Microsoft Foundry adds Claude Opus 5.5 with two hosting options

Microsoft said Claude Opus 5.5 is now available through Microsoft Foundry, adding Anthropic’s latest Opus model to its enterprise model catalog. Microsoft’s model documentation lists it as generally available in both Azure-hosted and Anthropic-hosted configurations.

The Foundry release is a new distribution option, not the launch of a Microsoft-built model. It follows Microsoft’s GPT-6 Astra general-availability rollout through the same model catalog. Anthropic introduced Claude Opus 5.5 on September 22 and said it was available across its platforms, including Microsoft Azure.

Microsoft lists a 1 million-token context window and a maximum output of 128,000 tokens for the model in Foundry. It describes Opus 5.5 as suited to agentic coding across long-running sessions, including tracing root causes before changes are made and checking work as it proceeds. Microsoft also says the model can produce knowledge-work documents that need less editing than output from earlier models and positions it for long-running agents, enterprise workflows, financial analysis, computer use and vision. Those workload and quality descriptions are Microsoft’s, not findings from an independent evaluation.

Foundry’s model listing describes adaptive thinking as always on for Opus 5.5, with medium as the default effort and xhigh and max effort levels available. However, a detailed capability table lower on the same Microsoft page says thinking can be disabled at effort high or below. The documentation therefore gives conflicting guidance about whether adaptive thinking can be turned off.

The two configurations differ in where processing occurs. Under the Azure-hosted option, Microsoft says requests, API services and GPU inference run end to end on Azure infrastructure. Under the Anthropic-hosted option, prompts and outputs are processed on Anthropic infrastructure and may be handled outside Azure or the selected Azure region. Microsoft’s hosting comparison says Azure-hosted deployments support Global Standard and US Data Zone Standard, while Anthropic-hosted deployments support Global Standard.

Anthropic remains the seller and operator under both arrangements, according to Microsoft, and the Claude models are classified as non-Microsoft products. Access requires an Azure Marketplace subscription, and usage is metered in Claude Consumption Units and billed on the customer’s Azure invoice.