Copilot is a per-seat assistant inside Microsoft's apps. Heidi is a company brain above all your apps, Microsoft included, priced for the whole company with no seats, and readable by every AI tool you use, not just one vendor's.
Copilot is strongest where your work already lives in Microsoft 365, and it stays there. Heidi connects Microsoft 365 alongside Slack, your ticket system, your meetings, and your code, and consolidates them into one memory.
The structural difference is openness: Heidi's brain is a surface, REST and MCP, that any compliant tool can read. You are never locked to one assistant to benefit from your own context.