diff --git a/docs/private b/docs/private
index 81ec67f7..ccb716eb 160000
--- a/docs/private
+++ b/docs/private
@@ -1 +1 @@
-Subproject commit 81ec67f7757a3798bf5262a17a7c4c6a483ac56c
+Subproject commit ccb716eb04df47e79015ad98c587a401ace25828
diff --git a/src/mir/join_ir/lowering/mod.rs b/src/mir/join_ir/lowering/mod.rs
index 3ce488e6..4e6d4fd5 100644
--- a/src/mir/join_ir/lowering/mod.rs
+++ b/src/mir/join_ir/lowering/mod.rs
@@ -49,7 +49,10 @@ use crate::mir::{BasicBlockId, MirFunction};
 /// Phase 33-3: Try to lower if/else to JoinIR Select instruction
 ///
 /// Scope:
-/// - Only applies to functions matching "IfSelectTest.*"
+/// - Only applies to whitelisted functions:
+///   - IfSelectTest.* (Phase 33-2/33-3)
+///   - JsonShapeParser._read_value_from_pair/1 (Phase 33-4 Stage-1)
+///   - Stage1JsonScannerBox.value_start_after_key_pos/2 (Phase 33-4 Stage-B)
 /// - Requires NYASH_JOINIR_IF_SELECT=1 environment variable
 /// - Falls back to traditional if_phi on pattern mismatch
 ///
@@ -64,11 +67,15 @@ pub fn try_lower_if_to_joinir(
         return None;
     }
 
-    // 関数名で制限（IfSelectTest.* のみ）
-    if !func.signature.name.starts_with("IfSelectTest.") {
+    // Phase 33-4: 関数名ガード拡張（IfSelectTest + Stage-1/Stage-B 候補）
+    let is_allowed = func.signature.name.starts_with("IfSelectTest.")
+        || func.signature.name == "JsonShapeParser._read_value_from_pair/1"
+        || func.signature.name == "Stage1JsonScannerBox.value_start_after_key_pos/2";
+
+    if !is_allowed {
         if debug {
             eprintln!(
-                "[try_lower_if_to_joinir] skipping non-test function: {}",
+                "[try_lower_if_to_joinir] skipping non-allowed function: {}",
                 func.signature.name
             );
         }