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ADR 002 — Single multi-stage container for the AlphaSwarm client surface

Scope narrowing (2026-05-25): This ADR's decisions apply ONLY to the local-operator alphaswarm_client/ packaging. The cloud-hosted alphaswarm_ui/ surface (at alpha-swarm.ai / app.alpha-swarm.ai) is governed by ADR 011 and uses a clean Next.js standalone container with no ASGI proxy stage. See ADR 011 for the cloud rationale.

Context​

Today AlphaSwarm runs the Vite frontend on :3001 (compose :3002), the legacy Next.js webui on :3000 (now stopped), the legacy Solara UI on :8765, and the FastAPI API on :8000. Operators have to juggle four URLs and four health probes. The alphaswarm_client Docker image is a chance to collapse these into one.

Three packaging options were considered:

  1. One container per surface — separate alphaswarm-frontend, alphaswarm-solara, alphaswarm-api images; an external Ingress/NGINX layer fans traffic.
  2. Sidecar pattern — one Pod per surface, sharing localhost via an nginx sidecar.
  3. Single multi-stage build — Stage 1 builds Vite, Stage 2 prepares Solara, Stage 3 (production) is a python:3.11-slim runtime that serves both as static + ASGI mount and proxies API traffic.

Decision​

alphaswarm_client is one image built from a three-stage Dockerfile that ships:

  • Stage 1 (ui-builder, node:20-alpine) — runs pnpm --dir alphaswarm_client build, output to /app/out/. Node is dropped after this stage.
  • Stage 2 (solara-builder, python:3.11-slim) — installs Solara + legacy UI deps, pre-warms component caches, verifies legacy_ui.app is importable.
  • Stage 3 (production, python:3.11-slim) — installs FastAPI + uvicorn + httpx + websockets + python-jose + alphaswarm_core. Copies Vite assets from Stage 1 and Solara from Stage 2. Exposes port 8080. No Node, no npm.

The Stage 3 runtime mounts:

  • /static → Vite assets from Stage 1
  • /legacy → Solara ASGI app
  • /webui → legacy Next.js export (rollback only)
  • /api/* → reverse-proxied to ALPHASWARM_CORE_API_URL
  • /ml/* → reverse-proxied to ALPHASWARM_ML_API_URL
  • /mcp/* → reverse-proxied to ALPHASWARM_MCP_URL
  • /manage/* → reverse-proxied to ALPHASWARM_CONTROL_PLANE_URL
  • /ws/* → WebSocket proxy with reconnect-with-backoff

Consequences​

Positive

  • One image, one health probe (/health), one set of securityContext rules.
  • Stable URL surface for operators — bookmarks, dashboards, and runbooks don't break when backends move.
  • All backend addresses live in ConnectivityConfig env vars. The same image runs in compose with ALPHASWARM_*_URL=http://alphaswarm-core:8000 or in K8s with http://alphaswarm-core.default.svc.cluster.local.
  • Auth0 callback URLs stay constant. The Vite app sees one origin; the FastAPI proxy injects M2M Authorization headers for cross-service calls.
  • Smaller blast radius. The control plane is a separate container on a separate Docker network (alphaswarm-admin vs alphaswarm-internal) — they only talk over the proxy.

Negative

  • Builds are larger and slower than per-surface images. Mitigated by Docker layer caching and buildx (~3 min cold, ~30s incremental).
  • Scaling assumes Vite + Solara + proxy throughput grow together. In practice Vite assets are CDN-fronted by NGINX Ingress and the proxy is the bottleneck — a single container HPA on CPU is fine.
  • Rolling back to webui-only or Solara-only means env-flag toggles (ALPHASWARM_CLIENT_ENABLE_LEGACY_UI, ALPHASWARM_CLIENT_ENABLE_SOLARA) rather than swapping deployments.

Alternatives considered​

  • One container per surface — rejected. Adds 3 health probes, 3 Ingress rules, 3 image tags to keep in lockstep on every release. The operator experience regresses.
  • Sidecar pattern — rejected. Mixing sidecars + multi-process supervision in one Pod adds significant Pod-startup ordering risk for marginal CPU savings.

Implementation references​

  • Multi-stage Dockerfile: alphaswarm_platform/build/docker/alphaswarm_client/Dockerfile
  • FastAPI proxy: alphaswarm/api/proxy.py
  • WebSocket proxy with reconnect: alphaswarm/api/ws/proxy.py
  • ConnectivityConfig: alphaswarm_core/connectivity/config.py