diff --git a/lang/src/compiler/entry/compiler_stageb.hako b/lang/src/compiler/entry/compiler_stageb.hako
index dbf90fe6..22c01a17 100644
--- a/lang/src/compiler/entry/compiler_stageb.hako
+++ b/lang/src/compiler/entry/compiler_stageb.hako
@@ -1,7 +1,6 @@
 // Stage-B compiler entry — ParserBox → FlowEntry emit-only
 
 using lang.compiler.parser.box as ParserBox
-using lang.compiler.pipeline_v2.flow_entry as FlowEntryBox
 
 static box StageBMain {
   // Minimal Stage‑B driver: parse args/env, extract main body if wrapped in `box Main { static method main(){...} }`,
@@ -68,13 +67,11 @@ static box StageBMain {
 
     if body_src == null { body_src = src }
 
-    // 5) Parse and emit MIR(JSON v0)
+    // 5) Parse and emit Stage‑1 JSON v0 (Program)
+    // Bridge(JSON v0) が Program v0 を受け取り MIR に lowering するため、ここでは AST(JSON v0) を出力する。
+    // 既定で MIR 直出力は行わない（重い経路を避け、一行出力を保証）。
     local ast_json = p.parse_program2(body_src)
-    local prefer = 1
-    local out = FlowEntryBox.emit_v0_from_ast_with_context(ast_json, prefer, usings_json, null, externs_json)
-    if out == null || out == "" { out = FlowEntryBox.emit_v0_from_ast(ast_json, prefer) }
-    // TTL OFF: do not fallback to dummy JSON when emit fails. Empty output surfaces failure to caller.
-    print(out)
+    print(ast_json)
     return 0
   }
 }
diff --git a/lang/src/compiler/pipeline_v2/flow_entry.hako b/lang/src/compiler/pipeline_v2/flow_entry.hako
index 59151c1e..6aeda5a7 100644
--- a/lang/src/compiler/pipeline_v2/flow_entry.hako
+++ b/lang/src/compiler/pipeline_v2/flow_entry.hako
@@ -16,6 +16,13 @@ static box FlowEntryBox {
 
   // Emit v0 with optional using / extern metadata（Stage‑B entry）
   emit_v0_from_ast_with_context(ast_json, prefer_cfg, usings_json, modules_json, externs_json) {
+    // 1) Prefer lightweight v1→v0 経路（簡単な return/binop/compare/call/new はここで完結）
+    {
+      local j1 = PipelineV2.lower_stage1_to_mir_v1(ast_json, prefer_cfg)
+      if j1 != null { return MirJsonV1Adapter.to_v0(j1) }
+    }
+
+    // 2) using 情報があれば using 解決つきの v0 経路を試す
     local used_with_usings = 0
     local out = null
     if usings_json != null && usings_json != "" && usings_json != "[]" {
@@ -25,9 +32,10 @@ static box FlowEntryBox {
     if out == null {
       out = PipelineV2.lower_stage1_to_mir(ast_json, prefer_cfg)
     }
+    // 3) externs が指定され、まだ v1 経路を使っていない場合は v1+meta → v0 を試す
     if externs_json != null && externs_json != "" && externs_json != "[]" && used_with_usings == 0 {
-      local j1 = PipelineV2.lower_stage1_to_mir_v1_with_meta(ast_json, prefer_cfg, externs_json)
-      if j1 != null { out = MirJsonV1Adapter.to_v0(j1) }
+      local j2 = PipelineV2.lower_stage1_to_mir_v1_with_meta(ast_json, prefer_cfg, externs_json)
+      if j2 != null { out = MirJsonV1Adapter.to_v0(j2) }
     }
     return out
   }
diff --git a/lang/src/compiler/pipeline_v2/pipeline.hako b/lang/src/compiler/pipeline_v2/pipeline.hako
index ac934fce..7e25a018 100644
--- a/lang/src/compiler/pipeline_v2/pipeline.hako
+++ b/lang/src/compiler/pipeline_v2/pipeline.hako
@@ -457,10 +457,15 @@ flow PipelineV2 {
   }
   // Overload: resolve names via UsingResolverBox before emit
   lower_stage1_to_mir_with_usings(ast_json, prefer_cfg, usings_json, modules_json) {
-    print("[DEBUG] === lower_stage1_to_mir_with_usings ENTRY ===")
-    print("[DEBUG] ast_json length=" + ast_json.length())
-    print("[DEBUG] usings_json=" + usings_json)
-    print("[DEBUG] modules_json=" + modules_json)
+    // Debug logs are noisy: emit only when prefer_cfg is a large debug value (>=9)
+    local _dbg = 0
+    if prefer_cfg != null { if (""+prefer_cfg) == "9" { _dbg = 1 } }
+    if _dbg == 1 {
+      print("[DEBUG] === lower_stage1_to_mir_with_usings ENTRY ===")
+      print("[DEBUG] ast_json length=" + ast_json.length())
+      print("[DEBUG] usings_json=" + usings_json)
+      print("[DEBUG] modules_json=" + modules_json)
+    }
     if ast_json == null { return PipelineV2.lower_stage1_to_mir(ast_json, prefer_cfg) }
     // Build resolver context
     local r = UsingResolverBox.state_new()
@@ -468,7 +473,7 @@ flow PipelineV2 {
     if modules_json != null { UsingResolverBox.load_modules_json(r, modules_json) }
     // Upgrade alias→namespace mapping now that modules are loaded (Module‑First)
     UsingResolverBox.upgrade_aliases(r)
-    print("[DEBUG] upgrade_aliases complete")
+    if _dbg == 1 { print("[DEBUG] upgrade_aliases complete") }
 
     // Prefer Call/Method/New branches with name normalization; otherwise fallback to default
     {
@@ -479,12 +484,12 @@ flow PipelineV2 {
           local scan0 = Stage1JsonScannerBox.extract_name_args(ast_json, kq)
           if scan0 != null {
             local raw_head = scan0.get("name")
-            print("[DEBUG] preflight raw_head=" + raw_head)
+            if _dbg == 1 { print("[DEBUG] preflight raw_head=" + raw_head) }
             local dot = RegexFlow.find_from(raw_head, ".", 0)
             if dot >= 0 {
               local head = raw_head.substring(0, dot)
               local resolved = UsingResolverBox.resolve_namespace_alias(r, head)
-              print("[DEBUG] preflight head=" + head + " resolved=" + resolved)
+              if _dbg == 1 { print("[DEBUG] preflight head=" + head + " resolved=" + resolved) }
               if resolved == null {
                 print("[ERROR] Unresolved using alias: " + head)
                 return null
@@ -514,7 +519,7 @@ flow PipelineV2 {
         if kc != null {
           local kn = NormalizerBox.normalize_call_ints(kc)
           if kn == null {
-            print("[DEBUG] normalize_call_ints returned null")
+                if _dbg == 1 { print("[DEBUG] normalize_call_ints returned null") }
             return null
           }
           local raw_name = kn.get("name")