diff --git a/skills/productivity/google-workspace/SKILL.md b/skills/productivity/google-workspace/SKILL.md
index be5c824d67..b141afe397 100644
--- a/skills/productivity/google-workspace/SKILL.md
+++ b/skills/productivity/google-workspace/SKILL.md
@@ -1,9 +1,14 @@
 ---
 name: google-workspace
 description: "Gmail, Calendar, Drive, Docs, Sheets via gws CLI or Python."
-version: 1.0.0
+version: 1.0.1
 author: Nous Research
 license: MIT
+required_credential_files:
+  - path: google_token.json
+    description: Google OAuth2 token (created by setup script)
+  - path: google_client_secret.json
+    description: Google OAuth2 client credentials (downloaded from Google Cloud Console)
 metadata:
   hermes:
     tags: [Google, Gmail, Calendar, Drive, Sheets, Docs, Contacts, Email, OAuth]
diff --git a/tests/skills/test_google_workspace_credential_files.py b/tests/skills/test_google_workspace_credential_files.py
new file mode 100644
index 0000000000..de59b2fe6e
--- /dev/null
+++ b/tests/skills/test_google_workspace_credential_files.py
@@ -0,0 +1,102 @@
+"""Regression test: google-workspace SKILL.md must declare required_credential_files.
+
+PR #9931 accidentally removed the required_credential_files header, which broke
+credential file mounting in Docker/Modal remote backends (#16452). This test
+prevents the regression from silently reappearing.
+"""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+SKILL_MD = (
+    Path(__file__).resolve().parents[2]
+    / "skills/productivity/google-workspace/SKILL.md"
+)
+
+_EXPECTED_PATHS = {"google_token.json", "google_client_secret.json"}
+
+
+def _parse_frontmatter(content: str) -> dict:
+    from agent.skill_utils import parse_frontmatter
+
+    fm, _ = parse_frontmatter(content)
+    return fm
+
+
+class TestGoogleWorkspaceCredentialFiles:
+    def test_required_credential_files_present_in_skill_md(self):
+        content = SKILL_MD.read_text(encoding="utf-8")
+        fm = _parse_frontmatter(content)
+        entries = fm.get("required_credential_files")
+        assert entries, "required_credential_files missing from google-workspace SKILL.md"
+        assert isinstance(entries, list), "required_credential_files must be a list"
+        paths = {
+            (e["path"] if isinstance(e, dict) else e)
+            for e in entries
+        }
+        assert _EXPECTED_PATHS <= paths, (
+            f"Missing entries in required_credential_files: {_EXPECTED_PATHS - paths}"
+        )
+
+    def test_entries_are_registered_when_files_exist(self, tmp_path):
+        hermes_home = tmp_path / ".hermes"
+        hermes_home.mkdir()
+        (hermes_home / "google_token.json").write_text("{}")
+        (hermes_home / "google_client_secret.json").write_text("{}")
+
+        from tools.credential_files import (
+            clear_credential_files,
+            get_credential_file_mounts,
+            register_credential_files,
+        )
+
+        clear_credential_files()
+        try:
+            content = SKILL_MD.read_text(encoding="utf-8")
+            fm = _parse_frontmatter(content)
+            entries = fm.get("required_credential_files", [])
+
+            with patch.dict(os.environ, {"HERMES_HOME": str(hermes_home)}):
+                missing = register_credential_files(entries)
+
+            assert missing == [], f"Unexpected missing files: {missing}"
+            mounts = get_credential_file_mounts()
+            container_paths = {m["container_path"] for m in mounts}
+            assert "/root/.hermes/google_token.json" in container_paths
+            assert "/root/.hermes/google_client_secret.json" in container_paths
+        finally:
+            clear_credential_files()
+
+    def test_missing_token_is_reported(self, tmp_path):
+        """google_token.json absent (first-time setup) — reported as missing, client secret still mounts."""
+        hermes_home = tmp_path / ".hermes"
+        hermes_home.mkdir()
+        (hermes_home / "google_client_secret.json").write_text("{}")
+
+        from tools.credential_files import (
+            clear_credential_files,
+            get_credential_file_mounts,
+            register_credential_files,
+        )
+
+        clear_credential_files()
+        try:
+            content = SKILL_MD.read_text(encoding="utf-8")
+            fm = _parse_frontmatter(content)
+            entries = fm.get("required_credential_files", [])
+
+            with patch.dict(os.environ, {"HERMES_HOME": str(hermes_home)}):
+                missing = register_credential_files(entries)
+
+            assert "google_token.json" in missing
+            mounts = get_credential_file_mounts()
+            container_paths = {m["container_path"] for m in mounts}
+            assert "/root/.hermes/google_client_secret.json" in container_paths
+            assert "/root/.hermes/google_token.json" not in container_paths
+        finally:
+            clear_credential_files()