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Early Release (v0.1.x) — Trailproof is under active development. The core API is functional and tested, but interfaces may change between minor versions. Pin your dependency to a specific version in production.
Trailproof = Trail + Proof. Every event is cryptographically chained — tamper one, and the entire chain proves it.

Why Trailproof?

AI agents make autonomous decisions — approving requests, writing to memory, calling external APIs. Regulators (EU AI Act Article 19) and customers increasingly demand proof that these actions were logged faithfully and that nothing was altered after the fact. Traditional logging can’t provide that guarantee.

The Trailproof Pipeline

Every event flows through a validation, hashing, optional signing, and append-only storage pipeline. Verification walks the chain backwards to check integrity. Trailproof pipeline: Your App → Event Builder (validate + envelope) → Hash Chain Engine (SHA-256) → Optional HMAC Signer → Append-Only Store (Memory or JSONL) → Verify + Query

Core Pillars

Tamper-Evident Chain

SHA-256 hash chain links every event to the previous one. Modify event 5 in a chain of 100 — events 5 through 100 all fail verification. You can’t silently tamper with history.

Dual SDK Parity

Native libraries for Python and TypeScript with identical behavior. Same canonical JSON algorithm, same genesis hash, same test vectors. Emit in Python, verify in TypeScript.

Zero Dependencies

Stdlib-only in Python (hashlib, json, uuid), Node.js built-ins only in TypeScript (crypto, fs). No supply chain risk from your audit trail.

HMAC Signing

Optional HMAC-SHA256 signatures prove event provenance — that events were created by the holder of a specific secret key. Uses timing-safe comparison to prevent timing attacks.

Quick Example

The 10-Field Event Envelope

Next Steps

Quickstart

Install and emit your first event in 5 minutes.

Event Envelope

Deep dive into the 10-field event structure.

Hash Chain

How events are cryptographically linked.

API Reference

Full API documentation for both SDKs.