Skip to content
Apex

Agentic coding for mobile and web, fluent in React.

A cost-effective, general-purpose model for everyday agent work. Frontier-level where React runs: React Native on mobile, Next.js on the web.

Try Apex
import { generateText } from "ai" const { text } = await generateText({  model: "apex",  prompt: "Ship this React Native screen.",})
  • Within 1 point of Claude Opus 5.5 on React Native evals
  • 3.7× lower cost per React Native task than Claude Opus 5.5
  • Up to 3× higher TPS than GPT 6.1 Sol

[01] Why Apex

Apex is optimized for React Native. That's why it's sharper on the platform, a fraction of the cost, and answers without reading entire docs first.

Apex works with Claude Code, Cursor, Codex, or whatever your team already use. Swap the endpoint, keep the workflow.

  • Outdated library and API choices
  • Raising daily tasks costs
  • Security and data-location limits

[02] React Native benchmarks

Frontier-level React Native quality

Claude Opus 5.5

88.6%

Apex

87.8%

GPT 6.1 Sol

86.3%

Frontier labs build for everyone, optimizing for single framework isn’t where they spend their effort.

Lower daily tasks cost

$7.72

Apex

$11.50

GPT 6.1 Sol

$28.75

Claude Opus 5.5

Put agents on every React Native ticket without watching the bill climb.

High throughput

Apex

Up to 250 tokens/s

Up to 3× faster than GPT 6.1 Sol

Keep long agent runs moving and increase capacity for parallel work.

Source: rn-evals.vercel.app

[03] Next.js benchmarks

Frontier-level Next.js quality

Apex

$0.067* per task

96.8%

90.3% w/o docs

GPT 6 Astra

13× the cost

96.8%

90.3% w/o docs

Claude Opus 5.5

3.5× the cost

96.8%

96.8% w/o docs

Matches GPT 6 Astra out of the box, and the leaderboard’s best score once Next.js docs are in context.

Lower Next.js task cost

$0.067*

Apex

$0.234

Claude Opus 5.5

$0.891

GPT 6 Astra

13× cheaper per task than GPT 6 Astra on the same Next.js evals.

*Source: nextjs.org/evals (Sep 25, 2026), 31 tasks, pass@4. Cost is the average list cost per task. Apex is estimated at $0.50 / $3.00 per 1M input / output tokens from the token usage of its published eval runs, with cached input billed at 10% of the input rate. Other models use the leaderboard’s figures.

[04] Apex model

One model across all React Native work.

Apex works across everyday development, large refactors, reviews, tests, and upgrades. Its 256K context window gives coding agents room for longer repository context.

Try Apex
import { View, Text } from "react-native"

export function PayWall() {
  return (
    <View className="flex-1 p-6">
      <Text>Unlock Pro</Text>
    </View>
  )
}

Built for React Native

Training draws on documentation, source code, public API symbols, libraries, and conversations grounded in real repositories.

Kept up to date

We curate our training dataset to ensure it reflects the most current, high-quality React Native knowledge available.

Ready for enterprise

Control data residency through EU hosting, SOC 2-compliant infrastructure, or on-premise deployment.

[05] Setup

Connect Apex in about two minutes.

Use an OpenAI-compatible or Anthropic-compatible configuration to run Apex inside your existing coding tool.

npx @callstack/apex init

[05] integration

  • Claude
  • Zed
  • Codex
  • Claude Code
  • Ollama
  • VS Code
  • Cursor

[06] Security

Security and deployment control for your code.

The hosted Apex service runs in the EU with zero data retention enabled by default. Customer requests are not kept for later model training.

Hosted in the EU

Use the shared endpoint with EU processing and zero data retention.

Security review ready

Enterprise customers can receive a security package and Data Processing Agreement.

Dedicated or on-premise

Deploy Apex in a dedicated environment, your cloud, or your data center when shared hosting does not fit your requirements.

[07] Pricing

API Access

  • $0.50 / 1M input tokens
  • $0.20 / 1M cached input tokens
  • $3.00 / 1M output tokens

Request an API key, connect your preferred tool, and pay for actual token usage. Available to business accounts. Prices in USD, excluding applicable taxes.

Try Apex

On Premise

  • Custom quote

Run a structured benchmark pilot with representative React Native tasks. Dedicated and on-premise deployments are available for teams with stricter infrastructure, security, or legal requirements.

Plan a pilot

[08] faq

What is Apex?
Callstack's agentic coding model for mobile and web development. It's general-purpose, and strongest where React runs. You reach it through an API, so it runs inside the coding tools you already use.
What can Apex do?
Plan features, write code, debug build and runtime failures, review changes, write tests, and carry out React Native, Next.js, and library upgrades. It also questions incorrect assumptions, and lays out changes in the order you should make them.
Which tools can I use?
Claude Code, Cursor, OpenCode, Codex, VS Code and GitHub Copilot. The API is OpenAI- and Anthropic-compatible, so most tools take it as a config change.
Is Apex only for React Native?
No. It's general-purpose and handles everyday agent work across stacks. The depth shows where React runs: React Native, then Next.js and React on the web. Frontier models still perform better on broad general-knowledge tasks.
Should Apex replace our frontier model?
Make it the default for everyday work, and for anything in React. Keep a frontier model for the occasional task that needs broader knowledge.
How much does Apex cost?
$0.50 per million input tokens, $0.20 per million cached input tokens, $3.00 per million output tokens, all in USD and excluding applicable taxes. Apex is currently available to business accounts. Dedicated and on-premise deployments are quoted per setup, based on infrastructure, GPUs, security, and support. Get a quote
Try Apex