If you run Microsoft 365 Copilot for a UK, EU or EFTA organisation and nobody has touched the Anthropic setting, every user in your tenant gets Claude on December 9. Microsoft announced it in two Message Center posts: MC1546438 for EU and EFTA tenants and MC1546435 for the UK. On the same day it retires the "Microsoft 365 apps only" scope and moves those tenants to All users. EU and EFTA processing is due to move inside the EU Data Boundary in early December. UK processing will not. You have about three weeks to pick one of three settings on purpose: No users, Specific users and groups, or All users.
Doing nothing counts as a choice. The Register put it bluntly: leaving the setting untouched is opting in.
What Changes on December 9
Tenants that have never set the Anthropic subprocessor control flip from off to All users. According to MC1546438, published November 10 with an "act by" date of December 9, tenants that already enabled Claude keep their user and group assignments, tenants that explicitly disabled it stay disabled, and tenants on "Copilot in Microsoft 365 apps only" move to All users unless an admin changes the setting first. The UK post carries the same three rules, per Modern Workspace Pro's summary of MC1546435.
"All users" is a wide grant. Microsoft's Anthropic subprocessor page lists where Claude shows up once it is on: Microsoft Copilot, Researcher, Copilot Studio, Power Platform and Copilot in Microsoft 365 apps. In Copilot Studio, makers pick the model when they build an agent. In Researcher and Edit with Copilot, users can select Claude themselves.
This brings Europe into line with everyone else. Outside the EU, EFTA and UK, Claude has been on by default in commercial tenants since January 7, 2026, when Anthropic became a Microsoft subprocessor under Microsoft's Product Terms and Data Protection Addendum instead of Anthropic's own contract. Government clouds are mostly untouched: Claude is unavailable to federal GCC customers, GCC High and DoD, per the same Learn page.
Why EU and UK Tenants Get Different Data Commitments
EU and EFTA tenants get in-boundary processing, and UK tenants get the same switch-on with no such promise. The EU Data Boundary is the geographic area, the EU's 27 countries plus Iceland, Liechtenstein, Norway and Switzerland, where Microsoft commits to store and process customer data for its enterprise online services, as Microsoft defines it. Claude has sat outside it until now. That is why Europe was off by default in the first place.
Charles Lamanna, Microsoft's executive vice president for Copilot, agents and platform, wrote on November 5 that Claude processing in Copilot would move inside the EU Data Boundary "by the end of 2026" for EU and EFTA organisations. The Message Center post narrows that to "early December," and says Claude is not covered by the boundary's processing commitment until the move happens.
The UK is a separate jurisdiction for this purpose. UK tenants are not in scope for the EU Data Boundary, MC1546435 says, and processing locations are whatever Microsoft's subprocessor list states. The Register reports that, according to Microsoft's documentation, Anthropic processes that data in the United States. A UK bank, insurer or public body that told its regulator or customers "Microsoft 365 data stays in the UK" needs to check whether that statement covered Copilot model inference. If it did, Claude-on breaks it.
Two details narrow the EU's advantage further:
- Multi-Geo tenants are outside the boundary. Microsoft's own EU Data Boundary page says customers who bought Multi-Geo Capabilities are not in scope even if their tenant is registered in an EU or EFTA country. If you run Multi-Geo, the December move does not cover you.
- In-country processing is a separate question. The Learn page still says Claude in Copilot is excluded from the EU Data Boundary and, where applicable, from in-country processing commitments. Lamanna's post mentions in-country data residency for data at rest in 10 EU and EFTA countries. It does not say Claude inference will run in-country. If you are a German or French tenant relying on an in-country commitment, the EU Data Boundary move is the most you have been promised.
There is also a sequencing risk. The default flips on a fixed date, December 9. The processing move is scheduled for "early December," with no exact date given. If it slips, an EU tenant that did nothing gets Claude for every user while processing is still outside the boundary. As of November 15 the Learn page still describes Claude as excluded.
Who Gets Widened Without Noticing
The tenants most exposed on December 9 are the ones that think they already decided. The "All users for Microsoft 365 apps only" option limits Claude to Copilot inside Excel, PowerPoint and Word, and Microsoft notes that processing there already happens outside the EU Data Boundary. The same page says the option is enabled by default for EU, EFTA and UK tenants created after March 25, 2026, and that it was called "Allow Anthropic models in Copilot experiences within Microsoft 365 apps" until mid-September.
So a tenant can be on apps-only without anyone having chosen it, and on December 9 that tenant moves to All users: Copilot Chat, Researcher, Copilot Studio agents and Power Platform, on top of the three Office apps. LazyAdmin's write-up flags the same trap, noting that the apps-only toggle was on by default for many EU tenants and that some will get Claude across every Copilot experience without anyone choosing it.
Copilot Studio deserves its own look. Once Anthropic is enabled in the Microsoft 365 admin center, Microsoft says further controls appear in the Power Platform admin center to allow Anthropic in Copilot Studio and Power Platform. LazyAdmin reports that Claude becomes available in Copilot Studio by default once enabled, and can be restricted per environment there. If your makers build customer-facing agents, the model choice is a design decision your agent review process should see.
What the Setting Can and Cannot Control
The control works per provider, and you cannot use it to pick individual models. Microsoft's assignment documentation says AI provider assignments apply "at the AI provider level, not the AI model level," and are enforced across the Microsoft 365 admin center, the Power Platform admin center and Copilot Studio. You can assign individual users, Entra ID security groups and nested security groups, up to 999 combined user and group assignments per provider. Use groups. A list of named users will hit the ceiling at any real size.
The one model-level split Microsoft does offer is for "Anthropic models with Data Retention." These are advanced models such as Claude Fable 5 and Claude Mythos 5 that Anthropic requires to retain data, and they sit behind a separate admin setting that stays off by default everywhere, per the Learn page. The December 9 change does not touch them. If an admin does turn them on, Anthropic acts as an independent processor under its own Commercial Terms and Data Protection Addendum. Microsoft says Anthropic stores most inputs and outputs for up to 30 days, keeps flagged content for up to two years and keeps trust and safety classification scores for up to seven years. Microsoft's DPA does not cover that data.
We covered the same retention split on Anthropic's own API in the Fable 5.2 launch piece. Inside Copilot, keep the two toggles on separate approval paths so a general Claude approval does not get read as approval for retention models too.
The Case for Leaving Claude On
For many EU and EFTA tenants, the December change removes the original objection. Microsoft says Claude in Copilot falls under its Enterprise Data Protection, Product Terms and DPA, and that its Customer Copyright Commitment covers Claude used in Copilot and Copilot Studio. Lamanna's post says customer data is not used to train foundation models. LazyAdmin's author concludes the boundary move "removes the main reason" to keep Claude off and says they would allow it for all users, because Sonnet is included in the Copilot licence under fair use.
That holds once processing is actually inside the boundary. It is weaker for the UK, for Multi-Geo tenants and for anyone with an in-country commitment. It also leaves cost to manage. LazyAdmin notes that Copilot Cowork, Code, Autopilot and frontier models bill in Copilot Credits at $0.01 each pay-as-you-go, with no per-model price published, and that usage billing stays off until an admin creates a spending policy. We covered how those credits sit outside the seat in our Autopilot billing piece.
Some large buyers already run both. Barclays split Claude and Copilot by role rather than picking one vendor. The December change gives every Copilot tenant that option by default. Make sure you also have a record of how you chose.
What to Do Before December 9
This Week:
- Have an AI Administrator or Global Administrator open Microsoft 365 admin center > Copilot > Settings > View all > AI providers operating as Microsoft subprocessors > Anthropic and write down the current value. If it says no selection or "Microsoft 365 apps only," your tenant changes on December 9.
- Check whether the tenant uses Multi-Geo and where it is registered. A UK sign-up location, or Multi-Geo anywhere, means the EU Data Boundary move does not apply to you.
- Ask your DPO whether any customer contract, regulator filing or residency statement promises UK or in-country processing for Microsoft 365. Pull the exact wording. That answer decides the UK default for you.
Before December 9:
- Pick a setting on purpose. For a cautious rollout, choose Specific users and groups, assign one Entra ID security group as a pilot, and widen it later. If the answer is no, choose No users and save. Either beats inheriting All users.
- Add Anthropic to your record of processing and subprocessor register, with the processing location your tenant actually gets: EU Data Boundary for EU and EFTA after the move, the subprocessor list's stated location for the UK. Our LLM data residency guide covers how other providers handle the same question.
- Review Copilot Studio and Power Platform environment settings in the Power Platform admin center so Claude-backed agents go through the same review as any other model change.
- Tell the helpdesk and compliance teams, as both Message Center posts recommend. Users will see Claude indicators in Copilot and will ask.
After December 9:
- Recheck the Anthropic subprocessor Learn page. If it still says Claude is excluded from the EU Data Boundary, the processing move has not landed. Narrow access to your pilot group until it does.
- Keep the Data Retention toggle off unless legal has signed Anthropic's own terms. It is a separate contract with a different retention clock.
- Set a Copilot Credits spending policy before anyone pilots Cowork or Autopilot on Claude.
The Bigger Picture
Default-on is now how Microsoft rolls out models to its own tenants. Most non-European commercial tenants got Claude this way in January. Europe and the UK held out only because processing sat outside the boundary, and Microsoft is now removing that reason for the EU while switching the UK on regardless. Vendors have changed the model under a product before with nothing more than a subprocessor notice, as Replit did with its agent. Microsoft at least gave a date and a toggle. Whatever your tenant shows on December 9 is the decision you made, so set it this week.
Continue Reading
- LLM Data Residency: Which Providers Actually Keep Data In Region
- Barclays Picks Claude for Half Its Developers, Copilot for Desks
- Claude Fable 5.2 Requires 30-Day Retention for Most Buyers
- Microsoft's New Copilot Bills Autopilot Outside the $30 Seat
- Replit's DPA Doesn't Require Notice for OpenAI Agent Switch
- AI Vendor Security Review: 6 Questions That Change the Answer
- Copilot Studio Agents Keep Shared Memory, No User Opt-Out