diff --git a/docs/next-release-20260930.md b/docs/next-release-20260930.md
index 832f1cef..7309281e 100644
--- a/docs/next-release-20260930.md
+++ b/docs/next-release-20260930.md
@@ -385,3 +385,16 @@ are restored with the safe script. Dev's native Bitcoin/LND stayed running;
 all-container dev acceptance remains pending the companion-loop backend fix.
 Final-source UI suite: 1,133 passed. Heavy backend compilation is serialized with
 remaining build steps to reduce memory/IO pressure on the syncing dev node.
+
+Final source release gates at `96fb5a4f`: 1,613 backend tests passed, zero failed,
+four explicitly ignored; 1,133 UI tests passed; type-check, production UI build,
+catalog/trust, shell, pruning, LND readiness, NPM migration and doctor regressions
+passed. The isolated companion-loop regression passed independently as well.
+
+ISO cache hardening: the installer now carries the current doctor script and
+service/timer separately from rootfs.tar and overwrites both historical and active
+script locations before first boot. This prevents a cached base image restoring
+the old recovery code. A regression executes the actual installer block against
+stale disposable files twice and confirms a missing safety payload fails closed.
+The mounted-ISO smoke test also compares all three overlay files to source.
+The final ISO build captures the exact newly deployed OTA UI/runtime payload.
diff --git a/image-recipe/_archived/build-auto-installer-iso.sh b/image-recipe/_archived/build-auto-installer-iso.sh
index b4f70394..5e273033 100755
--- a/image-recipe/_archived/build-auto-installer-iso.sh
+++ b/image-recipe/_archived/build-auto-installer-iso.sh
@@ -2607,6 +2607,11 @@ if [ -f "$SCRIPT_DIR/../../scripts/image-versions.sh" ]; then
     echo "   ✅ Bundled image-versions.sh"
 fi
 
+# Always overlay the current doctor, including when rootfs.tar is cached.
+cp "$SCRIPT_DIR/../../scripts/container-doctor.sh" "$ARCH_DIR/scripts/"
+cp "$SCRIPT_DIR/../configs/archipelago-doctor.service" "$ARCH_DIR/scripts/"
+cp "$SCRIPT_DIR/../configs/archipelago-doctor.timer" "$ARCH_DIR/scripts/"
+
 # Build-source apps need their complete contexts even on unbundled ISOs.
 # Keep this identical to the OTA runtime payload; a per-app allowlist silently
 # omitted GitWorkshop, FIPS and Cuprate and made fresh installs fail at 70%.
@@ -3230,6 +3235,18 @@ for test_script in run-e2e-tests.sh run-post-install-tests.sh; do
     fi
 done
 
+# BEGIN DOCTOR OVERLAY
+# Replace both the active and historical script locations before first boot.
+# A cached rootfs can contain the unsafe network recovery implementation.
+mkdir -p /mnt/target/opt/archipelago/scripts /mnt/target/home/archipelago/archy/scripts
+for doctor_dir in /mnt/target/opt/archipelago/scripts /mnt/target/home/archipelago/archy/scripts; do
+    install -m 755 "$BOOT_MEDIA/archipelago/scripts/container-doctor.sh" "$doctor_dir/container-doctor.sh" || exit 1
+done
+for doctor_unit in archipelago-doctor.service archipelago-doctor.timer; do
+    install -m 644 "$BOOT_MEDIA/archipelago/scripts/$doctor_unit" "/mnt/target/etc/systemd/system/$doctor_unit" || exit 1
+done
+# END DOCTOR OVERLAY
+
 # Copy self-update script
 if [ -f "$BOOT_MEDIA/archipelago/scripts/self-update.sh" ]; then
     cp "$BOOT_MEDIA/archipelago/scripts/self-update.sh" /mnt/target/opt/archipelago/scripts/
diff --git a/scripts/iso-smoke-test.sh b/scripts/iso-smoke-test.sh
index 6f4470ab..8a2f5c15 100755
--- a/scripts/iso-smoke-test.sh
+++ b/scripts/iso-smoke-test.sh
@@ -71,6 +71,25 @@ else
     bad "incomplete app build payload"
 fi
 
+# The cached rootfs must never restore the unsafe historical doctor on boot.
+for doctor_file in container-doctor.sh archipelago-doctor.service archipelago-doctor.timer; do
+    if [[ "$doctor_file" == container-doctor.sh ]]; then
+        doctor_source="$REPO/scripts/$doctor_file"
+    else
+        doctor_source="$REPO/image-recipe/configs/$doctor_file"
+    fi
+    if cmp -s "$doctor_source" "$MNT/archipelago/scripts/$doctor_file"; then
+        ok "current doctor payload: $doctor_file"
+    else
+        bad "missing/stale doctor overlay: $doctor_file"
+    fi
+done
+if grep -Fq '# BEGIN DOCTOR OVERLAY' "$MNT/archipelago/auto-install.sh"; then
+    ok "installer replaces cached doctor before first boot"
+else
+    bad "installer lacks cached doctor replacement"
+fi
+
 # ── GRUB must boot the live system ───────────────────────────────────
 if grep -q "boot=live" "$MNT/boot/grub/grub.cfg" 2>/dev/null; then
     ok "grub.cfg has boot=live"
diff --git a/tests/regression/iso-doctor-overlay.py b/tests/regression/iso-doctor-overlay.py
new file mode 100644
index 00000000..729f4937
--- /dev/null
+++ b/tests/regression/iso-doctor-overlay.py
@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+"""Execute the installer's actual overlay against a stale disposable rootfs."""
+import pathlib, subprocess, tempfile, shutil, unittest
+ROOT = pathlib.Path(__file__).resolve().parents[2]
+class DoctorOverlayTests(unittest.TestCase):
+    def test_cached_rootfs_and_missing_payload(self):
+        source = (ROOT / 'image-recipe/_archived/build-auto-installer-iso.sh').read_text()
+        block = source.split('# BEGIN DOCTOR OVERLAY\n', 1)[1].split('# END DOCTOR OVERLAY', 1)[0]
+        with tempfile.TemporaryDirectory() as temp:
+            base = pathlib.Path(temp)
+            target = base / 'target'
+            media = base / 'media'
+            payload = media / 'archipelago/scripts'
+            payload.mkdir(parents=True)
+            units = target / 'etc/systemd/system'
+            units.mkdir(parents=True)
+            for directory in ['opt/archipelago/scripts', 'home/archipelago/archy/scripts']:
+                dest = target / directory
+                dest.mkdir(parents=True)
+                (dest / 'container-doctor.sh').write_text('UNSAFE OLD SCRIPT')
+            files = [ROOT / 'scripts/container-doctor.sh',
+                     ROOT / 'image-recipe/configs/archipelago-doctor.service',
+                     ROOT / 'image-recipe/configs/archipelago-doctor.timer']
+            for path in files:
+                shutil.copyfile(path, payload / path.name)
+            script = block.replace('/mnt/target', str(target))
+            for _ in range(2):
+                subprocess.run(['bash', '-c', script], env={'BOOT_MEDIA': str(media), 'PATH': '/usr/bin:/bin'}, check=True)
+                for directory in ['opt/archipelago/scripts', 'home/archipelago/archy/scripts']:
+                    dest = target / directory / 'container-doctor.sh'
+                    self.assertEqual(dest.read_bytes(), files[0].read_bytes())
+                    self.assertEqual(dest.stat().st_mode & 0o777, 0o755)
+                for path in files[1:]:
+                    self.assertEqual((units / path.name).read_bytes(), path.read_bytes())
+            (payload / 'container-doctor.sh').unlink()
+            failed = subprocess.run(['bash', '-c', script], env={'BOOT_MEDIA': str(media), 'PATH': '/usr/bin:/bin'}, capture_output=True)
+            self.assertNotEqual(failed.returncode, 0, 'Missing safety overlay must fail installation')
+if __name__ == '__main__':
+    unittest.main()
diff --git a/tests/release/run.sh b/tests/release/run.sh
index 1c04af14..9102a1fb 100755
--- a/tests/release/run.sh
+++ b/tests/release/run.sh
@@ -74,6 +74,7 @@ stage "cargo-fmt"        timeout 240 cargo fmt --manifest-path core/Cargo.toml -
 stage "app-build-contexts" python3 tests/regression/app-build-contexts.py
 stage "manifest-shell"  python3 scripts/check-manifest-shell.py
 stage "npm-tunnel-migration" python3 -m unittest discover -s scripts/tests -p test_repair_npm_tunnel.py
+stage "iso-doctor-overlay" python3 tests/regression/iso-doctor-overlay.py
 stage "doctor-egress" bash tests/regression/container-doctor-egress.sh
 stage "doctor-ports" bash tests/regression/container-doctor-ports.sh
 stage "bitcoin-pruning" python3 tests/regression/bitcoin-prune-entrypoint.py