Add support for `/add-dir` (let Codex see multiple projects, not just one folder)

What feature would you like to see?

Right now Codex feels kinda nearsighted 👓 — it only looks at the folder where I launched it.
But in real life, projects aren’t that clean. I’ve got a frontend repo talking to a backend repo, plus a shared/ folder with types, plus an infra repo with scripts… you get the idea.

Today, my “workflow” is basically:

• copy stuff manually across repos
• or start another Codex session and lose context
• or do symlink shenanigans that make me feel like a hacker from the 90s

Meanwhile, Claude Code already has this cute trick: --add-dir (at startup) and /add-dir (mid-session). You just point it at another repo, and boom, it can see it. Super handy when you’re juggling FE/BE or polyrepos.

I’d love Codex to get the same superpower:

• codex --add-dir ../backend ../shared at launch
• /add-dir ../infra while chatting
• maybe even /remove-dir when you realize you went too far 🗑️

Are you interested in implementing this feature?

I don’t mind testing or writing up real-world examples, but I’ll leave the actual code to you folks.

Additional information

_No response_

// config.toml
[sandbox_workspace_write]
writable_roots = ["/Users/xxxxx/Dir_1", "/Users/xxxxx/Dir_2"]