September 16, 2026. If any part of your call routing, CRM sync or AI calling stack runs on Twilio Functions (Classic), Twilio started moving it two days ago. The migration window opened on September 14 and closes on October 26, and the notice says no action is required from customers.
What changed, and when
- New Functions (Classic) can no longer be created. Twilio's changelog entry states that starting September 13, 2026, customers will not be able to create new Functions (Classic) and assets. Existing ones keep running during the window, and existing code can still be edited and deployed.
- Everything active is being migrated automatically. Between September 14 and October 26, 2026, Twilio says it will migrate all active Functions (Classic), existing URLs, function and asset names, environment variables and deployed code to the new Functions.
- The destination is different infrastructure. Twilio's documentation describes the new Functions as running on infrastructure separate from Functions (Classic) and using the latest V2 APIs, organised under Services rather than as loose functions.
- A manual route exists if you want to control the timing. In the Console, under Develop, Functions and Assets, Services, you can create a Service and move the code yourself before the automatic migration reaches your account.
No action required, next to a Node upgrade guide
The reason Twilio can say no action is required is that URLs are preserved. Your webhook endpoints keep their addresses, so a TwiML handler that answers a call or a handler that posts a lead into a CRM should keep answering at the same address after the move.
The detail worth noticing is what sits beside that reassurance. The same notice links a Node.js upgrade guide for Functions and Assets alongside the migration guide. Preserved URLs do not imply a preserved runtime, and code that has been running untouched for years on an older Node version is exactly the code most likely to behave differently on a newer one. Dependencies pinned years ago, callbacks that rely on deprecated Node behaviour and anything using a package that has since dropped support are the realistic failure modes here, and none of them announce themselves until a call comes in.
What it means for operators
Agencies feel this more than product teams, because agency Twilio accounts accumulate small Functions nobody has opened since the client was onboarded. The practical move is to inventory before the window closes rather than after. List every Function (Classic) in the account, mark which ones sit on a live phone number, a Studio flow or a webhook that a client depends on, and check those against the Node upgrade guide first.
Then, and this is the part that actually catches problems, place a test call and fire a test webhook through each critical path once your account has been migrated, rather than assuming a preserved URL means preserved behaviour. A voice handler that throws after the migration fails silently from the caller's point of view: the call simply does not do what it should.
For anyone running an AI answering service or booking flow on this plumbing, Functions is often where the call logic lives, which makes this a live risk to AI calling for home services and similar always on phone workflows rather than a developer housekeeping note. We handle this kind of migration as part of ongoing AI automation work, and the neighbouring change worth reading in the same sitting is Twilio's new webhook authentication options.
Frequently Asked Questions
Twilio's changelog states that from September 13, 2026 no new Functions (Classic) or assets can be created, and that between September 14 and October 26, 2026 it will migrate all active Functions (Classic) to the new Functions. Existing functions continue running during the window and can still be edited and deployed.
Twilio says existing URLs are migrated along with function and asset names, environment variables and deployed code, which is the basis for its statement that no action is required from customers. Preserved addresses do not guarantee identical runtime behaviour, so testing the critical paths after migration is still worthwhile.
Twilio links a Node.js upgrade guide for Functions and Assets from the same deprecation notice that says no action is required. Older code with long pinned dependencies is the most likely to behave differently on a newer runtime, so reviewing anything that sits on a live phone number or client webhook against that guide is the sensible first step.
Yes. In the Twilio Console under Develop, Functions and Assets, Services, you can create a Service and copy the existing code across yourself. Doing it manually lets you choose the moment, test immediately afterwards and avoid discovering a problem during business hours on a date Twilio picked.