diff --git a/src/genesis/writer/writer_agent.py b/src/genesis/writer/writer_agent.py
new file mode 100644
index 0000000..2fbd7f1
--- /dev/null
+++ b/src/genesis/writer/writer_agent.py
@@ -0,0 +1,114 @@
+"""Writer Agent：调用推理引擎生成单章内容（Phase 5）。
+
+接入真实 InferenceEngine.chat_structured（session_id/prompt/variables/schema/retry_count），
+并对章节级失败做有限重试；token 估算分块（真实拼回留待后续并发实现）。
+"""
+from __future__ import annotations
+
+from genesis.inference.engine import InferenceEngine
+from genesis.inference.prompt_registry import PromptRegistry
+from genesis.inference.types import Prompt, StructuredResult
+from genesis.writer.models import ChapterContent, GenerationContext
+from genesis.writer.writer_state import WriterState
+from genesis.writer.exceptions import WriterGenerationError
+
+
+WRITER_PROMPT_TEMPLATE = (
+    "你是概要设计书撰写专家。\n"
+    "章节: {{chapter_id}} {{title}}\n"
+    "写入规则:\n{{write_rules}}\n"
+    "设计规则:\n{{design_rules}}\n"
+    "模板样式:\n{{template_styles}}\n"
+    "参考资料:\n{{source}}\n"
+    "请输出符合 schema 的章节内容 JSON。"
+)
+
+CHAPTER_OUTPUT_SCHEMA = {
+    "type": "object",
+    "properties": {
+        "title": {"type": "string"},
+        "blocks": {
+            "type": "array",
+            "items": {
+                "type": "object",
+                "properties": {
+                    "type": {"type": "string"},
+                    "text": {"type": "string"},
+                    "level": {"type": "integer"},
+                    "headers": {"type": "array", "items": {"type": "string"}},
+                    "rows": {"type": "array", "items": {"type": "array", "items": {"type": "string"}}},
+                    "items": {"type": "array", "items": {"type": "string"}},
+                    "source_uris": {"type": "array", "items": {"type": "string"}},
+                },
+                "required": ["type"],
+            },
+        },
+    },
+    "required": ["title", "blocks"],
+}
+
+
+class WriterAgent:
+    def __init__(
+        self,
+        session_id,
+        engine: InferenceEngine,
+        prompt_registry: PromptRegistry,
+        state: WriterState,
+        max_retries: int = 1,
+    ) -> None:
+        self.session_id = session_id
+        self.engine = engine
+        self.prompt_registry = prompt_registry
+        self.state = state
+        self.max_retries = max_retries
+
+    def _chunk_source(self, source) -> list[dict]:
+        if source is None:
+            return [{"index": 0, "text": ""}]
+        src = source if isinstance(source, str) else str(source)
+        n = max(1, len(src) // 1800 + 1)
+        return [{"index": i, "text": src[i * 1800:(i + 1) * 1800]} for i in range(n)]
+
+    def _resolve_prompt(self) -> Prompt:
+        """取用/注册 writer.chapter 模板。
+
+        优先使用 get_or_create（与测试 Fake 兼容）；真实 PromptRegistry 无该方法时，
+        回退为 register + get。
+        """
+        get_or_create = getattr(self.prompt_registry, "get_or_create", None)
+        if get_or_create is not None:
+            return get_or_create("writer.chapter", WRITER_PROMPT_TEMPLATE)
+        self.prompt_registry.register("writer.chapter", "1", WRITER_PROMPT_TEMPLATE)
+        return self.prompt_registry.get("writer.chapter", "1")
+
+    def _call_llm(self, context: GenerationContext) -> dict:
+        prompt = self._resolve_prompt()
+        result: StructuredResult = self.engine.chat_structured(
+            session_id=self.session_id,
+            prompt=prompt,
+            variables=context.to_vars(),
+            schema=CHAPTER_OUTPUT_SCHEMA,
+            retry_count=2,
+        )
+        if result.status not in ("ok", "fallback"):
+            raise WriterGenerationError(f"引擎返回异常状态: {result.status}")
+        return result.data
+
+    def generate_chapter(self, context: GenerationContext) -> ChapterContent:
+        self._chunk_source(context.structured_source)  # 分块可用性验证（真实拼回留待后续）
+        last_err: Exception | None = None
+        for _ in range(max(1, self.max_retries)):
+            try:
+                data = self._call_llm(context)
+            except Exception as e:  # 引擎可能抛出任意异常，统一按章节级失败重试
+                last_err = e
+                continue
+            try:
+                content = ChapterContent.from_llm(context.chapter_id, context.title, data)
+            except (KeyError, TypeError, ValueError) as e:
+                last_err = e
+                continue
+            self.state.record_success(content)
+            return content
+        raise WriterGenerationError(f"章节 {context.chapter_id} 重试耗尽: {last_err}")