diff --git a/backend/app/services/ingest_core.py b/backend/app/services/ingest_core.py
index be418b0..7f7dcab 100644
--- a/backend/app/services/ingest_core.py
+++ b/backend/app/services/ingest_core.py
@@ -128,6 +128,8 @@ class Ingester:
         reached_bottom = False
         budget_hit = False
         early_out = False
+        stopped = False  # plan #708 B4: operator hit Stop mid-walk
+        cancel_armed = False  # latched once we observe a live "running" state
 
         def _result(
             *, success: bool, return_code: int,
@@ -179,6 +181,18 @@ class Ingester:
                     # the live posts count alongside it so the badge climbs DURING
                     # the chunk, not only when it ends.
                     if checkpoint:
+                        # plan #708 B4: an operator Stop pops `_backfill_state` —
+                        # bail at the page boundary (progress already checkpointed)
+                        # before more network work, so the live chunk halts
+                        # promptly instead of running to its time-box. LATCH on the
+                        # first observed "running" state, so a run invoked WITHOUT a
+                        # running state (a unit test, or a stale call) never
+                        # spuriously self-cancels. A short SELECT, never held.
+                        if self._still_running(source_id):
+                            cancel_armed = True
+                        elif cancel_armed:
+                            stopped = True
+                            break
                         self._checkpoint_cursor(source_id, emitted_cursor)
                         self._checkpoint_posts(source_id, posts_base + chunk_new_posts)
 
@@ -283,6 +297,16 @@ class Ingester:
             # maps it to a typed error.
             return self._failure_result(exc, _result)
 
+        # plan #708 B4: a Stop already popped the backfill state (incl. cursor +
+        # posts), so don't re-write them — return PARTIAL (reads as "ok/progress",
+        # the lifecycle no-ops since state is gone) instead of a false "complete".
+        if stopped:
+            return _result(
+                success=False, return_code=-1,
+                error_type=ErrorType.PARTIAL,
+                error_message=f"Stopped by operator: {downloaded} file(s) this chunk",
+            )
+
         # Final authoritative posts count for the badge — captures the last page
         # after the last boundary write and the time-box break (plan #704 #5).
         if checkpoint:
@@ -389,6 +413,23 @@ class Ingester:
             )
             session.commit()
 
+    def _still_running(self, source_id: int) -> bool:
+        """True while the source is armed for a deep walk (plan #708 B4).
+
+        An operator Stop (`source_service.stop_backfill`) pops `_backfill_state`,
+        so a False here means "cancel this chunk now". One short SELECT on its own
+        session — never held across the walk
+        ([[db-connection-held-across-subprocess]])."""
+        with self.session_factory() as session:
+            state = session.execute(
+                text(
+                    "SELECT config_overrides::jsonb ->> '_backfill_state' "
+                    "FROM source WHERE id = :sid"
+                ),
+                {"sid": source_id},
+            ).scalar_one_or_none()
+        return state == "running"
+
     def _checkpoint_posts(self, source_id: int, posts: int) -> None:
         """Persist the live backfill posts-processed count mid-walk (plan #704 #5).
 
diff --git a/tests/test_patreon_ingester.py b/tests/test_patreon_ingester.py
index 3ca19a5..57a491b 100644
--- a/tests/test_patreon_ingester.py
+++ b/tests/test_patreon_ingester.py
@@ -382,6 +382,50 @@ async def test_backfill_budget_cut_returns_partial_with_progress(
     assert result.cursor == "CUR2"
 
 
+@pytest.mark.asyncio
+async def test_still_running_reads_backfill_state(source_id, sync_engine, tmp_path, db):
+    """plan #708 B4: _still_running reflects the source's `_backfill_state` — the
+    flag an operator Stop pops to cancel a live chunk."""
+    ing = _ingester(sync_engine, tmp_path, _FakeClient([]), _FakeDownloader(tmp_path))
+    assert ing._still_running(source_id) is False  # absent → not running
+    src = (await db.execute(select(Source).where(Source.id == source_id))).scalar_one()
+    src.config_overrides = {"_backfill_state": "running"}
+    await db.commit()
+    assert ing._still_running(source_id) is True
+
+
+@pytest.mark.asyncio
+async def test_backfill_stops_when_operator_cancels_mid_walk(
+    source_id, sync_engine, tmp_path,
+):
+    """plan #708 B4: with the running state latched, a later page boundary that
+    finds it gone (Stop) bails the chunk with PARTIAL instead of finishing."""
+    pages = [
+        ("CUR2", [("p1", [_media("p1", 1)])]),
+        ("CUR3", [("p2", [_media("p2", 1)])]),
+        ("CUR4", [("p3", [_media("p3", 1)])]),
+    ]
+    downloader = _FakeDownloader(tmp_path)
+    ing = _ingester(sync_engine, tmp_path, _FakeClient(pages), downloader)
+
+    # Latch on the page-2 boundary (running), then "Stop" before page 3.
+    calls = {"n": 0}
+
+    def fake_still_running(_source_id):
+        calls["n"] += 1
+        return calls["n"] == 1
+
+    ing._still_running = fake_still_running
+
+    result = ing.run(
+        source_id=source_id, campaign_id="c1", artist_slug="ingest",
+        url="https://patreon.com/ingest", mode="backfill",
+    )
+    assert result.error_type == ErrorType.PARTIAL
+    assert "Stopped by operator" in result.error_message
+    assert downloader.download_calls == 1  # only p1 ran; cancelled before p2
+
+
 # --- recovery -------------------------------------------------------------