diff --git a/milestones/README.md b/milestones/README.md
index f3f0943..4527157 100644
--- a/milestones/README.md
+++ b/milestones/README.md
@@ -5,10 +5,13 @@ repositories that install `docgen` and maintain their own demo bundle. The
 library no longer ships an in-repo dogfood; consumers are the integration test
 of record.
 
-**Active:** **[timing-stem-objects.md](timing-stem-objects.md)** —
-`timing.json` per-stem values must be JSON objects (not lists/scalars).
+**Active:** **[timing-inner-lists.md](timing-inner-lists.md)** —
+`timing.json` `words` / `segments` must be JSON arrays of objects.
 
 **Shipped:**
+- **[timing-stem-objects.md](timing-stem-objects.md)** —
+  `timing.json` per-stem values must be JSON objects (not lists/scalars)
+  (#126).
 - **[cli-segments-all.md](cli-segments-all.md)** —
   `narration-generate --all` / `scene-spec-generate --all` must use
   `Config.segments_all` (missing `all` falls back to `default`) (#125).
diff --git a/milestones/timing-inner-lists.md b/milestones/timing-inner-lists.md
new file mode 100644
index 0000000..298822f
--- /dev/null
+++ b/milestones/timing-inner-lists.md
@@ -0,0 +1,41 @@
+# Milestone: timing.json words/segments must be object arrays
+
+**Status:** Active  
+**PR:** [#127](https://github.com/jmjava/documentation-generator/pull/127)  
+**Depends on:** `milestones/timing-stem-objects.md` (PR #126)
+
+## Problem
+
+PR #126 required each ``timing.json`` stem to be a JSON object. Inner
+``words`` / ``segments`` were still untyped. A stem like
+``{"words": "x"}`` or ``{"words": ["hello"]}`` then:
+
+1. Compile / ``scene-spec-generate`` coerced a non-list to ``[]``
+   (``pace: none`` compiled as if timestamps had never been run).
+2. A list of non-objects kept LLM ``wait_word`` indices and later
+   crashed Manim on ``.get("start")``.
+3. ``sync_audio_tail_waits_in_scenes`` treated a truthy non-list
+   ``segments`` string as present and tried to patch ``scenes.py``.
+
+## Goal
+
+When ``words`` or ``segments`` is present and not null, it must be a
+JSON array of objects. Missing / null / ``[]`` stay allowed (empty still
+means no timings; paced compile already fails).
+
+## Done when
+
+- [x] ``load_bundle_timing`` rejects non-array ``words`` / ``segments``
+- [x] ``load_bundle_timing`` rejects non-object array items
+- [x] ``pace: none`` compile fails with the parse error (not silent empty)
+- [x] validate / wizard / ``extract_all`` surface the error and do not
+      rewrite the file
+- [x] `ruff check src/ tests/`
+- [x] `pytest tests/` (734 passed, 1 skipped)
+- [x] `docgen benchmark` (no clock change; meets baseline)
+
+## Out of scope
+
+- Empty ``segments.all`` still leaves ``timing.json`` unchanged (#78)
+- Requiring numeric ``start`` / ``end`` on every word row
+- Bootstrap ``_load_timing`` helpers inside compiled ``scenes.py``
diff --git a/milestones/timing-stem-objects.md b/milestones/timing-stem-objects.md
index 8c7482d..9d5f441 100644
--- a/milestones/timing-stem-objects.md
+++ b/milestones/timing-stem-objects.md
@@ -1,6 +1,6 @@
 # Milestone: timing.json per-stem values must be objects
 
-**Status:** Active  
+**Status:** Shipped  
 **PR:** [#126](https://github.com/jmjava/documentation-generator/pull/126)  
 **Depends on:** `milestones/timing-json-parse.md` (PR #89),
 `milestones/cli-segments-all.md` (PR #125)
diff --git a/src/docgen/asset_graph.py b/src/docgen/asset_graph.py
index deef277..3d69034 100644
--- a/src/docgen/asset_graph.py
+++ b/src/docgen/asset_graph.py
@@ -122,7 +122,8 @@ def _timing_entry_exists(cfg: "Config", seg_name: str, audio: Path | None) -> bo
     """True when ``timing.json`` has a stem for this segment.
 
     A missing file is ``False`` (timestamps not run yet). Corrupt JSON, a
-    non-object root, or a non-object per-stem value raises
+    non-object root, a non-object per-stem value, or a present ``words`` /
+    ``segments`` field that is not an array of objects raises
     :class:`~docgen.timestamps.TimestampError` so the wizard cannot treat
     garbage as “no entry”.
     """
diff --git a/src/docgen/timestamps.py b/src/docgen/timestamps.py
index 389d170..47113f0 100644
--- a/src/docgen/timestamps.py
+++ b/src/docgen/timestamps.py
@@ -28,11 +28,37 @@ class TimestampError(RuntimeError):
     """Raised when timestamps cannot be extracted for required segments."""
 
 
+def _json_kind(value: Any) -> str:
+    return "null" if value is None else type(value).__name__
+
+
+def _require_timing_object_list(
+    path_name: str, stem: str, payload: dict[str, Any], key: str
+) -> None:
+    """Require ``words`` / ``segments`` (when present and not null) to be object arrays."""
+    if key not in payload:
+        return
+    value = payload[key]
+    if value is None:
+        return
+    if not isinstance(value, list):
+        raise TimestampError(
+            f"{path_name}[{stem!r}].{key} must be a JSON array, not {_json_kind(value)}"
+        )
+    for i, item in enumerate(value):
+        if not isinstance(item, dict):
+            raise TimestampError(
+                f"{path_name}[{stem!r}].{key}[{i}] must be a JSON object, "
+                f"not {_json_kind(item)}"
+            )
+
+
 def load_bundle_timing(config: "Config") -> dict[str, Any]:
     """Load ``animations/timing.json``.
 
-    A missing file is ``{}``. Corrupt JSON, a non-object root, or a non-object
-    per-stem value raises :class:`TimestampError` so compile/validate cannot
+    A missing file is ``{}``. Corrupt JSON, a non-object root, a non-object
+    per-stem value, or a present ``words`` / ``segments`` field that is not an
+    array of objects raises :class:`TimestampError` so compile/validate cannot
     treat garbage as empty ``words``.
     """
     path = config.animations_dir / "timing.json"
@@ -49,14 +75,15 @@ def load_bundle_timing(config: "Config") -> dict[str, Any]:
         raise TimestampError(f"could not read {path}: {exc}") from exc
     if not isinstance(data, dict):
         raise TimestampError(
-            f"{path.name} root must be a JSON object, not {type(data).__name__}"
+            f"{path.name} root must be a JSON object, not {_json_kind(data)}"
         )
     for stem, payload in data.items():
         if not isinstance(payload, dict):
-            kind = "null" if payload is None else type(payload).__name__
             raise TimestampError(
-                f"{path.name}[{stem!r}] must be a JSON object, not {kind}"
+                f"{path.name}[{stem!r}] must be a JSON object, not {_json_kind(payload)}"
             )
+        _require_timing_object_list(path.name, str(stem), payload, "words")
+        _require_timing_object_list(path.name, str(stem), payload, "segments")
     return data
 
 
@@ -140,7 +167,8 @@ def extract_all(self, engine: str | None = None) -> None:
 
         Successful runs **merge** stems into the existing file (same as the
         wizard per-segment timestamps step) so extra keys not in
-        ``segments.all`` are not wiped. Corrupt JSON / a non-object root raises
+        ``segments.all`` are not wiped. Corrupt JSON, a non-object root, a
+        non-object stem, or a non-array ``words`` / ``segments`` field raises
         :class:`TimestampError` and the file is not rewritten.
         """
         chosen = self.resolve_engine(engine)
diff --git a/tests/test_asset_graph.py b/tests/test_asset_graph.py
index ebc6d38..b59f4b4 100644
--- a/tests/test_asset_graph.py
+++ b/tests/test_asset_graph.py
@@ -163,6 +163,21 @@ def test_segment_statuses_non_object_timing_stem_raises(tmp_path: Path) -> None:
         segment_step_statuses(cfg, "01")
 
 
+def test_segment_statuses_non_array_timing_words_raises(tmp_path: Path) -> None:
+    from docgen.timestamps import TimestampError
+
+    cfg = _bundle(tmp_path)
+    (cfg.animations_dir / "timing.json").write_text(
+        json.dumps({"01-demo": {"words": ["hello"]}}), encoding="utf-8"
+    )
+    with pytest.raises(
+        TimestampError,
+        match=r"timing.json\['01-demo'\].words\[0\] must be a JSON object",
+    ):
+        segment_step_statuses(cfg, "01")
+
+
+
 
 def test_api_segments_rejects_corrupt_timing_json(tmp_path: Path) -> None:
     cfg = _bundle(tmp_path)
diff --git a/tests/test_manim_scene_support.py b/tests/test_manim_scene_support.py
index a0f1072..d72b34a 100644
--- a/tests/test_manim_scene_support.py
+++ b/tests/test_manim_scene_support.py
@@ -418,6 +418,43 @@ def test_sync_audio_tail_waits_rejects_list_stem(tmp_path: Path) -> None:
         sync_audio_tail_waits_in_scenes(cfg)
 
 
+def test_sync_audio_tail_waits_rejects_non_array_segments(tmp_path: Path) -> None:
+    (tmp_path / "animations").mkdir(parents=True)
+    (tmp_path / "animations" / "scenes.py").write_text(
+        "# ── BEGIN GENERATED SCENE: 01 (OverviewScene) ──\n"
+        "class OverviewScene(_TimedScene):\n"
+        "    def construct(self):\n"
+        "        self.timed_play(Write(Text('x', font_size=24)), run_time=1.0)\n"
+        "# ── END GENERATED SCENE: 01 ──\n",
+        encoding="utf-8",
+    )
+    (tmp_path / "animations" / "timing.json").write_text(
+        json.dumps({"01-test": {"segments": "not-a-list"}}) + "\n",
+        encoding="utf-8",
+    )
+    raw = {
+        "dirs": {
+            "narration": "n",
+            "audio": "a",
+            "animations": "animations",
+            "recordings": "r",
+        },
+        "segments": {"all": ["01"], "default": ["01"]},
+        "segment_names": {"01": "01-test"},
+        "visual_map": {
+            "01": {"type": "manim", "scene": "OverviewScene", "source": "OverviewScene.mp4"}
+        },
+    }
+    (tmp_path / "docgen.yaml").write_text(yaml.dump(raw), encoding="utf-8")
+    cfg = Config.from_yaml(tmp_path / "docgen.yaml")
+    with pytest.raises(
+        SceneGenerationError,
+        match=r"timing.json\['01-test'\].segments must be a JSON array",
+    ):
+        sync_audio_tail_waits_in_scenes(cfg)
+
+
+
 
 _GOOD_CLASS = (
     "class DemoFunctionScene(_TimedScene):\n"
diff --git a/tests/test_scene_asset_validate.py b/tests/test_scene_asset_validate.py
index 10fca1d..09ba97f 100644
--- a/tests/test_scene_asset_validate.py
+++ b/tests/test_scene_asset_validate.py
@@ -369,3 +369,19 @@ def test_non_object_timing_stem_is_reported(tmp_path: Path) -> None:
     issues = scene_asset_violations_for_segment(cfg, "01")
     assert any("timing.json['01-x'] must be a JSON object, not null" in i for i in issues)
 
+
+def test_non_array_timing_words_is_reported(tmp_path: Path) -> None:
+    cfg = _bundle(tmp_path)
+    specs = cfg.animations_dir / "specs"
+    specs.mkdir(parents=True, exist_ok=True)
+    (specs / "01-x.scene.yaml").write_text(
+        yaml.dump(_spec([_box("Alpha")])),
+        encoding="utf-8",
+    )
+    (cfg.animations_dir / "timing.json").write_text(
+        json.dumps({"01-x": {"words": "corrupt"}}) + "\n", encoding="utf-8"
+    )
+    issues = scene_asset_violations_for_segment(cfg, "01")
+    assert any("timing.json['01-x'].words must be a JSON array, not str" in i for i in issues)
+
+
diff --git a/tests/test_scene_retime.py b/tests/test_scene_retime.py
index 7126254..da9cae5 100644
--- a/tests/test_scene_retime.py
+++ b/tests/test_scene_retime.py
@@ -313,6 +313,37 @@ def test_linted_class_block_fails_on_non_object_timing_stem(tmp_path: Path) -> N
         linted_class_block_from_spec(cfg, spec, timing_key="01-demo")
 
 
+def test_linted_class_block_fails_on_non_array_timing_words(tmp_path: Path) -> None:
+    cfg = _cfg(tmp_path)
+    (tmp_path / "animations" / "timing.json").write_text(
+        json.dumps({"01-demo": {"words": "not-a-list", "segments": []}}) + "\n",
+        encoding="utf-8",
+    )
+    spec = {
+        "segment_id": "01",
+        "class_name": "DemoScene",
+        "title": {"text": "Demo", "font_size": 36, "color": "C_WHITE"},
+        "rows": [
+            {
+                "run_time": 1.0,
+                "boxes": [
+                    {
+                        "label": "Hello",
+                        "color": "C_GREEN",
+                        "width": 3.0,
+                        "height": 0.9,
+                        "font_size": 18,
+                        "pace": "none",
+                    }
+                ],
+            }
+        ],
+    }
+    with pytest.raises(SceneGenerationError, match=r"timing.json\['01-demo'\].words must be a JSON array"):
+        linted_class_block_from_spec(cfg, spec, timing_key="01-demo")
+
+
+
 
 def test_retime_compile_spec_rewrites_scenes_py(tmp_path: Path) -> None:
     cfg = _cfg(tmp_path)
diff --git a/tests/test_timestamps_local.py b/tests/test_timestamps_local.py
index 726b7df..1996b51 100644
--- a/tests/test_timestamps_local.py
+++ b/tests/test_timestamps_local.py
@@ -271,3 +271,65 @@ def test_load_bundle_timing_accepts_object_stems(self, cfg) -> None:
         out.write_text(json.dumps(payload), encoding="utf-8")
         assert load_bundle_timing(cfg) == payload
 
+    def test_load_bundle_timing_accepts_missing_or_null_inner_lists(self, cfg) -> None:
+        from docgen.timestamps import load_bundle_timing
+
+        out = cfg.animations_dir / "timing.json"
+        out.parent.mkdir(parents=True, exist_ok=True)
+        payload = {"01-x": {"text": "ok", "words": None}, "legacy": {"text": "keep"}}
+        out.write_text(json.dumps(payload), encoding="utf-8")
+        assert load_bundle_timing(cfg) == payload
+
+    def test_load_bundle_timing_rejects_non_array_inner_lists(self, cfg) -> None:
+        from docgen.timestamps import TimestampError, load_bundle_timing
+
+        out = cfg.animations_dir / "timing.json"
+        out.parent.mkdir(parents=True, exist_ok=True)
+        cases = (
+            ({"01-x": {"words": "not-a-list"}}, r"timing.json\['01-x'\].words must be a JSON array, not str"),
+            ({"01-x": {"words": {}}}, r"timing.json\['01-x'\].words must be a JSON array, not dict"),
+            ({"01-x": {"segments": 3}}, r"timing.json\['01-x'\].segments must be a JSON array, not int"),
+        )
+        for payload, match in cases:
+            out.write_text(json.dumps(payload), encoding="utf-8")
+            with pytest.raises(TimestampError, match=match):
+                load_bundle_timing(cfg)
+
+    def test_load_bundle_timing_rejects_non_object_inner_items(self, cfg) -> None:
+        from docgen.timestamps import TimestampError, load_bundle_timing
+
+        out = cfg.animations_dir / "timing.json"
+        out.parent.mkdir(parents=True, exist_ok=True)
+        cases = (
+            (
+                {"01-x": {"words": ["hello"]}},
+                r"timing.json\['01-x'\].words\[0\] must be a JSON object, not str",
+            ),
+            (
+                {"01-x": {"segments": [1]}},
+                r"timing.json\['01-x'\].segments\[0\] must be a JSON object, not int",
+            ),
+            (
+                {"01-x": {"words": [None]}},
+                r"timing.json\['01-x'\].words\[0\] must be a JSON object, not null",
+            ),
+        )
+        for payload, match in cases:
+            out.write_text(json.dumps(payload), encoding="utf-8")
+            with pytest.raises(TimestampError, match=match):
+                load_bundle_timing(cfg)
+
+    def test_extract_all_rejects_non_array_words_without_rewrite(self, cfg, monkeypatch) -> None:
+        _fake_audio_env(monkeypatch)
+        (cfg.narration_dir / "01-x.md").write_text("Alpha begins the story.\n", encoding="utf-8")
+        (cfg.audio_dir / "01-x.mp3").write_bytes(b"fake-mp3")
+        out = cfg.animations_dir / "timing.json"
+        out.parent.mkdir(parents=True, exist_ok=True)
+        payload = json.dumps({"legacy-stem": {"words": "corrupt"}}) + "\n"
+        out.write_text(payload, encoding="utf-8")
+        from docgen.timestamps import TimestampError
+
+        with pytest.raises(TimestampError, match=r"timing.json\['legacy-stem'\].words must be a JSON array"):
+            TimestampExtractor(cfg).extract_all()
+        assert out.read_text(encoding="utf-8") == payload
+
diff --git a/tests/test_validate_timing_sync.py b/tests/test_validate_timing_sync.py
index 0374391..a3a5881 100644
--- a/tests/test_validate_timing_sync.py
+++ b/tests/test_validate_timing_sync.py
@@ -99,6 +99,17 @@ def test_non_object_timing_stem_fails_for_manim(self, cfg, monkeypatch) -> None:
         assert not check.passed
         assert any("timing.json['01-x'] must be a JSON object" in d for d in check.details)
 
+    def test_non_array_timing_words_fails_for_manim(self, cfg, monkeypatch) -> None:
+        (cfg.animations_dir / "timing.json").write_text(
+            json.dumps({"01-x": {"words": {"word": "hello"}, "segments": []}}) + "\n",
+            encoding="utf-8",
+        )
+        _patch_audio_duration(monkeypatch, 10.0)
+        check = Validator(cfg)._check_timing_sync("01")
+        assert not check.passed
+        assert any("timing.json['01-x'].words must be a JSON array" in d for d in check.details)
+
+
 
     def test_missing_timing_entry_skips_for_non_manim(self, tmp_path, monkeypatch) -> None:
         cfg = _bundle(tmp_path, visual_type="still")