gcal/gmail: update MCP servers + SKALD.md

connectors/gcal/gcal_mcp_server.py

@@ -36,6 +36,24 @@ def log(msg: str) -> None:
 # Protects all stdout writes (main thread + poll thread).
 _stdout_lock = threading.Lock()
 
+# Serializes every Calendar API call and the service/credential build.
+#
+# googleapiclient is built on httplib2, which is NOT thread-safe: a service object
+# owns a single Http holding one reused TLS connection. The poll thread and the
+# request thread sharing that object means two threads can drive the same OpenSSL
+# socket at once — which does not raise, it segfaults (this exact race killed the
+# Gmail connector in production with SIGSEGV, no traceback). `_creds` has the same
+# problem: google.auth refreshes it in place, so two concurrent refreshes corrupt
+# the token.
+#
+# Every API call in this file goes through `_call`, and the service and creds are
+# built in `_get_service`, so serializing those two entry points covers the whole
+# surface — including any call site added later. Reentrant because the two can nest.
+#
+# Held per-call, never per-batch: correctness needs non-concurrency on the socket,
+# not atomicity, and a poll tick must not wait for a long listing to finish.
+_api_lock = threading.RLock()
+
 # ── Push notifications ─────────────────────────────────────────────────────────
 
 def _emit_notification(method: str, params: dict) -> None:
@@ -215,9 +233,12 @@ def _build_service() -> Any:
 
 def _get_service() -> Any:
     global _service
-    if _service is None:
-        _service = _build_service()
-    return _service
+    # Locked: two threads racing here would build (and refresh) two services, and
+    # the loser's would be dropped while its connection was still in flight.
+    with _api_lock:
+        if _service is None:
+            _service = _build_service()
+        return _service
 
 
 # ── Error mapping & refresh-on-auth-error ──────────────────────────────────────
@@ -245,21 +266,25 @@ def _call(fn: Callable[[], Any], api_label: str) -> Any:
     or a RefreshError. We refresh once, persist the new token, and retry the call.
     Anything else (or a second failure) is re-raised so the caller can format it
     via _format_google_error.
+
+    Holds `_api_lock` for the whole body — see the lock's comment. This is the one
+    choke point every `.execute()` in this file passes through.
     """
-    try:
-        return fn()
-    except Exception as e:
-        if not _is_auth_error(e) or _creds is None or not getattr(_creds, "refresh_token", None):
-            raise
+    with _api_lock:
         try:
-            from google.auth.transport.requests import Request
-            _creds.refresh(Request())
-            _persist_creds()
-            log("Access token refreshed mid-session after auth error; retrying the call.")
-        except Exception as refresh_err:
-            log(f"Mid-session token refresh failed: {refresh_err}")
-            raise
-        return fn()
+            return fn()
+        except Exception as e:
+            if not _is_auth_error(e) or _creds is None or not getattr(_creds, "refresh_token", None):
+                raise
+            try:
+                from google.auth.transport.requests import Request
+                _creds.refresh(Request())
+                _persist_creds()
+                log("Access token refreshed mid-session after auth error; retrying the call.")
+            except Exception as refresh_err:
+                log(f"Mid-session token refresh failed: {refresh_err}")
+                raise
+            return fn()
 
 
 def _http_error_reason(e: Exception) -> str: