"Sorry, this conversation has reached its limit. Let's start a new chat."

I hope this helps,

Microsoft does not publish a specific conversation-length limit for Copilot for Microsoft 365. When the message “Sorry, this conversation has reached its limit. Let’s start a new chat.” appears, it is normal behavior and enforced by the Copilot service. This limit cannot be configured or changed by administrators.

Currently, there is no official Microsoft Learn documentation that defines the maximum number of messages, the token or context-size limit, or any differences between applications such as Teams, Outlook, Word, or Microsoft 365 Chat. Only Copilot Studio (custom agents) has publicly documented quotas. The built‑in Copilot for Microsoft 365 chat experience does not.

Although this limit is not formally documented, many customers observe that conversations tend to reach the limit after roughly 80 to 120 total messages or when the conversation reaches an approximate context size of 25,000 to 40,000 tokens. These numbers are based on common usage patterns and can vary depending on message length, the workload being used, and general service load. They are not official or guaranteed values.

The limit exists to maintain performance, reliability, and answer quality. As a conversation grows longer, Copilot must reprocess the entire thread each time it generates a response. Larger context windows increase compute requirements and can reduce clarity or accuracy in extended threads. Session limits also help minimize the risk of sensitive information being carried forward unnecessarily.

Example:
Consider a long conversation in which Copilot has already processed dozens of questions, references to documents, and earlier parts of the discussion. Each new message requires Copilot to reinterpret the entire history so it can respond correctly. As the conversation becomes larger, this processing becomes more resource-intensive and may slow performance or affect answer quality. The conversation limit ensures that responses remain accurate, efficient, and focused on the most relevant context.

For longer workflows, one effective approach is to ask Copilot to summarize the discussion and start a new chat using that summary. Another option is to move the ongoing context into a document such as Word, OneNote, or Loop and rely on that file instead of maintaining an increasingly long conversation thread.

Thanks! ✌️