Workaround for forcing Claude 5.5 Opus in long enterprise Microsoft Copilot sessions?

Hi everyone, I am trying to run a long-form project natively using Claude 5.5 Opus inside our corporate Microsoft Copilot ecosystem, but I am stuck in a frustrating interface loop:

In standard Copilot Chat, I can manually select Claude 3.5 Opus, but as the thread grows, the context window hits its limit and my recent interactions start disappearing.

In Copilot Notebooks(which handles long-form context much better), there is no model picker available, so it automatically defaults to OpenAI models.

The only workaround I've come up with so far is creating a manual handover document to summarize the context, clearing the thread, and starting a fresh chat with the file attached. However, doing this every 20-30 turns is incredibly disruptive to the workflow.

Has anyone found a better way to force/keep Claude Opus active in a long-form notebook or chat format without constantly resetting the thread? (Note: Looking for interface/workflow solutions, not coding via VS Code extensions). Thanks!