Shopify8 min readadvanced
Helix: The internal tool powering our Shopify app's native migration
Summary
Helix is Shopify’s internal LLM‑driven framework for migrating React Native screens to native iOS/Android. It breaks a screen into tiny, reviewable checkpoints and forces each through four strict gates—behavior tests via a CLI, Gemini‑powered visual diff, two adversarial code reviewers, and a final engineer sign‑off—while remembering feedback to become more autonomous over time.
- Incremental checkpoints keep LLM output small enough for a single‑page review and fit within LLM context windows.
- Four mandatory gates (behavior, UI visual review, adversarial code review, engineer approval) ensure functional, visual, and architectural correctness before any code is committed.
- Helix generates integration‑style behavior tests from the reference React Native app, running them against a CLI that mimics screen state without needing a simulator.
- Gemini (a vision‑capable LLM) acts as a pixel‑level design reviewer, reporting every UI discrepancy with severity and location; blockers must be fixed before proceeding.
By moving verification earlier and into small, repeatable loops, Helix reduces the cognitive load on engineers, cuts the risk of large, undiscovered regressions, and makes LLM‑generated code viable for production‑grade mobile apps—something most LLM tooling currently cannot guarantee.
7/10
