Guy Podjarny
4 min read16 Sept 2025
I’m excited to launch our first set of products, which unlock the power of AI agents in professional software development by using Spec-Driven Development. You can install and use the Spec Registry for free right now, and request access to the Tessl Framework’s beta here.
Agents are powerful, but they’re unreliable and overconfident. They rush to start coding, often wasting time building the wrong thing — and claiming success when they’re clearly not done. They hallucinate APIs and mix up versions of open source libraries, especially newer or less popular ones. And they regularly break existing functionality when attempting to add a feature, without realizing they did so.
As a result, using agents in production codebases is a real challenge. It requires endless reviewing of their work and frustrating attempts to correct mistakes after the fact, often eliminating the productivity gains they may bring.
The Era of Spec-Driven Development
The solution lies in Spec-Driven Development (SDD), where intents are captured in specs. It gives agents the information they need about both what and how you want them to build, bolstered by tests and hard guardrails.
We’re launching two products that pioneer SDD: the Tessl Framework and Tessl Spec Registry. Here's a 2 minute overview of what they do.
Introducing the Tessl Framework
The Tessl Framework keeps agents on rails. It uses specifications (specs) to define what you want to build before coding, enabling both carefully crafted specs and AI written “vibe-spec” workflows. It stores specs in the codebase as long-term memory, enabling agents to evolve the app further. And it simplifies creating and enforcing hard guardrails with tests, ensuring agents don’t break existing functionality.
Introducing the Tessl Spec Registry
The Tessl Spec Registry helps agents use open source better. It holds over 10,000 specs that explain how to use external libraries, preventing API hallucinations and version mixups. Usage specs become part of your project, providing any agent working on it with the right info. You can also use the registry to publish and distribute your own guidance on how you want agents to build.
Combined, our products help make agents reliable. They make it clear when a requirement was misunderstood, avoid expensive and hard to spot regressions, and keep agents from constantly reinventing the wheel.
The Spec Registry is now available in open beta - try it out and let us know what you think!
The Tessl Framework is available in closed beta - request access here, we’ll be in touch soon!
Want to know more?
There’s much more to say about Spec-Driven Development and Tessl’s journey. If you’d like to learn more, click here for a more detailed post, watch this overview demo of our products, and subscribe to the AI Native Dev podcast on YouTube or Spotify, where we’ll cover it in depth. Better yet, join our community on Discord, to share your own thoughts about SDD and AI Dev.
This launch day is a big moment for us, and our mission to make SDD a reality. I’m proud of and humbled by the incredible Tessl team, who kept inventing and iterating to find the right way to bring this new dev paradigm to life. Lastly, I want to share a huge thanks to our early users, who gave us priceless feedback, and are blazing this path with us. Can’t wait to see what we can build together!
