Last updated: 24 October 2026
Microsoft Foundry now hosts models from OpenAI, Anthropic, xAI, Microsoft, Moonshot AI and Cohere – and new versions arrive every few weeks. This page brings together all my hands-on guides for using them from C# and .NET: what each model is good at, how to call it, and working code you can run.
If you are new to building with LLMs in .NET, start with Prompt Engineering for .NET Developers, then pick a model below.
Which model should I use?
A quick guide to the posts on this page, by what you want to build:
- Agents and tool calling: GPT-6.1 Sol, GPT-6 Astra, Grok 4.7 and Grok 4.6.
- Coding and developer tooling: Claude Opus 5.5, Claude Code with Opus 5.5 in VS Code and Kimi K2.7 Code.
- High volume at low cost: Claude Haiku 5.5.
- Reasoning: MAI-Thinking-1 and Grok 4.3.
- Choosing between options instead of chatting: Microsoft-Decision-1.
- Chat and retrieval-grounded answers: GPT-5.6 Sol.
- Multilingual, long-context enterprise work: Cohere Command A+.
- Images: GPT-image-2.5, MAI Image 2.6, MAI-Image-2.5 Pro and GPT-Image-2.
- Voice: MAI-Voice-2 Flash.
All models at a glance
| Model | Provider | Best for | Guide |
|---|---|---|---|
| GPT-6.1 Sol | OpenAI | Production agents, coding, computer use | Oct 2026 |
| GPT-6 Astra | OpenAI | Planning agents, tool-driven workflows | Sep 2026 |
| GPT-5.6 Sol | OpenAI | Multi-turn chat, retrieval-grounded answers | Aug 2026 |
| GPT-5.5 | OpenAI | Enterprise agents, long context | Apr 2026 |
| Claude Opus 5.5 | Anthropic | Demanding coding and agent work (Anthropic.Foundry SDK) | Oct 2026 |
| Claude Haiku 5.5 | Anthropic | High-volume automation, support bots, subagents | Oct 2026 |
| Claude Code + Opus 5.5 | Anthropic | AI-assisted development in the CLI and VS Code | Oct 2026 |
| Claude Opus 4.8 | Anthropic | Coding and agentic workflows | Jun 2026 |
| Grok 4.7 | xAI | Tool calling, Entra ID auth, OpenAI-SDK compatible | Oct 2026 |
| Grok 4.6 | xAI | Agentic tool calling, selectable reasoning effort | Aug 2026 |
| Grok 4.3 | xAI | Reasoning for agentic apps | May 2026 |
| MAI-Thinking-1 | Microsoft | Reasoning | Aug 2026 |
| Microsoft-Decision-1 | Microsoft | Choosing between options (decision model, not chat) | Oct 2026 |
| MAI-Voice-2 Flash | Microsoft | Low-latency speech on Azure Speech | Jul 2026 |
| GPT-image-2.5 Flare & Sunburst | OpenAI | Fast iterative generation, precise editing | Sep 2026 |
| GPT-Image-2 | OpenAI | 4K, multilingual image generation | Apr 2026 |
| MAI Image 2.6 & 2.6 Flash | Microsoft | Image generation in Foundry | Sep 2026 |
| MAI-Image-2.5 Pro | Microsoft | Microsoft’s first-party image model | Jul 2026 |
| Kimi K2.7 Code | Moonshot AI | Coding | Jul 2026 |
| Cohere Command A+ | Cohere | 48 languages, multimodal input, 128K context | Jun 2026 |
OpenAI GPT models
The GPT family is the default choice for many Foundry projects, and each new version has pushed further into agents and coding.
- GPT-6.1 Sol for C# Developers – Production Agents in Foundry – stronger coding, computer use and professional work; what changed and how to build production agents from C#.
- GPT-6 Astra for C# Developers – working samples for planning agents and tool-driven workflows.
- GPT-5.6 Sol for C# Developers – multi-turn chat and retrieval-grounded answers in C#.
- GPT-5.5 in Microsoft Foundry (GA) – what improved for agents, coding, long context and computer use.
Anthropic Claude models
Claude models run in Foundry through the Anthropic.Foundry SDK, from the flagship Opus for demanding work to Haiku for speed and cost.
- Claude Opus 5.5 for C# Developers – C# samples with the Anthropic.Foundry SDK and real use cases.
- Claude Haiku 5.5 for C# Developers: Speed vs Cost – high-volume automation, customer support bots, and pairing Haiku with Opus as subagents.
- Using Opus 5.5 Claude Code with Microsoft Foundry in VS Code – pinning Opus 5.5 in the CLI and VS Code, setting effort, and keeping background tasks, subagents and cache under control.
- Claude Opus 4.8 in Microsoft Foundry – stronger coding, agentic workflows and enterprise features.
xAI Grok models
Grok in Foundry works with the OpenAI SDK you may already be using, which makes it easy to try alongside GPT.
- Using Grok 4.7 with C# – OpenAI-SDK samples, Entra ID authentication, tool calling and a compile-fix agent.
- Grok 4.6 in Microsoft Foundry for C# Developers – agentic tool calling and selectable reasoning effort.
- Grok 4.3 in Microsoft Foundry: A Practical C# Guide – a practical example of building agentic apps with improved reasoning.
Microsoft MAI and first-party models
Microsoft’s own models cover reasoning, decisions and voice – including model types that aren’t chat models at all.
- MAI-Thinking-1 in Foundry for C# Developers – what Microsoft’s reasoning model means for .NET developers and where it fits.
- Microsoft-Decision-1 for C# Developers – a decision model rather than a chat model: how its API works and a C# client for choosing between options.
- MAI-Voice-2 Flash for .NET Developers – low-latency voice on Azure Speech, with full setup and working C# code.
Image models
- GPT-image-2.5 Flare & Sunburst for C# Developers – fast iterative generation and precision editing.
- MAI Image 2.6 in Foundry for C# Developers – MAI-Image-2.6 and 2.6 Flash with in-depth C# code.
- MAI-Image-2.5 Pro for .NET Developers – Microsoft’s first-party image model, with working C# code.
- GPT-Image-2 in Microsoft Foundry – 4K image generation, multilingual support and scalability.
More models in Foundry
- Kimi K2.7 Code in Microsoft Foundry – Moonshot AI’s coding model: what it does and how it compares.
- Cohere Command A+ in Microsoft Foundry – a 218B mixture-of-experts model with 48 languages, multimodal input and 128K context.
Foundations
- Prompt Engineering for .NET Developers – practical prompt engineering in C# with seven runnable projects using Microsoft.Extensions.AI.
- From Prompt Injection to Permission Boundaries: Security for AI Agents – how to keep agents built on any of these models from doing real damage.
- Azure OpenAI: A Powerful Platform for Artificial Intelligence – background on the platform Foundry grew out of.
Stay up to date
New models land in Foundry every few weeks, and I add a guide for each one here. Subscribe to get them by email, or read my book Prompt Engineering for .NET Developers for the fundamentals behind all of them.