Triangle

Triangle is an embeddable chat service for websites that proxies conversations to square and ultimately to remote agents (for your setup, brute).

What is implemented

• Backend (@triangle/backend)

• Accepts frontend chat over HTTP (POST /v1/chat/message) and WebSocket (GET /v1/chat/ws).

• Proxies to Square using API key with transport fallback order:

  • a2a_stream (/a2a/messages/send/stream)
  • a2a_http (/a2a/messages/send)
  • proxy_http (/proxy/request)

• Supports multiple image and audio attachments from frontend.

• Converts messages into canonical A2A content[] for Square/Brute compatibility.

• Resolves target agent from Square API key via GET /agents/me (especially for sqi_... integration keys bound to one target agent).

• Frontend SDK (@triangle/sdk-core)

• Browser client with WS-first and HTTP fallback.

• Embeddable libraries

• @triangle/embed-js: plain JS/HTML widget.

• @triangle/embed-react: React component.

Compatibility findings

• square canonical A2A currently supports content[].type values:
  • text
  • image_url
  • image_base64
• brute A2A inbound currently consumes canonical text + image parts and legacy image fields.
• Audio is not yet a canonical A2A content type in current square/brute bridge code.

Triangle behavior for audio right now:

• Audio attachments are accepted from frontend.
• Audio is preserved under metadata.triangle.media.audio for forward compatibility.
• Canonical content[] remains valid (text/image_*) so Square accepts the request.

Run backend

cd /Users/artjom/git/a2gent/triangle
cp .env.example .env
npm install
set -a; source .env; set +a
npm run dev:backend

Run with Docker

cd /Users/artjom/git/a2gent/triangle
cp .env.example .env
# update TRIANGLE_SQUARE_* values in .env
docker compose up --build

Backend will be available at http://localhost:9080.

Square base URL

• Local development Square: TRIANGLE_SQUARE_BASE_URL=http://localhost:9000
• Production Square behind nginx/TLS: TRIANGLE_SQUARE_BASE_URL=https://a2gent.net
• Do not use external http://<host>:9000 for production traffic.

API key targeting behavior

• sqi_... integration key:
  • Triangle resolves the bound target agent from /agents/me.
  • Any provided recipientAgentId is ignored if it conflicts with the key target.
• sq_... agent key:
  • Triangle uses recipientAgentId from request or TRIANGLE_DEFAULT_RECIPIENT_AGENT_ID.
  • If neither is set and TRIANGLE_USE_API_KEY_TARGET=true, it falls back to /agents/me.

Build all packages

cd /Users/artjom/git/a2gent/triangle
npm install
npm run build

Embed examples

Plain JS

import { createTriangleWidget } from "@triangle/embed-js";

createTriangleWidget({
  baseUrl: "http://localhost:9080",
  recipientAgentId: "<target-agent-id>",
  mount: document.getElementById("widget")!
});

React

import { TriangleChat } from "@triangle/embed-react";

<TriangleChat
  baseUrl="http://localhost:9080"
  recipientAgentId="<target-agent-id>"
  title="Website Assistant"
/>

Next compatibility step for full audio agent handling

Implement an A2A extension in both square and brute to allow canonical content types like audio_url / audio_base64 and map them through NormalizeA2APayload + a2atunnel handlers.