Memory leak: 2.92 GB external ArrayBuffers after 34 min session (v2.1.72)

[RaiAnsar]

Description

Claude Code leaks ~490 MB/hour of external (native) ArrayBuffer memory. A 34-minute session accumulated 3.39 GB of external memory (2.92 GB in ArrayBuffers), while the V8 heap itself remained healthy at ~126 MB.

The memory is invisible to V8 heap snapshots — it lives in native/external allocations tracked by V8 but not captured in .heapsnapshot files. This points to a leak in the HTTP streaming layer (likely undici response body buffers not being freed).

Environment

• Claude Code version: 2.1.72
• Node.js version: v24.3.0
• Platform: macOS Darwin 25.3.0 (Apple Silicon)
• Model: claude-opus-4-6

Reproduction

1. Start a Claude Code session
2. Use it normally (chat, tool calls, web fetches, file reads)
3. After ~30 minutes, run /heapdump
4. Observe external memory growing at ~490 MB/hour

Diagnostics Data

From the diagnostics JSON (/heapdump output):

{
  "uptimeSeconds": 2033.87,
  "memoryUsage": {
    "heapUsed": 3511037332,
    "heapTotal": 136690688,
    "external": 3392535811,
    "arrayBuffers": 2915585335,
    "rss": 290684928
  },
  "memoryGrowthRate": {
    "bytesPerSecond": 142922.24,
    "mbPerHour": 490.68
  },
  "v8HeapStats": {
    "heapSizeLimit": 12440698880,
    "mallocedMemory": 3511299731,
    "peakMallocedMemory": 1244069888,
    "detachedContexts": 0,
    "nativeContexts": 1
  },
  "resourceUsage": {
    "maxRSS": 1273927565312
  }
}

Heap Snapshot Analysis

The V8 heap snapshot (76 MB serialized) shows the JS heap is healthy at ~126 MB. The top consumers are:

Category	Size	Notes
[object] Object	20.1 MB	419K objects — normal
[object] ArrayBuffer	19.0 MB	8 ArrayBuffers (V8-managed, tiny vs the 2.92 GB external)
[code] FunctionCodeBlock	14.0 MB	4,261 blocks — normal
[native] Blob	9.8 MB	7 Blobs retained by a single Array(6)
[closure] Function	4.3 MB	136K closures — normal

The 16 MB ArrayBuffer is retained by WebAssembly.Memory (expected — likely argon2/crypto).

Additional observations

• Duplicated skill definitions: Every skill appears twice in memory (~800 KB wasted)
• Duplicated conversation context: 6 copies of the same drizzle/postgres schema (~650 KB)
• Base64 PNG screenshots: 2x 582 KB each (1.1 MB)
• maxRSS reports 1.18 TB — clearly a Node v24.3.0 reporting bug on macOS (ru_maxrss units issue)

Root Cause Hypothesis

The 2.92 GB of external ArrayBuffers are not captured in the heap snapshot (V8 limitation for external/native memory). The most likely source is undici HTTP response body buffers from Anthropic API streaming responses not being garbage collected. The growth is linear (~490 MB/hour), suggesting each API response's buffer is retained indefinitely.

Workaround

Restart Claude Code sessions every 1-2 hours to reclaim memory.

[yassinbenelhajlahsen]

Restarting doesn't fix it. I ran /heapdump at 2.8 seconds uptime on a fresh session — no prompts sent, no tool calls, nothing. Already sitting at 445MB external and 186MB in ArrayBuffers.

This isn't accumulating from API streaming. It's there before I do anything.

Environment:

• Claude Code: 2.1.72
• Node.js: v24.3.0
• Platform: macOS (Apple Silicon)

Heapdump at 2.8s uptime (zero interaction):

{
  "timestamp": "2026-03-11T19:28:47.801Z",
  "sessionId": "3444b857-0dcd-4527-9975-54d626190507",
  "trigger": "manual",
  "dumpNumber": 0,
  "uptimeSeconds": 2.876653042,
  "memoryUsage": {
    "heapUsed": 502525535,
    "heapTotal": 42774528,
    "external": 466945830,
    "arrayBuffers": 195297817,
    "rss": 515702784
  },
  "memoryGrowthRate": {
    "bytesPerSecond": 179271805.27876812,
    "mbPerHour": 615480.8988605167
  },
  "v8HeapStats": {
    "heapSizeLimit": 5165875200,
    "mallocedMemory": 503836966,
    "peakMallocedMemory": 516587520,
    "detachedContexts": 0,
    "nativeContexts": 1
  },
  "resourceUsage": {
    "maxRSS": 528985620480,
    "userCPUTime": 1088119,
    "systemCPUTime": 188056
  },
  "activeHandles": 0,
  "activeRequests": 0,
  "analysis": {
    "potentialLeaks": [
      "High memory growth rate: 615480.9 MB/hour"
    ],
    "recommendation": "WARNING: 1 potential leak indicator(s) found. See potentialLeaks array."
  },
  "platform": "darwin",
  "nodeVersion": "v24.3.0",
  "ccVersion": "2.1.72"
}

The root cause hypothesis in this issue points to HTTP streaming buffers accumulating over time — but 445MB external at 2.8 seconds suggests something is allocated at initialization before any network activity. Worth checking what's happening during startup before the first API call goes out.

[Manuele99]

I'm having the same issue. I'll just report here my results from /heapdump to help you investigate.
The memory usage went up to 30+ Gb, then, without any intervention from me, it got back to around 10 and kept growing back up.

{
  "timestamp": "2026-03-11T19:50:51.536Z",
  "sessionId": "0bae3b23-6629-45f5-80f1-16f2654e841b",
  "trigger": "manual",
  "dumpNumber": 0,
  "uptimeSeconds": 1449.091198833,
  "memoryUsage": {
    "heapUsed": 34782349988,
    "heapTotal": 173487104,
    "external": 34670228932,
    "arrayBuffers": 33601072356,
    "rss": 6407684096
  },
  "memoryGrowthRate": {
    "bytesPerSecond": 4421863.924893281,
    "mbPerHour": 15181.265000930607
  },
  "v8HeapStats": {
    "heapSizeLimit": 38654705664,
    "mallocedMemory": 34783136644,
    "peakMallocedMemory": 6914211840,
    "detachedContexts": 0,
    "nativeContexts": 1
  },
  "resourceUsage": {
    "maxRSS": 7080152924160,
    "userCPUTime": 327287438,
    "systemCPUTime": 33906058
  },
  "activeHandles": 0,
  "activeRequests": 0,
  "analysis": {
    "potentialLeaks": [
      "High memory growth rate: 15181.3 MB/hour"
    ],
    "recommendation": "WARNING: 1 potential leak indicator(s) found. See potentialLeaks array."
  },
  "platform": "darwin",
  "nodeVersion": "v24.3.0",
  "ccVersion": "2.1.72"
}

[0xFFD]

Also experiencing the same problem on Windows, fresh session with no tool calls and no prompts. I added the /heapdump to help you investigate. Also on my M3 Macbook Air with Claude Code v2.1.70 there seems to be no problem.

Environment:

• Windows 11 Version 25H2 (OS Build 26200.8037)
• Claude Code Version: 2.1.73

{
  "timestamp": "2026-03-11T23:57:44.295Z",
  "sessionId": "1ccd4c83-db61-4114-95b4-6ed34a96bead",
  "trigger": "manual",
  "dumpNumber": 0,
  "uptimeSeconds": 233.18471739999998,
  "memoryUsage": {
    "heapUsed": 7317758821,
    "heapTotal": 66292736,
    "external": 7269795765,
    "arrayBuffers": 6738121758,
    "rss": 1967280128
  },
  "memoryGrowthRate": {
    "bytesPerSecond": 8436574.017092941,
    "mbPerHour": 28964.678250822628
  },
  "v8HeapStats": {
    "heapSizeLimit": 21648015360,
    "mallocedMemory": 7317758821,
    "peakMallocedMemory": 2164801536,
    "detachedContexts": 0,
    "nativeContexts": 1
  },
  "resourceUsage": {
    "maxRSS": 2164801536,
    "userCPUTime": 6046000,
    "systemCPUTime": 2765000
  },
  "activeHandles": 0,
  "activeRequests": 0,
  "analysis": {
    "potentialLeaks": [
      "High memory growth rate: 28964.7 MB/hour"
    ],
    "recommendation": "WARNING: 1 potential leak indicator(s) found. See potentialLeaks array."
  },
  "platform": "win32",
  "nodeVersion": "v24.3.0",
  "ccVersion": "2.1.71"
}

[yassinbenelhajlahsen]

Update 8:12PM ET: Issue seems resolved now, didn’t touch anything and fixed on its own.