Frequent 401: logged out from another device on idle multi-device sessions — is this server-side enforcement or client-side?

[kemevo]

Setup:

WuzAPI latest (image built 2026-05-27), PostgreSQL backend
~40 concurrent sessions, each with dedicated SOCKS5 proxy
Lifecycle events subscribed: Connected, Disconnected, LoggedOut, KeepAliveTimeout, etc.

Observed behavior:
Sessions disconnect in two distinct patterns, several times per night, with no message-sending activity at the time:

Disconnected from Whatsapp reason=&{} — followed by automatic reconnect + OfflineSyncCompleted. Recovers on its own.
Logged out reason="401: logged out from another device" — session is killed, requires full re-pairing. No other device was actually linked or logged out by us. We physically hold all SIMs; nobody touched the linked devices list.

Logs (pattern 2):
INFO Logged out reason="401: logged out from another device"
Data being sent to webhook ... {"event":{"OnConnect":false,"Reason":401},"type":"LoggedOut"}
Questions:

Is 401: logged out from another device always a genuine multi-device logout, or can WhatsApp send this code as a silent enforcement/flagging mechanism (similar to what's described in tulir/whatsmeow#877 and #989)?
Does the recent whatsmeow update change how 401 LoggedOut is surfaced?
For idle (no-send) sessions getting reason=&{} disconnects — is there any client-side keepalive tuning exposed via WuzAPI, or is this purely network/proxy-dependent?

Context: All sessions share the same proxy ASN range and paired with same mobilephone. We suspect IP reputation is a factor, but want to confirm whether the 401 code itself is diagnostic of multi-device logout vs. server-side enforcement before investing in proxy migration.

[kemevo]

Update after further investigation:
I was able to isolate two completely separate root causes:

1. Dead/expired proxies → reason=&{} disconnects. A batch of my SOCKS5 proxies silently expired. Sessions on those proxies kept emitting Disconnected reason=&{} and couldn't reconnect. After replacing the proxies, 9 out of 12 affected sessions reconnected immediately via /session/connect with no re-pairing needed — confirming these were never logged out, just network-isolated. So reason=&{} is purely proxy/network dependent, as expected.
2. 401: logged out from another device is unrelated to proxy health. One session (65 days old, high message volume, Phase 4) received this exact 401 logout while its proxy was fully working (verified the proxy returned a valid exit IP at the moment of logout). No other device was linked, SIM untouched.
   So my refined question is narrower now:
   When the proxy is confirmed healthy and no actual multi-device login occurred, is 401: logged out from another device ever generated by WhatsApp as a silent account-flagging / enforcement signal rather than a literal device logout?
   The pattern I see: older, higher-volume sessions get the 401, while freshly-paired or low-volume sessions on the same proxy ASN don't. This correlation suggests server-side enforcement tied to account behavior/age, not a client or transport issue — but I'd like to confirm whether whatsmeow surfaces any additional detail (e.g. the underlying stream error code) that could distinguish a genuine logout from an enforcement action.