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OpenBot / AG-UI (retired)

Fountain used to answer POST /api/agui/:agent_id with AG-UI's RunAgentInput and SSE event stream, so a Fountain agent could be registered as a Bot in OpenBot or any other AG-UI host with no plugin and no code. That endpoint is gone, removed in the release that carries ADR 0057.

This page stays because the URL is in other people's notes. It is not a page about a feature you can turn on.

What a call gets now

/api/agui/:agent_id matches no route and falls through to the ordinary unmatched-path handling for /api, which means the answer depends on the request rather than on anything AG-UI:

Request Answer
Authenticated, Accept: application/json 404 {"error": "Not found", "reason": "not_found"}
No API key 401 — authentication runs before dispatch
Accept: text/event-stream 406 — content negotiation refuses it first

The 406 is worth knowing about, because text/event-stream is exactly what an AG-UI client sends: such a client sees a content-negotiation failure rather than a clean "gone". Every one of these is what an /api path that never existed returns. No RUN_ERROR event and no AG-UI envelope survives.

Continuing a thread you already have

Do this before creating anything. A conversation OpenBot (or any AG-UI host) opened is still there, with its sandbox and everything the agent worked out in it. Creating a new one instead gets you a fresh sandbox and loses that.

Each host threadId was stored as the conversation's channel_id, prefixed agui:. Find it, check it is the one you mean, then prompt it by id.

# 1. Find candidates. Filter by the agent too: a thread key is only unique

#    within the agent it was used against, and `--data-urlencode` keeps a key

#    containing /, ?, & or a space from breaking the query.

curl -G -H "Authorization: Bearer ftn_..." \

  --data-urlencode "channel_id=agui:<threadId>" \

  --data-urlencode "agent_id=<agent-uuid>" \

  --data-urlencode "status=idle,running,pending" \

  "https://your-fountain/api/conversations"

This is a list, not an answer. It is ordered by updated_at, and without the status filter it also returns failed and terminated conversations, which cannot take a prompt.

# 2. For each candidate, fetch it by id. Only the show route loads the

#    sandbox — the list above renders `sandbox: null` for every row, so it

#    cannot tell you whether the machine is still there.

curl -H "Authorization: Bearer ftn_..." \

  "https://your-fountain/api/conversations/<id>"

Prompt a candidate only if all of this holds:

  • data.sandbox is not null, and its status is not terminated or failed. An idle conversation can still point at a dead sandbox; prompting that one provisions a fresh machine, which is the outcome this whole section exists to avoid.
  • data.agent_id, data.environment_id and data.vault_id are the identity the work was done under.

If several candidates come back, the thread key was reused across configurations — pick by that identity, not by recency, and expect some of them to have terminal sandboxes. If none survives both checks, there is nothing to continue and a fresh conversation is the right answer.

# 3. Prompt it by id. Same sandbox, same history.

curl -X POST -H "Authorization: Bearer ftn_..." -H "Content-Type: application/json" \

  -d '{"prompt":"..."}' \

  "https://your-fountain/api/conversations/<id>/prompts"

Do not replay the host transcript. An AG-UI host replays the whole message list on each run because it expects a stateless endpoint. Fountain never worked that way — the sandbox is the memory — and replaying it now feeds the agent its own words back.

If you resume by channel_id instead of prompting an id, send the same agent_id, environment_id and vault_id — an incomplete identity resolves to a different machine, which is the same lost-sandbox outcome by another route.

Existing agui: bindings are left intact by the retirement — nothing was renamed or migrated.

What to use instead

The native conversation API: create a conversation, prompt it, and follow GET /api/conversations/:id/stream. Fountain's own event stream carries the same turn — text, thinking, tool activity, lifecycle — in Fountain's shape rather than AG-UI's, so a host that speaks AG-UI needs a translation layer of its own that Fountain no longer provides.

Read Plug into Fountain for the routes in, and the TypeScript, Python, Elixir or Swift SDK for a client that already follows the stream.

What has no replacement

Registering a Fountain agent with an AG-UI host by pasting a URL. Fountain no longer speaks the protocol, and the native stream is not AG-UI. A host that needs AG-UI has to adapt Fountain's events itself.