Hi! Really sorry this edition is so late this time! 😬🙈 A lot of my time has been focused on creating an update to my Aspire course. I’ve just handed in the update, so now it's time to catch up on my to-do list! (with this newsletter being one of those todos!).
As always, feel free to reply to this email to get in touch. Or ping me on any of my socials, which can be found on my personal website, danclarke.com.
If you get value from this newsletter, please help me out by sharing it on your socials and with your tech friends and colleagues - it really helps me spread the word and keep the newsletter going 🙏 (at-mention me, and I’ll repost).
📰 News items and dev picks
Dotnet news
.NET 11 Preview 2 - Includes progress on runtime-native async and native OpenTelemetry tracing in ASP.NET Core.
C# 15 union types!!! - 🥳 We thought it would never come!
ReSharper for VS Code, Cursor, and compatible editors is out! - After a year in public preview, JetBrains officially launched ReSharper's C# tooling as an extension for VS Code, Cursor, and Google Antigravity. Supports C#, XAML, Razor, and Blazor. Free for non-commercial use.
Extend your coding agent with .NET Skills - The .NET team released
dotnet/skills- a repo of 10 curated agent skills that give AI coding assistants deep .NET knowledge.Ten Months with Copilot Coding Agent in dotnet/runtime - from the author of those epic infinite-scroll .NET performance blog posts - Stephen Toub.
AI news
Claude Code source code leaked - A missing
.npmignoreshipped a 59.8 MB source map containing 512K lines of unobfuscated TypeScript in the npm package. The leak revealed unreleased features, including KAIROS (autonomous daemon mode). A community rewrite (claw-code) hit 100K GitHub stars in a day - likely the fastest-growing repo in GitHub history. Anthropic issued DMCA takedowns across GitHub.Claude "Mythos" (Opus 5) leaked - A CMS misconfiguration exposed ~3,000 unpublished assets, including draft blog posts revealing "Claude Mythos" - a new tier above Opus, described as a "step change" in capability with dramatically higher scores in coding, reasoning, and cybersecurity. Initial access is restricted to vetted security researchers due to unprecedented risk concerns. Quite a month for Anthropic leaks!
1M context now GA for Opus 4.6 and Sonnet 4.6 - I’m a big Claude Code fan - and was a pretty exciting moment when I saw “Opus 4.6 (1M context)” appear in Claude Code’s UI!
Claude Code Auto Mode and Cloud Auto-Fix - Getting fed up of AI agents nagging you to approve permissions all the time? Auto Mode uses an AI classifier to approve safe tool calls without prompting.
Google Stitch redesigned with voice, canvas, and dev tool integrations - Google's AI design tool got a major update on March 19 with an infinite canvas, voice interaction, multi-screen generation, and integrations with coding assistants including Claude Code and Cursor. Features "Vibe Design" where you describe a feeling or objective and it generates matching designs. Exports to Figma format. Figma shares dropped 8% on the news!
OpenAI is developing a GitHub alternative - According to Reuters and The Information, OpenAI is building a code-hosting platform to compete with GitHub after engineers experienced recurring service disruptions. A direct competitive move against Microsoft, who are both a GitHub owner and a major OpenAI investor.
Claude Computer Use launched - Research preview for Pro and Max users. Claude can see, click, type, and navigate your Mac screen, opening apps and completing multi-step workflows.
Anthropic Institute launched - New research arm studying AI's impact on jobs, security, and society.
Codex app launches on Windows - Native sandbox, PowerShell support, parallel agent coordination, a plugin ecosystem, automated Triggers, and a Security Agent.
GitHub will use Copilot data for AI training - Just in case you missed the email from GitHub - data from Free, Pro, and Pro+ users will be used to train AI models by default (effective April 24th). Business and Enterprise users are exempt. You can opt out in the settings.
GPT-5.4 released - Combines GPT-5.3-Codex coding strengths with improved reasoning and agentic workflows. Native computer-use capabilities, up to 1M token context, and 33% fewer hallucinations vs GPT-5.2.
Cursor launches Composer 2 - Cursor's proprietary code-only model built on Kimi K2.5. Scores competitively against Opus 4.6 on coding benchmarks at a fraction of the cost. 200K token context.
MCP hits 97M monthly installs - Model Context Protocol now supported by every major AI provider. Updated spec includes Streamable HTTP transport and OAuth 2.1 authorisation framework.
Man uses ChatGPT to design a cancer vaccine for his dying dog - Australian tech entrepreneur Paul Conyngham, a data scientist with no biology background, used ChatGPT and AlphaFold to design a personalised mRNA cancer vaccine for his rescue dog Rosie. The tumour on Rosie's leg shrank by 75% within a month of the first injection. UNSW RNA Institute produced the physical vaccine.
Microsoft Copilot Cowork - Anthropic's Claude powers a new enterprise AI agent across Microsoft 365 (Outlook, Teams, Excel, Word, PowerPoint). Users hand off tasks, Cowork plans and executes them. Limited research preview.
OpenAI shuts down Sora - After just 6 months, OpenAI killed its AI video generator on March 24. The numbers say why!… ~$1M/day losses, under 500K users (down from a peak of ~1M). A planned $1B Disney deal also fell through, with no money ever changing hands.
Nvidia Unveils NemoClaw - NemoClaw is an open-source stack that wraps OpenClaw in a secure, sandboxed environment with privacy and security guardrails.
Others
Announcing Aspire 13.2 - Quite a big update, with its release timed to coincide with the Aspire Conf. Adding a TypeScript Apphost, many updates to the Aspire CLI (making it really powerful to use through AI agents). As mentioned at the start, I’ve also updated my Aspire course to cover these - including a brand new “AI” module!
Supply chain attacks - March was a brutal month for open-source supply chain security!…
Trivy vulnerability scanner compromised - Between March 19-22, threat actor "TeamPCP" compromised Aqua Security's Trivy scanner and published a malicious binary that harvested CI/CD secrets, cloud credentials, and Docker configs. This subsequently led to a breach of the European Commission's AWS infrastructure, with 92 GB of data stolen and leaked from ~30 EU institutions.
Axios npm package compromised by North Korean state actor - The official Axios npm package (100M+ weekly downloads) was compromised when attackers hijacked a maintainer's account and published backdoored versions containing a cross-platform RAT.
Five supply chain attacks in twelve days - Trivy, Checkmarx AST GitHub Actions, LiteLLM (PyPI), Telnyx (PyPI), and Axios (npm) all in rapid succession.
Java 26 released - 10 JEPs including HTTP/3 support for the HTTP Client API, ahead-of-time object caching with any GC, and post-quantum ready JAR signing. Launched alongside JavaOne 2026 (March 17-19).
TypeScript 6.0 released - the final JavaScript-based release - This is the last release based on the current JavaScript codebase; the compiler is being rewritten in Go for TypeScript 7.0 with 10x compile-time improvements. TS 6.0 defaults to strict mode and deprecates ES5 target.
Kubernetes Ingress-NGINX officially retired - Used by roughly half of cloud-native environments, retired on March 24 with no further updates. SIG Network recommends migrating to Gateway API.
Microsoft Build - June 2-3, 2026 / San Francisco and online
Dev Comic pick of the month
(source)
Dev Pick - OpenSpec
My dev pick this month is a project called OpenSpec. I’ve been using this a lot recently when coding using AI, and it’s making quite a big difference. It's a lightweight spec-driven development (SDD) framework. Spec files live in your source code, and there are various different workflows. However, the thing I’m finding is working really well, is starting a new feature or requirement with the ‘explore’ command (/opsx:explore). When you then tell the agent what you want to achieve, it does an amazing job of asking you questions about things you might not have thought about, or any unknowns. And it explores the codebase as part of this - so it’s asking very useful questions. Then, once everything is satisfied, it creates a proposal (which is source-controlled), and various artifacts are stored to disk (again, source-controlled) - including a task breakdown of what’s required to do the work. You can then run the /opsx:apply command to start the implementation. Because the proposal and task list are on disk, it’s able to tick off those tasks as it goes, which really helps keep the agent on track.
Sponsorship opportunities
I’m looking for sponsors for both the podcast and this newsletter. Details of podcast sponsorship can be found here. Feel free to reply to this email to discuss further.
The Podcast 🎙
I mentioned last month that I had recorded an episode with Chris Woody Woodruff, chatting about simplicity-first and keeping things simple in software development. I also said that it should go live at some point in March. Unfortunately, due to the above-mentioned mounting to-do list whilst I was focusing on the Aspire course, I didn’t get a chance to finish editing this. It is coming very soon though! :)
Also, just a reminder that we have a Discord community for the podcast! It would be great to see you there :)
Podcast Discord community
.NET Oxford user-group
In March, we also had the first of our quarterly .NET Oxford meetups this year (link). I did a lightning talk on AI and how it’s completely changed software development. And it was great to catch up with everyone - especially at the pub afterwards!
My Dometrain Courses
Below are details of my Dometrain courses. There’s also a bundle that includes both the Docker and Kubernetes courses, which can be found here.
Docker for Developers
This course will teach you everything you need to know about Docker and containers. From what containers and images are; to how to build your own; to security and networking; docker-compose; and much more!
Kubernetes for Developers
Once you understand Docker, containers, images, etc - it’s time to move onto the next level and learn a container orchestrator - and Kubernetes has clearly won the battle here! My Kubernetes course is rammed-packed full of demos (pretty much all the way through), which are easy to follow along with downloadable YAML files and scripts. We start with the basics, then later move on to more advanced topics like service meshes and operators.
JetBrains Rider
Rider is an amazing .NET IDE by JetBrains. This course is 6 hours of content - covering hotkeys, refactoring, navigation, debugging, git, testing, AI, profiling, remote collaboration, and much much more!
Aspire
Aspire is Microsoft's vision for how every developer will develop systems. It is a cloud-ready stack for production-ready, distributed applications, and it makes it extremely easy to develop, run, and test your systems locally. With unmatched dev-time orchestration, integrations with third-party services, and excellent tooling, Aspire aims to make working with the cloud and technologies like Docker and Kubernetes easier than ever.
(note that it’s called just “Aspire” now, not “.NET Aspire” → I need to update the graphic)
If you’ve made it this far into the newsletter - I’m hoping that means you’ve
both enjoyed it and found it useful. If you can help me out and share with your developer friends at work and on social media, that would be amazing!
Again - feel totally free to reach out to me, and let me know your thoughts on the newsletter. And see you back in your inbox next month for the next edition! 👋
Bluesky (my primary place)
Twitter (using less nowadays)
LinkedIn
Discord
Mastodon (rarely used)
Threads (rarely used)
Or just go to danclarke.com for links to all my stuff 😊
