[BUG] High mem usage in a new session: 8,619 ArrayBuffers (each 524,432 bytes = 512KB + 144 byte header), totaling ~4.3 GB, are held only by weak references from the GC root

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Include the diagnostics JSON — it has everything needed. Key details to highlight:

• Fresh session, 18s uptime
• 4.9 GB arrayBuffers before any tool calls
• CC version 2.1.73, Node v24.3.0

8,619 ArrayBuffers (each 524,432 bytes = 512KB + 144 byte header), totaling ~4.3 GB, are held only by weak references from the GC root.

This means:

• Nothing in the application code is holding strong references to them
• They're retained solely by weak refs from (root) — this is how V8 tracks ArrayBuffers for the GC
• They're marked as "attached" (not detached), meaning V8 considers them still alive

This is a V8/Node.js GC issue, not a Claude Code application-level leak. The buffers are orphaned (no strong JS references) but V8 hasn't collected them. With Node v18.20.8 (which
your system is running despite the diagnostics saying v24.3.0 — the script ran under v18), this could be a known issue with ArrayBuffer GC pressure.

The 224 MB Response object is likely the Anthropic API streaming response, and the 512KB chunks are the streaming read buffers — each fetch body chunk gets a 512KB ArrayBuffer. After
being consumed, they should be GC'd, but V8 is holding them via weak refs.

Summary: Claude Code's HTTP streaming allocates ~512KB per chunk. After reading, the chunks lose all strong references but V8 isn't collecting them promptly. This is a Node.js/V8 GC
bug — the weak references from (root) keep them alive. Upgrading Node or adding explicit ArrayBuffer detachment after consumption would fix it.

c63a6d1e-ae19-4712-b776-90684bd4b400-diagnostics.json

What Should Happen?

claude should use a reasonable amount of memory

Error Messages/Logs

Steps to Reproduce

I just started a new session in a new terminal tab and got a memory use warning

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.73

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

_No response_