diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2bd2560..5a82399 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,34 @@
 # Changelog
 
+## [Unreleased]
+
+### Fixed
+- **``tests/test_cli_help.py:_run_cli`` helper preferred the ASR-blocked
+  shim** — the pre-fix helper called ``shutil.which("truememory-mcp")``
+  and used the bare ``.exe`` shim when present, falling back to
+  ``python -m`` only if the shim wasn't on PATH. On Windows hosts with
+  Microsoft Defender ASR rule ``01443614`` ("Block executable files
+  from running unless they meet a prevalence, age, or trusted list
+  criteria") in **Block** mode, the shim is silently killed at launch
+  — making 7 of the 9 tests in this file fail with
+  ``PermissionError [WinError 5] Access is denied`` even on a healthy
+  install. Rewrote the helper to always invoke
+  ``[sys.executable, "-m", "truememory.mcp_server"]``, routing through
+  the signed ``python.exe`` wrapper. Sibling fix in PR #351 covered
+  the 2 remaining tests in this file that bypass the helper entirely.
+- **``mcp_server.py`` `__main__` block dropped exit codes under
+  ``python -m`` invocation** — the bottom-of-file
+  ``if __name__ == "__main__": main()`` discarded ``main()``'s return
+  value, so exit-code-2 paths (unknown flag, positional-arg typo)
+  silently exited 0 when the server was invoked via
+  ``python -m truememory.mcp_server``. The setuptools console-script
+  wrapper around ``truememory-mcp`` already does ``sys.exit(main())``,
+  so the bug was invisible until anything routed through ``-m``.
+  Changed to ``sys.exit(main() or 0)``. Surfaced by the ``_run_cli``
+  helper rewrite above — 2 tests asserting ``returncode != 0`` were
+  passing under the shim and silently regressed to passing-as-0 under
+  ``-m`` until this line landed.
+
 ## [0.6.8] — 2026-05-11
 
 ### Fixed
diff --git a/tests/test_cli_help.py b/tests/test_cli_help.py
index 4a9edd2..156aaa1 100644
--- a/tests/test_cli_help.py
+++ b/tests/test_cli_help.py
@@ -16,23 +16,25 @@
 from truememory import __version__
 
 
-def _truememory_mcp_bin() -> str | None:
-    """Locate the installed truememory-mcp console script, or None.
-
-    Prefer the script installed by pip. Fall back to invoking via
-    `python -m truememory.mcp_server` — slower because it re-runs all
-    module-level imports, but works in any environment where truememory
-    is importable.
-    """
-    return shutil.which("truememory-mcp")
-
-
 def _run_cli(args: list[str], timeout: int = 30) -> subprocess.CompletedProcess:
-    bin_path = _truememory_mcp_bin()
-    if bin_path:
-        cmd = [bin_path] + args
-    else:
-        cmd = [sys.executable, "-m", "truememory.mcp_server"] + args
+    """Run the truememory-mcp CLI via the module form.
+
+    Always invokes ``[sys.executable, "-m", "truememory.mcp_server"]``
+    rather than the bare ``truememory-mcp`` console-script shim. The
+    shim path is faster (cached imports) but is a setuptools / uv
+    trampoline with a per-install unique hash — Windows Defender's
+    Attack-Surface-Reduction rule ``01443614`` ("Block executable files
+    from running unless they meet a prevalence, age, or trusted list
+    criteria") silently kills it at launch on hardened Win11 baselines.
+    Routing through the signed ``python.exe`` wrapper passes ASR
+    everywhere; the per-test re-import cost is negligible at test scale.
+
+    Replaces the pre-fix two-arm helper that called ``shutil.which`` and
+    preferred the shim when present — that branch fired exactly on
+    Block-mode ASR boxes, making 7 of the tests in this file fail with
+    ``PermissionError [WinError 5] Access is denied``.
+    """
+    cmd = [sys.executable, "-m", "truememory.mcp_server"] + args
     return subprocess.run(cmd, capture_output=True, text=True, timeout=timeout)
 
 
diff --git a/truememory/mcp_server.py b/truememory/mcp_server.py
index dcbe604..ae74e4e 100644
--- a/truememory/mcp_server.py
+++ b/truememory/mcp_server.py
@@ -1519,4 +1519,12 @@ def main():
 
 
 if __name__ == "__main__":
-    main()
+    # `sys.exit(main())` rather than bare `main()` — so exit codes
+    # returned from `main()` propagate when invoked via
+    # ``python -m truememory.mcp_server``. The setuptools console-script
+    # wrapper around `truememory-mcp` already does `sys.exit(main())`
+    # for you; `-m` invocation does not, so the bare `main()` form
+    # silently masked exit-code-2 paths (unknown flag, positional arg
+    # typo) as exit 0 under `python -m`.
+    import sys as _sys
+    _sys.exit(main() or 0)