Dev: run multiple workers together locally

[AutumnsGrove]

Summary

Set up multi-worker local development using Wrangler's multi-config wrangler dev -c feature (GA September 2025). This allows all Grove workers to run in a single Miniflare instance with service bindings and DO RPC working between them.

Why

Currently, service bindings (AUTH, LUMEN, ZEPHYR, REVERIE) are dead in vite dev — they can't resolve other workers. This makes it impossible to test cross-service flows locally (login, AI, email). Multi-config dev mode resolves this by running all workers in one Miniflare instance.

Implementation

Core dev command

# Run aspen + heartwood + durable-objects together
wrangler dev \
  -c apps/aspen/wrangler.toml \
  -c services/heartwood/wrangler.toml \
  -c workers/grove-durable-objects/wrangler.toml

First config = primary (receives HTTP). Others accessible via service bindings.

What this unlocks

• Full login flow (Aspen → Heartwood → back)
• DO RPC from SvelteKit routes to Loom DOs
• Reverie → Lumen service binding chain
• Rate limiting via ThresholdDO

Tradeoffs

• Loses Vite HMR (runs in workerd, not Node.js)
• Requires building SvelteKit first (pnpm build then wrangler dev)
• Some bindings (Workers AI) need remote: true

What to build

• Create scripts/dev-multi.sh that orchestrates multi-config wrangler dev
• Add root script: pnpm dev:full (builds + runs multi-config)
• Add [dev] overrides for production-only vars (AUTH_BASE_URL → localhost, etc.)
• Document which bindings need remote: true (Workers AI, Vectorize)
• Test: login flow works end-to-end locally
• Test: DO RPC from Aspen routes to PostMetaDO
• Test: Reverie → Lumen service binding chain

Key Limitation

getPlatformProxy() (used by SvelteKit's adapter-cloudflare in vite dev) does NOT support multi-config yet (workers-sdk issue #9445). Until that ships, multi-config dev requires wrangler dev mode (no HMR). See Tier 3 issue for the hybrid workaround.

Context

• Wrangler multi-config changelog: September 2025
• Port assignments already added (Tier 1): aspen=5173, landing=5174, plant=5175, meadow=5176, heartwood=8787
• .dev.vars.example files already created (Tier 1)
• Related: #9445 (workers-sdk) — multi-config getPlatformProxy