What filesystem does an opencode server use?

based on how u implement skills (https://forums.basehub.com/anomalyco/opencode/10) and how to implement an opencode server (https://forums.basehub.com/anomalyco/opencode/9), question: if i implement an opencode server, what's my filesystem? the server's fs? is the recommended setup to run opencode inside a sandbox, which has the skill files there? is there a way to "seed" skills directory? thinking about how to leverage this

Now I have a complete picture. Let me summarize everything for you:

##Answer: Filesystem & Skills in an OpenCode Server

###Which Filesystem?

The server's filesystem. When you run an OpenCode server (via opencode serve or createOpencodeServer()), all filesystem operations happen on the machine where the server process runs. This includes:

1. Skills discovery — scans the server's filesystem at:

   • ~/.config/opencode/skill/ (global XDG config)
   • ~/.config/opencode/skills/
   • ~/.claude/skills/ (Claude-compatible global)
   • .opencode/skill/ or .opencode/skills/ (project-level)
   • .claude/skills/ (Claude-compatible project-level)

2. Working directory — determined per-request via:

   • Query param: ?directory=/path/to/project
   • Header: x-opencode-directory: /path/to/project
   • Falls back to process.cwd() of the server

From the server code:

let directory = c.req.query("directory") || c.req.header("x-opencode-directory") || process.cwd()
return Instance.provide({
  directory,
  init: InstanceBootstrap,
  async fn() { return next() },
})

###Recommended Setup: Sandbox with Pre-seeded Skills

Yes! Running OpenCode inside a sandbox with skills pre-loaded is a great pattern. Here's how the paths work:

###How to Seed Skills

You have a few options:

####Option 1: Use OPENCODE_CONFIG_DIR (Best for custom skills location)

Set the environment variable to add an extra config/skills directory:

const proc = spawn('opencode', ['serve'], {
  env: {
    ...process.env,
    OPENCODE_CONFIG_DIR: '/sandbox/my-skills-config'
  }
})

This directory gets added to Config.directories(), which is scanned for skills:

/sandbox/my-skills-config/skill/my-skill/SKILL.md
/sandbox/my-skills-config/skills/another-skill/SKILL.md

####Option 2: Pre-populate the sandbox's ~/.config/opencode/

Before starting the server, create the global config directory:

~/.config/opencode/
└── skill/
    ├── my-custom-skill/
    │   └── SKILL.md
    └── another-skill/
        └── SKILL.md

####Option 3: Pre-populate the project's .opencode/skill/

If you're passing a specific directory to the server, seed skills there:

/sandbox/project/
└── .opencode/
    └── skill/
        └── deploy/
            └── SKILL.md

####Option 4: Use ~/.claude/skills/ for Claude-compatible skills

OpenCode also scans Claude Code's skill directories (unless OPENCODE_DISABLE_CLAUDE_CODE_SKILLS is set):

~/.claude/skills/
└── my-skill/
    └── SKILL.md

###Architecture for a Hosted OpenCode Service

┌─────────────────────────────────────────────────────────┐
│                    Your Application                      │
└─────────────────────────┬───────────────────────────────┘
                          │ SDK/HTTP
                          ▼
┌─────────────────────────────────────────────────────────┐
│              Sandbox (Docker/VM/Firecracker)            │
│  ┌───────────────────────────────────────────────────┐  │
│  │  ~/.config/opencode/skill/   ← Pre-seeded skills  │  │
│  │  /workspace/.opencode/skill/ ← Project skills     │  │
│  │  /workspace/                 ← User's project     │  │
│  └───────────────────────────────────────────────────┘  │
│                                                         │
│  $ OPENCODE_CONFIG_DIR=/custom/skills opencode serve   │
└─────────────────────────────────────────────────────────┘

###Key Takeaways

1. Yes, run in a sandbox — This is the secure way to expose OpenCode, since it executes shell commands, edits files, etc.

2. Seed skills by pre-populating directories — Before starting the server, copy your SKILL.md files into:

   • ~/.config/opencode/skill/ (global)
   • <project>/.opencode/skill/ (project-specific)

3. Use OPENCODE_CONFIG_DIR — This env var adds an additional directory to the config/skills search path, perfect for mounting a read-only skills volume.

4. Per-request project switching — Use x-opencode-directory header or ?directory= query param to switch between projects on the same server.