hi-ogawa

DOM Snapshot / Replay Architecture Comparison

This is a related resarch for Vites trace view discussion vitest-dev/vitest#10156.

Note

This note may be shared publicly as extra background for the trace-view discussion. Sibling-repo references in this note assume these source repositories:

• rrweb: https://github.com/rrweb-io/rrweb/
• Playwright: https://github.com/microsoft/playwright/tree/v1.59.1
• Cypress: https://github.com/cypress-io/cypress/tree/v15.14.0

hi-ogawa

Trace View Ecosystem Candidates

Date: 2026-04-12

Goal: find real ecosystem projects, preferably component libraries, that already use Vitest Browser Mode and can exercise the new browser.traceView workflow.

Search Method

Initial GitHub code search signals:

hi-ogawa

maxConcurrency Scheduling Issue (issue #10097)

Issue: vitest-dev/vitest#10097

The Problem

With describe.concurrent and maxConcurrency: 5, users expect at most 5 tests' resources to be held simultaneously. Instead, all N concurrent tests fire their beforeEach hooks (allocating resources) before any test body runs — producing N simultaneous resource allocations regardless of maxConcurrency.

Root cause: the current scheduler is effectively BFS over the task tree. All nodes at depth N complete before depth N+1 begins.

hi-ogawa

Issue #9667 — Reporter hook after coverage HTML generation

Issue: vitest-dev/vitest#9667

Problem

The HTML reporter and UI mode need to act after coverage HTML is generated, but there's no public hook for this. The internal onFinishedReportCoverage method is duck-typed in core to fill this gap:

Location: packages/vitest/src/node/core.ts#L1455

hi-ogawa

RSC Member-Chain Binding Plan

Goal

Implement the feature gap called out in packages/plugin-rsc/src/transforms/scope.ts#L129 and the Next.js comparison note at packages/plugin-rsc/docs/notes/scope-manager-research/nextjs.md#L126:

• track config.api.key as a closure capture instead of only config
• keep declaration resolution anchored on the root identifier (config)
• preserve current shadowing correctness from the custom scope tree

hi-ogawa

Issue 10050: docs-only first pass for @vitest/pretty-format

Issue: vitest-dev/vitest#10050

Goal

Start with documentation only:

• remove leftover wording that points users at Jest's pretty-format docs
• give @vitest/pretty-format an actual Vitest-owned explanation

hi-ogawa

Self-contained HTML reporter

Plan for implementing a single-file output mode for @vitest/ui's HTML reporter. Tracking issue: vitest#6425

Goal

Add an option (e.g. reporter: [['html', { singleFile: true }]]) that produces a single index.html with no external dependencies.

hi-ogawa

AI Agent Integration for Vitest — Plan

Status: Draft Date: 2026-03-29 See also: ai-agent-integration-02-landscape.md (See next document)

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Background

hi-ogawa

Cross-Platform Merge Reports

Issue Title

feat: support merging reports for non-sharded multi-environment runs

Feature Request

Clear and concise description of the problem

hi-ogawa

Custom Snapshot Matchers (#9948)

• Issue: vitest-dev/vitest#9948
• Draft PR: vitest-dev/vitest#9973
• Related: #9081 (add method name to InlineSnapshot), #9080 (how to write custom inline snapshot matcher?)

Layer diagram

expect.extend (user custom matcher)