known issue for events in 1.19 and 1.20 (#849)

Adding a known issue with event subscriptions in Vault 1.19 and 1.20 ENT.

Author: tvoran

content/vault/global/partials/important-changes/summary-tables/1_19.mdx

@@ -42,3 +42,4 @@ Found  | Fixed  | Workaround | Edition    | Issue
 1.19.1 | 1.19.4 | **Yes**    | All        | [Azure authN fails to authenticate Uniform VMSS instances](/vault/docs/v1.19.x/updates/important-changes#azure-vmss)
 1.18.4 | No     | **Yes**    | All        | [Failing credential refresh for Snowflake DB secrets engine key pair authentication](/vault/docs/v1.19.x/updates/important-changes#snowflake-keypair-refresh)
 1.19.0 | No     | No         | All        | [Writing configuration to local auth mount (ldap, aws, gcp, azure) ignores local flag](/vault/docs/v1.19.x/updates/important-changes#local-auth-known-issue)
+1.19.0 | No     | **Yes**    | Enterprise | [Missed events with multiple event clients](/vault/docs/v1.19.x/updates/important-changes#missed-events)

content/vault/global/partials/important-changes/summary-tables/1_20.mdx

@@ -30,3 +30,4 @@ Found  | Fixed  | Workaround | Edition    | Issue
 1.18.4 | No     | **Yes**    | All        | [Failing credential refresh for Snowflake DB secrets engine key pair authentication](/vault/docs/v1.20.x/updates/important-changes#snowflake-keypair-refresh)
 1.20.0 | 1.20.1 | **Yes**    | All        | [Duplicate LDAP password rotations on standby node check-in](/vault/docs/v1.20.x/updates/important-changes#ldap-checkin)
 1.19.0 | No     | No         | All        | [Writing configuration to local auth mount (ldap, aws, gcp, azure) ignores local flag](/vault/docs/v1.20.x/updates/important-changes#local-auth-known-issue)
+1.19.0 | No     | **Yes**    | Enterprise | [Missed events with multiple event clients](/vault/docs/v1.20.x/updates/important-changes#missed-events)

content/vault/v1.19.x/content/docs/updates/important-changes.mdx

@@ -15,7 +15,7 @@ valid_change_types: >-
 
 # Important changes
 
-**Last updated**: 2025-06-12
+**Last updated**: 2025-09-12
 
 Always review important or breaking changes and remediation recommendations
 before upgrading Vault.
@@ -498,3 +498,21 @@ Incorrect forwarding leads to two distinct failure modes:
 Do not attempt to configure local auth mounts on performance replication
 secondaries.
 
+### Missed events with multiple event clients ((#missed-events)) <EnterpriseAlert inline="true" />
+
+| Change      | Affected version | Fixed version
+| ----------- | ---------------- | -------------
+| Known issue | 1.19.0+ent       | None
+
+Users may miss events when multiple clients subscribe to the same performance
+standby node in a cluster with the same namespace and event type filters because
+one client disconnecting effectively unsubscribes the remaining clients who no
+longer receive events.
+
+#### Recommendation
+
+If you have multiple event subscribers with the same namespace and event type
+filters you have two options:
+
+1. Spread them out among the nodes of the Vault cluster.
+1. Only subscribe to events on the active node of the cluster.

content/vault/v1.20.x/content/docs/updates/important-changes.mdx

@@ -14,7 +14,7 @@ valid_change_types: >-
 
 # Important changes
 
-**Last updated**: 2025-08-13
+**Last updated**: 2025-09-12
 
 Always review important or breaking changes and remediation recommendations
 before upgrading Vault.
@@ -382,3 +382,21 @@ Incorrect forwarding leads to two distinct failure modes:
 Do not attempt to configure local auth mounts on performance replication
 secondaries.
 
+### Missed events with multiple event clients ((#missed-events)) <EnterpriseAlert inline="true" />
+
+| Change      | Affected version | Fixed version
+| ----------- | ---------------- | -------------
+| Known issue | 1.20.0+ent       | None
+
+Users may miss events when multiple clients subscribe to the same performance
+standby node in a cluster with the same namespace and event type filters because
+one client disconnecting effectively unsubscribes the remaining clients who no
+longer receive events.
+
+#### Recommendation
+
+If you have multiple event subscribers with the same namespace and event type
+filters you have two options:
+
+1. Spread them out among the nodes of the Vault cluster.
+1. Only subscribe to events on the active node of the cluster.