diff --git a/src/mir/loop_builder/if_lowering.rs b/src/mir/loop_builder/if_lowering.rs
index dba0179e..b887f609 100644
--- a/src/mir/loop_builder/if_lowering.rs
+++ b/src/mir/loop_builder/if_lowering.rs
@@ -253,13 +253,12 @@ impl<'a> LoopBuilder<'a> {
         if !joinir_success {
             // Phase 26-E: PhiBuilderBox SSOT統合（If PHI生成）
             // Legacy: merge_modified_with_control() → New: PhiBuilderBox::generate_phis()
+            // Phase 61-6.1: set_if_context削除、直接IfPhiContextを生成
             let mut phi_builder = crate::mir::phi_core::phi_builder_box::PhiBuilderBox::new();
-
-            // Phase 26-F-3: ループ内if-mergeコンテキスト設定（ChatGPT設計）
-            phi_builder.set_if_context(
-                true, // in_loop_body = true
-                carrier_names.clone(),
-            );
+            phi_builder.if_context = Some(crate::mir::phi_core::phi_builder_box::IfPhiContext {
+                in_loop_body: true,
+                loop_carrier_names: carrier_names.clone(),
+            });
 
             // Phase 35-5: if_body_local_merge.rs削除、ロジックはPhiBuilderBox内に統合
             let post_snapshots = if let Some(ref else_map) = else_var_map_end_opt {
diff --git a/src/mir/phi_core/phi_builder_box.rs b/src/mir/phi_core/phi_builder_box.rs
index f167e8b1..7166bd3c 100644
--- a/src/mir/phi_core/phi_builder_box.rs
+++ b/src/mir/phi_core/phi_builder_box.rs
@@ -20,7 +20,7 @@
 //! # Phase 36 Responsibility Classification
 //!
 //! ## Loop-only methods (if-in-loop PHI)
-//! - `set_if_context()`: Set loop context for if-in-loop PHI generation
+//! - (Phase 61-6.1: set_if_context削除、if_context直接代入に)
 //!
 //! ## If-only methods (Phase 37 target)
 //! - `generate_if_phis()`: Generate If PHI nodes
@@ -72,7 +72,8 @@ use std::collections::BTreeMap;
 /// - **ピュア関数的**: 入力 → PHI生成 → 出力（副作用最小化）
 pub struct PhiBuilderBox {
     /// If PHI生成時のコンテキスト（将来拡張用）
-    if_context: Option<IfPhiContext>,
+    /// Phase 61-6.1: pub化（set_if_context削除、直接代入可能に）
+    pub if_context: Option<IfPhiContext>,
     // Phase 30: loop_context 削除（完全未使用、将来 JoinIR で代替予定）
 }
 
@@ -114,42 +115,16 @@ impl PhiBuilderBox {
         Self { if_context: None }
     }
 
-    /// Phase 26-F-3: ループ内if-mergeコンテキストを設定
-    ///
-    /// # Responsibility: Loop-only (if-in-loop PHI)
-    ///
-    /// This method is ONLY called from loop_builder.rs for if-in-loop PHI generation.
-    /// It sets the loop context (carrier variable names) for proper PHI generation
-    /// in "片腕のみの変数" cases (e.g., `if i >= n { break }`).
-    ///
-    /// ## Phase 36 Scope
-    /// - Called via loop_builder.rs directly (no wrapper needed)
-    /// - Minimal indirection for performance
-    ///
-    /// ## Phase 37+ Consideration
-    /// - May be internalized when loop-in-loop PHI is refactored
-    /// - Consider merging with IfPhiContext initialization
-    ///
-    /// # Arguments
-    /// - `in_loop_body`: ループbody内のif-mergeか
-    /// - `loop_carrier_names`: ループキャリア変数名（Pinned + Carrier）
-    ///
-    /// # Usage (LoopBuilder側で呼ぶ)
-    /// ```ignore
-    /// let mut phi_builder = PhiBuilderBox::new();
-    /// phi_builder.set_if_context(true, carrier_names_set);
-    /// phi_builder.generate_phis(...);
-    /// ```
-    pub fn set_if_context(
-        &mut self,
-        in_loop_body: bool,
-        loop_carrier_names: std::collections::BTreeSet<String>,
-    ) {
-        self.if_context = Some(IfPhiContext {
-            in_loop_body,
-            loop_carrier_names,
-        });
-    }
+    // Phase 61-6.1: set_if_context() 削除（薄いラッパー）
+    // 呼び出し側（loop_builder/if_lowering.rs）で直接 IfPhiContext を生成
+    //
+    // Before:
+    //   phi_builder.set_if_context(true, carrier_names.clone());
+    // After:
+    //   phi_builder.if_context = Some(IfPhiContext {
+    //       in_loop_body: true,
+    //       loop_carrier_names: carrier_names.clone(),
+    //   });
 
     // Phase 26-F-2: set_body_local_filter() 削除
     // Phase 35-5: if_body_local_merge.rs削除、ロジックをcompute_modified_names_if()内に直接実装