Fountain
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fountain

Lets an agent start more Fountain conversations from inside its own sandbox, and stream them.

Summary
Bundled Yes, in each sandbox.
Declared by Nobody. Fountain always adds it.
Source apps/fountain/priv/sprite_skills/fountain/SKILL.md
Reads FOUNTAIN_BASE_URL, FOUNTAIN_TOKEN, FOUNTAIN_CONVERSATION_ID, FOUNTAIN_SANDBOX_ID

What it gives the agent

Fountain's own API, from the inside. An agent that has it can fan work out across other agents, then collect the answers.

The skill writes two patterns out. It can fan out N conversations in parallel and gather their results. It can also drive one sub-conversation over several turns.

That is what makes "delegate to another agent" work when a user asks for it.

The credential it uses

FOUNTAIN_TOKEN is a key for one conversation, scoped to that conversation's owner. It is not a long-lived admin token.

Fountain rotates it at each fresh provision and at each reattach, such as after a deploy or a BEAM restart, and revokes the previous value. A request that returns 401 with "reason": "api_key_revoked" means the agent cached a stale copy. The agent must read the variable from its environment again.

Provenance comes for free

FOUNTAIN_CONVERSATION_ID is always in the sandbox's environment. Send X-Fountain-Parent-Conversation-Id: $FOUNTAIN_CONVERSATION_ID on a POST /api/conversations, and Fountain records the parent. An operator can then rebuild the whole spawn chain.

A child on the same machine

FOUNTAIN_SANDBOX_ID is the id of the sandbox the agent runs on. Send it as sandbox_id on a POST /api/conversations. The child conversation then runs on that same machine, with the same disk, at the same time. That only works for a child of the agent the machine belongs to, with the same environment and vault. When the sandbox is a guest on another agent's machine, that is the other agent, not its own. A child of any other agent, such as a codex agent beside a claude one, needs a full-scope key, and the sandbox's own token isn't one: the skill tells the agent to ask you to attach it, or to give the child a machine of its own. See a second agent on a machine.

Without it, each child gets a sandbox of its own. When the agent runs in persistent mode, the child gets that machine instead. To name the other mode for one child, send sandbox_mode on the same call. See Sandboxes.

GET /api/sandboxes lists the machines the token's owner has, with the conversations on each. Read Sandboxes and Conversations for the fields.

Limits

A spawned agent has the same skill. Nothing stops recursion, so the skill tells the agent to cap the depth itself with a MAX_DEPTH check. A runaway fan-out is a real way to spend money.

Each conversation is a real sandbox. The skill says plainly that an orphaned conversation runs until the idle timeout, and that the agent must terminate it without delay. Read Change sandbox lifetimes.

The bare /conversations path returns 404. The API is under /api.