diff --git a/src/genesis/writer/template_mapper.py b/src/genesis/writer/template_mapper.py
new file mode 100644
index 0000000..436879d
--- /dev/null
+++ b/src/genesis/writer/template_mapper.py
@@ -0,0 +1,22 @@
+"""模板 → 有序章节规格映射（Phase 5）。"""
+from __future__ import annotations
+
+from genesis.writer.models import ChapterSpec
+
+
+def map_template(parsed) -> list[ChapterSpec]:
+    """按模板 Heading 层级顺序产出有序章节列表。
+
+    `parsed.chapters` 为 WordTemplateParser 产出的章节标记列表，
+    每项含 chapter_id / title / section_placeholder 属性。
+    """
+    specs: list[ChapterSpec] = []
+    for ch in getattr(parsed, "chapters", []):
+        specs.append(
+            ChapterSpec(
+                chapter_id=getattr(ch, "chapter_id", ""),
+                title=getattr(ch, "title", ""),
+                section_placeholder=getattr(ch, "section_placeholder", None),
+            )
+        )
+    return specs
diff --git a/tests/test_phase5_template_mapper.py b/tests/test_phase5_template_mapper.py
new file mode 100644
index 0000000..001e160
--- /dev/null
+++ b/tests/test_phase5_template_mapper.py
@@ -0,0 +1,17 @@
+from types import SimpleNamespace
+from genesis.writer.template_mapper import map_template
+from genesis.writer.models import ChapterSpec
+
+
+def _fake_parsed():
+    ch1 = SimpleNamespace(chapter_id="intro", title="はじめに", section_placeholder="{{section:introduction}}")
+    ch2 = SimpleNamespace(chapter_id="db_design", title="DB 設計", section_placeholder=None)
+    return SimpleNamespace(chapters=[ch1, ch2])
+
+
+def test_map_template_ordered():
+    specs = map_template(_fake_parsed())
+    assert [s.chapter_id for s in specs] == ["intro", "db_design"]
+    assert specs[0].section_placeholder == "{{section:introduction}}"
+    assert specs[1].section_placeholder is None
+    assert all(isinstance(s, ChapterSpec) for s in specs)