LocalStack Broke Your Testcontainers Pipeline — Here's Every Fix Path

If you're here because your CI pipeline is throwing something like this: RuntimeError: Unable to start LocalStack container. LocalStack requires an account and auth token as of March 2026. Set LOCALSTACK_AUTH_TOKEN in your environment to continue. You're not alone. LocalStack's auth requirement — announced quietly on March 23, 2026 — broke a lot of Testcontainers workflows overnight. The localstack/localstack Docker image now checks for a valid auth token on startup. If you don't have one, the container exits and your tests fail. This post covers every fix path, ranked by how fast you can ship them. Some take five minutes. One takes two weeks but removes the problem permanently. What Actually Changed LocalStack's community image ( localstack/localstack , the one almost everyone uses with Testcontainers) now requires LOCALSTACK_AUTH_TOKEN in the container environment. The Hobby tier is free, but it requires account creation. The paid plans start at $39/month. Two things that are less ba