diff --git a/agent/file_safety.py b/agent/file_safety.py
index 0c6e4cc8da6..d2b830a1970 100644
--- a/agent/file_safety.py
+++ b/agent/file_safety.py
@@ -97,28 +97,36 @@ def is_write_denied(path: str) -> bool:
         if resolved.startswith(prefix):
             return True
 
-    # New: Check for Hermes control files and mcp-tokens directory
-    hermes_home = _hermes_home_path()
-    hermes_home_real = os.path.realpath(hermes_home)
+    # Hermes control-plane files: block both the ACTIVE profile's view
+    # (hermes_home) AND the global root view. Without the root pass, a
+    # profile-mode session leaves <root>/auth.json + <root>/config.yaml
+    # writable — letting a prompt-injected write_file overwrite the global
+    # files that every profile inherits from (same shape as #15981).
+    control_file_names = ("auth.json", "config.yaml", "webhook_subscriptions.json")
+    mcp_tokens_dir_name = "mcp-tokens"
 
-    # Check for exact control files
-    hermes_control_files = [
-        os.path.join(hermes_home_real, "auth.json"),
-        os.path.join(hermes_home_real, "config.yaml"),
-        os.path.join(hermes_home_real, "webhook_subscriptions.json"),
-    ]
-    for control_file in hermes_control_files:
-        if resolved == os.path.realpath(control_file):
-            return True
+    hermes_dirs = []
+    for base in (_hermes_home_path(), _hermes_root_path()):
+        try:
+            real = os.path.realpath(base)
+            if real not in hermes_dirs:
+                hermes_dirs.append(real)
+        except Exception:
+            continue
 
-    # Check for anything inside mcp-tokens directory
-    mcp_tokens_dir = os.path.join(hermes_home_real, "mcp-tokens")
-    try:
-        mcp_tokens_dir_real = os.path.realpath(mcp_tokens_dir)
-        if resolved.startswith(mcp_tokens_dir_real + os.sep):
-            return True
-    except Exception:
-        pass
+    for base_real in hermes_dirs:
+        for name in control_file_names:
+            try:
+                if resolved == os.path.realpath(os.path.join(base_real, name)):
+                    return True
+            except Exception:
+                continue
+        try:
+            mcp_real = os.path.realpath(os.path.join(base_real, mcp_tokens_dir_name))
+            if resolved == mcp_real or resolved.startswith(mcp_real + os.sep):
+                return True
+        except Exception:
+            pass
 
     safe_root = get_safe_write_root()
     if safe_root and not (resolved == safe_root or resolved.startswith(safe_root + os.sep)):
diff --git a/tests/tools/test_file_operations.py b/tests/tools/test_file_operations.py
index 266921ebfab..db4f490f73b 100644
--- a/tests/tools/test_file_operations.py
+++ b/tests/tools/test_file_operations.py
@@ -104,6 +104,42 @@ class TestIsWriteDenied:
         """Unrelated paths must still be allowed."""
         assert _is_write_denied(path) is False
 
+    @pytest.mark.parametrize(
+        "name",
+        ["auth.json", "config.yaml", "webhook_subscriptions.json"],
+    )
+    def test_control_files_protected_in_profile_mode(self, tmp_path, monkeypatch, name):
+        """Under a profile, BOTH <profile>/X and <root>/X must be denied (#15981 shape).
+
+        Without the root-level pass, a profile-mode session leaves the
+        global ~/.hermes/{auth.json,config.yaml,webhook_subscriptions.json}
+        writable — the same gap PR #15981 fixed for .env.
+        """
+        # Simulate a profile-mode HERMES_HOME layout:
+        #   <root>/profiles/coder/{auth.json,config.yaml,...}
+        #   <root>/{auth.json,config.yaml,...}        ← must also be denied
+        root = tmp_path / "hermes"
+        profile = root / "profiles" / "coder"
+        profile.mkdir(parents=True)
+        monkeypatch.setenv("HERMES_HOME", str(profile))
+
+        # Profile copy
+        assert _is_write_denied(str(profile / name)) is True
+        # Root copy — the gap this widening closes
+        assert _is_write_denied(str(root / name)) is True
+
+    def test_mcp_tokens_dir_protected_in_profile_mode(self, tmp_path, monkeypatch):
+        """mcp-tokens/ under profile AND under root must both be denied."""
+        root = tmp_path / "hermes"
+        profile = root / "profiles" / "coder"
+        profile.mkdir(parents=True)
+        monkeypatch.setenv("HERMES_HOME", str(profile))
+
+        assert _is_write_denied(str(profile / "mcp-tokens" / "tok.json")) is True
+        assert _is_write_denied(str(root / "mcp-tokens" / "tok.json")) is True
+        # The directory itself must also be denied (not just files inside)
+        assert _is_write_denied(str(root / "mcp-tokens")) is True
+
 
 
 # =========================================================================