diff --git a/src/genesis/writer/exceptions.py b/src/genesis/writer/exceptions.py
new file mode 100644
index 0000000..b096ff7
--- /dev/null
+++ b/src/genesis/writer/exceptions.py
@@ -0,0 +1,6 @@
+"""Writer 子系统异常。"""
+from __future__ import annotations
+
+
+class WriterGenerationError(Exception):
+    """LLM 章节生成失败（引擎 status 非 ok/fallback、或解析耗尽）。"""
diff --git a/tests/test_phase5_exceptions.py b/tests/test_phase5_exceptions.py
new file mode 100644
index 0000000..b5943f4
--- /dev/null
+++ b/tests/test_phase5_exceptions.py
@@ -0,0 +1,9 @@
+import pytest
+from genesis.writer.exceptions import WriterGenerationError
+
+
+def test_writer_generation_error_is_exception():
+    with pytest.raises(WriterGenerationError):
+        raise WriterGenerationError("生成失败")
+    with pytest.raises(Exception):
+        raise WriterGenerationError("x")