diff --git a/tests/test_litellm/litellm_core_utils/test_no_log_spend_tracking.py b/tests/test_litellm/litellm_core_utils/test_no_log_spend_tracking.py
new file mode 100644
index 00000000000..2193d48416f
--- /dev/null
+++ b/tests/test_litellm/litellm_core_utils/test_no_log_spend_tracking.py
@@ -0,0 +1,128 @@
+"""`no-log` must not disable spend tracking.
+
+`no-log` means "do not send this request to logging integrations". It is not a
+way for a caller to opt out of being billed, and `Logging.should_run_callback`
+has always intended to exempt the proxy's cost-tracking callback from it. The
+exemption used to be a case-sensitive substring test for `"_PROXY_"` in the
+callback's class name, which never matched the cost callback's actual class
+(`_ProxyDBLogger`), so spend tracking was silently skipped for every `no-log`
+request. Callbacks now declare the behaviour explicitly via `runs_on_no_log`.
+"""
+
+import os
+import sys
+
+import pytest
+
+sys.path.insert(0, os.path.abspath("../../.."))
+
+import litellm
+from litellm.integrations.custom_logger import CustomLogger
+from litellm.litellm_core_utils.litellm_logging import Logging as LiteLLMLogging
+from litellm.proxy.hooks.proxy_track_cost_callback import _ProxyDBLogger
+
+
+class _ObservabilityLogger(CustomLogger):
+    """A stand-in for langfuse/datadog/etc. -- must be skipped on no-log."""
+
+
+class _MeteringLogger(CustomLogger):
+    """A stand-in for a billing callback -- must still run on no-log."""
+
+    runs_on_no_log = True
+
+
+def _logging_obj() -> LiteLLMLogging:
+    return LiteLLMLogging(
+        model="gpt-4o",
+        messages=[{"role": "user", "content": "hi"}],
+        stream=False,
+        call_type="acompletion",
+        start_time=None,
+        litellm_call_id="test-call-id",
+        function_id="test-function-id",
+    )
+
+
+def test_cost_callback_still_runs_on_no_log():
+    """The regression: _ProxyDBLogger must survive a no-log request."""
+    assert _ProxyDBLogger.runs_on_no_log is True
+    assert (
+        _logging_obj().should_run_callback(
+            callback=_ProxyDBLogger(),
+            litellm_params={"no-log": True},
+            event_hook="async_log_success_event",
+        )
+        is True
+    )
+
+
+def test_observability_callback_is_skipped_on_no_log():
+    """no-log still does what it says for logging integrations."""
+    assert _ObservabilityLogger.runs_on_no_log is False
+    assert (
+        _logging_obj().should_run_callback(
+            callback=_ObservabilityLogger(),
+            litellm_params={"no-log": True},
+            event_hook="async_log_success_event",
+        )
+        is False
+    )
+
+
+def test_runs_on_no_log_is_opt_in_for_any_callback():
+    """Any callback can declare itself as infrastructure, not just the proxy's."""
+    assert (
+        _logging_obj().should_run_callback(
+            callback=_MeteringLogger(),
+            litellm_params={"no-log": True},
+            event_hook="async_log_success_event",
+        )
+        is True
+    )
+
+
+@pytest.mark.parametrize("litellm_params", [{}, {"no-log": False}])
+def test_everything_runs_when_no_log_is_absent_or_false(litellm_params):
+    for callback in (_ObservabilityLogger(), _ProxyDBLogger()):
+        assert (
+            _logging_obj().should_run_callback(
+                callback=callback,
+                litellm_params=litellm_params,
+                event_hook="async_log_success_event",
+            )
+            is True
+        )
+
+
+def test_legacy_underscore_proxy_naming_still_exempt():
+    """Callbacks named _PROXY_* keep working without setting the new flag."""
+
+    class _PROXY_LegacyHandler(CustomLogger):
+        pass
+
+    assert _PROXY_LegacyHandler.runs_on_no_log is False
+    assert (
+        _logging_obj().should_run_callback(
+            callback=_PROXY_LegacyHandler(),
+            litellm_params={"no-log": True},
+            event_hook="async_log_success_event",
+        )
+        is True
+    )
+
+
+def test_global_disable_no_log_param_overrides_everything():
+    original = litellm.global_disable_no_log_param
+    litellm.global_disable_no_log_param = True
+    try:
+        assert (
+            _logging_obj().should_run_callback(
+                callback=_ObservabilityLogger(),
+                litellm_params={"no-log": True},
+                event_hook="async_log_success_event",
+            )
+            is True
+        )
+    finally:
+        litellm.global_disable_no_log_param = original