diff --git a/src/backend/mir_interpreter/exec.rs b/src/backend/mir_interpreter/exec.rs
index 8b130dc6..35cb6480 100644
--- a/src/backend/mir_interpreter/exec.rs
+++ b/src/backend/mir_interpreter/exec.rs
@@ -172,7 +172,7 @@ impl MirInterpreter {
             self.last_block = Some(block.id);
             self.last_inst_index = Some(idx);
             self.last_inst = Some(inst.clone());
-            if let MirInstruction::Phi { dst, inputs } = inst {
+            if let MirInstruction::Phi { dst, inputs, .. } = inst {
                 let dst_id = *dst;
                 if trace_phi {
                     let in_preds: Vec<_> = inputs.iter().map(|(bb, _)| *bb).collect();
diff --git a/src/mir/basic_block.rs b/src/mir/basic_block.rs
index 10d1e339..d11931b9 100644
--- a/src/mir/basic_block.rs
+++ b/src/mir/basic_block.rs
@@ -324,7 +324,7 @@ impl BasicBlock {
         incoming: (BasicBlockId, ValueId),
     ) -> Result<(), String> {
         for inst in &mut self.instructions {
-            if let MirInstruction::Phi { dst, inputs } = inst {
+            if let MirInstruction::Phi { dst, inputs, .. } = inst {
                 if *dst == phi_dst {
                     inputs.push(incoming);
                     return Ok(());
@@ -580,6 +580,7 @@ mod tests {
         let phi_inst = MirInstruction::Phi {
             dst: ValueId::new(0),
             inputs: vec![(BasicBlockId::new(1), ValueId::new(1))],
+            type_hint: None, // Phase 63-6: Test code, no type hint
         };
         bb.add_instruction(phi_inst);
 
diff --git a/src/mir/builder.rs b/src/mir/builder.rs
index 0286faca..ae9953d9 100644
--- a/src/mir/builder.rs
+++ b/src/mir/builder.rs
@@ -604,7 +604,7 @@ impl MirBuilder {
             .map(|f| f.signature.name.clone());
         let _dbg_region_id = self.debug_current_region_id();
         // P0: PHI の軽量補強と観測は、関数ブロック取得前に実施して借用競合を避ける
-        if let MirInstruction::Phi { dst, inputs } = &instruction {
+        if let MirInstruction::Phi { dst, inputs, .. } = &instruction {
             origin::phi::propagate_phi_meta(self, *dst, inputs);
             observe::ssa::emit_phi(self, *dst, inputs);
         }
@@ -815,7 +815,7 @@ impl MirBuilder {
             if let Some(block_data) = function.get_block_mut(block) {
                 // Find PHI instruction with matching dst
                 for inst in &mut block_data.instructions {
-                    if let MirInstruction::Phi { dst, inputs } = inst {
+                    if let MirInstruction::Phi { dst, inputs, .. } = inst {
                         if *dst == phi_id {
                             *inputs = new_inputs;
                             return Ok(());
diff --git a/src/mir/builder/control_flow.rs b/src/mir/builder/control_flow.rs
index 5b55b058..75873efb 100644
--- a/src/mir/builder/control_flow.rs
+++ b/src/mir/builder/control_flow.rs
@@ -542,7 +542,7 @@ impl super::MirBuilder {
                     values.insert(*v);
                 }
             }
-            MirInstruction::Phi { dst, inputs } => {
+            MirInstruction::Phi { dst, inputs, type_hint: None } => {
                 values.insert(*dst);
                 for (_, val) in inputs {
                     values.insert(*val);
@@ -651,12 +651,13 @@ impl super::MirBuilder {
             MirInstruction::Return { value } => MirInstruction::Return {
                 value: value.map(remap_value),
             },
-            MirInstruction::Phi { dst, inputs } => MirInstruction::Phi {
+            MirInstruction::Phi { dst, inputs, type_hint: None } => MirInstruction::Phi {
                 dst: remap_value(*dst),
                 inputs: inputs
                     .iter()
                     .map(|(bb, val)| (remap_block(*bb), remap_value(*val)))
                     .collect(),
+                type_hint: None, // Phase 63-6: Preserve no type hint during remapping
             },
             MirInstruction::Copy { dst, src } => MirInstruction::Copy {
                 dst: remap_value(*dst),
diff --git a/src/mir/builder/exprs_peek.rs b/src/mir/builder/exprs_peek.rs
index 5ee694c8..bc3b4dad 100644
--- a/src/mir/builder/exprs_peek.rs
+++ b/src/mir/builder/exprs_peek.rs
@@ -130,6 +130,7 @@ impl super::MirBuilder {
             self.emit_instruction(super::MirInstruction::Phi {
                 dst: result_val,
                 inputs: phi_inputs,
+                type_hint: None, // Phase 63-6: Legacy path, no type hint
             })?;
         }
         Ok(result_val)
diff --git a/src/mir/builder/if_form.rs b/src/mir/builder/if_form.rs
index 69742d07..e49f0c57 100644
--- a/src/mir/builder/if_form.rs
+++ b/src/mir/builder/if_form.rs
@@ -32,7 +32,7 @@ impl<'a> PhiBuilderOps for ToplevelOps<'a> {
                 self.0.current_span,
             );
         } else {
-            self.0.emit_instruction(MirInstruction::Phi { dst, inputs })?;
+            self.0.emit_instruction(MirInstruction::Phi { dst, inputs, type_hint: None })?;
         }
         Ok(())
     }
diff --git a/src/mir/builder/phi.rs b/src/mir/builder/phi.rs
index 7002bbb5..30a98cef 100644
--- a/src/mir/builder/phi.rs
+++ b/src/mir/builder/phi.rs
@@ -91,6 +91,7 @@ impl MirBuilder {
                         self.emit_instruction(MirInstruction::Phi {
                             dst: merged,
                             inputs,
+                            type_hint: None, // Phase 63-6: Legacy path, no type hint
                         })?;
                     }
                     self.variable_map.insert(pin_name.clone(), merged);
diff --git a/src/mir/instruction.rs b/src/mir/instruction.rs
index 1b81b0fd..ba9f30c2 100644
--- a/src/mir/instruction.rs
+++ b/src/mir/instruction.rs
@@ -129,9 +129,17 @@ pub enum MirInstruction {
     // === SSA Phi Function ===
     /// SSA phi function for merging values from different paths
     /// `%dst = phi [%val1 from %bb1, %val2 from %bb2, ...]`
+    ///
+    /// # Phase 63-6: Type Hint Support
+    ///
+    /// `type_hint` field stores type information from JoinIR (Select/IfMerge)
+    /// to enable type inference without scanning PHI inputs.
+    /// - `Some(MirType)`: Type is known from JoinIR (P1 cases: IfSelectTest.simple/local)
+    /// - `None`: Type must be inferred from PHI inputs (legacy behavior)
     Phi {
         dst: ValueId,
         inputs: Vec<(super::BasicBlockId, ValueId)>,
+        type_hint: Option<super::MirType>, // Phase 63-6: JoinIR type hint
     },
 
     // === Box Operations ===
diff --git a/src/mir/instruction_kinds/mod.rs b/src/mir/instruction_kinds/mod.rs
index 54cc6a88..73204708 100644
--- a/src/mir/instruction_kinds/mod.rs
+++ b/src/mir/instruction_kinds/mod.rs
@@ -541,7 +541,7 @@ inst_meta! {
 inst_meta! {
     pub struct PhiInst { dst: ValueId, inputs: Vec<(BasicBlockId, ValueId)> }
     => {
-        from_mir = |i| match i { MirInstruction::Phi { dst, inputs } => Some(PhiInst { dst: *dst, inputs: inputs.clone() }), _ => None };
+        from_mir = |i| match i { MirInstruction::Phi { dst, inputs, .. } => Some(PhiInst { dst: *dst, inputs: inputs.clone() }), _ => None };
         effects = |_: &Self| EffectMask::PURE;
         dst = |s: &Self| Some(s.dst);
         used = |s: &Self| s.inputs.iter().map(|(_, v)| *v).collect();
diff --git a/src/mir/join_ir/lowering/loop_form_intake.rs b/src/mir/join_ir/lowering/loop_form_intake.rs
index d0cefc77..11e4ba93 100644
--- a/src/mir/join_ir/lowering/loop_form_intake.rs
+++ b/src/mir/join_ir/lowering/loop_form_intake.rs
@@ -94,7 +94,7 @@ pub(crate) fn intake_loop_form(
     let mut carrier_hint: Vec<String> = Vec::new();
 
     for inst in query.insts_in_block(loop_form.header) {
-        if let MirInstruction::Phi { dst, inputs } = inst {
+        if let MirInstruction::Phi { dst, inputs, .. } = inst {
             let name = inputs
                 .iter()
                 .find_map(|(_, v)| value_to_name.get(v).cloned())
diff --git a/src/mir/join_ir_vm_bridge/convert.rs b/src/mir/join_ir_vm_bridge/convert.rs
index 108f1a70..dc75834e 100644
--- a/src/mir/join_ir_vm_bridge/convert.rs
+++ b/src/mir/join_ir_vm_bridge/convert.rs
@@ -491,17 +491,18 @@ Call {{\n\
                 cond,
                 then_val,
                 else_val,
-                type_hint: _, // Phase 63-3: MIR変換では現時点で未使用
+                type_hint, // Phase 63-6: Type hint propagated to MIR Phi
             } => {
                 // Phase 33-2: Select を MIR の if/phi に変換
-                // 最小実装: cond/then/else/merge の 4 ブロック構造
+                // Phase 63-6: PHI instruction with type hint from JoinIR
 
                 debug_log!(
-                    "[joinir_vm_bridge] Converting Select: dst={:?}, cond={:?}, then={:?}, else={:?}",
+                    "[joinir_vm_bridge] Converting Select: dst={:?}, cond={:?}, then={:?}, else={:?}, type_hint={:?}",
                     dst,
                     cond,
                     then_val,
-                    else_val
+                    else_val,
+                    type_hint
                 );
 
                 // 1. cond ブロック（現在のブロック）
@@ -532,32 +533,29 @@ Call {{\n\
                     branch_terminator,
                 );
 
-                // 6. then ブロック: dst = then_val; jump merge
+                // 6. then ブロック: jump merge (no Copy, PHI will handle it)
                 let mut then_block_obj = crate::mir::BasicBlock::new(then_block);
-                then_block_obj.instructions.push(MirInstruction::Copy {
-                    dst: *dst,
-                    src: *then_val,
-                });
-                then_block_obj.instruction_spans.push(Span::unknown());
                 then_block_obj.terminator = Some(MirInstruction::Jump {
                     target: merge_block,
                 });
                 mir_func.blocks.insert(then_block, then_block_obj);
 
-                // 7. else ブロック: dst = else_val; jump merge
+                // 7. else ブロック: jump merge (no Copy, PHI will handle it)
                 let mut else_block_obj = crate::mir::BasicBlock::new(else_block);
-                else_block_obj.instructions.push(MirInstruction::Copy {
-                    dst: *dst,
-                    src: *else_val,
-                });
-                else_block_obj.instruction_spans.push(Span::unknown());
                 else_block_obj.terminator = Some(MirInstruction::Jump {
                     target: merge_block,
                 });
                 mir_func.blocks.insert(else_block, else_block_obj);
 
-                // 8. merge ブロック作成（空）
-                let merge_block_obj = crate::mir::BasicBlock::new(merge_block);
+                // 8. merge ブロック: PHI instruction with type hint
+                let mut merge_block_obj = crate::mir::BasicBlock::new(merge_block);
+                // Phase 63-6: Create PHI with type hint from JoinIR Select
+                merge_block_obj.instructions.push(MirInstruction::Phi {
+                    dst: *dst,
+                    inputs: vec![(then_block, *then_val), (else_block, *else_val)],
+                    type_hint: type_hint.clone(), // Phase 63-6: Propagate type hint from JoinIR
+                });
+                merge_block_obj.instruction_spans.push(Span::unknown());
                 mir_func.blocks.insert(merge_block, merge_block_obj);
 
                 // 9. merge ブロックに移動
diff --git a/src/mir/loop_builder/loop_form.rs b/src/mir/loop_builder/loop_form.rs
index acaf6e44..8b42354c 100644
--- a/src/mir/loop_builder/loop_form.rs
+++ b/src/mir/loop_builder/loop_form.rs
@@ -395,6 +395,7 @@ impl<'a> LoopBuilder<'a> {
                             merge_block.add_instruction(MirInstruction::Phi {
                                 dst: phi_id,
                                 inputs: final_inputs,
+                type_hint: None, // Phase 63-6
                             });
                         }
                     }
diff --git a/src/mir/loop_builder/phi_ops.rs b/src/mir/loop_builder/phi_ops.rs
index 6aaf647a..d9af8709 100644
--- a/src/mir/loop_builder/phi_ops.rs
+++ b/src/mir/loop_builder/phi_ops.rs
@@ -36,6 +36,7 @@ impl<'a> LoopBuilder<'a> {
                         MirInstruction::Phi {
                             dst: d,
                             inputs: ins,
+                            .. // Phase 63-6: Ignore type_hint in pattern matching
                         } if *d == dst => {
                             *ins = inputs.clone();
                             if block.instruction_spans.len() <= idx {
@@ -58,6 +59,7 @@ impl<'a> LoopBuilder<'a> {
                     let phi_inst = MirInstruction::Phi {
                         dst,
                         inputs: inputs.clone(),
+                        type_hint: None, // Phase 63-6: Legacy path, no type hint
                     };
                     block.instructions.insert(0, phi_inst);
                     block.instruction_spans.insert(0, span);
diff --git a/src/mir/phi_core/if_phi.rs b/src/mir/phi_core/if_phi.rs
index 3be62398..9a3cd97a 100644
--- a/src/mir/phi_core/if_phi.rs
+++ b/src/mir/phi_core/if_phi.rs
@@ -136,7 +136,8 @@ pub fn infer_type_from_phi(
 ) -> Option<MirType> {
     for (_bid, bb) in function.blocks.iter() {
         for inst in bb.instructions.iter() {
-            if let MirInstruction::Phi { dst, inputs } = inst {
+            if let MirInstruction::Phi { dst, inputs, .. } = inst {
+                // Phase 63-6: type_hint is ignored here, will be used in lifecycle.rs
                 if *dst == ret_val {
                     let mut it = inputs.iter().filter_map(|(_, v)| types.get(v));
                     if let Some(first) = it.next() {
diff --git a/src/mir/printer_helpers.rs b/src/mir/printer_helpers.rs
index 183e249b..89831eda 100644
--- a/src/mir/printer_helpers.rs
+++ b/src/mir/printer_helpers.rs
@@ -248,7 +248,7 @@ pub fn format_instruction(
             }
         }
 
-        MirInstruction::Phi { dst, inputs } => {
+        MirInstruction::Phi { dst, inputs, .. } => {
             let inputs_str = inputs
                 .iter()
                 .map(|(bb, val)| format!("[{}, {}]", val, bb))
diff --git a/src/mir/ssot/cf_common.rs b/src/mir/ssot/cf_common.rs
index ca5d4316..e1205770 100644
--- a/src/mir/ssot/cf_common.rs
+++ b/src/mir/ssot/cf_common.rs
@@ -72,7 +72,7 @@ pub fn insert_phi_at_head_spanned(
     inputs.sort_by_key(|(bb, _)| bb.0);
     if let Some(bb) = f.get_block_mut(bb_id) {
         bb.insert_spanned_after_phis(SpannedInstruction {
-            inst: MirInstruction::Phi { dst, inputs },
+            inst: MirInstruction::Phi { dst, inputs, type_hint: None },
             span,
         });
     }
diff --git a/src/mir/utils/phi_helpers.rs b/src/mir/utils/phi_helpers.rs
index 487d1092..d8a18c37 100644
--- a/src/mir/utils/phi_helpers.rs
+++ b/src/mir/utils/phi_helpers.rs
@@ -84,6 +84,7 @@ impl MirBuilder {
             self.emit_instruction(MirInstruction::Phi {
                 dst: phi_val,
                 inputs,
+                type_hint: None, // Phase 63-6: Legacy path, no type hint
             })?;
         }
 
@@ -146,7 +147,11 @@ impl MirBuilder {
             );
         } else {
             // フォールバック: 直接emit（主にテストや特殊ケース用）
-            self.emit_instruction(MirInstruction::Phi { dst, inputs })?;
+            self.emit_instruction(MirInstruction::Phi {
+                dst,
+                inputs,
+                type_hint: None, // Phase 63-6: Legacy path, no type hint
+            })?;
         }
 
         Ok(())
diff --git a/src/runner/json_v0_bridge/lowering/loop_.rs b/src/runner/json_v0_bridge/lowering/loop_.rs
index b40d590a..63b86178 100644
--- a/src/runner/json_v0_bridge/lowering/loop_.rs
+++ b/src/runner/json_v0_bridge/lowering/loop_.rs
@@ -163,6 +163,7 @@ impl LoopFormOps for LoopFormJsonOps<'_> {
                 if let MirInstruction::Phi {
                     dst,
                     inputs: phi_inputs,
+                    .. // Phase 63-6: Ignore type_hint
                 } = inst
                 {
                     if *dst == phi_id {
diff --git a/src/runner/json_v1_bridge.rs b/src/runner/json_v1_bridge.rs
index 4b53dedd..25be3685 100644
--- a/src/runner/json_v1_bridge.rs
+++ b/src/runner/json_v1_bridge.rs
@@ -273,6 +273,7 @@ pub fn try_parse_v1_to_module(json: &str) -> Result<Option<MirModule>, String> {
                         block_ref.add_instruction(MirInstruction::Phi {
                             dst: ValueId::new(dst),
                             inputs: pairs,
+                type_hint: None, // Phase 63-6
                         });
                         max_value_id = max_value_id.max(dst + 1);
                     }
diff --git a/src/runner/mir_json_emit.rs b/src/runner/mir_json_emit.rs
index d2512636..9c070eb8 100644
--- a/src/runner/mir_json_emit.rs
+++ b/src/runner/mir_json_emit.rs
@@ -227,7 +227,7 @@ pub fn emit_mir_json_for_harness(
                         }
                         continue;
                     }
-                    if let I::Phi { dst, inputs } = inst {
+                    if let I::Phi { dst, inputs, .. } = inst {
                         let incoming: Vec<_> = inputs
                             .iter()
                             .map(|(b, v)| json!([v.as_u32(), b.as_u32()]))
@@ -642,7 +642,7 @@ pub fn emit_mir_json_for_harness_bin(
                 let mut emitted_defs: std::collections::HashSet<u32> =
                     std::collections::HashSet::new();
                 for inst in &bb.instructions {
-                    if let I::Phi { dst, inputs } = inst {
+                    if let I::Phi { dst, inputs, .. } = inst {
                         let incoming: Vec<_> = inputs
                             .iter()
                             .map(|(b, v)| json!([v.as_u32(), b.as_u32()]))
diff --git a/src/runner/mir_json_v0.rs b/src/runner/mir_json_v0.rs
index 44869828..827ae75c 100644
--- a/src/runner/mir_json_v0.rs
+++ b/src/runner/mir_json_v0.rs
@@ -179,6 +179,7 @@ pub fn parse_mir_v0_to_module(json: &str) -> Result<MirModule, String> {
                         block_ref.add_instruction(MirInstruction::Phi {
                             dst: ValueId::new(dst),
                             inputs: pairs,
+                type_hint: None, // Phase 63-6
                         });
                         max_value_id = max_value_id.max(dst + 1);
                     }