diff --git a/CHANGELOG.md b/CHANGELOG.md
index f766f9cf..6439b950 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,15 @@
 
 # Changelog
 
+## Sprint 72 Mobile overflow hardening (2026-06-20)
+
+- Clamped page-level horizontal overflow for the workbench shell on mobile.
+- Kept sidebar navigation and workspace shortcut chips as contained horizontal scroll areas.
+- Added wrapping/containment for long QA identifiers, dataset links and inspector values.
+- Made inspector tabs two-column on narrow screens to avoid header overflow.
+- Added static regression coverage for mobile overflow and long-identifier wrapping contracts.
+- No API contracts, migrations, backend behavior, provider fetching or AI model behavior changed.
+
 ## Sprint 71 QA/QC metric card polish (2026-06-19)
 
 - Added core metric evidence cards for precision, recall, F1, mean IoU and false positive/negative counts.
diff --git a/backend/tests/test_sprint72_mobile_overflow_hardening.py b/backend/tests/test_sprint72_mobile_overflow_hardening.py
new file mode 100644
index 00000000..5e53877b
--- /dev/null
+++ b/backend/tests/test_sprint72_mobile_overflow_hardening.py
@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[2]
+
+
+def test_mobile_overflow_hardening_css_contracts() -> None:
+    css = (ROOT / "frontend" / "src" / "styles" / "app.css").read_text(encoding="utf-8")
+
+    assert "overflow-x: hidden;" in css
+    assert ".workbench-shell" in css
+    assert "max-width: 100vw;" in css
+    assert ".workbench-sidebar nav" in css
+    assert ".workspace-nav-cluster" in css
+    assert ".inspector-tabs" in css
+    assert "repeat(2, minmax(0, 1fr))" in css
+    assert "overflow-x: clip;" in css
+    assert "overscroll-behavior-x: contain;" in css
+
+
+def test_long_identifier_wrapping_contracts() -> None:
+    css = (ROOT / "frontend" / "src" / "styles" / "app.css").read_text(encoding="utf-8")
+
+    assert ".quality-check-dataset-link" in css
+    assert ".quality-score-row strong" in css
+    assert ".inspector-field strong" in css
+    assert "overflow-wrap: anywhere;" in css
+    assert "word-break: break-word;" in css
diff --git a/docs/CODEX_EXECUTION_LOG.md b/docs/CODEX_EXECUTION_LOG.md
index 6fd5a79a..910f9a5d 100644
--- a/docs/CODEX_EXECUTION_LOG.md
+++ b/docs/CODEX_EXECUTION_LOG.md
@@ -2697,3 +2697,32 @@ Limitations:
 
 Next recommended pass:
 - Continue with QA/QC metric/result filtering or result-card density for long-lived demo projects.
+
+## Sprint 72 Mobile overflow hardening (2026-06-20)
+
+Changed:
+- Clamped page-level horizontal overflow for `html`, `body` and the workbench shell.
+- Kept mobile sidebar navigation and workspace shortcut chips as contained horizontal scroll regions with overscroll containment.
+- Added min-width/max-width containment for the workbench layout, main area, inspector panel and card surfaces.
+- Allowed long QA check IDs, dataset links and inspector values to wrap instead of widening result cards.
+- Switched inspector tabs to a two-column layout on narrow screens.
+- Added `backend/tests/test_sprint72_mobile_overflow_hardening.py`.
+- Updated `frontend/README.md`, `docs/TODO.md` and `CHANGELOG.md`.
+
+Tested:
+- Red step: `python -m pytest backend/tests/test_sprint72_mobile_overflow_hardening.py -q` failed on missing mobile overflow and identifier wrapping contracts.
+- `python -m pytest backend/tests/test_sprint72_mobile_overflow_hardening.py backend/tests/test_sprint71_quality_metric_polish.py backend/tests/test_sprint62_frontend_visual_polish.py backend/tests/test_sprint30_workbench_components.py -q` (`11 passed`)
+- `cd frontend && npm run typecheck`
+- `cd frontend && npm run build`
+- Local browser check against `http://127.0.0.1:5176` with live API proxy at a 390px viewport: QA/QC workspace rendered 2 quality cards and 12 metric cards; body, shell, inspector, inspector panel and inspector tabs stayed within viewport width; sidebar/workspace nav retained contained horizontal scrolling; no console warnings/errors.
+- Screenshot captured under `artifacts/sprint72-mobile-overflow-hardening/`.
+- `bash scripts/run_readiness_check.sh` (`255 passed`)
+
+Open:
+- Redeploy Tower and verify live mobile overflow after deployment.
+
+Limitations:
+- Frontend CSS hardening only; no UI flow, API, persistence, migration, provider or AI/model changes.
+
+Next recommended pass:
+- Continue with QA/QC result filtering/density for long-lived demo projects, or a broader mobile visual pass across Data and Map once the overflow baseline is stable.
diff --git a/docs/TODO.md b/docs/TODO.md
index 55067570..c214ee7e 100644
--- a/docs/TODO.md
+++ b/docs/TODO.md
@@ -343,3 +343,4 @@ This file now starts with the current implementation status. Older preparation/b
 - [x] Add Data catalog action polish for map, metadata, export and QA affordances.
 - [x] Add QA/QC handoff polish for candidate/reference context and persisted results.
 - [x] Add QA/QC metric card polish for precision, recall, F1, IoU and error counts.
+- [x] Add mobile overflow hardening for workbench navigation, inspector and long QA identifiers.
diff --git a/frontend/README.md b/frontend/README.md
index bedb98a6..60b5b4ef 100644
--- a/frontend/README.md
+++ b/frontend/README.md
@@ -285,6 +285,8 @@ The frontend API client uses same-origin requests by default. In Docker Compose,
 
 The QA/QC workspace promotes core metrics into evidence cards before the raw metric list, keeping precision, recall, F1, mean IoU and false positive/negative counts scan-friendly while preserving the persisted raw metrics.
 
+The workbench shell clamps page-level horizontal overflow on mobile while keeping the sidebar and workspace shortcut rows intentionally scrollable. Long QA identifiers and inspector values wrap inside their cards instead of widening the viewport.
+
 ## Useful repository scripts
 
 - `bash scripts/frontend_install.sh`
diff --git a/frontend/src/styles/app.css b/frontend/src/styles/app.css
index 01b6e61f..11b0ae0f 100644
--- a/frontend/src/styles/app.css
+++ b/frontend/src/styles/app.css
@@ -25,10 +25,12 @@
 }
 
 html {
+  overflow-x: hidden;
   background: var(--bg);
 }
 
 body {
+  overflow-x: hidden;
   margin: 0;
   font-family: Inter, 'Avenir Next', 'Segoe UI', sans-serif;
   color: var(--text);
@@ -39,6 +41,11 @@ body {
   text-rendering: optimizeLegibility;
 }
 
+.workbench-shell {
+  max-width: 100vw;
+  overflow-x: clip;
+}
+
 button,
 input,
 select,
@@ -514,7 +521,8 @@ section li strong + div {
 
 .workbench-shell {
   width: 100%;
-  max-width: none;
+  max-width: 100vw;
+  overflow-x: clip;
   padding: 0;
   background: #eef4f1;
 }
@@ -579,10 +587,13 @@ section li strong + div {
   gap: 0;
   height: calc(100vh - 4.35rem);
   min-height: 42rem;
+  max-width: 100vw;
+  min-width: 0;
 }
 
 .workbench-sidebar,
 .workbench-inspector {
+  min-width: 0;
   min-height: 0;
   overflow: auto;
   border-color: var(--line);
@@ -640,6 +651,7 @@ section li strong + div {
 .workbench-main {
   min-width: 0;
   min-height: 0;
+  max-width: 100%;
   overflow: auto;
   padding: 0.9rem 1.05rem 1.15rem;
 }
@@ -1066,6 +1078,7 @@ button.entity-card {
 .export-card,
 .latest-export-card,
 .empty-state {
+  min-width: 0;
   padding: 0.85rem;
 }
 
@@ -1270,6 +1283,7 @@ button.entity-card {
 .quality-dataset-name,
 .quality-check-dataset-link {
   overflow-wrap: anywhere;
+  word-break: break-word;
 }
 
 .quality-dataset-name {
@@ -1301,7 +1315,13 @@ button.entity-card {
   font-size: 0.9rem;
   line-height: 1.25;
   text-overflow: ellipsis;
-  white-space: nowrap;
+  white-space: normal;
+}
+
+.quality-score-row strong,
+.inspector-field strong {
+  overflow-wrap: anywhere;
+  word-break: break-word;
 }
 
 .quality-metric-section {
@@ -1710,11 +1730,17 @@ button.entity-card {
 .workbench-inspector-panel {
   display: grid;
   gap: 0.68rem;
+  max-width: 100%;
+  min-width: 0;
+  overflow-x: clip;
 }
 
 .inspector-header {
   display: grid;
   gap: 0.2rem;
+  max-width: 100%;
+  min-width: 0;
+  overflow-x: clip;
 }
 
 .inspector-header h2 {
@@ -1734,12 +1760,14 @@ button.entity-card {
 }
 
 .inspector-tab {
+  min-width: 0;
   min-height: 2.2rem;
   padding: 0.38rem 0.42rem;
   background: #ffffff;
   box-shadow: none;
   font-size: 0.78rem;
   line-height: 1.2;
+  overflow-wrap: anywhere;
 }
 
 .inspector-tab-active {
@@ -1882,6 +1910,7 @@ button.entity-card {
     position: sticky;
     top: 5.8rem;
     z-index: 10;
+    max-width: 100vw;
     border-right: 0;
     border-bottom: 1px solid var(--line);
   }
@@ -1941,16 +1970,26 @@ button.entity-card {
     padding: 0.75rem;
   }
 
+  .workbench-inspector {
+    overflow-x: hidden;
+  }
+
   .context-bar,
   .quick-action-grid,
   .workspace-nav-cluster {
     grid-template-columns: 1fr;
   }
 
+  .inspector-tabs {
+    grid-template-columns: repeat(2, minmax(0, 1fr));
+  }
+
   .workbench-sidebar nav {
     display: flex;
     gap: 0.5rem;
+    max-width: 100%;
     overflow-x: auto;
+    overscroll-behavior-x: contain;
     padding-bottom: 0.2rem;
   }
 
@@ -1961,7 +2000,9 @@ button.entity-card {
   .workspace-nav-cluster {
     display: flex;
     flex-wrap: nowrap;
+    max-width: 100%;
     overflow-x: auto;
+    overscroll-behavior-x: contain;
     padding-bottom: 0.1rem;
   }