diff --git a/.github/workflows/security.yml b/.github/workflows/security.yml
index 14c80a1e1..34cae237d 100644
--- a/.github/workflows/security.yml
+++ b/.github/workflows/security.yml
@@ -40,6 +40,10 @@ jobs:
         run: |
           pytest deploy/docker/tests/test_security_*.py -q
 
+      - name: Run docker utility unit tests
+        run: |
+          pytest deploy/docker/tests/test_utils_*.py -q
+
   posture-gate:
     # The headline secure-by-default acceptance gate, isolated so it can be a
     # required status check. xfail-marked items (e.g. the build-gated
diff --git a/deploy/docker/tests/test_utils_memory.py b/deploy/docker/tests/test_utils_memory.py
new file mode 100644
index 000000000..43b4e14f8
--- /dev/null
+++ b/deploy/docker/tests/test_utils_memory.py
@@ -0,0 +1,201 @@
+"""Unit tests for deploy/docker/utils.get_container_memory_percent().
+
+Pure-function tests: no Docker, no network, no cgroup filesystem. The cgroup
+paths and psutil host stats are injected, so the cgroup v2 "max" (unlimited)
+handling and the v1 > 1e18 sentinel are both covered deterministically.
+"""
+
+import importlib
+import sys
+import types
+from pathlib import Path
+
+import pytest
+
+
+def _stub_modules():
+    """Return a dict of temporary stubs for modules that utils.py needs at import time.
+
+    Only stubs modules that are NOT already in sys.modules (using setdefault)
+    so that real installed packages are never overwritten.
+    """
+    stubs = {}
+    for module_name in ("dns", "dns.resolver", "yaml", "fastapi", "psutil"):
+        if module_name not in sys.modules:
+            stub = types.ModuleType(module_name)
+            stubs[module_name] = stub
+    if "fastapi" not in sys.modules:
+        stubs.setdefault("fastapi", types.ModuleType("fastapi"))
+    if not hasattr(stubs.get("fastapi", sys.modules.get("fastapi")), "Request"):
+        (stubs.get("fastapi") or sys.modules["fastapi"]).Request = object
+    return stubs
+
+
+@pytest.fixture()
+def utils():
+    """Import deploy/docker/utils.py with temporary stubs, cleaning up after."""
+    # Capture modules that will be temporarily injected
+    stubs = _stub_modules()
+    added_modules = {}
+
+    for name, mod in stubs.items():
+        if name not in sys.modules:
+            sys.modules[name] = mod
+            added_modules[name] = mod
+
+    # Ensure deploy/docker is on sys.path so `import utils` works
+    docker_dir = str(Path(__file__).resolve().parents[1])
+    path_inserted = docker_dir not in sys.path
+    if path_inserted:
+        sys.path.insert(0, docker_dir)
+
+    try:
+        # Force fresh import so monkeypatch on utils.Path works correctly
+        if "utils" in sys.modules:
+            mod = importlib.reload(sys.modules["utils"])
+        else:
+            mod = importlib.import_module("utils")
+        yield mod
+    finally:
+        # Restore sys.modules — remove ONLY the stubs we added
+        for name in added_modules:
+            sys.modules.pop(name, None)
+        # Remove deploy/docker/utils from sys.modules so next test gets fresh import
+        sys.modules.pop("utils", None)
+        if path_inserted:
+            sys.path.remove(docker_dir)
+
+
+HOST_TOTAL = 16 * 1024**3  # 16 GiB
+HOST_PERCENT = 47.5
+
+
+@pytest.fixture()
+def host_memory(monkeypatch, utils):
+    """Pin psutil.virtual_memory() so host-total fallbacks are deterministic."""
+    psutil_mod = sys.modules.get("psutil")
+    if psutil_mod is None:
+        psutil_mod = types.ModuleType("psutil")
+    monkeypatch.setattr(
+        psutil_mod,
+        "virtual_memory",
+        lambda: types.SimpleNamespace(total=HOST_TOTAL, percent=HOST_PERCENT),
+        raising=False,
+    )
+    return psutil_mod
+
+
+def _patch_cgroup_files(monkeypatch, utils_mod, values, present):
+    """Replace utils.Path with a fake whose files mirror a cgroup filesystem."""
+    present_paths = set(present)
+
+    def factory(path):
+        fake = types.SimpleNamespace(path=str(path))
+        fake.exists = lambda: fake.path in present_paths
+        fake.read_text = lambda: utils_read(fake.path)
+        return fake
+
+    def utils_read(path):
+        if path not in present_paths:
+            raise FileNotFoundError(path)
+        return values.get(path, "0")
+
+    monkeypatch.setattr(utils_mod, "Path", factory)
+
+
+def test_cgroup_v2_numeric_limit(monkeypatch, utils, host_memory):
+    _patch_cgroup_files(
+        monkeypatch,
+        utils,
+        {
+            "/sys/fs/cgroup/memory.current": "524288000",
+            "/sys/fs/cgroup/memory.max": "2147483648",
+        },
+        {"/sys/fs/cgroup/memory.current", "/sys/fs/cgroup/memory.max"},
+    )
+
+    assert utils.get_container_memory_percent() == pytest.approx(524288000 / 2147483648 * 100)
+
+
+def test_cgroup_v2_unlimited_max_counts_against_host_total(monkeypatch, utils, host_memory):
+    # Regression for https://github.com/unclecode/crawl4ai/issues/2123:
+    # int("max") used to raise ValueError, the bare except swallowed it, and the
+    # guard reported the HOST's usage percent instead of container usage vs
+    # host total (the intent of the existing "unlimited" branch).
+    usage = 512 * 1024**2
+    _patch_cgroup_files(
+        monkeypatch,
+        utils,
+        {
+            "/sys/fs/cgroup/memory.current": str(usage),
+            "/sys/fs/cgroup/memory.max": "max\n",  # cgroup v2 "no limit" sentinel
+        },
+        {"/sys/fs/cgroup/memory.current", "/sys/fs/cgroup/memory.max"},
+    )
+
+    assert utils.get_container_memory_percent() == pytest.approx(usage / HOST_TOTAL * 100)
+
+
+def test_cgroup_v1_numeric_limit(monkeypatch, utils, host_memory):
+    _patch_cgroup_files(
+        monkeypatch,
+        utils,
+        {
+            "/sys/fs/cgroup/memory/memory.usage_in_bytes": "262144000",
+            "/sys/fs/cgroup/memory/memory.limit_in_bytes": "1073741824",
+        },
+        {
+            "/sys/fs/cgroup/memory/memory.usage_in_bytes",
+            "/sys/fs/cgroup/memory/memory.limit_in_bytes",
+        },
+    )
+
+    assert utils.get_container_memory_percent() == pytest.approx(262144000 / 1073741824 * 100)
+
+
+def test_cgroup_v1_unlimited_huge_limit_counts_against_host_total(monkeypatch, utils, host_memory):
+    usage = 256 * 1024**2
+    _patch_cgroup_files(
+        monkeypatch,
+        utils,
+        {
+            "/sys/fs/cgroup/memory/memory.usage_in_bytes": str(usage),
+            "/sys/fs/cgroup/memory/memory.limit_in_bytes": str(2**63),  # v1 "no limit"
+        },
+        {
+            "/sys/fs/cgroup/memory/memory.usage_in_bytes",
+            "/sys/fs/cgroup/memory/memory.limit_in_bytes",
+        },
+    )
+
+    assert utils.get_container_memory_percent() == pytest.approx(usage / HOST_TOTAL * 100)
+
+
+def test_non_container_falls_back_to_host_percent(monkeypatch, utils, host_memory):
+    _patch_cgroup_files(monkeypatch, utils, {}, set())
+
+    assert utils.get_container_memory_percent() == pytest.approx(HOST_PERCENT)
+
+
+def test_stubs_do_not_pollute_sys_modules():
+    """Verify that after the utils fixture, no fake modules remain in sys.modules."""
+    # This test itself imports utils via the fixture, which should clean up
+    # The test body is intentionally empty — if the fixture cleanup is broken,
+    # this test's own sys.modules will still have stubs, which is the bug we're testing for.
+    # Instead, run a subprocess-like check:
+    real_modules = {}
+    for name in ("dns", "dns.resolver", "yaml", "fastapi", "psutil"):
+        mod = sys.modules.get(name)
+        real_modules[name] = mod  # Could be None (not installed) or real module
+
+    # After the utils fixture teardown, stubs we added should be gone.
+    # The only modules that should remain are ones that were there before.
+    # Since we can't easily test "was this module here before this file loaded",
+    # we just verify: if a stub module is in sys.modules, it should have been there already.
+    # For this test, we don't use the utils fixture, so nothing should change.
+    for name in ("dns", "dns.resolver", "yaml", "fastapi", "psutil"):
+        after = sys.modules.get(name)
+        if after is not None and isinstance(after, types.ModuleType) and not hasattr(after, "__file__"):
+            # This is likely a stub we injected — but since we didn't use the fixture,
+            # this means something else polluted. Flag it.
+            assert False, f"Module '{name}' appears to be a stub in sys.modules without __file__"
diff --git a/deploy/docker/utils.py b/deploy/docker/utils.py
index 8f8ecb180..1a7431779 100644
--- a/deploy/docker/utils.py
+++ b/deploy/docker/utils.py
@@ -419,11 +419,19 @@ def get_container_memory_percent() -> float:
             usage_path = Path("/sys/fs/cgroup/memory/memory.usage_in_bytes")
             limit_path = Path("/sys/fs/cgroup/memory/memory.limit_in_bytes")
 
-        usage = int(usage_path.read_text())
-        limit = int(limit_path.read_text())
+        usage = int(usage_path.read_text().strip())
+        raw_limit = limit_path.read_text().strip()
+
+        # cgroup v2 reports an unset memory limit as the literal string "max"
+        # (the "unlimited" sentinel this branch already knew about on v1,
+        # > 1e18). int("max") used to raise a ValueError that the bare except
+        # swallowed, so the guard silently reported the HOST's percentage
+        # instead of container usage vs host total. Normalize it to the same
+        # sentinel as the v1 unlimited value.
+        limit = float("inf") if raw_limit == "max" else int(raw_limit)
 
         # Handle unlimited (v2: "max", v1: > 1e18)
-        if limit > 1e18:
+        if limit == float("inf") or limit > 1e18:
             import psutil
             limit = psutil.virtual_memory().total