What is Tessl?
Tessl helps AI agents stay reliable and aligned by grounding their work in specs. Agents are powerful, but they can drift — misinterpreting requests, hallucinating APIs, or breaking existing features when adding new ones. Tessl integrates with most agents and uses spec-driven development to give agents (and you) a structured way to capture intent, run tests, and evolve codebases with fewer mistakes.
This workflow makes agent output easier to trust and closer to production-ready by default, since it’s checked against explicit requirements and backed by living tests.
Tessl is available today in two complementary modes:
Spec Registry (open beta): open to everyone. Follow this link to explore more than 10,000 usage specs for widely used open-source libraries.
Framework (closed beta): available to selected users. Join the waitlist here to unlock the full framework that keeps AI agents on track with specs, tests, and context management.
Get started
Get started with Tessl Registry
Get started with Tessl Framework
Create your first spec-driven project
Why we built Tessl
AI coding agents are powerful, but without structure they can drift: misinterpreting requests, hallucinating APIs, or breaking old features while adding new ones. This leads to endless reviews, rework, and code that isn’t ready for production.
Tessl exists because we believe there’s a better path. By making specs the source of truth, we give both humans and agents a shared, durable context. Specs reduce effort on individual tasks, capture intent in a form that can be tested, and provide long-term memory that survives beyond any single agent session.
Tessl's philosophy
Today, most development starts with intent — an idea, a feature request, or a wireframe — but often dissolves into code-centric chaos. Code becomes the only source of truth, and every discussion about what the system should do depends on reverse-engineering what the code already does. As a result:
Requirements go stale
Tests fall behind
Collaboration gets messy
And AI agents struggle without clear guidance
Tessl flips this model. We believe spec-driven development is essential for professional development with agents to happen. Specs provide the structure agents need to stay on track and the durable artifacts teams need to stay aligned. That means:
Describing intent in structured, testable language
Using agents to generate (and regenerate) code and tests, with those tests automatically verifying and guiding corrections until the generated code matches the intent
Treating specs — not code — as the long-lived, reviewable, shareable artifacts of software work
With specs at the center, agents stay on track, outputs move closer to production-ready, and teams have a shared source of truth. Whether you’re working solo or across engineering, and product, Tessl helps you ground development in something legible, testable, and stable.
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