diff --git a/lang/src/llvm_ir/boxes/aot_prep/passes/numeric_core.hako b/lang/src/llvm_ir/boxes/aot_prep/passes/numeric_core.hako
index 76b10340..24e07fd0 100644
--- a/lang/src/llvm_ir/boxes/aot_prep/passes/numeric_core.hako
+++ b/lang/src/llvm_ir/boxes/aot_prep/passes/numeric_core.hako
@@ -22,10 +22,41 @@ static box AotPrepNumericCoreBox {
 
     // Phase 25 MVP: Build type table and transform BoxCall → Call
     local tmap = AotPrepNumericCoreBox.build_type_table(text, trace)
-    // Propagate MatI64 type through simple PHI chains（全incomingがMatI64ならdstもMatI64とみなす）
-    tmap = AotPrepNumericCoreBox.propagate_phi_types(text, tmap, trace)
     local copy_map = AotPrepNumericCoreBox.build_copy_map(text, trace)
 
+    // Iterative type propagation: alternate copy and phi propagation to handle chains
+    // like: MatI64.new() → r2 → copy → r10 → phi → r15 → copy → r31
+    local iter = 0
+    loop(iter < 4) {
+      tmap = AotPrepNumericCoreBox.propagate_copy_types(text, tmap, trace)
+      tmap = AotPrepNumericCoreBox.propagate_phi_types(text, tmap, trace)
+      iter = iter + 1
+    }
+
+    // Diagnostic: show all MatI64 vids if trace enabled
+    if trace != null && ("" + trace) == "1" {
+      local mat_vids = new ArrayBox()
+      local keys = tmap.keys()
+      local ki = 0
+      loop(ki < keys.size()) {
+        local key = keys.get(ki)
+        if tmap.get(key) == "MatI64" {
+          mat_vids.push("r" + key)
+        }
+        ki = ki + 1
+      }
+      if mat_vids.size() > 0 {
+        local vids_str = ""
+        local vi = 0
+        loop(vi < mat_vids.size()) {
+          if vi > 0 { vids_str = vids_str + "," }
+          vids_str = vids_str + mat_vids.get(vi)
+          vi = vi + 1
+        }
+        print("[aot/numeric_core] MatI64 vids: " + vids_str)
+      }
+    }
+
     local result = AotPrepNumericCoreBox.transform_boxcalls(text, tmap, copy_map, trace)
 
     // If nothing happened and trace is ON, surface a hint
@@ -94,13 +125,6 @@ static box AotPrepNumericCoreBox {
             }
           }
         }
-      } else if op == "copy" {
-        // Propagate type through copy
-        local dst = AotPrepNumericCoreBox.read_digits_field(inst, "dst")
-        local src = AotPrepNumericCoreBox.read_digits_field(inst, "src")
-        if dst != "" && src != "" && tmap.has(src) {
-          tmap.set(dst, tmap.get(src))
-        }
       }
 
       pos = obj_end + 1
@@ -149,6 +173,42 @@ static box AotPrepNumericCoreBox {
     return cmap
   }
 
+  // Propagate MatI64 type through copy instructions
+  // Scans all copy ops and propagates type from src to dst
+  propagate_copy_types(text, tmap, trace) {
+    local pos = 0
+    loop(true) {
+      local op_marker = text.indexOf("\"op\":\"", pos)
+      if op_marker < 0 { break }
+
+      local obj_start = text.substring(0, op_marker).lastIndexOf("{")
+      if obj_start < 0 { pos = op_marker + 1 continue }
+
+      local obj_end = AotPrepHelpers._seek_object_end(text, obj_start)
+      if obj_end <= obj_start { pos = op_marker + 1 continue }
+
+      local inst = text.substring(obj_start, obj_end + 1)
+      local op = AotPrepNumericCoreBox.read_field(inst, "op")
+
+      if op == "copy" {
+        local dst = AotPrepNumericCoreBox.read_digits_field(inst, "dst")
+        local src = AotPrepNumericCoreBox.read_digits_field(inst, "src")
+        if dst != "" && src != "" && tmap.has(src) && !tmap.has(dst) {
+          local src_type = tmap.get(src)
+          if src_type == "MatI64" {
+            tmap.set(dst, "MatI64")
+            if trace != null && ("" + trace) == "1" {
+              print("[aot/numeric_core] copy-prop MatI64: r" + src + " → r" + dst)
+            }
+          }
+        }
+      }
+
+      pos = obj_end + 1
+    }
+    return tmap
+  }
+
   // Propagate MatI64 type information through phi nodes.
   // Policy: 「少なくとも1つ MatI64 で、かつMatI64以外の型が混ざっていない」場合に dst を MatI64 とみなす。
   propagate_phi_types(text, tmap, trace) {
@@ -158,10 +218,17 @@ static box AotPrepNumericCoreBox {
       changed = 0
       local pos = 0
       loop(true) {
-        local obj_start = text.indexOf("{", pos)
-        if obj_start < 0 { break }
+        // Find next "op":" marker (same pattern as build_type_table/propagate_copy_types)
+        local op_marker = text.indexOf("\"op\":\"", pos)
+        if op_marker < 0 { break }
+
+        // Find the start of this instruction object (the { before "op")
+        local obj_start = text.substring(0, op_marker).lastIndexOf("{")
+        if obj_start < 0 { pos = op_marker + 1 continue }
+
+        // Find the end of this instruction object
         local obj_end = AotPrepHelpers._seek_object_end(text, obj_start)
-        if obj_end <= obj_start { pos = obj_start + 1 continue }
+        if obj_end <= obj_start { pos = op_marker + 1 continue }
 
         local inst = text.substring(obj_start, obj_end + 1)
         local op = AotPrepNumericCoreBox.read_field(inst, "op")
@@ -197,7 +264,7 @@ static box AotPrepNumericCoreBox {
                     tmap.set(dst, "MatI64")
                     changed = 1
                     if trace != null && ("" + trace) == "1" {
-                      print("[aot/numeric_core] phi-prop MatI64 at r" + dst)
+                      print("[aot/numeric_core] phi-prop MatI64: r" + dst)
                     }
                   }
                 }
@@ -259,6 +326,23 @@ static box AotPrepNumericCoreBox {
         }
       }
 
+      // Diagnostic logging for skipped transformations
+      if should_transform == 0 && method == "mul_naive" {
+        local reason = "unknown"
+        if box_vid == "" {
+          reason = "no_box_vid"
+        } else if !tmap.has(box_vid) {
+          reason = "type_unknown"
+        } else if tmap.get(box_vid) != "MatI64" {
+          reason = "type_conflict (expected MatI64, got " + tmap.get(box_vid) + ")"
+        }
+
+        if trace != null && ("" + trace) == "1" {
+          local dst = AotPrepNumericCoreBox.read_digits_field(inst, "dst")
+          print("[aot/numeric_core] skip mul_naive@r" + dst + ": box=r" + box_vid + " reason=" + reason)
+        }
+      }
+
       if should_transform == 1 {
         // Transform BoxCall → Call
         // Copy text before this boxcall