diff --git a/content/en/history/bibliography/_index.md b/content/en/history/bibliography/_index.md
index 3f5110ed..d1c6a953 100644
--- a/content/en/history/bibliography/_index.md
+++ b/content/en/history/bibliography/_index.md
@@ -3,9 +3,12 @@ title: Bibliography
 heading: Interlisp Bibliography
 type: bibliography
 robots: "noindex, follow"
+# Keep this section visible in the sidebar. Hugo merges a section's own
+# cascade into its own Params, so cascade.toc_hide alone would hide it.
+toc_hide: false
 cascade:
     type: bibliography
-    toc_hide: false
+    toc_hide: true
 weight: 5
 aliases:
  - /bibliography/
diff --git a/content/en/history/bibliography/intake/_index.md b/content/en/history/bibliography/intake/_index.md
index 97991332..0c0843ec 100644
--- a/content/en/history/bibliography/intake/_index.md
+++ b/content/en/history/bibliography/intake/_index.md
@@ -2,6 +2,10 @@
 title: Interlisp Bibliography Intake Guide
 weight: 1
 type: docs
+# Explicitly visible in the sidebar: the parent bibliography section's
+# cascade sets toc_hide:true (to keep generated entries out of the nav),
+# and Hugo merges cascade into children's Params too.
+toc_hide: false
 ---
 
 ## I have something I think belongs in the Interlisp Bibliography!
diff --git a/tests/test_hugo_build.py b/tests/test_hugo_build.py
index 24596afc..55c22fee 100644
--- a/tests/test_hugo_build.py
+++ b/tests/test_hugo_build.py
@@ -160,6 +160,75 @@ def test_bibliography_section_present(self):
         )
 
 
+class TestHistorySidebarNavigation:
+    """The Bibliography section must be reachable from History navigation.
+
+    Regression tests for PR #347: setting only ``cascade.toc_hide`` hid the
+    Bibliography entry itself from the History sidebar (Hugo merges a
+    section's own cascade into its own Params). The empty
+    ``layouts/_partials/section-index.html`` override is intentional and
+    must keep suppressing the subpage cards. Either deviation must break
+    the build tests.
+    """
+
+    @pytest.fixture(autouse=True)
+    def history_page(self, production_build):
+        self.build_result = production_build
+        path = PROD_PUBLIC / "history" / "index.html"
+        if not path.exists():
+            pytest.skip("history/index.html not found — run a production build first")
+        self.content = path.read_text(encoding="utf-8", errors="ignore")
+
+    def test_bibliography_in_sidebar_nav(self) -> None:
+        """The sidebar nav on /history/ must link to /history/bibliography/."""
+        nav = re.search(
+            r'<nav[^>]*id="td-section-nav".*?</nav>',
+            self.content,
+            re.DOTALL,
+        )
+        assert nav, "sidebar nav #td-section-nav not found on history page"
+        assert "/history/bibliography/" in nav.group(0), (
+            "Bibliography entry missing from the History sidebar navigation"
+        )
+
+    def test_intake_guide_in_sidebar_nav(self) -> None:
+        """The Intake Guide must be listed under Bibliography, while the
+        hundreds of generated entries must stay out of the nav."""
+        nav = re.search(
+            r'<nav[^>]*id="td-section-nav".*?</nav>',
+            self.content,
+            re.DOTALL,
+        )
+        assert nav, "sidebar nav #td-section-nav not found on history page"
+        nav_html = nav.group(0)
+        assert "/history/bibliography/intake/" in nav_html, (
+            "Intake Guide entry missing from the sidebar navigation"
+        )
+        stray_entries = re.findall(
+            r'href="/history/bibliography/(?!intake/)[a-z0-9]+/"', nav_html
+        )
+        assert not stray_entries, (
+            "Generated bibliography entries leaking into sidebar navigation:\n"
+            + "\n".join(stray_entries[:10])
+        )
+
+    def test_no_subpage_cards(self) -> None:
+        """The History page must not render section-index subpage cards;
+        subpage navigation lives in the sidebar. The empty
+        ``layouts/_partials/section-index.html`` override suppresses them."""
+        assert '<div class="section-index">' not in self.content, (
+            "section-index subpage list should be suppressed on the History page"
+        )
+
+    def test_no_sidebar_truncation_warning(self) -> None:
+        """Hugo must not truncate sidebar entries — a flood of unhidden
+        bibliography entries (e.g. from a stale Zotero cache without
+        ``toc_hide``) would trigger this Docsy warning."""
+        assert "sidebar entries have been truncated" not in (
+            self.build_result.stderr or ""
+        ), "Sidebar entries were truncated — bibliography entries may be leaking into navigation"
+
+
 class TestInternalLinks:
     """All internal href links in the built HTML must resolve to existing pages."""