claude-cloud/meta/box-spec.md

Machine spec

The image is the disk. To match Anthropic's sandbox, configure the VM around it like this. Companion docs: env-contract.md, filestore-api.md, ../README.md.

Setting	Value
vCPU	1
RAM	3.9 GiB (4,093,820 kB), no swap
/dev/shm	their images assume it equals full RAM; see the OOM note below
Disk	256 GiB rw ext4, plus read-only layers for skills if you want the layout
Privilege	commands run as root, 40 capabilities (-CAP_SYS_RESOURCE), no seccomp, no LSM, no PID namespace
Cgroups	all unlimited. They account per session but enforce nothing
Per-call budget	about 300 seconds
Kernel	any 6.x. They ship a custom 6.18 Firecracker build; not required
Network	egress allowlist: PyPI, npm, GitHub, Ubuntu archives, Anthropic API (swap in your own LLM host). They also TLS-inspect outbound; optional

Run it

# Docker
docker run -it --memory=3900m --memory-swap=3900m --cpus=1 --shm-size=3900m wiggle bash

# e2b / Modal / Firecracker hosts: vCPU=1, RAM about 3.9 GiB, no swap

Exec environment

Inject these. This is what Claude's commands actually see.

IS_SANDBOX=yes  HOME=/root  PYTHONUNBUFFERED=1  DEBIAN_FRONTEND=noninteractive
PATH=/home/claude/.npm-global/bin:/usr/local/bin:...
PLAYWRIGHT_BROWSERS_PATH=/opt/pw-browsers
NODE_PATH=/usr/local/lib/node_modules_global
PIP_ROOT_USER_ACTION=ignore

Two intentional oddities: HOME is /root but PATH leads with /home/claude, and LANG is left unset. Full list with rationale: meta/env-contract.md.

Gotchas (all present in the original)

• pandoc x.md -o x.pdf fails until you add fonts-lmodern or use a fallback engine. See ../README.md.
• ImageMagick has no SVG coder and ignores -quality on webp. Use Pillow or sharp.
• pip install is blocked by PEP 668. Use uv. The offline cache is included.
• Do not trust tool exit codes. Verify the artifact (test -s out && file out).
• /dev/shm at full RAM is a hazard on a 3.9 GiB box under heavy writes. Anthropic ships it that way. Drop --shm-size to about 1 GiB if you do not need the big one.