By Kylan Gibbs, CEO and Co-founder, Inworld AI
Last updated: April 2026
An AI gateway provides a single API endpoint for accessing multiple AI model providers, handling authentication, routing, failover, and observability in one layer. Inworld AI's
Realtime Router is the intelligent routing variant: it routes to hundreds of LLMs with conditional logic, native A/B testing, and direct integration into a full voice pipeline. In 2026 the category has matured from simple proxy tools into infrastructure that determines how production AI applications select, test, and optimize across models. The leading AI gateways are
Vercel AI Gateway, Realtime Router,
OpenRouter,
Portkey, and
LiteLLM.
This comparison evaluates each gateway on the criteria that matter in production: routing intelligence, model coverage, failover handling, experimentation support, and integration depth.
Quick Comparison: AI Gateways in 2026
| Feature | Vercel AI Gateway | Realtime Router | OpenRouter | Portkey | LiteLLM |
|---|
| Type | Managed proxy + fallback | Intelligent router + gateway | Managed marketplace proxy | AI gateway + LLMOps | Open-source proxy + SDK |
| Models | Major frontier providers | Hundreds across all major providers | Broadest catalog including open-weight hosts | Largest catalog with multimodal | Self-hosted catalog |
| Routing logic | Static fallback; uptime/latency-based | Conditional routing (CEL expressions), cost/latency/intelligence optimization | Availability-based; manual model selection | Conditional, guardrails, compliance | Latency, cost, weighted |
| A/B testing | No | Native with sticky user assignment | No | Basic traffic splitting | No |
| Failover | Automatic provider switching | Automatic with full attempt chain in response metadata | Automatic | Error-based triggering | Fallback chains with cooldowns |
| Voice pipeline | No | Yes (Realtime TTS, Realtime STT, Realtime API) | No | Audio modality support | No |
| Self-hosted | No | No (fully managed) | No (fully managed) | Optional (cloud or self-hosted) | Yes |
| Best for | Teams on Vercel wanting consolidated model access | Teams needing intelligent routing, A/B testing, voice integration | Exploring and prototyping across many models | Compliance, guardrails, prompt management | Full control, self-hosting |
Vercel AI Gateway: Strengths and Limitations
Vercel AI Gateway launched in 2025 and provides a single endpoint for major frontier models from OpenAI, Anthropic, Google, xAI, and others. Zero friction for teams already deployed on Vercel.
Strengths: zero-friction setup for Vercel teams. Built-in failovers. Compatible with OpenAI and Anthropic SDKs. Natural choice for Next.js applications.
Limitations: no conditional routing, A/B testing, or traffic splitting. Tightly coupled to the Vercel platform with no self-hosted option. Serverless execution limits constrain long-running agentic workflows. Routing is limited to static fallback chains.
Realtime Router: Intelligent Routing for Production
Realtime Router provides a single API endpoint for hundreds of models with conditional routing through CEL expressions. The router evaluates request metadata and directs each request to the right model based on engineering-defined rules: user tier, query complexity, region, language, or any custom metadata.
Strengths: the only AI gateway with native A/B testing and sticky user assignment, so the same user consistently sees the same variant for clean experiments. Full attempt chain returned in response metadata for debugging. Drop-in replacement for OpenAI and Anthropic SDKs (change
base_url to
https://api.inworld.ai/v1). Currently free during Research Preview. Integrates with
Realtime TTS (#1 on the
Artificial Analysis Speech Arena, three of the top five) and the
Realtime API for voice-aware applications.
Limitations: currently in Research Preview, not yet at full enterprise SLA tier. Focused on routing rather than the broader LLMOps surface (Portkey is stronger on observability dashboards and governance tooling). Not open source.
from openai import OpenAI
client = OpenAI(
base_url="https://api.inworld.ai/v1",
api_key="<your-api-key>"
)
response = client.chat.completions.create(
model="gpt-5.5",
messages=[{"role": "user", "content": "Hello"}],
)
OpenRouter: Widest Catalog for Prototyping
OpenRouter is a managed marketplace proxy providing unified access to a broad model catalog including frontier models and open-weight models hosted by third-party providers. Credit-based billing with no subscription requirement.
Strengths: broadest model catalog. Fully managed, no self-hosted infrastructure or supply-chain risk. Low-friction entry for evaluation.
Limitations: proxy, not intelligent router. Routing is availability-based or manual. No A/B testing, traffic splitting, or conditional routing. Limited observability beyond basic usage tracking. Adds 25-40ms latency per request, which can be unacceptable for real-time voice applications.
Portkey: Compliance-First Gateway
Portkey positions itself as an AI gateway with strong emphasis on observability, guardrails, and governance. Available as both cloud-managed and self-hosted.
Strengths: strongest governance tooling for regulated industries. Real-time dashboards tracking latency, cost, and error rates. Anomaly detection and proactive alerts. Open-source core with paid enterprise features. Semantic caching for cost reduction on repetitive queries.
Limitations: governance-oriented, not optimization-oriented. Routing is rule-based and compliance-driven, not dynamically optimized for cost-per-quality or task-model matching. Basic traffic splitting only, no sticky user A/B testing. No voice pipeline integration.
LiteLLM: Open-Source Self-Hosted Proxy
LiteLLM is an open-source Python proxy providing unified API access across many LLM providers. Free, flexible, and easy to set up.
Strengths: full source-code visibility. Self-hosted (you control the infrastructure). Free at the routing layer. Strong community.
Limitations: routing is fallback-based, not intelligent. No conditional routing on business logic. No A/B testing. Self-hosted infrastructure carries supply-chain risk: any open-source software distributed via public package registries (PyPI, npm) is structurally vulnerable to dependency-injection attacks. Requires engineering time to deploy, scale, and maintain.
When to Use Which AI Gateway
- Choose Vercel AI Gateway if you are already on Vercel, need consolidated model access with simple fallback, and your routing needs are basic.
- Choose Realtime Router if you need routing based on business logic, A/B testing in production, voice-enabled applications, or a unified speech-to-speech pipeline.
- Choose OpenRouter if you need the broadest model catalog for evaluation and prototyping across many providers.
- Choose Portkey if compliance, guardrails, and governance are your primary requirements.
- Choose LiteLLM if you need full control over gateway infrastructure (open source, self-hosted) and accept the operational ownership that comes with it.
The Routing Intelligence Gap
The fundamental differentiator between AI gateways in 2026 is routing intelligence. Most gateways are effectively proxies: they accept a request, forward it to the named model, and return the response. The Realtime Router analyzes request metadata, matches it against model capabilities, and routes dynamically based on conditions the engineering team defines. Production deployments routinely achieve substantial cost reductions when the routing layer matches model spend to task complexity.
FAQ
What is an AI gateway?
An AI gateway is a layer between your application and multiple AI model providers that provides a single API endpoint for sending requests, handling authentication, routing, failover, and billing. Leading AI gateways include Vercel AI Gateway,
Realtime Router, OpenRouter, Portkey, and LiteLLM.
Is Vercel AI Gateway free?
Vercel AI Gateway includes a monthly free credit per account. Beyond that, you pay provider list rates with no markup from Vercel. See their pricing page for current details.
How does the Realtime Router compare to Vercel AI Gateway?
Realtime Router provides conditional routing with CEL expressions, native A/B testing with sticky user assignment, and detailed per-request observability. Vercel AI Gateway does not support conditional routing, A/B testing, or traffic splitting. Realtime Router is also the only gateway in this category with direct integration into a full voice AI pipeline (Realtime TTS, Realtime STT, Realtime API).
Do AI gateways add latency?
AI gateways introduce minimal overhead, typically sub-20ms routing latency. In practice, the added latency is offset by reliability improvements from built-in retries and intelligent routing. OpenRouter's 25-40ms overhead is on the higher end and may matter for real-time voice applications.
Which AI gateway has the most models?
Catalog size varies, with several gateways supporting hundreds to thousands of models. In production, routing intelligence and reliability matter more than raw catalog breadth. Realtime Router routes to hundreds of models from OpenAI, Anthropic, Google, Mistral, DeepSeek, xAI, Meta, and other providers with conditional routing built in.