Microsoft Foundry Forced Migration: Developers Report Agents Went Dark on Cutoff Day
Microsoft Corp. switched off its agent-hosting preview today — and developers woke up to find the autonomous software agents they built to automate tasks had gone dark with no automatic replacement.
At 12:47 AM Japan time, a developer on Microsoft's own support forum reported that the agents their company had deployed across multiple regions had stopped responding simultaneously. The cause, according to Microsoft's own migration guide: the initial preview hosting backend was retired on May 22, 2026, and existing deployments were not migrated automatically.
The cutoff document — published on Microsoft's developer documentation site — describes what developers must move to. The new hosted agents run in session-based sandboxes: each conversation gets its own compute environment that provisions on request and deprovisions after 15 minutes of inactivity, with file storage that persists across turns. Each agent also receives its own dedicated identity through Entra ID, Microsoft's enterprise identity system — replacing a shared project-level credential that multiple agents previously shared. The old framework-specific adapter packages are gone; they have been replaced by protocol-specific libraries that handle agent responses and invocations differently.
The developer report, posted in the early hours of May 22, described the failure in concrete terms: the legacy endpoint returned an error, and the new endpoint rejected their agents as unsupported. "Since today, all our workflow-kind agents stopped working across multiple regions, subscriptions, and projects," they wrote. It is unclear how many organizations remain on the old preview hosting backend — Microsoft has not disclosed the number of affected deployments, and some developers may have migrated during the extended beta period before today's cutoff.
Workflow-kind agents are the category most likely to be running in production rather than experiment: autonomous software designed to execute multi-step processes like data processing, customer service, or workflow automation. The new endpoint currently lists support for prompt-kind and hosted agents, but explicitly notes that the workflow kind is not yet supported — leaving a gap between what was retired and what is available.
Microsoft's Azure OpenAI Assistants API — a separate but related service — carries its own retirement date of August 26, 2026, with Foundry Agents Service positioned as the replacement. Developers who built on both services face two concurrent forced migrations with different technical requirements. Microsoft's February release notes described the Microsoft Agent Framework 1.0.0 release candidate as containing "major breaking changes in credentials, sessions, and response patterns", with a migration guide published alongside. A developer blog noted that because the SDKs remain in preview, "things change rapidly, which can break things when updating."
Competitors have noted the migration burden. LangChain and Google ADK have both positioned their agent development platforms as offering more stable interfaces and gentler upgrade paths — an implicit argument that Microsoft's preview-stage instability creates an opening for developers who want to avoid the next forced migration. Whether that argument converts into actual defections depends on whether competing platforms have production tooling mature enough to absorb displaced Foundry workloads.
Microsoft positions the new architecture as a genuine improvement: per-agent identity isolation, automatic compute lifecycle without manual replica management, and persistent storage across idle periods. The new hosted agents preview launched April 22 — giving developers roughly a month before today's retirement of the old backend.
What to watch: whether Microsoft extends any grace period or patches the new endpoint to support workflow-kind agents before affected developers exhaust their debugging options.