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Dejavu

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CI Maven Central Compose License

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Guard your Compose UI efficiency. Catch recomposition regressions before your users.

The Problem

Compose's recomposition behavior is an implicit contract — composables should recompose when their inputs change and stay stable otherwise. But that contract breaks silently, and today's options for catching it are limited:

  • Layout Inspector — manual, requires a running app, can't automate, can't run in CI
  • Manual tracking code — SideEffect counters, LaunchedEffect logging, wrapper composables; invasive, doesn't scale, and ships in your production code
  • Neither gives you a testable, automatable contract you can enforce on every PR

What Dejavu Does

Dejavu is a test-only library that turns recomposition behavior into assertions. Tag your composables with standard Modifier.testTag(), write expectations against recomposition counts, and get structured diagnostics when something changes — whether from a teammate, a library upgrade, an AI agent rewriting your UI code, or a refactor that silently destabilizes a lambda.

  • Zero production code changes — just Modifier.testTag()
  • One-line test setup — createRecompositionTrackingRule()
  • Rich diagnostics — source location, recomposition timeline, parameter diffs, causality analysis
  • Per-instance tracking — multiple instances of the same composable get independent counters

Dejavu 0.4.x supports Compose 1.11 (BOM 2026.05.00 through 2026.06.01); the release baseline is Compose Multiplatform 1.11.1 and Android Compose BOM 2026.06.01. For Compose 1.10, use Dejavu 0.3.1. The 0.4.x test harness uses the Compose testing v2 APIs (which default to StandardTestDispatcher). Instrumented BOM gates run the supported BOM range, and the compose-experimental module (a staging area for experimental-API recomposition coverage) validates Dejavu against Compose 1.11's new composables (Grid, FlexBox, derivedMediaQuery, the Styles API) and the LinkBuffer runtime path. See How It Works for the full compatibility table and details.

Next Steps

  • Getting Started — add the dependency and write your first test
  • Use Cases — locking in UI efficiency, AI agent guardrails, and CI enforcement
  • Examples — test patterns for common scenarios
  • API Reference — all assertions and utilities
  • How It Works — internals, compatibility, and limitations

Using Claude Code?

Install the bundled Dejavu skills globally — they cover initial install (dejavu-onboarding), authoring tests (dejavu-test-writer), diagnosing single failures (dejavu-error-triage), and the iterative perf-optimization loop (dejavu-perf-loop):

/plugin marketplace add mttmcknn/dejavu
/plugin install dejavu@dejavu

See Use Cases → Give AI Agents a Recomposition Signal for what each skill does.