Azure Just Became the Only Cloud With Both OpenAI and Anthropic Models—Here’s What It Means for Your .NET Apps

TL;DR: Claude Sonnet 4.5, Opus 4.1, and Haiku 4.5 are now part of Microsoft Foundry, making Azure the only cloud offering both OpenAI and Anthropic models . For .NET developers, this unlocks model flexibility for agents, reasoning tasks, and code generation—without vendor lock-in. Anthropic has committed to purchase $30 billion of Azure compute capacity , signaling serious infrastructure backing.

The Strategic Play: Model Choice as Competitive Advantage

For years, Azure developers faced a practical reality: you got OpenAI models, or you went elsewhere. That changed overnight at Ignite 2025. Azure is now the only cloud providing access to both Claude and GPT frontier models to customers on one platform .

Why does this matter? Because not every model excels at every task. This expansion brings Anthropic’s reasoning-first intelligence into the tools, platforms, and workflows organizations depend on every day . If you’re building a .NET agent that needs deep multi-document reasoning, Claude Opus 4.1 might be your answer. For real-time chat, GPT-4o might be faster. Now you can benchmark both on the same platform.

What’s Actually Available (and When)

Customers of Microsoft Foundry can access Anthropic’s frontier Claude models including Claude Sonnet 4.5, Claude Opus 4.1, and Claude Haiku 4.5 . The lineup mirrors OpenAI’s strategy: a fast, lightweight model (Haiku), a balanced workhorse (Sonnet), and a heavyweight reasoner (Opus). These frontier AI models bring specialized capabilities including advanced code generation, complex reasoning with ultra-long context (up to 1 million tokens), and robust tool-use skills . For .NET developers building RAG systems or multi-step agents, that 1 million token context is a game-changer.

Integration with .NET: The Practical Path

If you’re shipping .NET on Azure, here’s the integration story: AI-focused capabilities expand through the Microsoft Agent Framework, Microsoft.Extensions.AI, and first-class Model Context Protocol (MCP) support, which aim to standardize patterns for building agentic workflows, integrating external tools, enabling telemetry, and working across multiple AI providers .

Translation: you’re not locked into one model provider. Microsoft Agent Framework enables developers to build AI agents with minimal code requirements, with examples showing functional agents created in fewer than twenty lines of code .

Here’s a sketch of how you’d swap models in a .NET agent:

// Using Microsoft.Extensions.AI abstractions
var client = new AzureOpenAIClient(
    endpoint: new Uri(endpoint),
    credential: new DefaultAzureCredential()
);

// Or switch to Claude—same abstraction layer
var claudeClient = new AnthropicClient(apiKey);

// Your agent code doesn't care which model backs it
var response = await client.CompleteAsync("Your prompt");

The beauty: These packages provide the .NET ecosystem with essential abstractions for integrating artificial intelligence services into .NET applications and libraries, developed in collaboration with the .NET community, including Semantic Kernel .

Cost and Latency Implications

Model router is now generally available in Microsoft Foundry, delivering intelligent workload routing, performance benchmarking, and cost optimization across models, with Priority Processing (Public Preview) providing SLA-backed, low-latency inference for mission-critical workloads .

What this means: you can route cheaper queries to Haiku, reserve Claude Opus for complex reasoning, and let model router automatically pick the best fit per request. Priority Processing is a premium, SLA-backed low-latency option built for latency-sensitive scenarios like real-time decisioning, healthcare triage, financial transactions, and live customer experiences .

The Bigger Picture: Enterprise Agents on Azure

Microsoft Foundry is introducing the next evolution of Foundry Agent Service—the agent-native runtime in Microsoft Foundry, delivering expanded enterprise capabilities and a unified developer experience across the Foundry portal and SDK, enabling seamless orchestration, deployment, and governance for agents built with any framework or model . The service is designed to work with any agent framework, model, or tool—built on open standards such as Model Context Protocol (MCP), Agent2Agent (A2A), and OpenAPI for interoperability and developer freedom .

For .NET shops, that’s gold. You’re not betting the farm on a single model vendor. You can mix Claude for code review agents, GPT for customer support, and Cohere for semantic search—all orchestrated from one Azure control plane.

The Infrastructure Bet

Anthropic is scaling its rapidly-growing Claude AI model on Microsoft Azure, powered by NVIDIA, and has committed to purchase $30 billion of Azure compute capacity and to contract additional compute capacity up to one gigawatt . Translation: Microsoft and Anthropic are betting serious capital that Claude on Azure will be a durable, first-class citizen—not an afterthought.

What’s Next for You

If you’re shipping .NET on Azure today:

Audit your model dependencies. Are you hardcoded to OpenAI? Microsoft plans to collaborate with package authors across the .NET ecosystem to integrate these abstractions into client libraries, encouraging developers who maintain .NET client libraries for AI services to implement these abstractions .
Experiment with model router. Model router enables AI apps and agents to dynamically select the best-fit model for each prompt—balancing cost, performance, and quality, with model router in Foundry Agent Service in public preview enabling developers to build more adaptable and efficient agents .
Plan for multi-agent orchestration. Multi-agent workflows let developers visually design or programmatically orchestrate complex, multi-step processes that coordinate multiple specialized agents, providing a structured way to define how agents collaborate, share state, recover from errors, and maintain context over long-running operations .

The era of single-model dependency is ending. Azure just made sure you have a choice—and the infrastructure to back it.

Azure Just Became the Only Cloud With Both OpenAI and Anthropic Models—Here's What It Means for Your .NET Apps