Den Delimarsky
Lead Maintainer of the Model Context Protocol; author of GitHub's Spec Kit launch post
Den Delimarsky is a Lead Maintainer of the Model Context Protocol (MCP) project and a product manager and engineer focused on developer tools. As a Principal Product Manager for GitHub Copilot, Delimarsky wrote GitHub's September 2025 post introducing Spec Kit, an open-source toolkit for spec-driven development with AI coding agents. Delimarsky also builds PowerToys Awake for Windows and is listed as a maintainer of the MCP C# SDK. The April 2026 MCP announcement of Delimarsky's move from Core Maintainer to Lead Maintainer described Delimarsky as a Member of Technical Staff at Anthropic and, before that, a Principal Product Engineer in Microsoft's CoreAI division.1234
Career
Delimarsky describes steering a career toward developer tools, combining product management with hands-on coding, mainly in C# and Python. Delimarsky presented at Microsoft Build in 2023 and 2024 on authentication brokers and single sign-on with Microsoft Entra ID.1
In September 2025, writing as a Principal Product Manager for GitHub Copilot, Delimarsky introduced Spec Kit on the GitHub Blog. In April 2026 the MCP project announced that Delimarsky was moving from Core Maintainer to Lead Maintainer, describing Delimarsky as a Member of Technical Staff at Anthropic working across the specification, SDKs and governance, and crediting Delimarsky with co-authoring the authorization specification and leading the 2025-11-25 specification release. Delimarsky's site describes the Lead Maintainer role, and the project's maintainers file lists Delimarsky among its two Lead Maintainers.3412
Open-source work
Spec Kit structures AI-assisted development around a living specification: the developer provides a high-level description of what to build and why, and the coding agent produces a detailed specification that then drives the implementation, checklists and task breakdowns. The toolkit works with coding agents including GitHub Copilot, Claude Code and Gemini CLI.3
Outside MCP and Spec Kit, Delimarsky has built PowerToys Awake, a .NET library for the Stream Deck based on its USB protocol, and an open-source list of resources for product managers.1
Work
Spec KitOpen-source code
Wrote GitHub's launch post introducing Spec Kit as an open-source toolkit that makes the specification the centre of a coding agent's workflow.3
Model Context ProtocolOpen-source code
Listed as a Lead Maintainer of the Model Context Protocol project and as a maintainer of its C# SDK.21
PowerToys Awake (external site: den.dev)Open-source code
Built and continues to build PowerToys Awake, a Windows utility that keeps a machine awake.1
Career timeline
Aug 2018
Presented on documentation as a core part of the product at Open Source Summit North America.1
2023
Co-presented a Microsoft Build session on authentication brokers for public client applications.1
2024
Presented at Microsoft Build on authentication brokers and single sign-on with Microsoft Entra ID.1
Sep 2, 2025
Introduced Spec Kit, an open-source toolkit for spec-driven development, on the GitHub Blog.3
Apr 8, 2026
Announced as a new Lead Maintainer of the Model Context Protocol, moving up from Core Maintainer.4
Oct 1, 2026
Listed as a Lead Maintainer in the Model Context Protocol maintainers file updated on this date.2
Other documented roles
Roles the sources document but that are not confirmed as current.
Related people
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- Mario RodriguezAlso at GitHub
- Amjad MasadDeveloper tools
- Vladimir FedorovAlso at GitHub
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