/smokes/v2/README.md b/tools/smokes/v2/README.md
index a1607f95..6f6f6566 100644
--- a/tools/smokes/v2/README.md
+++ b/tools/smokes/v2/README.md
@@ -82,6 +82,18 @@ tools/smokes/v2/
 - `SMOKES_ENABLE_CORE_CANARY=1` — Core interpreter canaries（emit→nyvm/core, Gate‑C Core）。
 - Stage‑B canaries are default‑ON in quick (`core/stageb/*`).
   - Selfhost Stage‑B helpers under `core/selfhost_stageb_*` remain opt‑in for dev.
+
+Bridge canonicalize (diff canaries)
+- 目的: v1 JSON の ModuleFunction を Method へ決定的に正規化することを保証する。
+- ON/OFF/FAIL 規約:
+  - ON: `HAKO_BRIDGE_INJECT_SINGLETON=1` で mutated JSON（dump）が生成され、`callee.type": "Method"` へ書き換わる。
+  - OFF: 変異しない（dumpが生成されない or `ModuleFunction` のまま）。
+  - FAIL: 無効な JSON/未対応のcallee などは Fail‑Fast（stderrに安定文言）。
+- 常時テスト（quick/core/bridge）:
+  - canonicalize_diff_on_off_vm.sh（LLVMPhiInstructionBox.lower_phi ベース）
+  - canonicalize_array_len_on_off_vm.sh（ArrayBox.len → Method(ArrayBox.size)）
+  - canonicalize_map_len_on_off_vm.sh（MapBox.len → Method(MapBox.len)）
+  - canonicalize_static_lower_*（binop/compare/branch/jump/return）
 - `SMOKES_ENABLE_STAGEB_V1=1` — Stage‑B v1 互換カナリア（`selfhost_stageb_v1_compat_vm.sh`）。未配線時は SKIP。
 
 ## 🔧 テスト作成規約
diff --git a/tools/smokes/v2/profiles/quick/core/bridge/canonicalize_static_lower_branch_on_off_vm.sh b/tools/smokes/v2/profiles/quick/core/bridge/canonicalize_static_lower_branch_on_off_vm.sh
new file mode 100644
index 00000000..71db3ea5
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/bridge/canonicalize_static_lower_branch_on_off_vm.sh
@@ -0,0 +1,42 @@
+#!/bin/bash
+# canonicalize_static_lower_branch_on_off_vm.sh — Verify LLVMBranchInstructionBox.lower_branch rewrite
+
+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
+
+json_path="/tmp/ny_v1_lower_branch_$$.json"
+mut_on="/tmp/ny_v1_lower_branch_on_$$.json"
+mut_off="/tmp/ny_v1_lower_branch_off_$$.json"
+
+cat >"$json_path" <<'JSON'
+{"schema_version":"1.0","functions":[{"name":"main","blocks":[{"id":0,"instructions":[{"op":"mir_call","mir_call":{"callee":{"type":"ModuleFunction","name":"LLVMBranchInstructionBox.lower_branch"},"args":[1]}},{"op":"ret"}]}]}]}
+JSON
+
+set +e
+HAKO_NYVM_V1_DOWNCONVERT=1 HAKO_BRIDGE_INJECT_SINGLETON=1 HAKO_DEBUG_NYVM_BRIDGE_DUMP_MUT="$mut_on" \
+  "$ROOT/target/release/nyash" --json-file "$json_path" >/dev/null 2>&1
+set -e || true
+if [ ! -f "$mut_on" ] || ! grep -q '"type":"Method"' "$mut_on" || ! grep -q '"box_name":"LLVMBranchInstructionBox"' "$mut_on" || ! grep -q '"method":"lower_branch"' "$mut_on"; then
+  echo "[FAIL] canonicalize_static_lower_branch_on_off_vm (ON)" >&2; exit 1
+fi
+
+set +e
+HAKO_NYVM_V1_DOWNCONVERT=1 HAKO_DEBUG_NYVM_BRIDGE_DUMP_MUT="$mut_off" \
+  "$ROOT/target/release/nyash" --json-file "$json_path" >/dev/null 2>&1
+set -e || true
+if [ -f "$mut_off" ] && ! grep -q '"type":"ModuleFunction"' "$mut_off"; then
+  echo "[FAIL] canonicalize_static_lower_branch_on_off_vm (OFF)" >&2; exit 1
+fi
+
+echo "[PASS] canonicalize_static_lower_branch_on_off_vm"
+rm -f "$json_path" "$mut_on" "$mut_off"
+exit 0
+
diff --git a/tools/smokes/v2/profiles/quick/core/bridge/canonicalize_static_lower_compare_on_off_vm.sh b/tools/smokes/v2/profiles/quick/core/bridge/canonicalize_static_lower_compare_on_off_vm.sh
new file mode 100644
index 00000000..5e6a4a66
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/bridge/canonicalize_static_lower_compare_on_off_vm.sh
@@ -0,0 +1,42 @@
+#!/bin/bash
+# canonicalize_static_lower_compare_on_off_vm.sh — Verify LLVMCompareInstructionBox.lower_compare rewrite
+
+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
+
+json_path="/tmp/ny_v1_lower_compare_$$.json"
+mut_on="/tmp/ny_v1_lower_compare_on_$$.json"
+mut_off="/tmp/ny_v1_lower_compare_off_$$.json"
+
+cat >"$json_path" <<'JSON'
+{"schema_version":"1.0","functions":[{"name":"main","blocks":[{"id":0,"instructions":[{"op":"mir_call","mir_call":{"callee":{"type":"ModuleFunction","name":"LLVMCompareInstructionBox.lower_compare"},"args":[1,2]}},{"op":"ret"}]}]}]}
+JSON
+
+set +e
+HAKO_NYVM_V1_DOWNCONVERT=1 HAKO_BRIDGE_INJECT_SINGLETON=1 HAKO_DEBUG_NYVM_BRIDGE_DUMP_MUT="$mut_on" \
+  "$ROOT/target/release/nyash" --json-file "$json_path" >/dev/null 2>&1
+set -e || true
+if [ ! -f "$mut_on" ] || ! grep -q '"type":"Method"' "$mut_on" || ! grep -q '"box_name":"LLVMCompareInstructionBox"' "$mut_on" || ! grep -q '"method":"lower_compare"' "$mut_on"; then
+  echo "[FAIL] canonicalize_static_lower_compare_on_off_vm (ON)" >&2; exit 1
+fi
+
+set +e
+HAKO_NYVM_V1_DOWNCONVERT=1 HAKO_DEBUG_NYVM_BRIDGE_DUMP_MUT="$mut_off" \
+  "$ROOT/target/release/nyash" --json-file "$json_path" >/dev/null 2>&1
+set -e || true
+if [ -f "$mut_off" ] && ! grep -q '"type":"ModuleFunction"' "$mut_off"; then
+  echo "[FAIL] canonicalize_static_lower_compare_on_off_vm (OFF)" >&2; exit 1
+fi
+
+echo "[PASS] canonicalize_static_lower_compare_on_off_vm"
+rm -f "$json_path" "$mut_on" "$mut_off"
+exit 0
+
diff --git a/tools/smokes/v2/profiles/quick/core/bridge/canonicalize_static_lower_jump_on_off_vm.sh b/tools/smokes/v2/profiles/quick/core/bridge/canonicalize_static_lower_jump_on_off_vm.sh
new file mode 100644
index 00000000..d2e72496
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/bridge/canonicalize_static_lower_jump_on_off_vm.sh
@@ -0,0 +1,42 @@
+#!/bin/bash
+# canonicalize_static_lower_jump_on_off_vm.sh — Verify LLVMJumpInstructionBox.lower_jump rewrite
+
+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
+
+json_path="/tmp/ny_v1_lower_jump_$$.json"
+mut_on="/tmp/ny_v1_lower_jump_on_$$.json"
+mut_off="/tmp/ny_v1_lower_jump_off_$$.json"
+
+cat >"$json_path" <<'JSON'
+{"schema_version":"1.0","functions":[{"name":"main","blocks":[{"id":0,"instructions":[{"op":"mir_call","mir_call":{"callee":{"type":"ModuleFunction","name":"LLVMJumpInstructionBox.lower_jump"},"args":[1]}},{"op":"ret"}]}]}]}
+JSON
+
+set +e
+HAKO_NYVM_V1_DOWNCONVERT=1 HAKO_BRIDGE_INJECT_SINGLETON=1 HAKO_DEBUG_NYVM_BRIDGE_DUMP_MUT="$mut_on" \
+  "$ROOT/target/release/nyash" --json-file "$json_path" >/dev/null 2>&1
+set -e || true
+if [ ! -f "$mut_on" ] || ! grep -q '"type":"Method"' "$mut_on" || ! grep -q '"box_name":"LLVMJumpInstructionBox"' "$mut_on" || ! grep -q '"method":"lower_jump"' "$mut_on"; then
+  echo "[FAIL] canonicalize_static_lower_jump_on_off_vm (ON)" >&2; exit 1
+fi
+
+set +e
+HAKO_NYVM_V1_DOWNCONVERT=1 HAKO_DEBUG_NYVM_BRIDGE_DUMP_MUT="$mut_off" \
+  "$ROOT/target/release/nyash" --json-file "$json_path" >/dev/null 2>&1
+set -e || true
+if [ -f "$mut_off" ] && ! grep -q '"type":"ModuleFunction"' "$mut_off"; then
+  echo "[FAIL] canonicalize_static_lower_jump_on_off_vm (OFF)" >&2; exit 1
+fi
+
+echo "[PASS] canonicalize_static_lower_jump_on_off_vm"
+rm -f "$json_path" "$mut_on" "$mut_off"
+exit 0
+
diff --git a/tools/smokes/v2/profiles/quick/core/map/map_bad_key_field_vm.sh b/tools/smokes/v2/profiles/quick/core/map/map_bad_key_field_vm.sh
new file mode 100644
index 00000000..1f9f5298
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/map/map_bad_key_field_vm.sh
@@ -0,0 +1,26 @@
+#!/bin/bash
+# map_bad_key_field_vm.sh — Map.getField/ setField with non-string key returns [map/bad-key]
+
+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 "$ROOT/tools/smokes/v2/lib/test_runner.sh"
+require_env || exit 2
+
+code='static box Main { main() { local m=new MapBox(); print(m.getField(123)); m.setField(456, 1); return 0 } }'
+out=$(run_nyash_vm -c "$code")
+if echo "$out" | grep -q "\[map/bad-key\]"; then
+  echo "[PASS] map_bad_key_field_vm"
+  exit 0
+else
+  echo "[FAIL] map_bad_key_field_vm" >&2
+  echo "--- output ---" >&2
+  echo "$out" >&2
+  exit 1
+fi
+