RelayPlane vs Braintrust Gateway
Braintrust Gateway is a hosted LLM proxy built for eval and logging workflows. RelayPlane is an npm-native cost-intelligence proxy that routes and governs live traffic locally. Different tools solving different problems.
TL;DR
Choose RelayPlane if you want:
- npm install in 30 seconds, no account or SaaS signup
- Local-first proxy with no vendor dependency or cloud routing
- Per-request USD cost tracking and per-agent spend attribution
- Dynamic routing to cheaper models for cost reduction
- Runaway loop detection and budget enforcement in production
Braintrust Gateway is the right fit if you need:
- Full prompt evaluation with golden datasets and custom scorers
- Team-based eval workflows with annotation and regression testing
- A unified platform combining gateway, logging, and evals in one SaaS
Feature Comparison
| Feature | RelayPlane | Braintrust Gateway |
|---|---|---|
| Installation / setup RelayPlane is a single npm command. No account needed, no dashboard to configure. Braintrust Gateway requires creating an account, setting up a project in the Braintrust SaaS platform, and configuring API keys through their web UI before you can route a single request. | npm install -g @relayplane/proxy | Account signup required, SaaS dashboard |
| Setup time RelayPlane runs on localhost immediately after install with zero configuration. Braintrust Gateway requires account creation, project setup, and wiring API keys for each provider you want to use through their hosted platform. | ~30 seconds | Minutes to hours (account, project, API key config) |
| Self-hosted vs cloud RelayPlane runs on localhost. Your LLM traffic and cost data stay on your machine. Braintrust Gateway is a hosted service -- your requests are routed through Braintrust's infrastructure. There is no self-hosted option for the gateway component. | Local-first, cloud optional | Cloud-only SaaS |
| Primary use case RelayPlane is purpose-built to reduce and govern LLM spend: it routes requests to cheaper models, tracks per-request cost, and stops runaway loops. Braintrust focuses on evaluation workflows: logging traces, running evals against datasets, and improving prompt quality before and after deployment. | Cost routing and spend governance for AI agents | Prompt evaluation, logging, and testing for AI products |
| Pricing model RelayPlane's core proxy is free and open source. You install it with npm and it runs locally at no cost. Braintrust charges based on usage and team size through a SaaS subscription model. | Free npm package, paid tiers for advanced features | SaaS subscription, usage-based pricing |
| Per-request USD cost tracking RelayPlane computes exact USD cost per request using live pricing tables and stores results locally in SQLite. Braintrust captures token usage in trace logs primarily for evaluation purposes, not for production spend governance. | Token counts in logs, limited cost attribution | |
| Intelligent model routing RelayPlane routes dynamically: simple tasks go to cheaper models, complex tasks to more capable ones. Braintrust Gateway provides provider routing as a reliability feature but does not perform cost-optimization routing based on task complexity. | Cost-optimized routing by task complexity | Basic provider routing, no cost-optimization logic |
| Prompt evaluation / evals Braintrust is purpose-built for evals: golden datasets, custom scorers, human annotation, and automated regression testing for prompts. RelayPlane does not run evaluations. These are complementary tools solving different problems. | ||
| Local / offline support RelayPlane works entirely offline. Your cost data, routing rules, and proxy logic live on your machine. Braintrust Gateway requires an internet connection and routes through their cloud infrastructure -- no offline mode is available. | ||
| Open source RelayPlane's proxy core is open source on GitHub. Braintrust is a closed-source commercial product. You can inspect RelayPlane's routing and cost logic; you cannot inspect Braintrust Gateway's internals. | Core proxy is open source | Closed source SaaS |
| npm-native RelayPlane is a standard npm package. It fits naturally into any Node.js or TypeScript project. Braintrust Gateway is not available as an npm package -- it is a SaaS product accessed via their hosted API endpoint. | ||
| Zero config startup RelayPlane starts with one command and no configuration required. Braintrust Gateway requires configuring provider API keys, project settings, and routing rules in their dashboard before your first request can be proxied. | ||
| Production monitoring RelayPlane provides a local dashboard showing spend by model, agent, and time period with p50/p95 latency. Braintrust's monitoring focuses on eval results, trace inspection, and prompt performance rather than production cost and routing analytics. | Cost, latency, and routing metrics locally | Trace logging and eval monitoring in SaaS dashboard |
| Multi-model support Both tools support multiple LLM providers including OpenAI, Anthropic, and others. RelayPlane routes across providers based on cost and capability. Braintrust Gateway supports multiple providers for logging and eval purposes. | ||
| Team collaboration features Braintrust is designed for teams from the ground up: shared eval results, annotation workflows, and collaborative prompt iteration. RelayPlane's team features are available on paid tiers and focus on shared cost dashboards and budget policies. | Team dashboards on paid tiers | |
| API compatibility Both tools expose an OpenAI-compatible API. RelayPlane runs on localhost with no vendor dependency. Braintrust Gateway provides a hosted endpoint at a Braintrust URL -- replacing localhost with a cloud endpoint and adding a vendor dependency to your infrastructure. | OpenAI-compatible drop-in proxy (localhost:4100) | OpenAI-compatible proxy endpoint |
| Per-agent cost attribution RelayPlane fingerprints system prompts to attribute cost and usage to individual agents. You can see exactly which agent is driving which spend. Braintrust organizes traces by project and prompt variant, not by per-agent spend attribution. | ||
| Runaway loop detection RelayPlane detects agents caught in repetitive loops and stops them before unexpected spend accumulates. Braintrust does not provide spend-based anomaly detection because its gateway focuses on logging and eval rather than cost governance. |
Why developers choose RelayPlane
npm install in 30 seconds, no account or dashboard required
RelayPlane is npm install -g @relayplane/proxy && relayplane start. That is the complete setup. No account to create, no dashboard to configure, no API keys to wire through a web UI. Braintrust Gateway requires account signup, project creation, and provider configuration before you can proxy a single request. For a developer who wants cost visibility today, not after a 30-minute onboarding flow, RelayPlane is the faster path.
Cost governance in the live call path, not just logging after the fact
RelayPlane sits in the live API call path on localhost. Every request your agent makes flows through it, so cost, latency, and routing decisions happen in real time. It can stop a runaway agent mid-loop before costs spiral. Braintrust Gateway logs requests for evaluation and analysis, but its primary value is quality improvement through evals, not real-time cost governance.
Local-first: your data stays on your machine
RelayPlane stores all cost and routing data locally in SQLite. Nothing leaves your machine unless you opt into cloud sync. Braintrust Gateway routes your LLM traffic through their hosted infrastructure, which introduces a vendor dependency and a latency hop for every request. If data residency, offline support, or infrastructure control matters to your team, RelayPlane is the right choice.
Purpose-built for cost reduction, not added as a side feature
RelayPlane was designed from the ground up to answer: how much did each AI agent cost, and how can I reduce that? It includes dynamic routing to cheaper models, per-agent spend attribution, runaway loop detection, and budget enforcement. Braintrust was designed for prompt evaluation and quality improvement. Cost governance is not its core use case, and it shows in the feature set.
When Braintrust Gateway is the right fit
If your team is invested in Braintrust's eval platform and wants a gateway that integrates tightly with prompt logging, eval datasets, and annotation workflows, Braintrust Gateway makes sense as part of that ecosystem. The gateway is designed to funnel trace data into Braintrust's broader eval and quality-improvement toolchain.
Braintrust is also a reasonable choice for enterprise teams that want a managed, fully hosted platform and are comfortable routing production traffic through a SaaS vendor. If your team is already using Braintrust for evals, extending to their gateway keeps your tooling consolidated.
When RelayPlane is the right fit
If you want to understand what your AI agents are costing you today, without signing up for a SaaS platform or routing traffic through a vendor, RelayPlane is the right tool. It installs in 30 seconds with a single npm command, proxies every LLM call through localhost, and stores cost and latency data locally with no cloud dependency required.
RelayPlane also handles the cost governance layer that Braintrust Gateway does not: routing simple tasks to cheaper models automatically, stopping runaway agent loops before costs spiral, and attributing spend to individual agents so you know which part of your system is expensive. These are production-traffic concerns that eval platforms are not designed to address.