5 Copilot and Cowork Updates from September 2026 That Actually Matter
September is a good example of why a monthly ‘what’s new’ needs context. Cowork itself is not new – we covered its general availability in June. Model choice is not new either. What changed this month is what Copilot and Cowork can do, where they can do it, and how much control organizations have over them.
The bigger story is that Cowork is moving from delegated work toward creating things, while Copilot keeps becoming more reusable, mobile, and governable.
At a Glance
BRAND NEW | Cowork can build lightweight interactive apps from a conversation. |
UPDATED / BETTER | The model lineup expanded again, including Claude Opus 5.5 and GPT-6 Sol. |
UPDATED / BETTER | Cowork plugins are now discoverable and configurable on mobile. |
BRAND NEW IN POWERPOINT | Brand Kit and Skills are generally available in Copilot in PowerPoint. |
UPDATED / RESTORED | Domain Exclusion is available again and also applies to Cowork. |
The Pattern I’m Seeing
September is less about another chatbot trick and more about making Copilot useful as a working layer across the business. AI can create, connect, reuse proven workflows, and operate inside clearer boundaries. Capability matters, but repeatability and control are what make it scalable.
1. Cowork Can Build Apps
Status: BRAND NEW – Frontier preview
Microsoft added an App skill to Copilot Cowork in September. Describe a lightweight interactive app and Cowork can create it, refine it through conversation, connect it to supported Microsoft 365 data, then publish and share it inside your organization.
This one is genuinely new, but it is a Frontier preview, not general availability. I would use it to turn an idea into something testable faster – not to skip normal security, ownership, and application-lifecycle thinking.
2. Model Choice Keeps Expanding
Status: UPDATED / BETTER
We already talked about model choice in June, so the September story is expansion, not invention. Early this month, Claude Fable 5.1 replaced Fable 5 in Cowork and GPT-6 Astra joined the selector. On September 22, Microsoft announced that Claude Opus 5.5 and GPT-6 Sol had begun rolling out across Word, Excel, PowerPoint, Chat, Cowork, and Copilot Studio.
Availability can vary by license, access, and region. The practical point is not to make model selection a hobby. Use the model that fits the work and let the platform keep making that choice easier.
3. Cowork Plugins Move onto Mobile
Status: UPDATED / BETTER
Plugins are not new in Cowork, and mobile Cowork is not new either. September’s improvement is that plugins are now discoverable and configurable directly in the mobile app through the attach menu and Skills.
That closes an important usability gap. If Cowork is supposed to help with real work, connections to business tools should not disappear the moment someone leaves a desktop.
4. PowerPoint Gets Brand Kit and Reusable Skills
Status: BRAND NEW IN POWERPOINT – Generally available
Microsoft says Brand Kit and Skills in Copilot in PowerPoint are now generally available with a Microsoft 365 Copilot license. Brand Kit brings approved templates, imagery, icons, fonts, and other assets into the creation experience. Skills make repeatable work – such as reviewing a deck or preparing for questions – easier to reuse.
Branding concepts existed before September, and Cowork already had brand-template support. What is new is the generally available PowerPoint experience that combines organizational brand assets with reusable Copilot workflows where people build the deck.
5. Domain Exclusion Is Back
Status: UPDATED / RESTORED
Domain Exclusion is not brand new. Microsoft introduced it earlier, rolled it back in August, and made it available again on September 9. Admins can exclude up to 1,000 sites from web grounding in Microsoft Copilot and Copilot Chat. Cowork follows the organization’s domain-exclusion policy too.
This matters more as Copilot becomes more capable. Better AI is useful. Better control over which outside sources can influence it is part of making that AI trustworthy enough for real business use.
My Take
September is not five brand-new AI toys, and I think that is a good thing. Mature products get better in layers: a capability moves to mobile, model choice gets broader, a governance control comes back, branding becomes reusable inside PowerPoint, and one genuinely new capability – app building in Cowork – pushes the boundary of what we can delegate.
For leaders, the question is simpler: where does this remove meaningful friction without creating a bigger mess behind it? Prototype the useful app. Standardize the presentation work you repeat. Set boundaries where they matter.
Do not chase every new model. Build better ways of working.
Final Thought
June was about Cowork becoming available. September is about what happens next: more creation, more reach, more reusable work, and more governance. I am less interested in one more impressive AI demo than in whether Copilot is becoming dependable enough to fit into how the business actually works.
