# socketio/socket.io · RepoSense Release & Migration Intelligence

> types: export ExtendedError for connect_error event (#5548. Drop-in upgrade. Migration: None.

## Metadata
- **Repository URL**: https://github.com/socketio/socket.io
- **Primary Package**: `socket.io` (NPM)
- **Categories**: `ECOSYSTEM`, `BACKEND`
- **Latest Version**: `socket.io-client@4.8.4`
- **Semantic Status**: `COMPATIBLE`
- **Bundle Size Impact (unavailable)**: `Size Unavailable`
- **Atom Ingestion Feed**: https://github.com/socketio/socket.io/releases.atom

## The Human Context (Plain-English Pitch)
socket.io is an open-source library and developer tool in the socketio/socket.io 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])
types: export ExtendedError for connect_error event (#5548. Drop-in upgrade. Migration: None.

## Breaking Changes & Required Actions
- **types:** export ExtendedError for connect_error event (#5548) (c0d5450)
- **types:** export reserved event interfaces (#5533) (03945df)
- `engine.io-client@~6.6.1` (no change)
- `ws@~8.21.0` (diff)

## Migration Snippet
```ts
npm install socket.io@socket.io-client@4.8.4
```

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

## Zero-Noise Release Timeline
- **socket.io-client@4.8.4** (2026-09-25) [COMPATIBLE]: types: export ExtendedError for connect_error event (#5548. Drop-in upgrade. Migration: None.

## Upgrade & Migration Q&A (GEO Direct Answers)
### Is socketio/socket.io socket.io-client@4.8.4 safe to upgrade in production?
socketio/socket.io socket.io-client@4.8.4 is classified as COMPATIBLE (PATCH release). types: export ExtendedError for connect_error event (#5548. Drop-in upgrade. Migration: None.

### What breaking changes or compatibility risks exist in socketio/socket.io socket.io-client@4.8.4?
No breaking API changes or peer dependency conflicts are recorded for socketio/socket.io socket.io-client@4.8.4 in the RepoSense compatibility graph.

### What is the bundle size impact of socket.io socket.io-client@4.8.4?
Measured bundle size telemetry is currently unavailable for socket.io socket.io-client@4.8.4; verify build output locally before deploying.

### How do I upgrade socket.io to socket.io-client@4.8.4?
Upgrade socket.io to socket.io-client@4.8.4 by running "npm install socket.io@socket.io-client@4.8.4" and applying the migration steps: npm install socket.io@socket.io-client@4.8.4