diff --git a/app/harness/runner.py b/app/harness/runner.py
index 30693e1..463f52e 100644
--- a/app/harness/runner.py
+++ b/app/harness/runner.py
@@ -2269,7 +2269,9 @@ class Runner:
 
         def _read(name: str) -> str:
             p = Path("prompts") / name
-            return p.read_text(encoding="utf-8") if p.exists() else ""
+            if not p.exists():
+                raise FileNotFoundError(f"缺进化/诊断模板: {p}（请从 TRM4 迁移或检查 prompts/）")
+            return p.read_text(encoding="utf-8")
 
         return EvolvePrompts(
             evolve_skill=_read("evolve_skill.md"),
@@ -2284,7 +2286,9 @@ class Runner:
 
         def _read(name: str) -> str:
             p = Path("prompts") / name
-            return p.read_text(encoding="utf-8") if p.exists() else ""
+            if not p.exists():
+                raise FileNotFoundError(f"缺进化/诊断模板: {p}（请从 TRM4 迁移或检查 prompts/）")
+            return p.read_text(encoding="utf-8")
 
         return DiagnosePrompts(
             defect_vs_lapse=_read("defect_vs_lapse.md"),
diff --git a/app/harness/video_split_cli.py b/app/harness/video_split_cli.py
index 9f04277..a924554 100644
--- a/app/harness/video_split_cli.py
+++ b/app/harness/video_split_cli.py
@@ -365,7 +365,9 @@ def _load_diagnose_prompts() -> Any:
 
     def _read(name: str) -> str:
         p = Path("prompts") / name
-        return p.read_text(encoding="utf-8") if p.exists() else ""
+        if not p.exists():
+            raise FileNotFoundError(f"缺进化/诊断模板: {p}（请从 TRM4 迁移或检查 prompts/）")
+        return p.read_text(encoding="utf-8")
 
     return DiagnosePrompts(
         defect_vs_lapse=_read("defect_vs_lapse.md"),
diff --git a/tests/unit/test_evolve_prompts_present.py b/tests/unit/test_evolve_prompts_present.py
index a9308e9..b72e3b8 100644
--- a/tests/unit/test_evolve_prompts_present.py
+++ b/tests/unit/test_evolve_prompts_present.py
@@ -23,3 +23,32 @@ def test_evolve_template_present_and_contract(name: str, required_tokens: list[s
     assert text.strip(), f"模板为空: {path}"
     for token in required_tokens:
         assert token in text, f"{name} 缺输出契约关键词 {token!r}（与解析代码不对齐）"
+
+
+def test_video_split_loader_fail_loud_on_missing(tmp_path, monkeypatch):
+    """video_split_cli 的真实 diagnose 加载器缺模板必须 FileNotFoundError。"""
+    monkeypatch.chdir(tmp_path)  # 空目录，无 prompts/*.md
+    from app.harness.video_split_cli import _load_diagnose_prompts
+
+    with pytest.raises(FileNotFoundError, match="缺进化/诊断模板"):
+        _load_diagnose_prompts()
+
+
+def test_runner_evolve_loader_fail_loud_on_missing(tmp_path, monkeypatch):
+    """runner 的真实 evolve 加载器缺模板必须 FileNotFoundError。"""
+    monkeypatch.chdir(tmp_path)
+    from app.harness.runner import Runner
+
+    r = object.__new__(Runner)  # 绕过 __init__，仅测无状态加载器方法
+    with pytest.raises(FileNotFoundError, match="缺进化/诊断模板"):
+        r._load_evolve_prompts()
+
+
+def test_runner_diagnose_loader_fail_loud_on_missing(tmp_path, monkeypatch):
+    """runner 的真实 diagnose 加载器缺模板必须 FileNotFoundError。"""
+    monkeypatch.chdir(tmp_path)
+    from app.harness.runner import Runner
+
+    r = object.__new__(Runner)
+    with pytest.raises(FileNotFoundError, match="缺进化/诊断模板"):
+        r._load_diagnose_prompts()