# vitest-dev/vitest · RepoSense Release & Migration Intelligence

> Add `--last-failed` to run only failed tests - by @shereme. Drop-in upgrade. Migration: None.

## Metadata
- **Repository URL**: https://github.com/vitest-dev/vitest
- **Primary Package**: `vitest` (NPM)
- **Categories**: `BUILD_TOOL`, `TESTING`
- **Latest Version**: `v5.1.0`
- **Semantic Status**: `COMPATIBLE`
- **Bundle Size Impact (unavailable)**: `Size Unavailable`
- **Atom Ingestion Feed**: https://github.com/vitest-dev/vitest/releases.atom

## The Human Context (Plain-English Pitch)
vitest is an open-source library and developer tool in the vitest-dev/vitest ecosystem. It saves developers from writing repetitive low-level boilerplate from scratch by providing a battle-tested, open-source implementation ready for production.

## Stage 1 Executive Summary ([Core Change] + [Required Action] + [Migration Effort])
Add `--last-failed` to run only failed tests - by @shereme. Drop-in upgrade. Migration: None.

## Breaking Changes & Required Actions
- Add `--last-failed` to run only failed tests - by @sheremet-va in #11558 (82f63)
- Support `Temporal.Instant` and `Temporal.ZonedDateTime` in `vi.setSystemTime()` - by @Prajwal2246, **Prajwal2246**, **Claude Opus 5.5 (1M context)**, @hi-ogawa and **Codex (GPT-...
- Introduce `--since-last-run` flag - by @sheremet-va in #11516 (08bd9)
- Expose per-retry/repeat attempt result - by @hi-ogawa, **Codex (GPT-6)** and **Claude Opus 5.5 (1M context)** in #11232 (21be4)

## Migration Snippet
```ts
npm install vitest@5.1.0
```

## Ecosystem Compatibility Matrix & Graph Warnings
- **TypeScript 5.x** [`COMPATIBLE`]: Ships standard TypeScript declaration files without type regressions.

## Zero-Noise Release Timeline
- **v5.1.0** (2026-11-02) [COMPATIBLE]: Add `--last-failed` to run only failed tests - by @shereme. Drop-in upgrade. Migration: None.

## Upgrade & Migration Q&A (GEO Direct Answers)
### Is vitest-dev/vitest v5.1.0 safe to upgrade in production?
vitest-dev/vitest v5.1.0 is classified as COMPATIBLE (MINOR release). Add `--last-failed` to run only failed tests - by @shereme. Drop-in upgrade. Migration: None.

### What breaking changes or compatibility risks exist in vitest-dev/vitest v5.1.0?
No breaking API changes or peer dependency conflicts are recorded for vitest-dev/vitest v5.1.0 in the RepoSense compatibility graph.

### What is the bundle size impact of vitest v5.1.0?
Measured bundle size telemetry is currently unavailable for vitest v5.1.0; verify build output locally before deploying.

### How do I upgrade vitest to v5.1.0?
Upgrade vitest to v5.1.0 by running "npm install vitest@5.1.0" and applying the migration steps: npm install vitest@5.1.0