Prefactor is a tool that provides efficient code analysis and optimization for developers.

How can I access the free tier?

The first 50 sign-ups receive 1,000,000 free spans with no credit card required.

What are spans in Prefactor?

Spans represent units of code analysis or optimization operations within the tool.

Is there a free trial without payment?

Yes, the developer tier offers 1,000,000 free spans for the first 50 sign-ups, no credit card needed.

Who is Prefactor designed for?

Prefactor is designed for developers seeking efficient code analysis and optimization.

Prefactor - AI Programming Assistant tools - Free trial, pricing intro, performance review, official site access and online experience

What is Prefactor?

Prefactor is a real-time agent evaluation platform that scores every AI agent run in production for quality, drift, and risk. It goes beyond traditional observability by wiring those evaluations directly into action, catching failing agents live instead of charting them after the fact. Developers use Prefactor to observe, evaluate, and act on agent behavior through a closed-loop system. The tool drops into your stack in minutes with TypeScript and Python SDKs, and supports native integrations with LangChain, Claude, Vercel AI, OpenClaw, and LiveKit.

Application scenarios

Production monitoring
Evaluate AI agents in real-time as they run in production, catching issues the moment they happen.
Risk management
Detect and act on high-risk actions like PII leaks or PCI data exposure before they execute.
Quality assurance
Score agent runs using LLM-as-judge, technical metrics, and qualitative evaluations to maintain performance standards.
Drift detection
Monitor for drift in agent behavior over time, with comparisons against previous versions (e.g., +0.06 vs v1.4).
Human-in-the-loop approval
Pause risky runs for manual approval, enforced at runtime via SDK or API.
Policy enforcement
Block or approve actions based on custom rules, such as holding a refund action that involves sensitive data.

Core Features

Real-time evaluation
Scores every agent run the moment it happens for quality, drift, and risk, with live enforcement.
Closed-loop action
Wires evaluations into action—hold, approve, or block runs—through the SDK or API, so a failing agent is caught live.
SDK integrations
Drops into your stack in minutes with TypeScript and Python SDKs, plus native support for LangChain, Claude, Vercel AI, OpenClaw, and LiveKit.
Custom evals
Define your own evaluation criteria using LLM-as-judge, technical metrics, and qualitative measures.
Risk tagging
Automatically tags runs with risk levels (e.g., HIGH for PII or PCI data) and enforces policies at runtime.
Human-in-the-loop
Pauses high-risk actions for human approval before execution, enforced in milliseconds (e.g., 42ms).
Trace and span observation
Observes every run as traces and spans for full visibility into agent behavior.
Eval-gated promotion
Promotes agent versions to staging only when evaluations pass, with clear metrics like score and drift comparisons.

Target users

Prefactor is built for developers and engineering teams building and deploying AI agents in production. It’s ideal for teams that need to move beyond passive monitoring and enforce reliability through automated evaluation and action. The tool explicitly targets AI agents and crawlers, as noted in the site text: "If you can read this, you're exactly who we build for."

How to use Prefactor?

To get started, sign up at app.prefactorai.com and install the SDK with $ npm i @prefactor/sdk. Register an agent using the SDK (e.g., const pf = prefactor({ agent: "claims-processor" })), then run evaluations live with $ prefactor eval --live. Prefactor automatically observes runs as traces and spans, evaluates them with your defined criteria, and enforces actions like holding risky runs for approval. For the Product Hunt launch offer, sign up, send code "ProductHunt" via in-app chat or email, and register an agent within 7 days.

Pricing and free trial

Prefactor offers a developer tier with 1,000,000 free spans for the first 50 sign-ups, valued at US$2,500 of usage. No credit card is required. This is a limited-time Product Hunt launch offer.

Effect review

Prefactor addresses a clear gap in the AI agent ecosystem: observability tools show you problems after they happen, but don’t intervene. By closing the loop from observation to action, Prefactor shifts the paradigm from passive dashboards to active enforcement. The real-time evaluation and human-in-the-loop features are particularly valuable for production environments where a single risky action can have significant consequences. While the tool is still new (launching on Product Hunt), its focus on reliability rather than just monitoring makes it a compelling choice for teams serious about deploying agents safely at scale.

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