Between Sept. 30, 2023, and March 31, 2024, Google will upgrade Chat Spaces organized by conversation topics to the new in-line threaded spaces. 

The upgrade will primarily occur during non-peak hours on weekends for minimal disruption and will take from a few minutes to up to 12 hours to complete. Users will not have access to Chat Space during this time.

A few weeks before the upgrade begins, users will see a notification banner in Chat Space about the upcoming upgrade. This message will also have a link to a Google Help Center article with more upgrade details.

During the Chat Space upgrade:

• When users attempt to open a space during the upgrade, they will see the following error message: “Space is temporarily not available. We are updating this space to an inline threaded space.”
• If users are viewing a space when the upgrade starts, most features, including sending and receiving messages, will become unavailable until the upgrade completes.

After the Chat Space upgrade:

• Messages sent before the upgrade will be retained and will be arranged chronologically, not by topic. There will also be a separator titled “Begin New Topic” to indicate when a new topic is started.
• In some cases, when people have responded to older topics, the new chronological order takes precedence. This means that messages may not appear next to the original topic, but rather according to the time that they were sent. When this occurs, the new response will quote the last corresponding message.
• Users will see a separator between the last message sent before the upgrade and a notification in the space indicating that the space has been upgraded to use in-line replies.
• The upgraded spaces will have their conversation history turned on by default to match the existing history behavior of spaces organized by conversation topic, which always have history on. Depending on organization-level history controls, space history settings may be changed by space managers. New messages sent after the upgrade will respect applicable organization-level history controls configured by administrators.
• Users might need to close and reopen Chat to access the upgraded spaces.
  

For more details on this update, see Existing spaces organized by conversation topic will be upgraded to the new in-line threaded experience by the end of Q1 2024.