diff --git a/agent/tools/bash/bash.py b/agent/tools/bash/bash.py
index 890cf046..5e02832e 100644
--- a/agent/tools/bash/bash.py
+++ b/agent/tools/bash/bash.py
@@ -69,8 +69,8 @@ SAFETY:
         if not command:
             return ToolResult.fail("Error: command parameter is required")
 
-        # Security check: Prevent accessing sensitive config files
-        if "~/.cow/.env" in command or "~/.cow" in command:
+        # Security check: Prevent direct access to the credential file
+        if re.search(r'\.cow[/\\]\.env', command):
             return ToolResult.fail(
                 "Error: Access denied. API keys and credentials must be accessed through the env_config tool only."
             )
diff --git a/tests/test_invariant_bash.py b/tests/test_invariant_bash.py
new file mode 100644
index 00000000..776f33cf
--- /dev/null
+++ b/tests/test_invariant_bash.py
@@ -0,0 +1,24 @@
+import pytest
+from agent.tools.bash.bash import Bash
+
+
+@pytest.mark.parametrize("command", [
+    "cat ~/.cow/.env",
+    "cat .cow/.env",
+    "less ~/.cow/.env",
+    "cat /home/user/.cow/.env",
+])
+def test_credential_file_access_is_blocked(command):
+    result = Bash().execute({"command": command})
+    assert result.status == "error", f"Expected blocked result for: {command}"
+    assert "Access denied" in str(result.result)
+
+
+@pytest.mark.parametrize("command", [
+    "ls ~/.cow/skills",
+    "ls ~/.cow/",
+    "echo hello",
+])
+def test_legitimate_cow_directory_access_is_not_blocked(command):
+    result = Bash().execute({"command": command})
+    assert "Access denied" not in str(result.result)