Updated December 16, 2025: We have updated the timeline. Thank you for your patience.
[Introduction]
Microsoft 365 Copilot declarative agents are upgrading to the GPT-5.1 model, which uses an “auto” architecture. The orchestrator will automatically select the best model for each scenario, either the fast “chat” model or the advanced reasoning model, based on the user prompt.
[When this will happen]General Availability (Worldwide): Rollout will begin early January 2026 (previously mid-December 2025) and is expected to complete by mid-January 2026.
[How this affects your organization]Who is affected: All tenants using Microsoft 365 Copilot declarative agents.
What will happen:
- Declarative agents will upgrade to GPT-5.1.
- The advanced reasoning model will be available for complex queries.
- No admin configuration changes are required.
- Feature will be enabled by default for all applicable tenants.
No action is required.
[Compliance considerations]No compliance considerations identified. Review as appropriate for your organization.
Source: Microsoft
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