Consider disabling WebSocket message splitting when permessage-deflate is off

まず ipc.net.ts を確認し、特に MaxWebSocketMessageLength と、issue で説明されている enableMessageSplitting の動作を確認します。高遅延の proxied 接続で splitting するパスと splitting しないパスを比較し、そのうえで、完了の意味を CLI で設定可能な設定とするのか、レイテンシーおよび圧縮の安全性チェックによって裏付けられたデフォルト値の変更とするのかを定義します。

WebSocket message splitting adds significant latency for large files on proxied connections

When serving code-server behind a proxy (which is the common production deployment), the 256KB WebSocket message splitting introduced in microsoft/vscode#174278 multiplies per-message RTT overhead significantly for large file operations like image previews.

Background

VS Code splits large IPC messages into 256KB chunks (MaxWebSocketMessageLength = 256 * 1024 in ipc.net.ts) to avoid blocking the Node.js event loop during zlib compression. Each chunk becomes a separate WebSocket message.

The latency problem in proxied deployments

In a proxied deployment (e.g. a gateway in front of a devbox), each WebSocket message incurs a full round-trip. With 100ms RTT between the proxy and the devbox:

• A 10MB file generates ~40 chunks (10MB ÷ 256KB)
• Each chunk = one WebSocket message = one round-trip
• Total overhead: ~40 × 100ms = ~4 seconds of pure latency

We tested image preview times (time from opening a file in the explorer to the image fully rendering) across different file sizes at 100ms simulated RTT:

Is disabling splitting safe? (Does zlib actually block?)

A few basic tests didn't seem to indicate this issue in our case, but more investigation may be needed

Question

Would you consider making enableMessageSplitting configurable via a CLI flag, or defaulting it to false for single-user deployments?

Happy to submit a PR if there's agreement on the right approach.