postinstall runs `opencode --version`, so `sudo npm install -g` leaves `/tmp/opencode` root-owned

Description

opencode-ai's npm postinstall ends with a smoke test that runs the binary it just downloaded, verifyBinary() → opencode --version. That is enough to create every global directory, because global.ts does the mkdirs at module top level, before any command dispatch.

So sudo npm install -g opencode-ai, which is the normal way to install globally and the only way when the npm prefix is under /usr, leaves /tmp/opencode owned by root. The user can never write to it afterwards.

Nothing warns, because fs.mkdir(..., { recursive: true }) on an existing directory succeeds whoever owns it, so opencode itself starts fine. But the shell tool description tells every agent that directory "has already been created, already exists, and is pre-approved for external directory access", which is then false. Agents go there first and get Permission denied.

The $HOME directories usually escape, since sudo gives the command root's own HOME. With sudo -E they land in the user's home owned by root and opencode fails outright.

#44696 is the same broken state reached without root: /tmp/opencode is a fixed name in a shared namespace, so on a multi-user box whoever runs opencode first owns it. It was read there as host provisioning, but installing as root gets you there before anyone runs opencode at all.

I think a simple fix would be making --version have no side effects (stop creating files/dirs when just querying the version).

At the moment we needed to add a workaround to clean up after the installation in our container environment:

• https://github.com/frequenz-floss/contai/pull/17

Plugins

None

OpenCode version

1.18.30

Steps to reproduce

1. sudo npm install -g opencode-ai
2. ls -ld /tmp/opencode → drwxr-xr-x 2 root root ... /tmp/opencode
3. As the normal user, touch /tmp/opencode/x → Permission denied

The side effects on their own, no root needed:

$ mkdir -p probe/home probe/tmp
$ env -i PATH=/usr/bin:/bin HOME=$PWD/probe/home TMPDIR=$PWD/probe/tmp opencode --version
1.18.30
$ find probe -type d | sed 's|^probe||'
/home/.cache/opencode
/home/.cache/opencode/bin
/home/.config/opencode
/home/.local/share/opencode
/home/.local/share/opencode/log
/home/.local/share/opencode/repos
/home/.local/state/opencode
/tmp/opencode

Screenshot and/or share link

No response

Operating System

Ubuntu 25.10, Node 24, npm prefix /usr

Terminal

No response (happens at install time, no terminal involved)