Spec27 – Spec-driven validation for AI agents
Hi HN! We’re a team of ML validation specialists and we’ve been building /Spec27, a tool for testing whether AI agents still do their job safely and reliably as models, prompts, tools, and surrounding systems change. We started working on this because a lot of current LLM evaluation work seems aimed at scoring general model behavior, while many teams are deploying systems that have a specific mission to fulfill. Many of the tools also assume you have full access to the agent stack and traces so you can place SDKs and Gateways, but a lot of agents are being created on vendor platforms…
In plain words
Spec27 is a testing tool for AI agents that validates whether they perform their intended tasks safely and reliably as underlying models, prompts, and tools change. Built by ML validation specialists, it takes a spec-driven approach to testing by examining agent behavior from the outside in, without requiring access to internal infrastructure or the ability to install SDKs. The tool is designed for teams deploying agents on vendor platforms who need ongoing validation beyond general model benchmarks.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
Hi HN! We’re a team of ML validation specialists and we’ve been building /Spec27, a tool for testing whether AI agents still do their job safely and reliably as models, prompts, tools, and surrounding systems change. We started working on this because a lot of current LLM evaluation work seems aimed at scoring general model behavior, while many teams are deploying systems that have a specific mission to fulfill. Many of the tools also assume you have full access to the agent stack and traces so you can place SDKs and Gateways, but a lot of agents are being created on vendor platforms where this isn’t possible. As a result, we approaches it from the outside in: all tests just run to the primary interfaces of an Agent and don’t assume anything about internals. The other important things about the approach is spec-driven. Instead of treating testing as a one-off benchmark or static eval set, we let teams define reusable specifications for the behavior they want from an agent, then generate tests against those specs. With this you can automatically generate adversarial and robustness checks, so you can see what an agent is sensitive to and what kinds of changes cause it to fail. We’ve worked on validation for other AI systems before, including vision and tabular workflows, and /Spec27 is our new product for language-model-based agents. Currently in early access, so we’d love feedback! The current version is strongest for single-turn agent and application validation. We do not fully support multi-turn interactions yet, and better telemetry/tool-call integration is still on our roadmap. We’ve made the product open to try for HN readers, with a sample flow so it’s easy to poke around without much setup. We’d especially love feedback from people deploying internal agents, vendor agents, or other AI systems where reliability matters more than benchmark scores.
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