diff --git a/cheap-worker/cheap_studio.py b/cheap-worker/cheap_studio.py
index 3e88326a..2b233038 100644
--- a/cheap-worker/cheap_studio.py
+++ b/cheap-worker/cheap_studio.py
@@ -91,6 +91,10 @@ def _closeout_gates(game_id, *, port, cdp_port) -> dict:
     sm = cheap_run.smoke(game_id, port=port, cdp_port=cdp_port)
     out["smoke_ok"] = sm["ok"]
     _rec(f"smoke {'PASS' if sm['ok'] else 'FAIL'}(抓 state 供 play-spec)")
+    if not sm["ok"]:
+        # smoke 失败真因必须可见(2026-07-04 bake_off 实证:并发争用致 100% FAIL→全场 key-cycle 回退考卷,
+        #   而失败原因被吞在 raw 里,烧掉一轮诊断)——打印 raw 尾供归因。
+        _rec(f"smoke raw 尾:{(sm.get('raw') or '')[-300:]}")
     ps = cheap_run.ensure_play_spec(game_id, sm.get("state"))
     # driver 类型:本轮新产的直接带;复用旧 spec(hash 一致)时读盘补(spec 是判卷单一来源)。
     dt = ps.get("driverType")
@@ -312,6 +316,8 @@ async def run_studio(game_id, brief, *, max_iters=40, max_resumes=6, max_tokens=
                 sm = cheap_run.smoke(game_id, port=port, cdp_port=cdp_port)
                 smoke_ok = sm["ok"]
                 _rec(f"smoke {'PASS' if smoke_ok else 'FAIL'}(抓 state 供 play-spec)")
+                if not smoke_ok:
+                    _rec(f"smoke raw 尾:{(sm.get('raw') or '')[-300:]}")  # 真因可见(同 _closeout_gates 注)
                 _rec("generation-only(run_gates=False):跳过 ensure_play_spec + 九门 play,交对照方注入金标 spec 后单独 play")
 
     tok_in, tok_out = model.usage_sum()  # 成本落盘(R4)：token 台账始终可取(RecordingOpenAIChatModel.records 累计)。