diff --git a/backend/tests/core/test_auth_logger.py b/backend/tests/core/test_auth_logger.py
new file mode 100644
index 00000000..89408461
--- /dev/null
+++ b/backend/tests/core/test_auth_logger.py
@@ -0,0 +1,88 @@
+# #region Test.AuthLogger [C:3] [TYPE Module] [SEMANTICS test,auth,audit,logging,security]
+# @BRIEF Tests for core/auth/logger.py — _mask_details, log_security_event.
+# @RELATION BINDS_TO -> [AuthLoggerModule]
+
+from pathlib import Path
+import sys
+
+sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
+
+from unittest.mock import patch, MagicMock
+import pytest
+
+
+class TestMaskDetails:
+    """_mask_details — masks sensitive field values."""
+
+    def test_none_returns_none(self):
+        from src.core.auth.logger import _mask_details
+        assert _mask_details(None) is None
+
+    def test_empty_dict(self):
+        from src.core.auth.logger import _mask_details
+        assert _mask_details({}) == {}
+
+    def test_password_masked(self):
+        from src.core.auth.logger import _mask_details
+        result = _mask_details({"password": "supersecret", "username": "admin"})
+        assert result["password"] == "***"
+        assert result["username"] == "admin"
+
+    def test_token_masked(self):
+        from src.core.auth.logger import _mask_details
+        result = _mask_details({"token": "abc123", "action": "login"})
+        assert result["token"] == "***"
+
+    def test_api_key_masked(self):
+        from src.core.auth.logger import _mask_details
+        result = _mask_details({"api_key": "sk-12345"})
+        assert result["api_key"] == "***"
+
+    def test_secret_masked(self):
+        from src.core.auth.logger import _mask_details
+        result = _mask_details({"secret": "my-secret"})
+        assert result["secret"] == "***"
+
+    def test_authorization_masked(self):
+        from src.core.auth.logger import _mask_details
+        result = _mask_details({"authorization": "Bearer xxx"})
+        assert result["authorization"] == "***"
+
+    def test_nested_dict_masked(self):
+        from src.core.auth.logger import _mask_details
+        result = _mask_details({"user": {"password": "secret", "name": "John"}})
+        assert result["user"]["password"] == "***"
+        assert result["user"]["name"] == "John"
+
+    def test_case_insensitive_masking(self):
+        from src.core.auth.logger import _mask_details
+        result = _mask_details({"Password": "secret", "TOKEN": "abc"})
+        assert result["Password"] == "***"
+        assert result["TOKEN"] == "***"
+
+    def test_non_sensitive_keys_preserved(self):
+        from src.core.auth.logger import _mask_details
+        result = _mask_details({"email": "user@example.com", "role": "admin"})
+        assert result["email"] == "user@example.com"
+        assert result["role"] == "admin"
+
+
+class TestLogSecurityEvent:
+    """log_security_event — logs audit events with masked details."""
+
+    def test_logs_without_details(self):
+        from src.core.auth.logger import log_security_event
+        with patch("src.core.auth.logger.logger.info") as mock_info:
+            log_security_event("LOGIN_SUCCESS", "admin")
+            assert mock_info.call_count >= 1
+
+    def test_logs_with_masked_details(self):
+        from src.core.auth.logger import log_security_event
+        with patch("src.core.auth.logger.logger.info") as mock_info:
+            log_security_event("LOGIN_FAILED", "admin", {"password": "wrong", "ip": "10.0.0.1"})
+            assert mock_info.call_count >= 1
+            # The details should contain masked password
+            args_list = [c[0] for c in mock_info.call_args_list]
+            details_call = [a for a in args_list if "Details" in a[0]]
+            assert len(details_call) >= 1
+# #endregion Test.AuthLogger
diff --git a/backend/tests/core/test_client_registry.py b/backend/tests/core/test_client_registry.py
new file mode 100644
index 00000000..b5854979
--- /dev/null
+++ b/backend/tests/core/test_client_registry.py
@@ -0,0 +1,254 @@
+# #region Test.SupersetClientRegistry [C:3] [TYPE Module] [SEMANTICS test,registry,superset,client,async]
+# @BRIEF Tests for core/utils/client_registry.py — get_client, get_superset_client, get_semaphore, get_auth_lock, shutdown.
+# @RELATION BINDS_TO -> [SupersetClientRegistryModule]
+
+from pathlib import Path
+import sys
+
+sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
+
+from unittest.mock import AsyncMock, MagicMock, patch
+import asyncio
+import pytest
+
+
+class TestBuildEnvId:
+    """_build_env_id — stable identifier from env config."""
+
+    def test_env_with_id(self):
+        from src.core.utils.client_registry import _build_env_id
+        env = MagicMock()
+        env.id = "env-1"
+        env.base_url = "http://superset:8088"
+        result = _build_env_id(env)
+        assert "env-1" in result
+        assert "superset" in result
+
+    def test_env_without_id_uses_object_id(self):
+        from src.core.utils.client_registry import _build_env_id
+        env = {"base_url": "http://x.com", "username": "admin"}
+        result = _build_env_id(env)
+        assert "x.com" in result
+        assert "admin" in result
+
+    def test_dict_env_fallback(self):
+        from src.core.utils.client_registry import _build_env_id
+        env = {"base_url": "http://test:8080", "username": "user"}
+        result = _build_env_id(env)
+        assert result
+
+
+@pytest.mark.asyncio
+class TestGetClient:
+    """get_client — create or return cached client."""
+
+    async def test_creates_new_client_from_model(self):
+        from src.core.utils.client_registry import get_client, shutdown
+
+        env = MagicMock()
+        env.id = "env-1"
+        env.url = "http://superset:8088"
+        env.username = "admin"
+        env.password = "pass"
+        env.verify_ssl = False
+        env.timeout = 30
+
+        with patch("src.core.utils.client_registry.AsyncAPIClient") as mock_client_cls:
+            mock_client = AsyncMock()
+            mock_client_cls.return_value = mock_client
+
+            client = await get_client(env)
+            assert client is mock_client
+            mock_client_cls.assert_called_once()
+
+        await shutdown()
+
+    async def test_returns_cached_client(self):
+        from src.core.utils.client_registry import get_client, shutdown, _registry
+
+        env = MagicMock()
+        env.id = "env-1"
+        env.url = "http://superset:8088"
+        env.username = "admin"
+        env.password = "pass"
+        env.verify_ssl = False
+        env.timeout = 30
+
+        with patch("src.core.utils.client_registry.AsyncAPIClient") as mock_client_cls:
+            mock_client = AsyncMock()
+            mock_client_cls.return_value = mock_client
+
+            client1 = await get_client(env)
+            client2 = await get_client(env)
+            assert client1 is client2
+            assert mock_client_cls.call_count == 1
+
+        await shutdown()
+
+    async def test_dict_env(self):
+        from src.core.utils.client_registry import get_client, shutdown
+
+        env = {"base_url": "http://superset:8088", "username": "admin", "password": "pass"}
+
+        with patch("src.core.utils.client_registry.AsyncAPIClient") as mock_client_cls:
+            mock_client = AsyncMock()
+            mock_client_cls.return_value = mock_client
+
+            client = await get_client(env)
+            assert client is mock_client
+
+        await shutdown()
+
+    async def test_unknown_env_type(self):
+        from src.core.utils.client_registry import get_client, shutdown
+
+        env = 42  # not a model or dict
+
+        with patch("src.core.utils.client_registry.AsyncAPIClient") as mock_client_cls:
+            mock_client = AsyncMock()
+            mock_client_cls.return_value = mock_client
+
+            client = await get_client(env)
+            assert client is mock_client
+
+        await shutdown()
+
+
+@pytest.mark.asyncio
+class TestGetSupersetClient:
+    """get_superset_client — wraps AsyncAPIClient in SupersetClient."""
+
+    async def test_returns_superset_client(self):
+        from src.core.utils.client_registry import get_superset_client, shutdown
+
+        env = MagicMock()
+        env.id = "env-1"
+        env.url = "http://superset:8088"
+        env.username = "admin"
+        env.password = "pass"
+        env.verify_ssl = False
+        env.timeout = 30
+
+        mock_shared = AsyncMock()
+
+        with (
+            patch("src.core.utils.client_registry.get_client", return_value=mock_shared),
+            patch("src.core.superset_client.SupersetClient") as mock_sc_cls,
+        ):
+            mock_sc = MagicMock()
+            mock_sc_cls.return_value = mock_sc
+
+            client = await get_superset_client(env)
+            assert client is mock_sc
+
+        await shutdown()
+
+
+@pytest.mark.asyncio
+class TestGetSemaphoreAndLock:
+    """get_semaphore and get_auth_lock — return shared resources."""
+
+    async def test_get_semaphore(self):
+        from src.core.utils.client_registry import get_semaphore, get_client, shutdown
+
+        env = MagicMock()
+        env.id = "env-1"
+        env.url = "http://superset:8088"
+        env.username = "admin"
+        env.password = "pass"
+        env.verify_ssl = False
+        env.timeout = 30
+
+        with patch("src.core.utils.client_registry.AsyncAPIClient") as mock_cls:
+            mock_cls.return_value = AsyncMock()
+            await get_client(env)
+            sem = await get_semaphore(env)
+            assert sem is not None
+
+        await shutdown()
+
+    async def test_get_auth_lock(self):
+        from src.core.utils.client_registry import get_auth_lock, get_client, shutdown
+
+        env = MagicMock()
+        env.id = "env-1"
+        env.url = "http://superset:8088"
+        env.username = "admin"
+        env.password = "pass"
+        env.verify_ssl = False
+        env.timeout = 30
+
+        with patch("src.core.utils.client_registry.AsyncAPIClient") as mock_cls:
+            mock_cls.return_value = AsyncMock()
+            await get_client(env)
+            lock = await get_auth_lock(env)
+            assert lock is not None
+
+        await shutdown()
+
+    async def test_get_semaphore_creates_client_if_missing(self):
+        from src.core.utils.client_registry import get_semaphore, shutdown, _registry
+
+        env = MagicMock()
+        env.id = "env-1"
+        env.url = "http://superset:8088"
+        env.username = "admin"
+        env.password = "pass"
+        env.verify_ssl = False
+        env.timeout = 30
+
+        _registry.clear()
+
+        with patch("src.core.utils.client_registry.AsyncAPIClient") as mock_cls:
+            mock_cls.return_value = AsyncMock()
+            sem = await get_semaphore(env)
+            assert sem is not None
+
+        await shutdown()
+
+
+@pytest.mark.asyncio
+class TestShutdown:
+    """shutdown — close all clients and clear registry."""
+
+    async def test_shutdown_closes_clients(self):
+        from src.core.utils.client_registry import get_client, shutdown
+
+        env = MagicMock()
+        env.id = "env-1"
+        env.url = "http://superset:8088"
+        env.username = "admin"
+        env.password = "pass"
+        env.verify_ssl = False
+        env.timeout = 30
+
+        with patch("src.core.utils.client_registry.AsyncAPIClient") as mock_cls:
+            mock_client = AsyncMock()
+            mock_cls.return_value = mock_client
+            await get_client(env)
+            await shutdown()
+            mock_client.aclose.assert_called_once()
+
+    async def test_shutdown_empty_registry(self):
+        from src.core.utils.client_registry import shutdown, _registry
+        _registry.clear()
+        await shutdown()  # should not raise
+
+    async def test_shutdown_handles_close_error(self):
+        from src.core.utils.client_registry import get_client, shutdown
+
+        env = MagicMock()
+        env.id = "env-1"
+        env.url = "http://superset:8088"
+        env.username = "admin"
+        env.password = "pass"
+        env.verify_ssl = False
+        env.timeout = 30
+
+        with patch("src.core.utils.client_registry.AsyncAPIClient") as mock_cls:
+            mock_client = AsyncMock()
+            mock_client.aclose.side_effect = ConnectionError("Close failed")
+            mock_cls.return_value = mock_client
+            await get_client(env)
+            await shutdown()  # should not raise
+# #endregion Test.SupersetClientRegistry
diff --git a/backend/tests/core/test_cot_logger.py b/backend/tests/core/test_cot_logger.py
new file mode 100644
index 00000000..73638879
--- /dev/null
+++ b/backend/tests/core/test_cot_logger.py
@@ -0,0 +1,199 @@
+# #region Test.CotLogger [C:3] [TYPE Module] [SEMANTICS test,logging,cot,trace,span,json]
+# @BRIEF Tests for core/cot_logger.py — trace_id, span, log markers, MarkerLogger.
+# @RELATION BINDS_TO -> [CotLoggerModule]
+
+from pathlib import Path
+import sys
+
+sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
+
+import logging
+import re
+from unittest.mock import patch, MagicMock, call
+import pytest
+
+
+class TestSeedTraceId:
+    """seed_trace_id — generates UUID and sets ContextVar."""
+
+    def test_returns_uuid_string(self):
+        from src.core.cot_logger import seed_trace_id
+        tid = seed_trace_id()
+        assert isinstance(tid, str)
+        assert len(tid) == 36  # UUID4 with hyphens
+        assert tid.count("-") == 4
+
+    def test_sets_trace_id(self):
+        from src.core.cot_logger import seed_trace_id, get_trace_id
+        tid = seed_trace_id()
+        assert get_trace_id() == tid
+
+
+class TestSetTraceId:
+    """set_trace_id — sets explicit trace ID."""
+
+    def test_sets_provided_id(self):
+        from src.core.cot_logger import set_trace_id, get_trace_id
+        set_trace_id("custom-trace-123")
+        assert get_trace_id() == "custom-trace-123"
+
+
+class TestGetTraceId:
+    """get_trace_id — returns current trace ID."""
+
+    def test_default_empty(self):
+        from src.core.cot_logger import get_trace_id
+        # After seed, get_trace_id returns non-empty
+        # In a fresh test the ContextVar may be empty
+        pass  # ContextVar has default ""
+
+    def test_after_seed_returns_value(self):
+        from src.core.cot_logger import seed_trace_id, get_trace_id
+        tid = seed_trace_id()
+        assert get_trace_id() == tid
+
+
+class TestPushPopSpan:
+    """push_span and pop_span — span stack operations."""
+
+    def test_push_returns_previous(self):
+        from src.core.cot_logger import push_span, pop_span
+        prev1 = push_span("span-1")
+        # Initially empty
+        prev2 = push_span("span-2")
+        assert prev2 == "span-1"
+        pop_span(prev2)
+        # After pop, current span is back to "span-1"
+
+    def test_push_pop_restores(self):
+        from src.core.cot_logger import push_span
+        prev = push_span("outer")
+        inner_prev = push_span("inner")
+        assert inner_prev == "outer"
+        # pop restores outer
+        from src.core.cot_logger import pop_span
+        pop_span(inner_prev)
+
+
+class TestLog:
+    """log — structured JSON logging with markers."""
+
+    def test_reason_marker_info_level(self):
+        from src.core.cot_logger import log
+        with patch("src.core.cot_logger.cot_logger.info") as mock_info:
+            log("TestModule", "REASON", "Testing reason")
+            mock_info.assert_called_once()
+            args, kwargs = mock_info.call_args
+            assert "Testing reason" in args[0]
+            extra = kwargs.get("extra", {})
+            assert extra["marker"] == "REASON"
+            assert extra["src"] == "TestModule"
+            assert extra["intent"] == "Testing reason"
+
+    def test_reflect_marker_info_level(self):
+        from src.core.cot_logger import log
+        with patch("src.core.cot_logger.cot_logger.info") as mock_info:
+            log("Test", "REFLECT", "Reflecting")
+            mock_info.assert_called_once()
+
+    def test_explore_marker_warning_level(self):
+        from src.core.cot_logger import log
+        with patch("src.core.cot_logger.cot_logger.warning") as mock_warn:
+            log("Test", "EXPLORE", "Exploring alternatives", error="Assumption violated")
+            mock_warn.assert_called_once()
+
+    def test_error_level_explicit(self):
+        from src.core.cot_logger import log
+        with patch("src.core.cot_logger.cot_logger.error") as mock_err:
+            log("Test", "REASON", "Error test", level="ERROR")
+            mock_err.assert_called_once()
+
+    def test_debug_level_explicit(self):
+        from src.core.cot_logger import log
+        with patch("src.core.cot_logger.cot_logger.debug") as mock_debug:
+            log("Test", "REASON", "Debug test", level="DEBUG")
+            mock_debug.assert_called_once()
+
+    def test_payload_included(self):
+        from src.core.cot_logger import log
+        with patch("src.core.cot_logger.cot_logger.info") as mock_info:
+            log("Test", "REASON", "With payload", payload={"key": "value"})
+            extra = mock_info.call_args[1]["extra"]
+            assert extra["payload"] == {"key": "value"}
+
+    def test_error_included(self):
+        from src.core.cot_logger import log
+        with patch("src.core.cot_logger.cot_logger.warning") as mock_warn:
+            log("Test", "EXPLORE", "Error case", error="Something broke")
+            extra = mock_warn.call_args[1]["extra"]
+            assert extra["error"] == "Something broke"
+
+    def test_payload_not_included_when_none(self):
+        from src.core.cot_logger import log
+        with patch("src.core.cot_logger.cot_logger.info") as mock_info:
+            log("Test", "REASON", "No payload")
+            extra = mock_info.call_args[1]["extra"]
+            assert "payload" not in extra
+
+    def test_error_not_included_when_none(self):
+        from src.core.cot_logger import log
+        with patch("src.core.cot_logger.cot_logger.info") as mock_info:
+            log("Test", "REASON", "No error")
+            extra = mock_info.call_args[1]["extra"]
+            assert "error" not in extra
+
+    def test_warning_level_inferred_from_explore(self):
+        from src.core.cot_logger import log
+        with patch("src.core.cot_logger.cot_logger.warning") as mock_warn:
+            log("Test", "EXPLORE", "Auto warning")
+            mock_warn.assert_called_once()
+
+
+class TestMarkerLogger:
+    """MarkerLogger — convenience proxy for .reason(), .reflect(), .explore()."""
+
+    @pytest.fixture
+    def logger(self):
+        from src.core.cot_logger import MarkerLogger
+        return MarkerLogger("MyComponent")
+
+    def test_reason(self, logger):
+        with patch("src.core.cot_logger.log") as mock_log:
+            logger.reason("Doing something", payload={"action": "test"})
+            mock_log.assert_called_once_with("MyComponent", "REASON", "Doing something", payload={"action": "test"})
+
+    def test_reflect(self, logger):
+        with patch("src.core.cot_logger.log") as mock_log:
+            logger.reflect("Done")
+            mock_log.assert_called_once_with("MyComponent", "REFLECT", "Done", payload=None)
+
+    def test_explore(self, logger):
+        with patch("src.core.cot_logger.log") as mock_log:
+            logger.explore("Failed", error="DB timeout")
+            mock_log.assert_called_once_with("MyComponent", "EXPLORE", "Failed", payload=None, error="DB timeout")
+
+    def test_explore_with_payload_and_error(self, logger):
+        with patch("src.core.cot_logger.log") as mock_log:
+            logger.explore("Retrying", payload={"attempt": 2}, error="Timeout")
+            mock_log.assert_called_once_with("MyComponent", "EXPLORE", "Retrying", payload={"attempt": 2}, error="Timeout")
+
+
+class TestTraceIdPropagation:
+    """Trace ID propagation across async contexts."""
+
+    def test_seed_then_get(self):
+        from src.core.cot_logger import seed_trace_id, get_trace_id
+        tid = seed_trace_id()
+        assert get_trace_id() == tid
+
+    def test_set_then_get(self):
+        from src.core.cot_logger import set_trace_id, get_trace_id
+        set_trace_id("abc-123")
+        assert get_trace_id() == "abc-123"
+
+    def test_set_overrides_seed(self):
+        from src.core.cot_logger import seed_trace_id, set_trace_id, get_trace_id
+        seed_trace_id()
+        set_trace_id("override")
+        assert get_trace_id() == "override"
+# #endregion Test.CotLogger
diff --git a/backend/tests/core/test_encryption.py b/backend/tests/core/test_encryption.py
new file mode 100644
index 00000000..f873f20e
--- /dev/null
+++ b/backend/tests/core/test_encryption.py
@@ -0,0 +1,112 @@
+# #region Test.Encryption [C:3] [TYPE Module] [SEMANTICS test,encryption,fernet,key,crypto]
+# @BRIEF Tests for core/encryption.py and core/encryption_key.py — Fernet key loading, encrypt/decrypt.
+# @RELATION BINDS_TO -> [EncryptionCore]
+
+from pathlib import Path
+import sys
+
+sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
+
+import os
+import tempfile
+from unittest.mock import patch, MagicMock
+import pytest
+
+
+class TestRequireFernetKey:
+    """_require_fernet_key — loads and validates Fernet key from environment."""
+
+    def test_valid_key(self):
+        from src.core.encryption import _require_fernet_key
+        key = "MldUHg5kwSAcPnnYxmhWDS6ASb6e_bWQRV5gtwHrjQ0="
+        with patch.dict(os.environ, {"ENCRYPTION_KEY": key}, clear=True):
+            result = _require_fernet_key()
+            assert result == key.encode()
+
+    def test_missing_key_raises(self):
+        from src.core.encryption import _require_fernet_key
+        with patch.dict(os.environ, {}, clear=True):
+            with pytest.raises(RuntimeError, match="ENCRYPTION_KEY must be set"):
+                _require_fernet_key()
+
+    def test_invalid_key_raises(self):
+        from src.core.encryption import _require_fernet_key
+        with patch.dict(os.environ, {"ENCRYPTION_KEY": "not-a-valid-fernet-key"}, clear=True):
+            with pytest.raises(RuntimeError, match="valid Fernet key"):
+                _require_fernet_key()
+
+    def test_empty_key_raises(self):
+        from src.core.encryption import _require_fernet_key
+        with patch.dict(os.environ, {"ENCRYPTION_KEY": "  "}, clear=True):
+            with pytest.raises(RuntimeError, match="ENCRYPTION_KEY must be set"):
+                _require_fernet_key()
+
+
+class TestEncryptionManager:
+    """EncryptionManager — encrypt and decrypt operations."""
+
+    def test_encrypt_decrypt_cycle(self):
+        from src.core.encryption import EncryptionManager
+        key = "MldUHg5kwSAcPnnYxmhWDS6ASb6e_bWQRV5gtwHrjQ0="
+        with patch.dict(os.environ, {"ENCRYPTION_KEY": key}, clear=True):
+            mgr = EncryptionManager()
+            encrypted = mgr.encrypt("my_secret_data")
+            assert encrypted != "my_secret_data"
+            decrypted = mgr.decrypt(encrypted)
+            assert decrypted == "my_secret_data"
+
+    def test_empty_string_encryption(self):
+        from src.core.encryption import EncryptionManager
+        key = "MldUHg5kwSAcPnnYxmhWDS6ASb6e_bWQRV5gtwHrjQ0="
+        with patch.dict(os.environ, {"ENCRYPTION_KEY": key}, clear=True):
+            mgr = EncryptionManager()
+            encrypted = mgr.encrypt("")
+            decrypted = mgr.decrypt(encrypted)
+            assert decrypted == ""
+
+    def test_decrypt_invalid_data_raises(self):
+        from src.core.encryption import EncryptionManager
+        key = "MldUHg5kwSAcPnnYxmhWDS6ASb6e_bWQRV5gtwHrjQ0="
+        with patch.dict(os.environ, {"ENCRYPTION_KEY": key}, clear=True):
+            mgr = EncryptionManager()
+            with pytest.raises(Exception):
+                mgr.decrypt("not-encrypted-data")
+
+
+class TestEnsureEncryptionKey:
+    """ensure_encryption_key — resolve key from env or .env file."""
+
+    def test_from_environment(self):
+        from src.core.encryption_key import ensure_encryption_key
+        key = "MldUHg5kwSAcPnnYxmhWDS6ASb6e_bWQRV5gtwHrjQ0="
+        with patch.dict(os.environ, {"ENCRYPTION_KEY": key}, clear=True):
+            result = ensure_encryption_key()
+            assert result == key
+
+    def test_from_env_file(self):
+        from src.core.encryption_key import ensure_encryption_key
+        key = "MldUHg5kwSAcPnnYxmhWDS6ASb6e_bWQRV5gtwHrjQ0="
+        with patch.dict(os.environ, {}, clear=True):
+            with tempfile.TemporaryDirectory() as tmpdir:
+                env_file = Path(tmpdir) / ".env"
+                env_file.write_text(f"ENCRYPTION_KEY={key}\nOTHER=value\n")
+                result = ensure_encryption_key(env_file)
+                assert result == key
+                # Should also set it in environment
+                assert os.environ.get("ENCRYPTION_KEY") == key
+
+    def test_env_file_not_found_raises(self):
+        from src.core.encryption_key import ensure_encryption_key
+        with patch.dict(os.environ, {}, clear=True):
+            with pytest.raises(RuntimeError, match="ENCRYPTION_KEY is not set"):
+                ensure_encryption_key(Path("/nonexistent/.env"))
+
+    def test_env_file_without_key_raises(self):
+        from src.core.encryption_key import ensure_encryption_key
+        with patch.dict(os.environ, {}, clear=True):
+            with tempfile.TemporaryDirectory() as tmpdir:
+                env_file = Path(tmpdir) / ".env"
+                env_file.write_text("OTHER=value\n")
+                with pytest.raises(RuntimeError, match="ENCRYPTION_KEY is not set"):
+                    ensure_encryption_key(env_file)
+# #endregion Test.Encryption
diff --git a/backend/tests/core/test_executors.py b/backend/tests/core/test_executors.py
new file mode 100644
index 00000000..257dcaf4
--- /dev/null
+++ b/backend/tests/core/test_executors.py
@@ -0,0 +1,187 @@
+# #region Test.BlockingExecutors [C:3] [TYPE Module] [SEMANTICS test,async,executors,blocking,threadpool]
+# @BRIEF Tests for core/utils/executors.py — init, shutdown, run_blocking, run_cpu_blocking.
+# @RELATION BINDS_TO -> [BlockingExecutorsModule]
+
+from pathlib import Path
+import sys
+
+sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
+
+import unittest
+from unittest.mock import MagicMock, patch, AsyncMock
+import asyncio
+import pytest
+
+
+class TestInitShutdown:
+    """init_executors and shutdown_executors."""
+
+    def test_init_creates_executors(self):
+        from src.core.utils.executors import init_executors
+        with patch("src.core.utils.executors.ThreadPoolExecutor") as mock_tpe:
+            init_executors(db_workers=5, file_workers=3, git_workers=2)
+            assert mock_tpe.call_count == 3
+
+    def test_shutdown_without_init(self):
+        # shutdown should not raise when executors are None
+        from src.core.utils.executors import shutdown_executors
+        shutdown_executors()
+
+    def test_shutdown_calls_shutdown(self):
+        from src.core.utils.executors import init_executors, shutdown_executors
+        import src.core.utils.executors as exec_mod
+        with patch.object(exec_mod, "_db_executor", None), \
+             patch.object(exec_mod, "_file_executor", None), \
+             patch.object(exec_mod, "_git_executor", None):
+            with patch("src.core.utils.executors.ThreadPoolExecutor") as mock_tpe:
+                mock_executor = MagicMock()
+                mock_tpe.return_value = mock_executor
+                init_executors()
+                shutdown_executors()
+                assert mock_executor.shutdown.call_count >= 1
+                for call in mock_executor.shutdown.call_args_list:
+                    assert call == unittest.mock.call(wait=True, cancel_futures=True)
+
+    def test_shutdown_no_wait(self):
+        from src.core.utils.executors import init_executors, shutdown_executors
+        import src.core.utils.executors as exec_mod
+        with patch.object(exec_mod, "_db_executor", None), \
+             patch.object(exec_mod, "_file_executor", None), \
+             patch.object(exec_mod, "_git_executor", None):
+            with patch("src.core.utils.executors.ThreadPoolExecutor") as mock_tpe:
+                mock_executor = MagicMock()
+                mock_tpe.return_value = mock_executor
+                init_executors()
+                shutdown_executors(wait=False, cancel_futures=False)
+                assert mock_executor.shutdown.call_count >= 1
+                for call in mock_executor.shutdown.call_args_list:
+                    assert call == unittest.mock.call(wait=False, cancel_futures=False)
+
+
+class TestGetExecutor:
+    """_get_executor — returns executor and semaphore by kind."""
+
+    def test_db_kind(self):
+        from src.core.utils.executors import _get_executor, init_executors, shutdown_executors
+        with patch("src.core.utils.executors.ThreadPoolExecutor"):
+            init_executors()
+            executor, sem = _get_executor("db")
+            assert executor is not None
+            assert sem is not None
+            shutdown_executors()
+
+    def test_file_kind(self):
+        from src.core.utils.executors import _get_executor, init_executors, shutdown_executors
+        with patch("src.core.utils.executors.ThreadPoolExecutor"):
+            init_executors()
+            executor, sem = _get_executor("file")
+            assert executor is not None
+            assert sem is not None
+            shutdown_executors()
+
+    def test_git_kind(self):
+        from src.core.utils.executors import _get_executor, init_executors, shutdown_executors
+        with patch("src.core.utils.executors.ThreadPoolExecutor"):
+            init_executors()
+            executor, sem = _get_executor("git")
+            assert executor is not None
+            assert sem is not None
+            shutdown_executors()
+
+    def test_unknown_kind_raises(self):
+        from src.core.utils.executors import _get_executor, init_executors, shutdown_executors
+        with patch("src.core.utils.executors.ThreadPoolExecutor"):
+            init_executors()
+            with pytest.raises(ValueError, match="Unknown executor kind"):
+                _get_executor("unknown")
+            shutdown_executors()
+
+
+class TestRunBlocking:
+    """run_blocking — execute blocking function in named executor."""
+
+    @pytest.mark.asyncio
+    async def test_runs_function(self):
+        from src.core.utils.executors import run_blocking, init_executors, shutdown_executors
+
+        with patch("src.core.utils.executors.ThreadPoolExecutor") as mock_tpe:
+            mock_executor = MagicMock()
+            mock_tpe.return_value = mock_executor
+            init_executors()
+
+            # Make run_in_executor work
+            mock_loop = AsyncMock()
+            mock_loop.run_in_executor.return_value = "result"
+            get_running_loop = asyncio.get_running_loop
+
+            with patch.object(asyncio, "get_running_loop", return_value=mock_loop):
+                result = await run_blocking("db", lambda: "hello")
+                assert result == "result"
+
+            shutdown_executors()
+
+    @pytest.mark.asyncio
+    async def test_semaphore_acquisition_failure(self):
+        from src.core.utils.executors import run_blocking, init_executors, shutdown_executors
+
+        with patch("src.core.utils.executors.ThreadPoolExecutor"):
+            init_executors(queue_timeout=0.1)
+
+            with (
+                patch("src.core.utils.executors._db_semaphore") as mock_sem,
+                pytest.raises(TimeoutError, match="queue timeout"),
+            ):
+                mock_sem.acquire.side_effect = TimeoutError()
+                await run_blocking("db", lambda: "hello", timeout=0.1)
+
+            shutdown_executors()
+
+    @pytest.mark.asyncio
+    async def test_semaphore_release_on_success(self):
+        from src.core.utils.executors import run_blocking, init_executors, shutdown_executors
+
+        with patch("src.core.utils.executors.ThreadPoolExecutor"):
+            init_executors()
+            mock_loop = AsyncMock()
+            mock_loop.run_in_executor.return_value = "done"
+
+            # Track semaphore acquire/release
+            with patch.object(asyncio, "get_running_loop", return_value=mock_loop):
+                result = await run_blocking("file", lambda: "work")
+                assert result == "done"
+
+            shutdown_executors()
+
+    @pytest.mark.asyncio
+    async def test_cancelled_error_propagates(self):
+        from src.core.utils.executors import run_blocking, init_executors, shutdown_executors
+
+        with patch("src.core.utils.executors.ThreadPoolExecutor"):
+            init_executors()
+            mock_loop = AsyncMock()
+            mock_loop.run_in_executor.side_effect = asyncio.CancelledError()
+
+            with (
+                patch.object(asyncio, "get_running_loop", return_value=mock_loop),
+                pytest.raises(asyncio.CancelledError),
+            ):
+                await run_blocking("git", lambda: "fail")
+
+            shutdown_executors()
+
+
+class TestRunCpuBlocking:
+    """run_cpu_blocking — CPU-bound work in default executor."""
+
+    @pytest.mark.asyncio
+    async def test_runs_in_default_executor(self):
+        from src.core.utils.executors import run_cpu_blocking
+
+        mock_loop = AsyncMock()
+        mock_loop.run_in_executor.return_value = 42
+
+        with patch.object(asyncio, "get_running_loop", return_value=mock_loop):
+            result = await run_cpu_blocking(lambda: 42)
+            assert result == 42
+            mock_loop.run_in_executor.assert_called_once_with(None, mock_loop.run_in_executor.call_args[0][1])
+# #endregion Test.BlockingExecutors
diff --git a/backend/tests/core/test_fileio_utils.py b/backend/tests/core/test_fileio_utils.py
new file mode 100644
index 00000000..3a8a72be
--- /dev/null
+++ b/backend/tests/core/test_fileio_utils.py
@@ -0,0 +1,310 @@
+# #region Test.FileIO.Utils [C:3] [TYPE Module] [SEMANTICS test,fileio,utils,filename,sanitize,crc32]
+# @BRIEF Tests for core/utils/fileio.py — pure utility functions: sanitize_filename, get_filename_from_headers, calculate_crc32, create_temp_file, remove_empty_directories.
+# @RELATION BINDS_TO -> [FileIO]
+
+from pathlib import Path
+import sys
+
+sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
+
+import os
+import tempfile
+import zipfile
+from unittest.mock import MagicMock, patch
+import pytest
+
+
+class TestSanitizeFilename:
+    """sanitize_filename — removes invalid filename characters."""
+
+    def test_already_clean(self):
+        from src.core.utils.fileio import sanitize_filename
+        assert sanitize_filename("dashboard_export.zip") == "dashboard_export.zip"
+
+    def test_replaces_backslash(self):
+        from src.core.utils.fileio import sanitize_filename
+        assert "\\" not in sanitize_filename("a\\b")
+        assert "_" in sanitize_filename("a\\b")
+
+    def test_replaces_colon(self):
+        from src.core.utils.fileio import sanitize_filename
+        assert ":" not in sanitize_filename("a:b")
+        assert "_" in sanitize_filename("a:b")
+
+    def test_replaces_angle_brackets(self):
+        from src.core.utils.fileio import sanitize_filename
+        assert "<" not in sanitize_filename("a<b")
+        assert ">" not in sanitize_filename("a>b")
+
+    def test_replaces_question_mark(self):
+        from src.core.utils.fileio import sanitize_filename
+        assert "?" not in sanitize_filename("a?b")
+        assert "_" in sanitize_filename("a?b")
+
+    def test_replaces_asterisk(self):
+        from src.core.utils.fileio import sanitize_filename
+        assert "*" not in sanitize_filename("a*b")
+        assert "_" in sanitize_filename("a*b")
+
+    def test_replaces_pipe(self):
+        from src.core.utils.fileio import sanitize_filename
+        assert "|" not in sanitize_filename("a|b")
+        assert "_" in sanitize_filename("a|b")
+
+    def test_replaces_quote(self):
+        from src.core.utils.fileio import sanitize_filename
+        assert '"' not in sanitize_filename('a"b')
+        assert "_" in sanitize_filename('a"b')
+
+    def test_strips_whitespace(self):
+        from src.core.utils.fileio import sanitize_filename
+        result = sanitize_filename("  file.txt  ")
+        assert result == "file.txt"
+        assert result == result.strip()
+
+    def test_empty_string(self):
+        from src.core.utils.fileio import sanitize_filename
+        assert sanitize_filename("") == ""
+
+
+class TestGetFilenameFromHeaders:
+    """get_filename_from_headers — extracts filename from Content-Disposition."""
+
+    def test_standard_header(self):
+        from src.core.utils.fileio import get_filename_from_headers
+        headers = {"Content-Disposition": 'attachment; filename="report.pdf"'}
+        assert get_filename_from_headers(headers) == "report.pdf"
+
+    def test_header_without_quotes(self):
+        from src.core.utils.fileio import get_filename_from_headers
+        headers = {"Content-Disposition": "attachment; filename=report.pdf"}
+        assert get_filename_from_headers(headers) == "report.pdf"
+
+    def test_missing_header(self):
+        from src.core.utils.fileio import get_filename_from_headers
+        assert get_filename_from_headers({}) is None
+
+    def test_empty_header(self):
+        from src.core.utils.fileio import get_filename_from_headers
+        headers = {"Content-Disposition": ""}
+        assert get_filename_from_headers(headers) is None
+
+    def test_no_filename_in_header(self):
+        from src.core.utils.fileio import get_filename_from_headers
+        headers = {"Content-Disposition": "inline"}
+        assert get_filename_from_headers(headers) is None
+
+    def test_filename_with_spaces(self):
+        from src.core.utils.fileio import get_filename_from_headers
+        headers = {"Content-Disposition": 'attachment; filename="my report.csv"'}
+        assert get_filename_from_headers(headers) == "my report.csv"
+
+    def test_utf8_filename_with_regular_format(self):
+        """The regex only matches filename=\"...\", not filename*=UTF-8''..."""
+        from src.core.utils.fileio import get_filename_from_headers
+        headers = {"Content-Disposition": 'attachment; filename="report.pdf"; filename*=UTF-8\'\'%D0%BE%D1%82%D1%87%D0%B5%D1%82.pdf'}
+        result = get_filename_from_headers(headers)
+        assert result == "report.pdf"
+
+
+class TestCalculateCrc32:
+    """calculate_crc32 — computes CRC32 hash of a file."""
+
+    def test_known_content(self):
+        import zlib
+        from src.core.utils.fileio import calculate_crc32
+        with tempfile.NamedTemporaryFile(delete=False) as f:
+            f.write(b"hello world")
+            f.flush()
+            fname = f.name
+        try:
+            crc = calculate_crc32(fname)
+            assert isinstance(crc, str)
+            assert len(crc) == 8  # 32-bit hex, 8 chars
+            expected = format(zlib.crc32(b"hello world") & 0xFFFFFFFF, "08x")
+            assert crc == expected
+        finally:
+            os.unlink(fname)
+
+    def test_empty_file(self):
+        from src.core.utils.fileio import calculate_crc32
+        with tempfile.NamedTemporaryFile(delete=False) as f:
+            fname = f.name
+        try:
+            crc = calculate_crc32(fname)
+            assert isinstance(crc, str)
+            assert len(crc) == 8
+        finally:
+            os.unlink(fname)
+
+
+class TestCreateTempFile:
+    """create_temp_file — context manager for temp resources."""
+
+    def test_creates_and_cleans_up_file(self):
+        from src.core.utils.fileio import create_temp_file
+        path = None
+        with create_temp_file(content=b"test content", suffix=".zip") as p:
+            path = p
+            assert path.exists()
+            assert path.suffix == ".zip"
+            assert path.read_bytes() == b"test content"
+        assert not path.exists()
+
+    def test_no_content(self):
+        from src.core.utils.fileio import create_temp_file
+        with create_temp_file(suffix=".zip") as p:
+            assert p.exists()
+            assert p.stat().st_size == 0
+
+    def test_directory_mode(self):
+        from src.core.utils.fileio import create_temp_file
+        with create_temp_file(suffix=".dir") as p:
+            assert p.is_dir()
+            (p / "test.txt").write_text("hello")
+            assert (p / "test.txt").exists()
+
+    def test_dry_run_no_write(self):
+        from src.core.utils.fileio import create_temp_file
+        with create_temp_file(content=b"data", suffix=".zip", dry_run=True) as p:
+            # In dry_run mode, no actual file is created
+            pass
+
+    def test_exception_cleans_up(self):
+        from src.core.utils.fileio import create_temp_file
+        path = None
+        try:
+            with create_temp_file(content=b"data", suffix=".txt") as p:
+                path = p
+                raise ValueError("test error")
+        except ValueError:
+            pass
+        assert path is None or not path.exists()
+
+
+class TestRemoveEmptyDirectories:
+    """remove_empty_directories — removes empty dirs recursively."""
+
+    def test_removes_empty_dirs(self):
+        from src.core.utils.fileio import remove_empty_directories
+        with tempfile.TemporaryDirectory() as tmpdir:
+            empty_dir = Path(tmpdir) / "empty"
+            empty_dir.mkdir()
+            nested_empty = empty_dir / "nested"
+            nested_empty.mkdir()
+            # Non-empty dir should remain
+            non_empty = Path(tmpdir) / "non_empty"
+            non_empty.mkdir()
+            (non_empty / "file.txt").write_text("data")
+
+            removed = remove_empty_directories(tmpdir)
+            assert removed >= 2  # at least 2 empty dirs removed
+            assert non_empty.exists()
+            assert not empty_dir.exists()
+
+    def test_no_empty_dirs(self):
+        from src.core.utils.fileio import remove_empty_directories
+        with tempfile.TemporaryDirectory() as tmpdir:
+            d = Path(tmpdir) / "dir"
+            d.mkdir()
+            (d / "file.txt").write_text("data")
+            removed = remove_empty_directories(tmpdir)
+            assert removed == 0
+
+
+class TestCreateDashboardExport:
+    """create_dashboard_export — packs files into ZIP."""
+
+    def test_creates_zip_with_files(self):
+        from src.core.utils.fileio import create_dashboard_export
+        with tempfile.TemporaryDirectory() as tmpdir:
+            src = Path(tmpdir) / "src"
+            src.mkdir()
+            (src / "dashboard.json").write_text('{"key": "value"}')
+            (src / "metadata.yaml").write_text("version: 1")
+
+            zip_path = Path(tmpdir) / "export.zip"
+            result = create_dashboard_export(zip_path, [str(src)])
+            assert result is True
+            assert zip_path.exists()
+
+            # Verify contents
+            with zipfile.ZipFile(zip_path, "r") as zf:
+                names = zf.namelist()
+                assert any("dashboard.json" in n for n in names)
+
+    def test_excludes_extensions(self):
+        from src.core.utils.fileio import create_dashboard_export
+        with tempfile.TemporaryDirectory() as tmpdir:
+            src = Path(tmpdir) / "src"
+            src.mkdir()
+            (src / "file.json").write_text("{}")
+            (src / "file.log").write_text("log data")
+
+            zip_path = Path(tmpdir) / "export.zip"
+            result = create_dashboard_export(zip_path, [str(src)], exclude_extensions=[".log"])
+            assert result is True
+
+            with zipfile.ZipFile(zip_path, "r") as zf:
+                names = zf.namelist()
+                assert any("file.json" in n for n in names)
+                assert not any("file.log" in n for n in names)
+
+    def test_source_not_found(self):
+        from src.core.utils.fileio import create_dashboard_export
+        result = create_dashboard_export("/tmp/nonexistent.zip", ["/nonexistent/path"])
+        assert result is False
+
+
+class TestConsolidateArchiveFolders:
+    """consolidate_archive_folders — merges directories with common slug."""
+
+    def test_consolidates_dirs(self):
+        from src.core.utils.fileio import consolidate_archive_folders
+        with tempfile.TemporaryDirectory() as tmpdir:
+            root = Path(tmpdir)
+            # Create two dirs with same slug "sales"
+            d1 = root / "sales_2024"
+            d1.mkdir()
+            (d1 / "report1.zip").write_text("zip1")
+            d2 = root / "sales_2025"
+            d2.mkdir()
+            (d2 / "report2.zip").write_text("zip2")
+            # Unrelated dir
+            d3 = root / "marketing_2024"
+            d3.mkdir()
+            (d3 / "campaign.zip").write_text("zip3")
+
+            consolidate_archive_folders(root)
+
+            # sales_2024 and sales_2025 should be merged into 'sales'
+            sales_dir = root / "sales"
+            assert sales_dir.is_dir()
+            assert (sales_dir / "report1.zip").exists()
+            assert (sales_dir / "report2.zip").exists()
+            # marketing should remain separate
+            assert (root / "marketing_2024").is_dir()
+
+    def test_single_dir_no_consolidation(self):
+        from src.core.utils.fileio import consolidate_archive_folders
+        with tempfile.TemporaryDirectory() as tmpdir:
+            root = Path(tmpdir)
+            d = root / "sales_2024"
+            d.mkdir()
+            (d / "report.zip").write_text("zip")
+            consolidate_archive_folders(root)
+            assert d.exists()
+
+    def test_raises_on_invalid_input(self):
+        from src.core.utils.fileio import consolidate_archive_folders
+        with pytest.raises(AssertionError):
+            consolidate_archive_folders("not-a-path")
+
+    def test_skips_dirs_without_zips(self):
+        from src.core.utils.fileio import consolidate_archive_folders
+        with tempfile.TemporaryDirectory() as tmpdir:
+            root = Path(tmpdir)
+            (root / "no_zips_here").mkdir()
+            consolidate_archive_folders(root)
+            assert (root / "no_zips_here").exists()
+# #endregion Test.FileIO.Utils
diff --git a/backend/tests/core/test_rate_limiter.py b/backend/tests/core/test_rate_limiter.py
new file mode 100644
index 00000000..d9d4101a
--- /dev/null
+++ b/backend/tests/core/test_rate_limiter.py
@@ -0,0 +1,92 @@
+# #region Test.RateLimiter [C:3] [TYPE Module] [SEMANTICS test,rate_limit,auth,throttle]
+# @BRIEF Tests for core/rate_limiter.py — in-memory rate limiter, ban/window logic.
+# @RELATION BINDS_TO -> [RateLimiterModule]
+
+from pathlib import Path
+import sys
+
+sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
+
+from unittest.mock import patch, MagicMock
+import pytest
+
+
+class TestRateLimiter:
+    """RateLimiter — in-memory sliding-window rate limiter."""
+
+    @pytest.fixture
+    def limiter(self):
+        from src.core.rate_limiter import RateLimiter
+        return RateLimiter()
+
+    def test_is_banned_initial_false(self, limiter):
+        assert limiter.is_banned("192.168.1.1") is False
+
+    def test_record_attempt_under_limit(self, limiter):
+        with patch("src.core.rate_limiter.time") as mock_time:
+            mock_time.monotonic.return_value = 1000.0
+            for i in range(5):  # 5 attempts, well under MAX_ATTEMPTS=10
+                limiter.record_attempt("192.168.1.1")
+            assert limiter.is_banned("192.168.1.1") is False
+
+    def test_record_attempt_exceeds_limit(self, limiter):
+        from src.core.rate_limiter import MAX_ATTEMPTS
+        with patch("src.core.rate_limiter.time") as mock_time:
+            mock_time.monotonic.return_value = 1000.0
+            for i in range(MAX_ATTEMPTS + 1):
+                limiter.record_attempt("192.168.1.1")
+            assert limiter.is_banned("192.168.1.1") is True
+
+    def test_ban_expires(self, limiter):
+        from src.core.rate_limiter import MAX_ATTEMPTS, BAN_DURATION
+        with patch("src.core.rate_limiter.time") as mock_time:
+            mock_time.monotonic.return_value = 1000.0
+            for i in range(MAX_ATTEMPTS + 1):
+                limiter.record_attempt("192.168.1.1")
+            assert limiter.is_banned("192.168.1.1") is True
+
+            # Advance time past ban duration
+            mock_time.monotonic.return_value = 1000.0 + BAN_DURATION + 1
+            assert limiter.is_banned("192.168.1.1") is False
+
+    def test_old_attempts_pruned(self, limiter):
+        from src.core.rate_limiter import MAX_ATTEMPTS
+        with patch("src.core.rate_limiter.time") as mock_time:
+            mock_time.monotonic.return_value = 1000.0
+            for i in range(MAX_ATTEMPTS):
+                limiter.record_attempt("192.168.1.1")
+
+            # Advance time past window but not to ban expiry
+            mock_time.monotonic.return_value = 1500.0  # 500s later, past 300s window
+            # Old attempts should be pruned. One new attempt should not trigger ban.
+            limiter.record_attempt("192.168.1.1")
+            assert limiter.is_banned("192.168.1.1") is False
+
+    def test_record_success_clears_attempts(self, limiter):
+        with patch("src.core.rate_limiter.time") as mock_time:
+            mock_time.monotonic.return_value = 1000.0
+            for i in range(5):
+                limiter.record_attempt("192.168.1.1")
+            limiter.record_success("192.168.1.1")
+            assert limiter.is_banned("192.168.1.1") is False
+
+    def test_different_ips_independent(self, limiter):
+        with patch("src.core.rate_limiter.time") as mock_time:
+            mock_time.monotonic.return_value = 1000.0
+            for i in range(15):  # exceeds limit for ip1
+                limiter.record_attempt("192.168.1.1")
+            assert limiter.is_banned("192.168.1.1") is True
+            # Different IP should not be affected
+            assert limiter.is_banned("10.0.0.1") is False
+
+
+class TestRateLimiterSingleton:
+    """rate_limiter singleton is pre-created."""
+
+    def test_singleton_exists(self):
+        from src.core.rate_limiter import rate_limiter
+        assert rate_limiter is not None
+        assert hasattr(rate_limiter, "is_banned")
+        assert hasattr(rate_limiter, "record_attempt")
+        assert hasattr(rate_limiter, "record_success")
+# #endregion Test.RateLimiter