Building an Agent with a Built-in Jev Model Router via Vercel AI Gateway

X postRiley BrownTutorial

Riley Brown and Agent Native share a single prompt to generate an AI agent featuring dynamic model routing via Claude or Codex. It uses Jev by typesafe through Vercel's AI Gateway and the eve framework.

Key points

  1. Developers can build an agent with built-in model routing using a single prompt in Codex or Claude.
  2. Routing is powered by Jev from typesafe, available through Vercel's AI Gateway.
  3. Access across all models requires only a single Vercel API key.
  4. The router directs simple queries to low-cost models and complex tasks to frontier models to optimise token spend.
  5. The generated application visualises inline which model Jev selects and why the choice was made.

Why it matters

Dynamic model routing reduces inference costs by avoiding unnecessary frontier model calls for simple tasks. Combining this with a unified gateway simplifies API key management and provider integration.

Analysis

This workflow abstracts provider complexity by relying on Jev for routing logic and Vercel AI Gateway for model access. While this speeds up rapid agent prototyping, real-world implementations need to balance routing overhead against potential provider latency.

Original post

Riley Brown

@rileybrown · 17 September 2026

In one prompt you can build an agent, with every model, with a built in model router powered by Jev. All you need is a vercel api key. (Vercel Gateway has Jev). Just ask codex or claude to build it full prompt in the post below ⬇️ t.co/rhpck1A0bj

319 likes8 replies498 bookmarks40.7k views

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Selected replies (5)
  • @notjazii @rileybrown hmm gonna play around with jev and let's see what I can cook
  • @digital_founder @rileybrown One prompt, every model, zero idea which one actually did the work
  • @georgehanu @rileybrown This feels like the natural architecture: cheap model decides, specialist model executes, fallback model handles uncertainty. Much better than sending every task to the biggest model by default.
  • @Tacdel0 @rileybrown The local + cloud version of this would be really interesting. Route cheap/simple queries to a local model, scale up locally for medium tasks, then only hit frontier APIs when the router actually needs them. Curious how well Jev handles that boundary in practice.
  • @MichaelMakelko @rileybrown I tried the planning/execution split in Codex: routing each phase separately made retries easier to isolate and cut blind re-runs.

Mentioned links

Summary generated by AI (Gemini 3.8 Flash, 27 September 2026). It may contain errors – the original source is authoritative.

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