diff --git a/src/runner/json_v0_bridge/README.md b/src/runner/json_v0_bridge/README.md
index bdf50903..8efc82d6 100644
--- a/src/runner/json_v0_bridge/README.md
+++ b/src/runner/json_v0_bridge/README.md
@@ -7,3 +7,26 @@
   3. break / continue / exit の snapshot を `LoopSnapshotMergeBox` に渡して canonical continue_merge/backedge を構築する。
 
 LoopForm/PHI の意味論を変更したい場合は、`loopform_builder.rs` / `loop_snapshot_merge.rs` を更新すること。`loop_.rs` 内での ad-hoc な PHI 実装は禁止。
+
+### Rust パーサー経路との関係
+
+- 共通 SSOT:
+  - 制御フロー: `src/mir/ssot/cf_common.rs`（branch/jump/compare/phi 挿入）
+  - 算術・比較: `src/mir/ssot/binop_lower.rs`（二項演算 lowering）
+  - ループ形: `src/mir/ssot/loop_common.rs` ＋ `LoopFormBuilder`
+- フロントエンド（入口）:
+  - Rust パーサー経路: `parser/*` + `mir/builder/*` が AST から MIR を構築する。
+  - JSON v0 経路: このディレクトリの lowering 群が `ProgramV0` から MIR を構築する。
+  - どちらも「PHI/LoopForm/CF の意味論」は mir/ssot 側に委譲し、入口側では構造準備のみに留める。
+
+### Bridge 固有ロジックの箱化方針
+
+- JSON v0 → MIR の際に必要な「ブリッジ固有」の処理は、入口ファイルにベタ書きしない:
+  - `hostbridge` / `env` / `me` ダミーなどの特別な変数解決
+  - Stage‑1/Stage‑B の try-result モードに合わせた throw ルーティング
+- これらは `lowering/globals.rs` / `lowering/throw_ctx.rs` などの小さなモジュールに閉じ込め、
+  - JSON v0 経路
+  - 将来の Rust パーサー self‑host 経路
+ から同じ箱を使い回せるようにする。
+
+このディレクトリでは「JSON → MIR 変換」と「最低限のブリッジ設定」だけを行い、その先の最適化や意味論変更は `mir/*`（optimizer/pass, LoopForm, VM/LLVM）側に任せる。
diff --git a/src/runner/json_v0_bridge/lowering.rs b/src/runner/json_v0_bridge/lowering.rs
index 46a477ec..38cd6b0c 100644
--- a/src/runner/json_v0_bridge/lowering.rs
+++ b/src/runner/json_v0_bridge/lowering.rs
@@ -13,11 +13,13 @@ mod merge;
 use merge::{merge_var_maps, new_block};
 // Feature splits (gradual extraction)
 pub(super) mod expr;
+pub(super) mod globals;
 pub(super) mod if_else;
 pub(super) mod loop_;
 pub(super) mod match_expr; // placeholder (not wired)
 pub(super) mod ternary; // placeholder (not wired)
 pub(super) mod throw_ctx;
+pub(super) mod throw_lower;
 pub(super) mod try_catch; // thread-local ctx for Result-mode throw routing
 
 #[derive(Clone, Copy)]
diff --git a/src/runner/json_v0_bridge/lowering/expr.rs b/src/runner/json_v0_bridge/lowering/expr.rs
index 9bd1d9c6..54403c5e 100644
--- a/src/runner/json_v0_bridge/lowering/expr.rs
+++ b/src/runner/json_v0_bridge/lowering/expr.rs
@@ -1,7 +1,9 @@
 use super::match_expr;
 use super::merge::new_block;
+use super::globals::resolve_bridge_global;
 use super::ternary;
 use super::BridgeEnv;
+use super::throw_lower::lower_throw;
 use crate::mir::{BasicBlockId, ConstValue, EffectMask, MirFunction, MirInstruction, ValueId};
 use crate::ast::Span;
 use std::collections::BTreeMap;
@@ -50,101 +52,15 @@ impl<'a> VarScope for MapVars<'a> {
         if let Some(&vid) = self.vars.get(name) {
             return Ok(Some(vid));
         }
-        // Phase 21.8: Check using-imported modules/boxes
-        if let Some(box_type) = env.imports.get(name) {
-            let dst = f.next_value_id();
-            if let Some(bb) = f.get_block_mut(cur_bb) {
-                // Treat as static box reference - create a const string representing the box type
-                bb.add_instruction(MirInstruction::Const {
-                    dst,
-                    value: ConstValue::String(box_type.clone()),
-                });
-            }
-            // Cache the resolution for subsequent uses
-            self.vars.insert(name.to_string(), dst);
-            return Ok(Some(dst));
-        }
-        // Phase 25.1a: Treat `hostbridge` as a well-known global for bridge lowering.
-        // The actual extern dispatch is handled at runtime; here we only need a stable
-        // placeholder value so that Program(JSON) containing hostbridge.extern_invoke(...)
-        // can be lowered without "undefined variable" errors.
-        if name == "hostbridge" {
-            let dst = f.next_value_id();
-            if let Some(bb) = f.get_block_mut(cur_bb) {
-                bb.add_instruction(MirInstruction::Const {
-                    dst,
-                    value: ConstValue::String("hostbridge".into()),
-                });
-            }
-            self.vars.insert(name.to_string(), dst);
-            return Ok(Some(dst));
-        }
-        // Phase 25.1b: Treat `env` as a well-known global for env.box_introspect.* etc.
-        // Similar to hostbridge, we need a placeholder value for the nested method pattern.
-        if name == "env" {
-            let dst = f.next_value_id();
-            if let Some(bb) = f.get_block_mut(cur_bb) {
-                bb.add_instruction(MirInstruction::Const {
-                    dst,
-                    value: ConstValue::String("env".into()),
-                });
-            }
-            self.vars.insert(name.to_string(), dst);
-            return Ok(Some(dst));
-        }
-        if name == "me" {
-            if env.allow_me_dummy {
-                let dst = f.next_value_id();
-                if let Some(bb) = f.get_block_mut(cur_bb) {
-                    bb.add_instruction(MirInstruction::NewBox {
-                        dst,
-                        box_type: env.me_class.clone(),
-                        args: vec![],
-                    });
-                }
-                self.vars.insert(name.to_string(), dst);
-                Ok(Some(dst))
-            } else {
-                Err("undefined 'me' outside box context (set NYASH_BRIDGE_ME_DUMMY=1 to inject placeholder)".into())
-            }
-        } else {
-            Ok(None)
-        }
-    }
-}
 
-fn lower_throw(
-    env: &BridgeEnv,
-    f: &mut MirFunction,
-    cur_bb: BasicBlockId,
-    exception_value: ValueId,
-) -> (ValueId, BasicBlockId) {
-    // Result-mode try context active: route to current catch via Jump and record incoming
-    if env.try_result_mode && super::throw_ctx::is_active() {
-        if crate::config::env::cli_verbose() {
-            eprintln!("[Bridge] lower_throw: routing to catch (Result-mode)");
+        // Bridge 固有のグローバル解決（imports/hostbridge/env/me dummy）は専用モジュールに委譲
+        if let Some(vid) =
+            resolve_bridge_global(name, env, f, cur_bb, self.vars)?
+        {
+            return Ok(Some(vid));
         }
-        let _ = super::throw_ctx::record_throw(f, cur_bb, exception_value);
-        return (exception_value, cur_bb);
-    }
-    // Legacy path: emit MIR Throw (if enabled) or degrade to const 0
-    if env.throw_enabled {
-        if let Some(bb) = f.get_block_mut(cur_bb) {
-            bb.set_terminator(MirInstruction::Throw {
-                exception: exception_value,
-                effects: EffectMask::PANIC,
-            });
-        }
-        (exception_value, cur_bb)
-    } else {
-        let dst = f.next_value_id();
-        if let Some(bb) = f.get_block_mut(cur_bb) {
-            bb.add_instruction(MirInstruction::Const {
-                dst,
-                value: ConstValue::Integer(0),
-            });
-        }
-        (dst, cur_bb)
+
+        Ok(None)
     }
 }
 
diff --git a/src/runner/json_v0_bridge/lowering/globals.rs b/src/runner/json_v0_bridge/lowering/globals.rs
new file mode 100644
index 00000000..a325776d
--- /dev/null
+++ b/src/runner/json_v0_bridge/lowering/globals.rs
@@ -0,0 +1,77 @@
+use super::BridgeEnv;
+use crate::mir::{BasicBlockId, ConstValue, MirFunction, MirInstruction, ValueId};
+use std::collections::BTreeMap;
+
+/// Resolve Bridge-specific globals (imports/hostbridge/env/me dummy).
+///
+/// - `vars`: current local/global value map (updated when a new value is synthesized)
+/// - returns Some(ValueId) when the name is handled here, or Ok(None) to let callers
+///   fallback to "undefined variable" handling.
+pub(super) fn resolve_bridge_global(
+    name: &str,
+    env: &BridgeEnv,
+    f: &mut MirFunction,
+    cur_bb: BasicBlockId,
+    vars: &mut BTreeMap<String, ValueId>,
+) -> Result<Option<ValueId>, String> {
+    // Phase 21.8: using-imported modules/boxes
+    if let Some(box_type) = env.imports.get(name) {
+        let dst = f.next_value_id();
+        if let Some(bb) = f.get_block_mut(cur_bb) {
+            bb.add_instruction(MirInstruction::Const {
+                dst,
+                value: ConstValue::String(box_type.clone()),
+            });
+        }
+        vars.insert(name.to_string(), dst);
+        return Ok(Some(dst));
+    }
+
+    // Phase 25.1a: well-known bridge globals
+    if name == "hostbridge" {
+        let dst = f.next_value_id();
+        if let Some(bb) = f.get_block_mut(cur_bb) {
+            bb.add_instruction(MirInstruction::Const {
+                dst,
+                value: ConstValue::String("hostbridge".into()),
+            });
+        }
+        vars.insert(name.to_string(), dst);
+        return Ok(Some(dst));
+    }
+
+    if name == "env" {
+        let dst = f.next_value_id();
+        if let Some(bb) = f.get_block_mut(cur_bb) {
+            bb.add_instruction(MirInstruction::Const {
+                dst,
+                value: ConstValue::String("env".into()),
+            });
+        }
+        vars.insert(name.to_string(), dst);
+        return Ok(Some(dst));
+    }
+
+    if name == "me" {
+        if env.allow_me_dummy {
+            let dst = f.next_value_id();
+            if let Some(bb) = f.get_block_mut(cur_bb) {
+                bb.add_instruction(MirInstruction::NewBox {
+                    dst,
+                    box_type: env.me_class.clone(),
+                    args: vec![],
+                });
+            }
+            vars.insert(name.to_string(), dst);
+            Ok(Some(dst))
+        } else {
+            Err(
+                "undefined 'me' outside box context (set NYASH_BRIDGE_ME_DUMMY=1 to inject placeholder)"
+                    .into(),
+            )
+        }
+    } else {
+        Ok(None)
+    }
+}
+
diff --git a/src/runner/json_v0_bridge/lowering/throw_lower.rs b/src/runner/json_v0_bridge/lowering/throw_lower.rs
new file mode 100644
index 00000000..79321ae8
--- /dev/null
+++ b/src/runner/json_v0_bridge/lowering/throw_lower.rs
@@ -0,0 +1,45 @@
+use super::BridgeEnv;
+use crate::mir::{BasicBlockId, ConstValue, EffectMask, MirFunction, MirInstruction, ValueId};
+
+/// Lower a throw expression/value according to BridgeEnv and throw_ctx.
+///
+/// - Result-mode try contextが有効なら、catch ブロックへ jump しつつ incoming に記録する。
+/// - それ以外では:
+///   - throw_enabled=1 のとき MIR Throw を発行
+///   - そうでなければ `const 0` にフォールバック
+pub(super) fn lower_throw(
+    env: &BridgeEnv,
+    f: &mut MirFunction,
+    cur_bb: BasicBlockId,
+    exception_value: ValueId,
+) -> (ValueId, BasicBlockId) {
+    // Result-mode try context active: route to current catch via Jump and record incoming
+    if env.try_result_mode && super::throw_ctx::is_active() {
+        if crate::config::env::cli_verbose() {
+            eprintln!("[Bridge] lower_throw: routing to catch (Result-mode)");
+        }
+        let _ = super::throw_ctx::record_throw(f, cur_bb, exception_value);
+        return (exception_value, cur_bb);
+    }
+
+    // Legacy path: emit MIR Throw (if enabled) or degrade to const 0
+    if env.throw_enabled {
+        if let Some(bb) = f.get_block_mut(cur_bb) {
+            bb.set_terminator(MirInstruction::Throw {
+                exception: exception_value,
+                effects: EffectMask::PANIC,
+            });
+        }
+        (exception_value, cur_bb)
+    } else {
+        let dst = f.next_value_id();
+        if let Some(bb) = f.get_block_mut(cur_bb) {
+            bb.add_instruction(MirInstruction::Const {
+                dst,
+                value: ConstValue::Integer(0),
+            });
+        }
+        (dst, cur_bb)
+    }
+}
+