Helicone: Proxy-Based LLM Observability

Overview

Helicone is an open-source LLM observability platform that works as a proxy: you change your base URL to route through Helicone, and it captures every request and response automatically. No SDK wrapping required. One line of code.

Pricing

Free tier: 10,000 requests per month, no credit card required. Paid plans start at $2.12/month and scale with request volume. Enterprise plans add SOC 2, GDPR compliance, and self-hosting options. The open-source core is available on GitHub for self-hosted deployments.

How it works

Helicone intercepts LLM API traffic at the network layer. Your application points to Helicone's proxy URL instead of Anthropic or OpenAI directly. Helicone forwards the request, captures the full request/response pair, and returns the response to your application. Latency overhead is minimal (single-digit milliseconds at the proxy layer).

This proxy model is the fastest integration path -- no code changes beyond a URL swap. The trade-off against Langfuse's SDK approach: Helicone captures what goes over the wire; Langfuse can capture richer trace context (nested spans, custom metadata, multi-step agent state) because it instruments at the code level.

Key features

Cost tracking per model, per user, per experiment
Latency and time-to-first-token metrics
Prompt versioning and A/B testing
Semantic caching: cache semantically similar requests (not just exact matches), reducing costs on repetitive prompts
Automatic failover and load balancing across providers
100+ model integrations via its gateway layer

Where it fits

Helicone is the fastest path to LLM visibility: two-minute integration, immediate cost tracking, request history. It suits individual developers and small teams that want observability without an SDK migration.

For teams that need evaluations, prompt management with rollbacks, and multi-step agent tracing, Langfuse covers more ground but requires more instrumentation. For teams that also need guardrails and enterprise governance, Portkey is the fuller stack.

Field notes

Helicone semantic caching feature confirmed active in May 2026: teams using repetitive prompts (e.g., classification with a fixed system prompt) report 40-60% request reduction on Helicone's semantic cache. Requires opt-in via request headers. [community-thread, 2026-04-20]