Memory leak in native addons: ~18 GB/hour growth, RSS reaches 2 GB in 7 minutes

[JahJajaka]

Description

Claude Code CLI process exhibits aggressive memory growth (~18 GB/hour), reaching ~2 GB RSS in under 7 minutes. The diagnostics indicate the leak is in native memory (outside V8 heap), likely in native addons such as node-pty.

Diagnostics (/heapdump output)

{
  "trigger": "manual",
  "uptimeSeconds": 404,
  "memoryUsage": {
    "heapUsed": 197405793,
    "heapTotal": 71928832,
    "external": 151865422,
    "arrayBuffers": 54231508,
    "rss": 2142371840
  },
  "memoryGrowthRate": {
    "bytesPerSecond": 5301361,
    "mbPerHour": 18200
  },
  "v8HeapStats": {
    "heapSizeLimit": 26947584000,
    "mallocedMemory": 197668190,
    "peakMallocedMemory": 2694758400
  },
  "analysis": {
    "potentialLeaks": [
      "Native memory > heap - leak may be in native addons (node-pty, sharp, etc.)",
      "High memory growth rate: 18200.8 MB/hour"
    ]
  },
  "platform": "darwin",
  "nodeVersion": "v24.3.0",
  "ccVersion": "2.1.71"
}

Key observations

• JS heap is only ~188 MB, but RSS is ~2 GB — the gap is in native/external memory
• external memory (151 MB) and arrayBuffers (52 MB) suggest buffer accumulation
• peakMallocedMemory (2.7 GB) vs current mallocedMemory (197 MB) shows large allocations happened and were freed, but RSS wasn't returned to OS
• Growth rate of ~5.3 MB/s is unsustainable for long sessions

Environment

• macOS (Darwin)
• Node.js v24.3.0
• Claude Code v2.1.71

[JahJajaka]

Related: #32720 (nearly identical symptoms — 1.9 GB RSS, /heapdump diagnostics pointing to native addon leak)

[github-actions]

Found 3 possible duplicate issues:

1. [BUG] Critical memory leak on idle session — 12,396 MB/hour growth rate (v2.1.71, WSL2/Linux) #32745
2. Memory leak: ArrayBuffers consuming 4+ GB within seconds of startup #32729
3. [BUG] Memory leak: RSS grows continuously (~1GB/min) with zero user interaction after session start #31414

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🤖 Generated with Claude Code

[cnnrshd]

Same problem on Fedora. I didn't have this problem yesterday, started today. It jumped to ~9GB then dropped to 2GB and climbed again. Claude Code was updated in the background and on 2.1.72 I don't see this issue.

[masasibata]

Additional Reproduction: Claude Code 2.1.72

Environment

• Claude Code version: 2.1.72
• Node.js: v24.3.0
• OS: Ubuntu 24.04.2 LTS x86_64
• Kernel: 6.17.0-14-generic
• CPU: AMD Ryzen 5 8400F (12 cores) @ 4.758 GHz
• RAM: 32 GB
• GPU: NVIDIA GeForce RTX 4060
• Shell: zsh 5.9

Diagnostic Dump (manual trigger, ~7 minutes uptime)

{
  "uptimeSeconds": 419,
  "memoryUsage": {
    "heapUsed":     27456865064,
    "heapTotal":      82151424,
    "external":     27406483703,
    "arrayBuffers": 26631060167,
    "rss":          22642749440
  },
  "memoryGrowthRate": {
    "bytesPerSecond": 54038255,
    "mbPerHour":      185525
  }
}

Analysis

Metric	Value	Note
V8 heapTotal	82 MB	Normal
external	27.4 GB	← leak lives here
arrayBuffers	26.6 GB	97% of external
RSS	22.6 GB	confirmed by smaps
Growth rate	185,525 MB/hour	system freeze in ~7 min

The V8 heap is fine (~82 MB). The leak is entirely in external/ArrayBuffer memory — consistent with a native addon (likely node-pty) allocating buffers without releasing them.

Also notable: 4.3 GB of swap was already in use at the time of the dump:

Swap: 4355880 kB

Reproduction

• Launch claude CLI
• Send no prompt, perform no task — memory grows immediately just from opening the session
• System freezes / becomes unresponsive within minutes

Impact

System hard freeze requiring reboot. The process cannot be killed gracefully once the OOM state is reached because the system itself becomes unresponsive.

Full diagnostics JSON attached: 809f1eb9-e861-4fd0-bb15-ab93bc3aa275-diagnostics.json

809f1eb9-e861-4fd0-bb15-ab93bc3aa275-diagnostics.json

[my-name-is-yu]

06e73d73-131a-45eb-9540-d547564c52c0-diagnostics.json
06e73d73-131a-45eb-9540-d547564c52c0.heapsnapshot.gz
1000f8de-e6c5-4dee-adbc-98d47cf9e1ed-diagnostics.json
1000f8de-e6c5-4dee-adbc-98d47cf9e1ed.heapsnapshot.gz

Additional data: ArrayBuffer leak confirmed on macOS (v2.1.72 / v2.1.73)

Environment

• macOS (Darwin 25.2.0)
• Node.js v24.3.0
• Claude Code v2.1.72 / v2.1.73

Heap dump 1 — Long-running session (v2.1.72)

• Uptime: 15.3 hours
• heapUsed: 7.04 GB
• arrayBuffers: 6.53 GB (93% of heap)
• mallocedMemory: 7.04 GB
• RSS: 573 MB
• Growth rate: ~35.7 MB/hour (slow steady accumulation)
• peakMallocedMemory: 867 MB

Note: The built-in analysis reported "No obvious leak indicators" despite heapUsed being 7 GB vs heapTotal of only 79 MB — the heuristic seems to miss ArrayBuffer-dominated leaks.

Heap dump 2 — Fresh session (v2.1.73)

• Uptime: 5 minutes
• heapUsed: 143 MB
• arrayBuffers: 35 MB
• RSS: 549 MB
• Growth rate: ~6,315 MB/hour (rapid growth from startup)
• peakMallocedMemory: 689 MB

Key observation

ArrayBuffers account for 93% of memory usage in the long-running session (6.53 GB out of 7.04 GB heapUsed). This strongly suggests binary buffers (likely from node-pty or streaming API responses) are being allocated but never freed.

The two sessions show different growth patterns — one slow (35 MB/hr over 15h), one fast (6,315 MB/hr in 5 min) — which may indicate multiple leak sources or a trigger-dependent leak.

Attached files

Heap snapshots and diagnostics attached as gzipped files below (gunzip before opening in Chrome DevTools).