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TopHat (Shopify mobile test infra)

TopHat is Shopify's internal mobile developer testing platform. Documented publicly in Shopify's 2021 "TopHat: Mobile Developer Testing" post (linked from the migration writeup); the migration writeup referenced here uses TopHat as the operational backbone for dual-architecture CI.

Role in the New Architecture migration

Per sources/2025-09-12-shopify-migrating-to-react-natives-new-architecture: Shopify used TopHat to generate builds for both React Native architectures on every PR — so that testing on old and new architectures didn't require local rebuilds, and so that new architecture-breaking changes were blocked from merging.

This is the concrete mechanism behind Shopify's dual-architecture compatibility discipline (see concepts/dual-architecture-compatibility, patterns/dual-architecture-ci-builds).

Why this matters for large React Native migrations

Without a system like TopHat, maintaining a dual-architecture build is operationally brittle:

  • Local CI builds are slow enough that developers skip the non-primary architecture when testing.
  • Architecture-specific breakage slips onto main; compounds over time; forces periodic rescue passes.
  • Feature velocity (Shopify ships weekly) gets held hostage to migration stability.

TopHat converts this from a "discipline" problem into a "gate" problem: if the PR doesn't build under both architectures, it can't merge.

Seen in

Stub

This page only covers what the migration writeup says. The 2021 Shopify TopHat post (linked as shopify.engineering/shopify-tophat-mobile-developer-testing) is not in the current ingest set — deeper architecture (build orchestration, distribution, device farm integration) would be covered by a dedicated ingest of that article.

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