diff --git a/src/runner/json_v0_bridge/lowering/loop_.rs b/src/runner/json_v0_bridge/lowering/loop_.rs
index 020b657c..cf7c964e 100644
--- a/src/runner/json_v0_bridge/lowering/loop_.rs
+++ b/src/runner/json_v0_bridge/lowering/loop_.rs
@@ -134,13 +134,65 @@ pub(super) fn lower_loop_stmt(
     if let Some(bb) = ops.f.get_block_mut(bend) {
         if !bb.is_terminated() { crate::mir::ssot::cf_common::set_jump(ops.f, bend, cond_bb); }
     }
-    let backedge_to_cond = matches!(
-        ops.f.blocks
-            .get(&bend)
-            .and_then(|bb| bb.terminator.as_ref()),
-        Some(MirInstruction::Jump { target, .. }) if *target == cond_bb
-    );
+    // Detect whether the "latch" block has a backedge to the loop header/cond.
+    // Note: loops with `break` often end the latch with a conditional Branch that
+    // targets both `cond_bb` (continue path) and `exit_bb` (break path). We must
+    // treat such branches as valid backedges as well; otherwise body-local vars
+    // will miss PHI nodes at the header and become undefined on the second iteration
+    // (BreakFinderBox._find_loops/2 などで観測されたバグ).
+    let backedge_to_cond = match ops
+        .f
+        .blocks
+        .get(&bend)
+        .and_then(|bb| bb.terminator.as_ref())
+    {
+        Some(MirInstruction::Jump { target, .. }) if *target == cond_bb => true,
+        Some(MirInstruction::Branch { then_bb, else_bb, .. })
+            if *then_bb == cond_bb || *else_bb == cond_bb =>
+        {
+            true
+        }
+        _ => false,
+    };
+    let trace_loop_phi = std::env::var("HAKO_LOOP_PHI_TRACE").ok().as_deref() == Some("1");
+    if trace_loop_phi {
+        eprintln!("[loop-phi] backedge_to_cond={}, base_vars={}, body_vars={}",
+            backedge_to_cond, base_vars.len(), body_vars.len());
+    }
     if backedge_to_cond {
+        // Phase 25.1c/k: body 内で新規宣言された local 変数も PHI に含める
+        // BreakFinderBox._find_loops/2 等で、loop body 内の local 変数が
+        // loop header に戻った時に undefined になる問題を修正
+        let mut body_local_count = 0;
+        for (var_name, &_latch_value) in body_vars.iter() {
+            if !base_vars.contains_key(var_name) {
+                // body で新規宣言された変数 → header に PHI ノードを追加
+                body_local_count += 1;
+                if trace_loop_phi {
+                    eprintln!("[loop-phi/body-local] Adding PHI for body-local var: {}", var_name);
+                }
+                let phi_id = ops.f.next_value_id();
+                let inc_phi = crate::mir::phi_core::loop_phi::IncompletePhi {
+                    phi_id,
+                    var_name: var_name.clone(),
+                    known_inputs: vec![],  // preheader には存在しないので空
+                };
+                // header に空の PHI ノードを挿入（seal_incomplete_phis_with で完成させる）
+                if let Some(bb) = ops.f.get_block_mut(cond_bb) {
+                    bb.insert_instruction_after_phis(MirInstruction::Phi {
+                        dst: phi_id,
+                        inputs: vec![],  // 空の PHI（後で latch/continue から完成）
+                    });
+                }
+                // 変数マップを PHI に rebind
+                ops.vars.insert(var_name.clone(), phi_id);
+                incomplete.push(inc_phi);
+            }
+        }
+        if trace_loop_phi && body_local_count > 0 {
+            eprintln!("[loop-phi/body-local] Total body-local vars added: {}", body_local_count);
+        }
+
         // 5) header の不完全PHIを完成（latch + continue スナップショット集約）
         let mut ops_seal = Ops { f: ops.f, vars: ops.vars, block_var_maps: &block_var_maps2 };
         crate::mir::phi_core::loop_phi::seal_incomplete_phis_with(