diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3c19f048..1dfbcc09 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,8 @@
   persistence and technical views.
 - Added widescreen layout guardrails for AI workspaces and regression coverage
   for project lifecycle, packaged cleanup and the new component boundaries.
+- Bounded the 15-theme selector on narrow mobile screens so the primary map
+  and result flow is no longer displaced by the complete theme inventory.
 - Hardened the packaged archive command for direct container execution and
   added a subprocess regression for the documented operator invocation.
 
diff --git a/backend/tests/test_sprint72_mobile_overflow_hardening.py b/backend/tests/test_sprint72_mobile_overflow_hardening.py
index 180f3ae3..28522c9e 100644
--- a/backend/tests/test_sprint72_mobile_overflow_hardening.py
+++ b/backend/tests/test_sprint72_mobile_overflow_hardening.py
@@ -27,6 +27,12 @@ def test_mobile_overflow_hardening_css_contracts() -> None:
     explorer_mobile_rule = explorer_mobile_css.split(".geo-explorer-layout", 1)[1]
     assert "display: block;" in explorer_mobile_rule.split("}", 1)[0]
 
+    compact_mobile_css = css.rsplit("@media (max-width: 620px)", 1)[1]
+    compact_theme_rule = compact_mobile_css.split(".geo-theme-list {", 1)[1].split("}", 1)[0]
+    assert "max-height: 16rem;" in compact_theme_rule
+    assert "overflow-y: auto;" in compact_theme_rule
+    assert "overscroll-behavior-y: contain;" in compact_theme_rule
+
 
 def test_long_identifier_wrapping_contracts() -> None:
     css = (ROOT / "frontend" / "src" / "styles" / "app.css").read_text(encoding="utf-8")
diff --git a/docs/CODEX_EXECUTION_LOG.md b/docs/CODEX_EXECUTION_LOG.md
index b791e168..e30abd08 100644
--- a/docs/CODEX_EXECUTION_LOG.md
+++ b/docs/CODEX_EXECUTION_LOG.md
@@ -10006,4 +10006,7 @@ Validation:
 - Live browser inspection found no console errors or document overflow at
   3440x1440. Map and Detection workspaces keep a bounded 1,680 px operational
   canvas, technical disclosures are collapsed and persisted AI internals now
-  use friendly labels in the ordinary result tables.
+  use friendly labels in the ordinary result tables. At 390x844 the document
+  stays within its 375 px client width; the theme inventory is bounded to a
+  compact scrollable selector so it no longer pushes the map behind all 15
+  theme cards.
diff --git a/frontend/src/styles/app.css b/frontend/src/styles/app.css
index 5a6bfadb..1f509211 100644
--- a/frontend/src/styles/app.css
+++ b/frontend/src/styles/app.css
@@ -6695,6 +6695,14 @@ section {
     grid-template-columns: 1fr;
   }
 
+  .geo-theme-list {
+    max-height: 16rem;
+    overflow-y: auto;
+    overscroll-behavior-y: contain;
+    padding-right: 0.18rem;
+    scrollbar-gutter: stable;
+  }
+
   .geo-temporal-summary > div {
     border-top: 1px solid #e1e8e5;
     border-left: 0;