---
title: "Model Evaluation"
description: "Benchmark candidate models against your real engineering tasks to pick the right one and prove it works."
url: https://www.callstack.com/services/model-evaluation
updated: 2026-11-09T15:58:56.168Z
---

# Model Evaluation

Benchmark candidate models against your real engineering tasks to pick the right one and prove it works.

_[Agentic Delivery](/agentic-delivery) › [Custom & Private Models](/capabilities/custom-private-models)_

**Choose models on your tasks, not leaderboards**

Public benchmarks do not predict performance on your codebase. We build evaluation suites from your real engineering tasks - the methodology behind our open-source React Native Evals - and benchmark candidates on evidence.

## Custom & Private Models

- 30/31 Next.js tasks as pixel canary · 85% Lower inference cost vs Opus 5.5
- Industry runs on our tooling · 50M+ OSS downloads / month
- 100+ Enterprise projects delivered
- React Foundation Founding Member · 300+ commits to React Native · Contributing since 2016
- ISO 27001 certified
- 32 Models tested against React Native

## What you get: Evidence before commitment.

- **Custom eval suite** Real tasks from your repositories turned into repeatable, scored evaluations.
- **Candidate benchmarking** Hosted, open-weight, and fine-tuned models compared on quality, latency, and cost.
- **Open methodology** Built like React Native Evals, our public benchmark - inspectable, not black-box.
- **Cost-performance frontier** Which model wins at which price point, per workflow.
- **Regression tracking** Re-runs on new model releases, so upgrades are decisions instead of gambles.
- **Defensible recommendation** A model choice security and finance can both read and challenge.

## Scope → Build → Scale: Deploy models where the workload fits.

### Scope (1 WEEK)
We select a product workflow, define where agents act, and agree the controls and success measures.
- Workflow and owners defined
- Baseline and controls agreed
- Token budgets confirmed
### Build (1-12 MONTHS)
We connect context, agents, and verification to your tools, then run the workflow on your product backlog.
- Running on your product backlog
- Speed and quality measured
- Business impact validated
### Scale (AS NEEDED)
We document the workflow, transfer ownership, and extend it across teams and products based on results.
- Your team owns the workflow
- Expand based on results
- Full knowledge handover

**Bet on measured, not marketed.** An evaluation harness that makes every model decision evidence-based. [Plan my model strategy](/contact)

> Their engineers proved to be a crucial part of our mobile app relaunch project.
>
> — Brian Aznar, Engineering Director, Major League Soccer

We’ll connect you with the right expert within 24 hours.

## Let’s find the right path for your product.

**How many evaluations does a useful suite need?**

Dozens of well-chosen tasks beat hundreds of generic ones. Our public React Native Evals ships 39 across animation, async state, and navigation - the same density works per client.
**Is this one-time or ongoing?**

The suite is an asset. Run it once for a selection decision, then re-run on every notable model release - the ecosystem moves monthly.
**Can our team run it themselves?**

Yes. The harness is handed over with documentation, and re-runs are a CI job, not a consulting engagement.
**Does it cover agentic workflows?**

Yes. Beyond single completions, we evaluate multi-step agent tasks - the mode your engineers actually work in.
**How fast do results go stale?**

Rankings shift with each major release, which is the argument for owning a suite instead of reading leaderboards.
**What about data privacy in evaluation?**

Eval tasks are built from your code under your controls, and candidate models can be tested through private endpoints or self-hosted deployments.

## Open source

- [React Native AI](https://github.com/callstackincubator/ai): On-device LLM execution in React Native with Vercel AI SDK compatibility
- [React Native Evals](https://github.com/callstackincubator/evals): A benchmark suite for evaluating how coding models solve real React Native tasks
- [Skill Gym](https://incubator.callstack.com/skillgym/): Prove your agent skills work before you ship them