Memory leak: ArrayBuffers grow ~980 MB/hour in long sessions

Description

Claude Code accumulates ~6 GB of memory (mostly ArrayBuffers) during a 6-hour session, growing at ~980 MB/hour. The JS heap itself stays small (~77 MB), indicating the leak is in external/native buffers rather than JS objects.

Diagnostics

From /heapdump diagnostics output (v2.1.72, Node v24.3.0, Linux):

{
  "uptimeSeconds": 22123,
  "memoryUsage": {
    "heapUsed": 6618384085,
    "heapTotal": 76737536,
    "external": 6572254960,
    "arrayBuffers": 6000788535,
    "rss": 6313570304
  },
  "memoryGrowthRate": {
    "bytesPerSecond": 285384,
    "mbPerHour": 979.79
  }
}

Key observations:

• ArrayBuffers: 6.0 GB — 95% of total memory
• JS Heap: 77 MB — normal, no JS-side leak
• External: 6.6 GB — native/C++ allocations not being freed
• Growth rate: ~980 MB/hour — linear, not bounded

Session characteristics

• Duration: ~6 hours
• Activity: heavy use of Agent tool (subagents), multiple git operations, SSH via Bash, file reads/edits
• MCP servers active: context7, sequential-thinking, memory, playwright
• Platform: Linux (Fedora 43), Node v24.3.0

Suspected cause

ArrayBuffers accumulating without GC — likely from:

• Conversation transcript compression buffers not being released
• MCP server communication buffers (stdin/stdout pipes)
• Subagent spawn/result buffers retained after completion

Workaround

Restarting the session (/exit → claude) reclaims all memory. But sessions over ~3-4 hours become problematic (swap pressure, system slowdown).

Environment

• Claude Code version: 2.1.72
• Node.js: v24.3.0
• OS: Linux 6.18.13-200.fc43.x86_64 (Fedora 43)
• RAM: 16 GB