seccomp filter not found after npm install -g @anthropic-ai/sandbox-runtime

Summary

/sandbox reports "seccomp filter: not installed" even after following the suggested install command (npm install -g @anthropic-ai/sandbox-runtime). The files are on disk but Claude Code never finds them, requiring a manual settings patch.

Steps to reproduce

1. Run /sandbox — see the message:

``
seccomp filter: not installed (required to block unix domain sockets)
· npm install -g @anthropic-ai/sandbox-runtime
``

1. Run npm install -g @anthropic-ai/sandbox-runtime — installs successfully.
2. Run /sandbox again — same message persists.

Root cause

Claude Code is a standalone binary and does not resolve Node.js global packages. The seccomp files (vendor/seccomp/x64/unix-block.bpf and apply-seccomp) are correctly installed under the global npm prefix (e.g. ~/.nvm/versions/node/v24.14.0/lib/node_modules/...), but Claude Code never looks there.

Current workaround

Manually add explicit paths to ~/.claude/settings.local.json:

{
  "sandbox": {
    "seccomp": {
      "bpfPath": "<npm-global-prefix>/lib/node_modules/@anthropic-ai/sandbox-runtime/vendor/seccomp/x64/unix-block.bpf",
      "applyPath": "<npm-global-prefix>/lib/node_modules/@anthropic-ai/sandbox-runtime/vendor/seccomp/x64/apply-seccomp"
    }
  }
}

Expected behavior

One of:

• npm install -g @anthropic-ai/sandbox-runtime should place the seccomp files where Claude Code actually looks for them, or
• Claude Code should probe common global npm prefixes ($(npm root -g), nvm paths, etc.) at startup, or
• The /sandbox instructions should mention that explicit settings.json configuration is required after install

Environment

• Claude Code 2.1.81 (standalone binary)
• Node v24.14.0 via nvm
• Ubuntu / Linux x86_64