Implementation:Cypress io Cypress SetupV8Snapshots

Knowledge Sources	Cypress
Domains	Performance, Build
Last Updated	2026-02-12 00:00 GMT

Overview

Concrete tool for generating V8 heap snapshots during the Electron packaging process provided by the after-pack hook and @tooling/v8-snapshot.

Description

The after-pack-hook.js (scripts/after-pack-hook.js:L42-213) is called by electron-builder after packaging. It invokes setupV8Snapshots from @tooling/v8-snapshot to generate the snapshot blob, consolidateDeps to optimize dependencies, and flipFuses from @electron/fuses to enable snapshot loading in Electron. The buildEntryPointAndCleanup function (scripts/binary/binary-cleanup.js:L157-189) prepares the entry point and removes unnecessary files.

Usage

This hook runs automatically as part of the electron-builder packaging pipeline. It is not invoked directly by developers.

Code Reference

Source Location

Repository: cypress-io/cypress
Files:
- scripts/after-pack-hook.js:L42-213 (main hook, calls setupV8Snapshots at L174-177, L198-204)
- scripts/binary/binary-cleanup.js:L157-189 (buildEntryPointAndCleanup)
- packages/server/v8-snapshot-entry.js (snapshot entry point)

Signature

// after-pack-hook.js default export
module.exports = async function afterPackHook(context) {
  // context.appOutDir: string - electron-builder output directory
  // Calls: setupV8Snapshots({ buildAppDir })
  // Calls: consolidateDeps({ buildAppDir })
  // Calls: flipFuses(electron, ...)
  // Calls: buildEntryPointAndCleanup(buildAppDir)
}

Import

// Referenced in electron-builder.json:
// "afterPack": "./scripts/after-pack-hook.js"
const { setupV8Snapshots, consolidateDeps } = require('@tooling/v8-snapshot')

I/O Contract

Inputs

Name	Type	Required	Description
context.appOutDir	string	Yes	Electron-builder output directory with packaged app
buildAppDir	string	Yes	Path to app resources directory within packaged output

Outputs

Name	Type	Description
V8 snapshot blob	binary file	Serialized V8 heap state for fast startup
Cleaned dependencies	directory	Optimized node_modules with unnecessary files removed

Usage Examples

electron-builder Configuration

{
  "afterPack": "./scripts/after-pack-hook.js",
  "afterSign": "./scripts/after-sign-hook.js"
}

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