fix: catch OSError from SETTINGS_FILE.exists() — Docker UID-mismatch 500 crash (#614)

Squash-merges PR #614. Fixes Docker 500-on-every-request crash from PermissionError in load_settings() (issue #570 follow-up).

Both SETTINGS_FILE.exists() call sites now catch OSError and fall back to defaults. Reviewer nits addressed: removed unused imports/var in tests, improved log message to say "inaccessible?" instead of "permission denied?". Rebased clean onto v0.50.73. 1373 tests passing, QA harness green.

api/config.py

@@ -1232,7 +1232,14 @@ _SETTINGS_LEGACY_DROP_KEYS = {"assistant_language"}
 def load_settings() -> dict:
     """Load settings from disk, merging with defaults for any missing keys."""
     settings = dict(_SETTINGS_DEFAULTS)
-    if SETTINGS_FILE.exists():
+    try:
+        settings_exists = SETTINGS_FILE.exists()
+    except OSError:
+        # PermissionError or other OS-level error (e.g. UID mismatch in Docker)
+        # Treat as missing — start with defaults rather than crashing.
+        logger.debug("Cannot stat settings file %s (inaccessible?)", SETTINGS_FILE)
+        settings_exists = False
+    if settings_exists:
         try:
             stored = json.loads(SETTINGS_FILE.read_text(encoding="utf-8"))
             if isinstance(stored, dict):
@@ -1316,7 +1323,11 @@ def save_settings(settings: dict) -> dict:
 # config must never shadow an explicit env-var override (Docker deployments
 # rely on this — otherwise deleting settings.json is the only escape).
 _startup_settings = load_settings()
-if SETTINGS_FILE.exists():
+try:
+    _settings_file_exists = SETTINGS_FILE.exists()
+except OSError:
+    _settings_file_exists = False
+if _settings_file_exists:
     if _startup_settings.get("default_model"):
         DEFAULT_MODEL = _startup_settings["default_model"]
     if not os.getenv("HERMES_WEBUI_DEFAULT_WORKSPACE"):

tests/test_issue570_permission.py

@@ -0,0 +1,56 @@
+"""
+Regression tests for GitHub issue #570 follow-up:
+PermissionError from SETTINGS_FILE.exists() in Docker UID-mismatch scenarios.
+
+When ~/.hermes is owned by a different UID than the container user (common in
+Docker setups), Path.exists() raises PermissionError instead of returning False.
+load_settings() must treat that as "file not accessible = use defaults" rather
+than propagating the exception up to crash the request handler.
+"""
+import stat
+import pytest
+import api.config as config
+
+
+def test_load_settings_returns_defaults_when_settings_file_unreadable(monkeypatch, tmp_path):
+    """PermissionError from SETTINGS_FILE.exists() must not propagate — return defaults instead.
+
+    Regression for issue #570 comment: Docker UID mismatch caused every request
+    to 500 because load_settings() called SETTINGS_FILE.exists() without catching OSError.
+    """
+    state_dir = tmp_path / "state"
+    state_dir.mkdir()
+    settings_file = state_dir / "settings.json"
+    # Create the file then make the parent unreadable so .exists() raises PermissionError
+    settings_file.write_text('{"send_key": "ctrl+enter"}', encoding="utf-8")
+    state_dir.chmod(stat.S_IWUSR)  # write-only: stat() on children will fail
+
+    monkeypatch.setattr(config, "SETTINGS_FILE", settings_file)
+
+    try:
+        result = config.load_settings()
+        # Must not raise; must return a dict with default values
+        assert isinstance(result, dict)
+        assert "send_key" in result
+        # The corrupted/inaccessible value should NOT appear — defaults win
+        assert result["send_key"] == config._SETTINGS_DEFAULTS["send_key"]
+    finally:
+        state_dir.chmod(stat.S_IRWXU)  # restore for cleanup
+
+
+def test_load_settings_returns_defaults_when_exists_raises_permission_error(monkeypatch, tmp_path):
+    """Direct simulation: monkeypatch SETTINGS_FILE.exists to raise PermissionError."""
+    from unittest import mock
+
+    state_dir = tmp_path / "state"
+    state_dir.mkdir()
+    settings_file = state_dir / "settings.json"
+
+    monkeypatch.setattr(config, "SETTINGS_FILE", settings_file)
+
+    with mock.patch.object(type(settings_file), "exists",
+                           side_effect=PermissionError("Permission denied")):
+        result = config.load_settings()
+
+    assert isinstance(result, dict)
+    assert result["send_key"] == config._SETTINGS_DEFAULTS["send_key"]