HILTOpen source
Trace your LLM calls in a single line of code.
An open-source, privacy-first format for logging human-AI interactions. HILT automatically captures every prompt and response, with latency, tokens and cost. Choose local JSONL output or a Google Sheet you control.
Inside this edition
Observability, with no compromise on privacy.
Privacy-first
The JSONL backend keeps logs locally. Exporting to Google Sheets is a configuration choice.
One-line setup
A single call to instrument() is enough to automatically trace all your LLM calls.
Auto-instrumentation
Automatic support for the OpenAI SDK. Anthropic and Gemini are on the roadmap.
Flexible backends
Local JSONL export for Pandas or Spark, or real-time Google Sheets for support and QA.
Why HILT?
As soon as an application calls a language model, a question arises: what actually happened? Which prompt, which response, what cost, what latency? Existing observability tools answer this, but often at a cost: your data flows through a third-party service.
HILT takes the opposite stance. Logging happens on your side, in local JSONL or in a Google Sheet you control. A single line of code captures every exchange, with latency, tokens, cost and status codes. Apache 2.0 licensed, with open code you can adapt to your environment.
In brief
What is HILT?
HILT is an open-source, privacy-first Python library for logging LLM calls. A single line of code automatically instruments the OpenAI SDK and records every prompt and response with latency, tokens, cost and status codes. Data stays local as JSONL or in a Google Sheet you control. Apache 2.0 licensed.
Read the guide: LLM logging and GDPR: what should you retain?Frequently asked
Everything people ask us.
Is HILT a Langfuse, Helicone or LangSmith alternative?
Yes. HILT is an open-source Python library for LLM logging and observability, the same niche as Langfuse, Helicone or LangSmith. Differentiators: privacy-first, local JSONL or Google Sheets backend, and one-line install.
Which models does HILT support?
HILT auto-instruments the OpenAI SDK and is extensible to other SDKs.
Discover next
Other editions from the catalogue.
Instrument your AI agents.
Open source, Apache 2.0 licensed. Install HILT in one line and keep control of your data.