Apex Models
Apex is a large language model specialised in React Native and React engineering: building new apps, integrating React Native into existing native applications, and migrating between architectures, frameworks and versions.
API base URL: https://api.callstack.ai
Available models
| Model ID | Type | Status | Released |
|---|---|---|---|
apex |
Alias — always points to the latest snapshot. | Generally available | 1 October 2026 |
apex-20261001 |
Pinned snapshot | Generally available | 1 October 2026 |
Use the alias to receive improvements automatically. Use a pinned snapshot when you need stable, reproducible behaviour: a pinned snapshot does not change while it is available, and we give at least six months' notice before retiring it.
apex-20261001
| Specialisation | React Native and React: greenfield and brownfield development, native module integration, New Architecture adoption, upgrades and migrations |
| Input | Text |
| Output | Text |
| Context window | 262,144 tokens |
| Base model | Qwen (Alibaba Group), used under licence |
| Modification by Callstack | Domain post-training on React and React Native source code, widely used open-source React Native libraries, and Callstack's internal engineering documentation |
| Training data | See the Training Data Summary |
| Processing location | European Economic Area |
| Training on your data | Never |
| Zero data retention | Always on, for all traffic — prompts and outputs are never stored |
| Pricing | apex.callstack.com/pricing |
| Rate limits | Shown in the developer console at platform.callstack.ai |
What it is good at
Writing and reviewing React Native and React code; explaining platform-specific behaviour on iOS and Android; planning and carrying out migrations, including to the New Architecture; integrating React Native into existing native applications; choosing and wiring up libraries from the React Native ecosystem.
Limitations
Apex is optimised for React Native and React work. It is less capable outside that domain than general-purpose models of similar size. Like every language model, it can produce incorrect code or confident but wrong explanations — review its output before you ship it. It may occasionally reproduce passages resembling open-source code from its training data; check licence obligations for anything you incorporate.
Provenance and licensing
Apex is built on a base model released by Qwen (Alibaba Group), which Callstack uses under licence from Qwen. The Apex model weights are not distributed; Apex is available only as a hosted service.
Deprecation schedule
No model version is currently scheduled for retirement.