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Announcements

ESDM Is Now Open Source

As of today, ESDM is available under the MIT license. The full source of the esdm toolchain, the schema that defines the language, and the documentation now live in a public repository on GitHub. You can read it, use it in any project, and build on it – at no cost and with no strings attached.

We introduced ESDM about two months ago, and we deliberately kept the source in our own hands at first, long enough to sharpen the language through a few rounds of real use before handing it to the world. That stretch is behind us. The core has settled, and today is the day we open it up.

Claude, Start My Database

When we released the Claude Code Plugin for EventSourcingDB at Easter, we proudly listed everything it did not need: no SDK, no MCP configuration, not even a Docker container. Claude had learned to speak EventSourcingDB fluently. But there was a quiet assumption baked into every conversation – that somewhere, someone had already started a database for Claude to talk to.

Version 1.1.0 of the plugin removes that assumption. Claude can now start a local EventSourcingDB on its own, and it has picked up a few habits that make longer sessions noticeably smoother: consistent event sources, uniform event type prefixes, and a deeper understanding of the CloudEvents format. In this post, we walk through what is new – along a session that begins with an empty terminal and ends with a queryable event store.

OpenCQRS 2.0: Tests That Read Like the Domain

In most software, testing is something you bolt on after the fact: you write the code, then you write tests to convince yourself the code does what you hoped. Event Sourcing quietly inverts that relationship. Because behavior is expressed as events, a test can read like a sentence about the domain: given these past events, when this command arrives, then these new events should follow. The test stops being scaffolding around the code and becomes the specification of what the system is supposed to do.

On June 26th, our friends at Digital Frontiers shipped OpenCQRS 2.0, and the change we keep coming back to leans all the way into that idea. The release modernizes plenty under the hood, but the part that matters most day to day is the redesigned testing support – a fluent DSL that makes those given/when/then specifications read less like test code and more like a conversation with the domain. Let's start with why that conversation is worth having at all.

Commanded, Meet EventSourcingDB

Today we're delighted to celebrate a new arrival in the EventSourcingDB ecosystem: Thomas Gossmann has released a Commanded event store adapter for EventSourcingDB. Commanded is the de-facto framework for building CQRS and Event Sourcing applications in Elixir, and with this adapter it can now store its events in EventSourcingDB. If you work in Elixir and you've wanted to put EventSourcingDB underneath your aggregates and process managers, that option exists today.

What makes this exciting isn't a new line in a dependency file. It's what that line unlocks: an entire language community gains a first-class path to EventSourcingDB, without giving up the framework they already know and trust. Let's look at what the adapter does, how you'd put it to work, and why this kind of growth is exactly what we'd hoped to see.

One Year of EventSourcingDB, and the Language That Belongs Beside It

A year ago today, on the 5th of May, 2025, we shipped EventSourcingDB 1.0. We've spent the months since watching teams take it into production, hearing the stories of what they built on top of it, and learning more about the rough edges of event-driven work than we did in the decade before. Today, exactly twelve months later, we're not here to celebrate the past. We're here to take the next step.

Because somewhere along that year, a quiet thought turned into a loud one: a great place to store your events isn't enough. The events themselves carry meaning that lives outside the database, in the model you and your team carry around in your heads, on whiteboards, in slide decks. That model deserves a home of its own. Today, we're giving it one. Meet ESDM, the Event-Sourced Domain Modeling language.

Welcoming Nimbus: Event-Driven Development for TypeScript

Today we're thrilled to celebrate the launch of Nimbus, a new event-driven application framework for TypeScript built by our friends at Overlap in Vienna, Austria. Nimbus integrates natively with EventSourcingDB and brings clear, explicit support for commands, events, and queries to the JavaScript and TypeScript world. We're genuinely grateful to be celebrating this with them. Overlap has built something thoughtful and substantial, and the JavaScript and TypeScript world is better for it.

We won't pretend Nimbus is the first attempt to bring CQRS and Event Sourcing into JavaScript. There have been several over the years, including our own historical effort, wolkenkit. What makes Nimbus stand out is not novelty, but approach: a deliberately minimalist, explicit design built from day one around a dedicated event store. It's also a sign of something larger, a quiet but unmistakable shift in how serious teams are choosing to build software.

Elixir Client SDK 1.0 Now Available

Today we're excited to announce the release of the official Elixir Client SDK for EventSourcingDB, version 1.0. If you're building event-sourced systems on the BEAM, you now have first-class support for writing, reading, and observing events from your Elixir applications.

Elixir has earned its place as one of the most compelling platforms for building fault-tolerant, distributed systems. With this SDK, we're bringing EventSourcingDB into that world, and we've made sure it feels like Elixir from the ground up.

Introducing Simple Mode

Over the past few months, we have received more feedback than ever before. Hundreds of conversations with developers, architects, and CTOs have painted a remarkably consistent picture. The message was clear, and we owe it to you to be honest about what we heard: Event Sourcing is too complex. Not in theory. In theory, everyone loves it. But in practice, teams struggle. They struggle with modeling, with naming, with the sheer cognitive overhead of thinking in events rather than rows.

Introducing the MCP Server 1.0 for EventSourcingDB

AI-powered agents are no longer a future promise. They are here, embedded in development workflows, automating decisions, analyzing data, and helping teams move faster. Tools like Claude, ChatGPT, and Gemini have become part of the daily toolkit for developers and architects alike. But until now, these agents had no way to talk to your event store. They could reason about code, summarize documents, and generate queries, but they could not read your events, explore your subjects, or run an EventQL query against live data. The most valuable data source in an event-sourced system was invisible to AI.

Today, we are changing that. We are releasing the MCP Server 1.0 for EventSourcingDB, an extension that connects large language models directly to a running EventSourcingDB instance. It implements the Model Context Protocol, an open standard that defines how AI models discover and invoke external tools. With this release, your AI agents can read events, write events, browse subjects, inspect event types, register schemas, and run EventQL queries, all through natural language.

Event-Driven Data Science: EventSourcingDB Meets Python and Pandas

Data analysis is more important than ever. Data science and AI have become essential tools for many companies. The tools keep getting better: more powerful models, faster computers, smarter algorithms.

But here's the problem: the underlying data is often garbage. And as always: garbage in, garbage out. The best models, the fastest computers, the smartest algorithms – none of it matters if your data doesn't tell the real story.