Introduction

Nexus is a Go library for building AI gateways. Route requests across multiple LLM providers, enforce content guardrails, cache responses, and manage multi-tenant access — all from a single composable API.

Nexus is a library — not a service. You bring your own providers, database, and HTTP server. Nexus provides the gateway orchestration plumbing.

What it does

• Multi-provider routing — Route to OpenAI, Anthropic, or any OpenAI-compatible API with priority, cost-optimized, or round-robin strategies.
• Content guardrails — PII detection, prompt injection blocking, content filtering with block/redact/warn actions.
• Response caching — Deterministic cache keys with optional semantic matching. Memory and Redis backends.
• Multi-tenant isolation — Tenant-scoped requests, API keys, rate limits, usage tracking, and model aliases.
• Model aliases — Map virtual model names to provider targets with per-tenant overrides and weighted routing.
• Input/output transforms — System prompt injection, RAG context, data anonymization, output normalization.
• Plugin system — 15 lifecycle hooks for metrics, audit trails, and custom processing.
• Three storage backends — PostgreSQL, SQLite, and in-memory.
• Forge integration — Drop-in forge.Extension with auto-discovery and DI-registered Gateway.
• OpenAI-compatible proxy — Drop-in replacement for the OpenAI API. Point any SDK at your gateway.

Design philosophy

Library, not service. Nexus is a set of Go packages you import. You control main, the database connection, and the process lifecycle.

Interfaces over implementations. Every subsystem defines a Go interface. Swap any provider, store, or cache with a single type change.

Tenant-scoped by design. nexus.WithTenant injects context enforced at every layer — routing, caching, usage, and guardrails.

Pipeline-driven. Every request flows through a priority-sorted middleware chain. Add, remove, or reorder middleware without touching engine code.

Quick look

package main

import (
    "context"
    "os"

    "github.com/xraph/nexus"
    "github.com/xraph/nexus/providers/openai"
    "github.com/xraph/nexus/store/memory"
)

func main() {
    gw := nexus.New(
        nexus.WithDatabase(memory.New()),
        nexus.WithProvider(openai.New(os.Getenv("OPENAI_KEY"))),
    )
    if err := gw.Initialize(context.Background()); err != nil {
        panic(err)
    }
}

Where to go next