Arceus

Arceus is a permanent, gold-framed orchestrator: summon a real Claude (or Codex) session that can hand work to any other session across every workspace in the garden, not just the one it was summoned in. Summoning replaces the garden view with the Hall of Origin — a full-bleed starfield scene with Arceus floating at its center, cycling through its type-plate formes, and a right-side HUD logging every dispatch and exchange.

Arceus’s own dispatch policy: identify which workspace a task belongs to (asking only when it’s genuinely ambiguous between two or more real candidates); if an idle agent already exists there, always offer a choice between continuing it or spawning a new one — never assumed silently; otherwise spawn directly. A relay to a specific already-running agent only happens when the user explicitly asks for one.

Three tools carry this out, all real Bash-invoked commands, all fire-and-return-immediately — Claude Code’s own Bash tool can’t block synchronously waiting on an external event, so each one returns a short acknowledgment and nothing more:

• poke-ask shows a picker in the UI with a question and a set of options; the user’s answer is injected back into Arceus’s own terminal as a fresh message once they respond.
• poke-spawn starts a fresh top-level session in a named workspace, the same as spawning one by hand; confirmation of which pokémon and session it became is likewise reported back into Arceus’s own terminal, once the renderer has actually created it.
• poke-relay injects a message into another live agent’s terminal, resolved by session id, title, or (if unambiguous) pokémon species, and delivered through the same idle-safety queue used everywhere else a message gets typed into a busy session — queued if the target isn’t idle yet, delivered the moment it is. It never messages Arceus back; a failed resolution already shows in the command’s own output before Arceus’s turn ends.

Each tool takes exactly one target and must be invoked as a plain, bare command — never chained with &&, piped, or given an env-var prefix — or it can miss the app’s permission allowlist and stall on a prompt nobody will answer. None of the three exist when Arceus is running on Codex; that’s a sandboxing limitation, and Arceus is told to say so plainly rather than pretend otherwise.

Provider and model aren’t fixed at summon time: the Hall of Origin HUD has an inline switch that reconfigures Arceus live — a cheap /model <name> for a same-provider model change, or a full re-summon for anything bigger, such as a provider change or any change involving Codex on either side.

See also Advisor — a different, narrower review-gate role every top-level session (not just Arceus) consults before big decisions.