Open-Source Article 12 Logging Infrastructure for the EU AI Act
EU legislation (which affects UK and US companies in many cases) requires being able to truly reconstruct agentic events. I've worked in a number of regulated industries off & on for years, and recently hit this gap. We already had strong observability, but if someone asked me to prove exactly what happened for a specific AI decision X months ago (and demonstrate that the log trail had not been altered), I could not. The EU AI Act has already entered force, and its Article 12 kicks-in in August this year, requiring automatic event recording and six-month retention for high-risk systems,…
In plain words
This open-source TypeScript library helps developers meet EU AI Act Article 12 requirements by creating append-only logs of AI inference events for high-risk systems. Built for Node.js applications using the Vercel AI SDK, it captures and preserves a tamper-evident record of AI decisions that can be reconstructed and audited months later. The tool addresses a compliance gap where standard observability solutions cannot reliably prove what an AI system did or verify that logs remain unaltered, requirements that take effect in August 2024 for regulated AI systems.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
EU legislation (which affects UK and US companies in many cases) requires being able to truly reconstruct agentic events. I've worked in a number of regulated industries off & on for years, and recently hit this gap. We already had strong observability, but if someone asked me to prove exactly what happened for a specific AI decision X months ago (and demonstrate that the log trail had not been altered), I could not. The EU AI Act has already entered force, and its Article 12 kicks-in in August this year, requiring automatic event recording and six-month retention for high-risk systems, which many legal commentators have suggested reads more like an append-only ledger requirement than standard application logging. With this in mind, we built a small free, open-source TypeScript library for Node apps using the Vercel AI SDK that captures inference as an append-only log. It wraps the model in middleware, automatically logs every inference call to structured JSONL in your own S3 bucket, chains entries with SHA-256 hashes for tamper detection, enforces a 180-day retention floor, and provides a CLI to reconstruct a decision and verify integrity. There is also a coverage command that flags likely gaps (in practice omissions are a bigger risk than edits). The library is deliberately simple: TS, targeting Vercel AI SDK middleware, S3 or local fs, linear hash chaining. It also works with Mastra (agentic framework), and I am happy to expand its integrations via PRs. Blog post with link to repo: https://systima.ai/blog/open-source-article-12-audit-logging I'd value feedback, thoughts, and any critique.
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