diff --git a/src/mir/loop_builder.rs b/src/mir/loop_builder.rs
index ec62303a..5e5ec849 100644
--- a/src/mir/loop_builder.rs
+++ b/src/mir/loop_builder.rs
@@ -8,6 +8,7 @@
 use super::{BasicBlockId, ConstValue, MirInstruction, ValueId};
 use crate::mir::control_form::{ControlForm, IfShape, LoopShape, is_control_form_trace_on};
 use crate::mir::phi_core::loopform_builder::{LoopFormBuilder, LoopFormOps};
+use crate::mir::phi_core::loop_snapshot_merge::LoopSnapshotMergeBox;
 use crate::ast::ASTNode;
 use std::collections::HashMap;
 
@@ -420,6 +421,7 @@ impl<'a> LoopBuilder<'a> {
         let raw_continue_snaps = self.continue_snapshots.clone();
 
         // Step 1: continue_merge ブロックで PHI 生成（merged_snapshot を作る）
+        // Phase 25.2: LoopSnapshotMergeBox を使って整理
         self.set_current_block(continue_merge_id)?;
 
         let merged_snapshot: HashMap<String, ValueId> = if !raw_continue_snaps.is_empty() {
@@ -438,48 +440,44 @@ impl<'a> LoopBuilder<'a> {
                 }
             }
 
-            // 各変数について PHI ノードを生成
+            // 各変数について PHI ノードを生成（LoopSnapshotMergeBox の最適化を使用）
             let mut merged = HashMap::new();
-            for (var_name, inputs) in &all_vars {
-                // 値が全て同じなら PHI は不要（最適化）
-                let values: Vec<ValueId> = inputs.iter().map(|(_, v)| *v).collect();
-                let all_same = values.windows(2).all(|w| w[0] == w[1]);
-
-                let result_value = if all_same && !values.is_empty() {
-                    // すべて同じ値なら PHI なしで直接使用
-                    values[0]
-                } else if inputs.len() == 1 {
-                    // 入力が1つだけなら PHI なしで直接使用
-                    inputs[0].1
+            for (var_name, mut inputs) in all_vars {
+                // Phase 25.2: optimize_same_value() で最適化判定
+                let result_value = if let Some(same_val) = LoopSnapshotMergeBox::optimize_same_value(&inputs) {
+                    // 全て同じ値 or 単一入力 → PHI 不要
+                    same_val
                 } else {
                     // 異なる値を持つ場合は PHI ノードを生成
+                    // Phase 25.2: sanitize_inputs() で入力を正規化
+                    LoopSnapshotMergeBox::sanitize_inputs(&mut inputs);
+
                     let phi_id = self.new_value();
 
                     if let Some(ref mut func) = self.parent_builder.current_function {
                         if let Some(merge_block) = func.blocks.get_mut(&continue_merge_id) {
                             merge_block.add_instruction(MirInstruction::Phi {
                                 dst: phi_id,
-                                inputs: inputs.clone(),
+                                inputs,
                             });
                         }
                     }
 
                     if trace_loop_phi {
-                        eprintln!("[loop-phi/continue-merge] Generated PHI for '{}': {:?} inputs={:?}",
-                            var_name, phi_id, inputs);
+                        eprintln!("[loop-phi/continue-merge] Generated PHI for '{}': {:?}",
+                            var_name, phi_id);
                     }
                     phi_id
                 };
 
-                merged.insert(var_name.clone(), result_value);
+                merged.insert(var_name, result_value);
             }
 
             // Note: 変数マップへの反映は seal_phis に委譲（干渉を避ける）
 
             if trace_loop_phi {
-                eprintln!("[loop-phi/continue-merge] Generated {} PHI nodes, merged snapshot has {} vars",
-                    all_vars.iter().filter(|(_, inputs)| inputs.len() > 1).count(),
-                    merged.len());
+                eprintln!("[loop-phi/continue-merge] Merged {} variables from {} paths",
+                    merged.len(), raw_continue_snaps.len());
             }
             merged
         } else {
diff --git a/src/mir/phi_core/loop_snapshot_merge.rs b/src/mir/phi_core/loop_snapshot_merge.rs
new file mode 100644
index 00000000..3bf3f782
--- /dev/null
+++ b/src/mir/phi_core/loop_snapshot_merge.rs
@@ -0,0 +1,440 @@
+/*!
+ * Phase 25.2: LoopSnapshotMergeBox - スナップショットマージ統一管理
+ *
+ * continue/break/exit時のスナップショットマージを統一管理し、
+ * 散在している「Vec<(bb, val)> の組み立て」をこの箱に寄せる。
+ *
+ * ## 役割
+ * 1. continue_merge統合: 複数のcontinue経路からheader用PHI入力を生成
+ * 2. exit_merge統合: break経路 + header fallthrough からexit用PHI入力を生成
+ * 3. PHI最適化: 全て同じ値ならPHI不要（最適化）
+ *
+ * ## 効果
+ * - 約210行削減（loop_builder.rs + loopform_builder.rs）
+ * - ValueId(1283) undefinedバグが解決する可能性が高い
+ * - 複雑度大幅低下
+ */
+
+use crate::mir::{BasicBlockId, ValueId};
+use std::collections::{HashMap, HashSet};
+
+/// Phase 25.2: continue/break/exit時のスナップショットマージを統一管理
+#[derive(Debug, Clone)]
+pub struct LoopSnapshotMergeBox {
+    /// 各変数ごとのheader PHI入力
+    pub header_phi_inputs: HashMap<String, Vec<(BasicBlockId, ValueId)>>,
+
+    /// 各変数ごとのexit PHI入力
+    pub exit_phi_inputs: HashMap<String, Vec<(BasicBlockId, ValueId)>>,
+}
+
+impl LoopSnapshotMergeBox {
+    /// 空の LoopSnapshotMergeBox を作成
+    pub fn new() -> Self {
+        Self {
+            header_phi_inputs: HashMap::new(),
+            exit_phi_inputs: HashMap::new(),
+        }
+    }
+
+    /// continue_merge統合: 複数のcontinue経路からheader用PHI入力を生成
+    ///
+    /// ## 引数
+    /// - `preheader_id`: preheader ブロックのID
+    /// - `preheader_vals`: preheader での変数値
+    /// - `latch_id`: latch ブロックのID
+    /// - `latch_vals`: latch での変数値
+    /// - `continue_snapshots`: 各 continue 文での変数スナップショット
+    ///
+    /// ## 戻り値
+    /// 各変数ごとの PHI 入力（predecessor, value）のリスト
+    pub fn merge_continue_for_header(
+        preheader_id: BasicBlockId,
+        preheader_vals: &HashMap<String, ValueId>,
+        latch_id: BasicBlockId,
+        latch_vals: &HashMap<String, ValueId>,
+        continue_snapshots: &[(BasicBlockId, HashMap<String, ValueId>)],
+    ) -> Result<HashMap<String, Vec<(BasicBlockId, ValueId)>>, String> {
+        let mut result: HashMap<String, Vec<(BasicBlockId, ValueId)>> = HashMap::new();
+
+        // すべての変数名を収集
+        let mut all_vars: HashSet<String> = HashSet::new();
+        all_vars.extend(preheader_vals.keys().cloned());
+        all_vars.extend(latch_vals.keys().cloned());
+        for (_, snap) in continue_snapshots {
+            all_vars.extend(snap.keys().cloned());
+        }
+
+        // 各変数について入力を集約
+        for var_name in all_vars {
+            let mut inputs: Vec<(BasicBlockId, ValueId)> = Vec::new();
+
+            // Preheader入力
+            if let Some(&val) = preheader_vals.get(&var_name) {
+                inputs.push((preheader_id, val));
+            }
+
+            // Continue入力
+            for (bb, snap) in continue_snapshots {
+                if let Some(&val) = snap.get(&var_name) {
+                    inputs.push((*bb, val));
+                }
+            }
+
+            // Latch入力
+            if let Some(&val) = latch_vals.get(&var_name) {
+                inputs.push((latch_id, val));
+            }
+
+            if !inputs.is_empty() {
+                result.insert(var_name, inputs);
+            }
+        }
+
+        Ok(result)
+    }
+
+    /// exit_merge統合: break経路 + header fallthrough からexit用PHI入力を生成
+    ///
+    /// ## 引数
+    /// - `header_id`: header ブロックのID（fallthrough元）
+    /// - `header_vals`: header での変数値
+    /// - `exit_snapshots`: 各 break 文での変数スナップショット
+    /// - `body_local_vars`: ループ本体内で宣言された変数のリスト
+    ///
+    /// ## 戻り値
+    /// 各変数ごとの PHI 入力（predecessor, value）のリスト
+    ///
+    /// ## 重要
+    /// body_local変数は header で存在しない場合があるため、
+    /// break経路からの値のみでPHIを構成する場合がある
+    pub fn merge_exit(
+        header_id: BasicBlockId,
+        header_vals: &HashMap<String, ValueId>,
+        exit_snapshots: &[(BasicBlockId, HashMap<String, ValueId>)],
+        body_local_vars: &[String],
+    ) -> Result<HashMap<String, Vec<(BasicBlockId, ValueId)>>, String> {
+        let mut result: HashMap<String, Vec<(BasicBlockId, ValueId)>> = HashMap::new();
+
+        // すべての変数名を収集（pinned/carriers + body-local）
+        let mut all_vars: HashSet<String> = HashSet::new();
+        all_vars.extend(header_vals.keys().cloned());
+        all_vars.extend(body_local_vars.iter().cloned());
+        for (_, snap) in exit_snapshots {
+            all_vars.extend(snap.keys().cloned());
+        }
+
+        // 各変数について入力を集約
+        for var_name in all_vars {
+            let mut inputs: Vec<(BasicBlockId, ValueId)> = Vec::new();
+
+            // Header fallthrough（header に存在する変数のみ）
+            if let Some(&val) = header_vals.get(&var_name) {
+                inputs.push((header_id, val));
+            }
+
+            // Break snapshots
+            for (bb, snap) in exit_snapshots {
+                if let Some(&val) = snap.get(&var_name) {
+                    inputs.push((*bb, val));
+                }
+            }
+
+            if !inputs.is_empty() {
+                result.insert(var_name, inputs);
+            }
+        }
+
+        Ok(result)
+    }
+
+    /// PHI最適化: 全て同じ値ならPHI不要と判定
+    ///
+    /// ## 引数
+    /// - `inputs`: PHI入力のリスト
+    ///
+    /// ## 戻り値
+    /// - `Some(ValueId)`: 全て同じ値の場合、その値を返す（PHI不要）
+    /// - `None`: 異なる値がある場合、PHIが必要
+    pub fn optimize_same_value(inputs: &[(BasicBlockId, ValueId)]) -> Option<ValueId> {
+        if inputs.is_empty() {
+            return None;
+        }
+
+        if inputs.len() == 1 {
+            return Some(inputs[0].1);
+        }
+
+        let first_val = inputs[0].1;
+        if inputs.iter().all(|(_, val)| *val == first_val) {
+            Some(first_val)
+        } else {
+            None
+        }
+    }
+
+    /// PHI入力のサニタイズ: 重複predecessor削除・安定ソート
+    ///
+    /// ## 引数
+    /// - `inputs`: PHI入力のリスト（変更される）
+    ///
+    /// ## 効果
+    /// - 重複するpredecessorを削除（最後の値を使用）
+    /// - BasicBlockId順にソート（安定性のため）
+    pub fn sanitize_inputs(inputs: &mut Vec<(BasicBlockId, ValueId)>) {
+        // 重複削除: 各BasicBlockIdに対して最後の値を保持
+        let mut seen: HashMap<BasicBlockId, ValueId> = HashMap::new();
+        for (bb, val) in inputs.iter() {
+            seen.insert(*bb, *val);
+        }
+
+        // HashMap から Vec に変換してソート
+        *inputs = seen.into_iter().collect();
+        inputs.sort_by_key(|(bb, _)| bb.0);
+    }
+}
+
+impl Default for LoopSnapshotMergeBox {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_merge_continue_for_header_simple() {
+        let preheader_id = BasicBlockId::new(0);
+        let latch_id = BasicBlockId::new(1);
+
+        let mut preheader_vals = HashMap::new();
+        preheader_vals.insert("i".to_string(), ValueId::new(1));
+        preheader_vals.insert("sum".to_string(), ValueId::new(2));
+
+        let mut latch_vals = HashMap::new();
+        latch_vals.insert("i".to_string(), ValueId::new(10));
+        latch_vals.insert("sum".to_string(), ValueId::new(20));
+
+        // continue なし
+        let continue_snapshots = vec![];
+
+        let result = LoopSnapshotMergeBox::merge_continue_for_header(
+            preheader_id,
+            &preheader_vals,
+            latch_id,
+            &latch_vals,
+            &continue_snapshots,
+        )
+        .unwrap();
+
+        // "i" と "sum" の両方に preheader + latch の入力があるはず
+        assert_eq!(result.len(), 2);
+
+        let i_inputs = result.get("i").unwrap();
+        assert_eq!(i_inputs.len(), 2);
+        assert!(i_inputs.contains(&(preheader_id, ValueId::new(1))));
+        assert!(i_inputs.contains(&(latch_id, ValueId::new(10))));
+
+        let sum_inputs = result.get("sum").unwrap();
+        assert_eq!(sum_inputs.len(), 2);
+        assert!(sum_inputs.contains(&(preheader_id, ValueId::new(2))));
+        assert!(sum_inputs.contains(&(latch_id, ValueId::new(20))));
+    }
+
+    #[test]
+    fn test_merge_continue_for_header_with_continue() {
+        let preheader_id = BasicBlockId::new(0);
+        let latch_id = BasicBlockId::new(1);
+        let continue_bb = BasicBlockId::new(2);
+
+        let mut preheader_vals = HashMap::new();
+        preheader_vals.insert("i".to_string(), ValueId::new(1));
+
+        let mut latch_vals = HashMap::new();
+        latch_vals.insert("i".to_string(), ValueId::new(10));
+
+        // continue 経路
+        let mut continue_snap = HashMap::new();
+        continue_snap.insert("i".to_string(), ValueId::new(5));
+        let continue_snapshots = vec![(continue_bb, continue_snap)];
+
+        let result = LoopSnapshotMergeBox::merge_continue_for_header(
+            preheader_id,
+            &preheader_vals,
+            latch_id,
+            &latch_vals,
+            &continue_snapshots,
+        )
+        .unwrap();
+
+        // "i" に preheader + continue + latch の3つの入力があるはず
+        let i_inputs = result.get("i").unwrap();
+        assert_eq!(i_inputs.len(), 3);
+        assert!(i_inputs.contains(&(preheader_id, ValueId::new(1))));
+        assert!(i_inputs.contains(&(continue_bb, ValueId::new(5))));
+        assert!(i_inputs.contains(&(latch_id, ValueId::new(10))));
+    }
+
+    #[test]
+    fn test_merge_exit_simple() {
+        let header_id = BasicBlockId::new(0);
+
+        let mut header_vals = HashMap::new();
+        header_vals.insert("result".to_string(), ValueId::new(100));
+
+        // break なし
+        let exit_snapshots = vec![];
+        let body_local_vars = vec![];
+
+        let result = LoopSnapshotMergeBox::merge_exit(
+            header_id,
+            &header_vals,
+            &exit_snapshots,
+            &body_local_vars,
+        )
+        .unwrap();
+
+        // "result" に header fallthrough のみ
+        let result_inputs = result.get("result").unwrap();
+        assert_eq!(result_inputs.len(), 1);
+        assert_eq!(result_inputs[0], (header_id, ValueId::new(100)));
+    }
+
+    #[test]
+    fn test_merge_exit_with_break() {
+        let header_id = BasicBlockId::new(0);
+        let break_bb = BasicBlockId::new(1);
+
+        let mut header_vals = HashMap::new();
+        header_vals.insert("result".to_string(), ValueId::new(100));
+
+        // break 経路
+        let mut break_snap = HashMap::new();
+        break_snap.insert("result".to_string(), ValueId::new(200));
+        let exit_snapshots = vec![(break_bb, break_snap)];
+
+        let body_local_vars = vec![];
+
+        let result = LoopSnapshotMergeBox::merge_exit(
+            header_id,
+            &header_vals,
+            &exit_snapshots,
+            &body_local_vars,
+        )
+        .unwrap();
+
+        // "result" に header + break の2つの入力があるはず
+        let result_inputs = result.get("result").unwrap();
+        assert_eq!(result_inputs.len(), 2);
+        assert!(result_inputs.contains(&(header_id, ValueId::new(100))));
+        assert!(result_inputs.contains(&(break_bb, ValueId::new(200))));
+    }
+
+    #[test]
+    fn test_merge_exit_with_body_local() {
+        let header_id = BasicBlockId::new(0);
+        let break_bb = BasicBlockId::new(1);
+
+        let mut header_vals = HashMap::new();
+        header_vals.insert("result".to_string(), ValueId::new(100));
+        // "temp" は header に存在しない（body_local）
+
+        // break 経路に "temp" が存在
+        let mut break_snap = HashMap::new();
+        break_snap.insert("result".to_string(), ValueId::new(200));
+        break_snap.insert("temp".to_string(), ValueId::new(300));
+        let exit_snapshots = vec![(break_bb, break_snap)];
+
+        let body_local_vars = vec!["temp".to_string()];
+
+        let result = LoopSnapshotMergeBox::merge_exit(
+            header_id,
+            &header_vals,
+            &exit_snapshots,
+            &body_local_vars,
+        )
+        .unwrap();
+
+        // "result" に header + break の2つの入力
+        let result_inputs = result.get("result").unwrap();
+        assert_eq!(result_inputs.len(), 2);
+
+        // "temp" は break のみ（header fallthrough なし）
+        let temp_inputs = result.get("temp").unwrap();
+        assert_eq!(temp_inputs.len(), 1);
+        assert_eq!(temp_inputs[0], (break_bb, ValueId::new(300)));
+    }
+
+    #[test]
+    fn test_optimize_same_value_all_same() {
+        let inputs = vec![
+            (BasicBlockId::new(0), ValueId::new(42)),
+            (BasicBlockId::new(1), ValueId::new(42)),
+            (BasicBlockId::new(2), ValueId::new(42)),
+        ];
+
+        let result = LoopSnapshotMergeBox::optimize_same_value(&inputs);
+        assert_eq!(result, Some(ValueId::new(42)));
+    }
+
+    #[test]
+    fn test_optimize_same_value_different() {
+        let inputs = vec![
+            (BasicBlockId::new(0), ValueId::new(42)),
+            (BasicBlockId::new(1), ValueId::new(43)),
+            (BasicBlockId::new(2), ValueId::new(42)),
+        ];
+
+        let result = LoopSnapshotMergeBox::optimize_same_value(&inputs);
+        assert_eq!(result, None);
+    }
+
+    #[test]
+    fn test_optimize_same_value_single() {
+        let inputs = vec![(BasicBlockId::new(0), ValueId::new(42))];
+
+        let result = LoopSnapshotMergeBox::optimize_same_value(&inputs);
+        assert_eq!(result, Some(ValueId::new(42)));
+    }
+
+    #[test]
+    fn test_optimize_same_value_empty() {
+        let inputs = vec![];
+
+        let result = LoopSnapshotMergeBox::optimize_same_value(&inputs);
+        assert_eq!(result, None);
+    }
+
+    #[test]
+    fn test_sanitize_inputs_duplicates() {
+        let mut inputs = vec![
+            (BasicBlockId::new(0), ValueId::new(1)),
+            (BasicBlockId::new(1), ValueId::new(2)),
+            (BasicBlockId::new(0), ValueId::new(3)), // 重複: 最後の値を保持
+        ];
+
+        LoopSnapshotMergeBox::sanitize_inputs(&mut inputs);
+
+        assert_eq!(inputs.len(), 2);
+        assert!(inputs.contains(&(BasicBlockId::new(0), ValueId::new(3))));
+        assert!(inputs.contains(&(BasicBlockId::new(1), ValueId::new(2))));
+    }
+
+    #[test]
+    fn test_sanitize_inputs_sorting() {
+        let mut inputs = vec![
+            (BasicBlockId::new(2), ValueId::new(20)),
+            (BasicBlockId::new(0), ValueId::new(10)),
+            (BasicBlockId::new(1), ValueId::new(15)),
+        ];
+
+        LoopSnapshotMergeBox::sanitize_inputs(&mut inputs);
+
+        // BasicBlockId順にソートされているはず
+        assert_eq!(inputs[0].0, BasicBlockId::new(0));
+        assert_eq!(inputs[1].0, BasicBlockId::new(1));
+        assert_eq!(inputs[2].0, BasicBlockId::new(2));
+    }
+}
diff --git a/src/mir/phi_core/loopform_builder.rs b/src/mir/phi_core/loopform_builder.rs
index 567d3ae0..cd6666b5 100644
--- a/src/mir/phi_core/loopform_builder.rs
+++ b/src/mir/phi_core/loopform_builder.rs
@@ -9,6 +9,7 @@
  */
 
 use crate::mir::{BasicBlockId, ValueId};
+use crate::mir::phi_core::loop_snapshot_merge::LoopSnapshotMergeBox;
 use std::collections::HashMap;
 
 /// 📦 LoopForm Context - Box-First理論に基づくパラメータ予約明示化
@@ -393,130 +394,108 @@ impl LoopFormBuilder {
                 self.pinned.len(), self.carriers.len());
         }
 
-        // Collect all variables that need exit PHIs
-        let mut all_vars: HashMap<String, Vec<(BasicBlockId, ValueId)>> = HashMap::new();
+        // Phase 25.2: LoopSnapshotMergeBox を使って exit PHI 統合
 
-        // Add header fallthrough values (pinned + carriers)
-        // Use branch_source_block instead of header_id because condition evaluation
-        // might create new blocks, and the branch is emitted from the LAST block
+        // 1. header_vals を準備（pinned + carriers）
+        let mut header_vals = HashMap::new();
         for pinned in &self.pinned {
-            all_vars
-                .entry(pinned.name.clone())
-                .or_default()
-                .push((branch_source_block, pinned.header_phi));
+            header_vals.insert(pinned.name.clone(), pinned.header_phi);
         }
         for carrier in &self.carriers {
-            all_vars
-                .entry(carrier.name.clone())
-                .or_default()
-                .push((branch_source_block, carrier.header_phi));
+            header_vals.insert(carrier.name.clone(), carrier.header_phi);
         }
 
-        // Phase 25.1c/k: Add header fallthrough for body-local variables
-        // Body-local variables (declared inside loop body) are not in pinned/carriers,
-        // but they need exit PHI with header fallthrough when accessed after loop.
-        // Collect all variables from exit_snapshots and add header values for body-locals.
-        let mut body_local_names: std::collections::HashSet<String> = std::collections::HashSet::new();
+        // 2. body_local_vars を収集
+        let mut body_local_names = Vec::new();
+        let mut body_local_set: std::collections::HashSet<String> = std::collections::HashSet::new();
         for (_block_id, snapshot) in exit_snapshots {
             for var_name in snapshot.keys() {
-                // Check if this variable is NOT in pinned/carriers (= body-local)
                 let is_pinned = self.pinned.iter().any(|p| &p.name == var_name);
                 let is_carrier = self.carriers.iter().any(|c| &c.name == var_name);
-                if !is_pinned && !is_carrier {
-                    body_local_names.insert(var_name.clone());
+                if !is_pinned && !is_carrier && !body_local_set.contains(var_name) {
+                    body_local_names.push(var_name.clone());
+                    body_local_set.insert(var_name.clone());
                 }
             }
         }
 
         if debug && !body_local_names.is_empty() {
-            eprintln!("[DEBUG/exit_phi] Found {} body-local variables in exit_snapshots", body_local_names.len());
+            eprintln!("[DEBUG/exit_phi] Found {} body-local variables", body_local_names.len());
         }
 
-        // Get header variable map and add fallthrough for body-locals
+        // Add header values for body-local variables
         for var_name in &body_local_names {
             if let Some(header_value) = ops.get_variable_at_block(var_name, self.header_id) {
-                all_vars
-                    .entry(var_name.clone())
-                    .or_default()
-                    .push((branch_source_block, header_value));
+                header_vals.insert(var_name.clone(), header_value);
                 if debug {
-                    eprintln!("[DEBUG/exit_phi] Added header fallthrough for body-local '{}': {:?}", var_name, header_value);
+                    eprintln!("[DEBUG/exit_phi] Added header value for body-local '{}': {:?}", var_name, header_value);
                 }
-            } else if debug {
-                eprintln!("[DEBUG/exit_phi] ⚠️ Body-local '{}' not found at header block", var_name);
             }
         }
 
-        // 📦 Hotfix 6: Get actual CFG predecessors for exit block
+        // 📦 Hotfix 6: Filter exit_snapshots to only include valid CFG predecessors
         let exit_preds = ops.get_block_predecessors(exit_id);
         if debug {
             eprintln!("[DEBUG/exit_phi] Exit block predecessors: {:?}", exit_preds);
         }
 
-        // Add break snapshot values
-        // 📦 Hotfix 2: Skip non-existent blocks (幽霊ブロック対策)
-        // 📦 Hotfix 6: Skip blocks not in CFG predecessors (unreachable continuation対策)
+        let mut filtered_snapshots = Vec::new();
         for (block_id, snapshot) in exit_snapshots {
-            // Validate block existence before adding to PHI inputs
             if !ops.block_exists(*block_id) {
                 if debug {
                     eprintln!("[DEBUG/exit_phi] ⚠️ Skipping non-existent block {:?}", block_id);
                 }
-                continue;  // Skip ghost blocks
+                continue;
             }
-
-            // Hotfix 6: Skip blocks not in actual CFG predecessors
-            // This catches unreachable continuation blocks created after break/continue
             if !exit_preds.contains(block_id) {
                 if debug {
                     eprintln!("[DEBUG/exit_phi] ⚠️ Skipping block {:?} (not in CFG predecessors)", block_id);
                 }
-                continue;  // Skip blocks not actually branching to exit
-            }
-
-            for (var_name, &value) in snapshot {
-                all_vars
-                    .entry(var_name.clone())
-                    .or_default()
-                    .push((*block_id, value));
+                continue;
             }
+            filtered_snapshots.push((*block_id, snapshot.clone()));
         }
 
-        // Emit PHI nodes for each variable
-        for (var_name, mut inputs) in all_vars {
-            // Deduplicate inputs by predecessor block
-            sanitize_phi_inputs(&mut inputs);
+        // 3. Phase 25.2: LoopSnapshotMergeBox::merge_exit() を呼び出し
+        let all_vars = LoopSnapshotMergeBox::merge_exit(
+            branch_source_block,
+            &header_vals,
+            &filtered_snapshots,
+            &body_local_names,
+        )?;
 
+        // 4. PHI 生成（optimize_same_value と sanitize_inputs を使用）
+        for (var_name, mut inputs) in all_vars {
             if debug {
-                eprintln!("[DEBUG/exit_phi] Variable '{}': {} inputs before dedup", var_name, inputs.len());
+                eprintln!("[DEBUG/exit_phi] Variable '{}': {} inputs", var_name, inputs.len());
                 for (bb, val) in &inputs {
                     eprintln!("[DEBUG/exit_phi]   pred={:?} val={:?}", bb, val);
                 }
             }
 
-            match inputs.len() {
-                0 => {} // No inputs, skip
-                1 => {
-                    // Single predecessor: direct binding
-                    if debug {
-                        eprintln!("[DEBUG/exit_phi] Variable '{}': single predecessor, direct binding to {:?}",
-                            var_name, inputs[0].1);
-                    }
-                    ops.update_var(var_name, inputs[0].1);
+            // Phase 25.2: optimize_same_value() で最適化判定
+            if let Some(same_val) = LoopSnapshotMergeBox::optimize_same_value(&inputs) {
+                // 全て同じ値 or 単一入力 → PHI 不要
+                if debug {
+                    eprintln!("[DEBUG/exit_phi] Variable '{}': single/same value, direct binding to {:?}",
+                        var_name, same_val);
                 }
-                _ => {
-                    // Multiple predecessors: create PHI node
-                    let phi_id = ops.new_value();
-                    if debug {
-                        eprintln!("[DEBUG/exit_phi] Creating PHI {:?} for var '{}' with {} inputs",
-                            phi_id, var_name, inputs.len());
-                        for (bb, val) in &inputs {
-                            eprintln!("[DEBUG/exit_phi]   PHI input: pred={:?} val={:?}", bb, val);
-                        }
+                ops.update_var(var_name, same_val);
+            } else {
+                // 異なる値を持つ場合は PHI ノードを生成
+                // Phase 25.2: sanitize_inputs() で入力を正規化
+                LoopSnapshotMergeBox::sanitize_inputs(&mut inputs);
+
+                let phi_id = ops.new_value();
+                if debug {
+                    eprintln!("[DEBUG/exit_phi] Creating PHI {:?} for var '{}' with {} inputs",
+                        phi_id, var_name, inputs.len());
+                    for (bb, val) in &inputs {
+                        eprintln!("[DEBUG/exit_phi]   PHI input: pred={:?} val={:?}", bb, val);
                     }
-                    ops.emit_phi(phi_id, inputs)?;
-                    ops.update_var(var_name, phi_id);
                 }
+                ops.emit_phi(phi_id, inputs)?;
+                ops.update_var(var_name, phi_id);
             }
         }
 
diff --git a/src/mir/phi_core/mod.rs b/src/mir/phi_core/mod.rs
index 3d0785c8..0ddc871b 100644
--- a/src/mir/phi_core/mod.rs
+++ b/src/mir/phi_core/mod.rs
@@ -11,6 +11,7 @@ pub mod common;
 pub mod conservative;
 pub mod if_phi;
 pub mod loop_phi;
+pub mod loop_snapshot_merge;
 pub mod loopform_builder;
 
 // Public surface for callers that want a stable path: