MC1194070 – (Updated) Microsoft 365 Copilot: Declarative agents model upgrade to GPT-5.1 (archived)

Product:

Copilot, Microsoft 365 Copilot

Platform:

Online, World tenant

Status:

Change type:

Updated message, New feature, User impact, Admin impact

Links:

Details:

Summary:
Microsoft 365 Copilot declarative agents will upgrade to the GPT-5.1 model with an auto architecture, rolling out worldwide from mid- to end-January 2026. The upgrade requires no admin changes, is enabled by default, and offers advanced reasoning for complex queries. No compliance issues identified.

Details:
Updated January 15, 2026: 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 mid-January 2026 (previously early January) and is expected to complete by end of January 2026 (previously mid-January).

Change Category:
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Scope:
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Release Phase:

Created:
2025-12-11

updated:
2026-01-16

Task Type

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Docu to Check

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MS How does it affect me

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MS Preperations

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MS Urgency

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MS workload name

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summary for non-techies**

Microsoft is updating its 365 Copilot with GPT-5.1, which will automatically optimize task handling, and this update will be implemented globally between mid and end of January 2026 without requiring any user intervention or compliance adjustments.

Direct effects for Operations**

Performance Variability
The upgrade to GPT-5.1 may lead to unpredictable performance changes, affecting response times and accuracy of outputs, especially during the initial rollout phase.
   - roles: End Users, IT Support
   - references: https://www.microsoft.com/en-us/microsoft-365/blog/2026/01/15/whats-new-in-microsoft-365-copilot-2026/

User Adaptation
Users may struggle to adapt to the new advanced reasoning capabilities, leading to confusion and decreased productivity as they learn to utilize the new features effectively.
   - roles: End Users, Training Coordinators
   - references: https://www.microsoft.com/en-us/microsoft-365/blog/2026/01/15/whats-new-in-microsoft-365-copilot-2026/

Integration Issues
The automatic selection of models may cause integration issues with existing workflows, leading to disruptions in user experience and potential data handling errors.
   - roles: End Users, Business Analysts
   - references: https://www.microsoft.com/en-us/microsoft-365/blog/2026/01/15/whats-new-in-microsoft-365-copilot-2026/

Configutation Options**

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Opportunities**

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Potentional Risks**

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Data Protection**

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IT Security**

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Hypothetical Work Council Statement**

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DPIA Draft**

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explanation for non-techies**

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