ESPHome: Faster builds

Before the September release you could speedup builds by setting the PlatformIO build flags to -j which enabled multi-threading. Like this in your Docker compose:

PLATFORMIO_BUILD_FLAGS=-j

But since the ESPHome 2026.9.0 update my builds became terribly slow. Turns out that PlatformIO support is dropped and replaced by native ESP IDF support. This is pretty cool because now you can specify how many threads each job can run:

IDF_PY_BUILD_JOBS=2

On my quadcore build server this change reduced the build time from over 3 minutes to 18 seconds!

In your Docker compose.yaml add it like this:

services:
  app:
    image: ghcr.io/esphome/esphome:latest
    container_name: esphome-builder
    restart: unless-stopped
    environment:
      - IDF_PY_BUILD_JOBS=2
    ports:
      - "6052:6052"
      - "6055:6055"
    volumes:
      - ./config:/config

And recreate it:

docker compose up -d