AWS has released AWS Emulator, a program that answers AWS API calls on your own machine so tests and coding agents can run without touching a real account. It has no additional service fee, and its source is on GitHub.
The emulator serves HTTPS on 127.0.0.1:9297, so only the local computer can reach it. The AWS CLI and SDKs talk to it by way of environment variables, which means application code stays unchanged. On Linux it installs from an RPM or Debian package. On macOS and Windows it runs in Docker, and AWS does not publish a ready-made image, so you build one from a short Dockerfile in the documentation.
Several details point at safety. The emulator generates fresh credentials each time it starts, and the access key IDs begin with EMULATOR so they cannot pass for real keys. It rejects requests signed with any other keys, requires Signature Version 4 signing, and uses a single account, 000000000000. It also sends anonymous usage and error data by default, which you can turn off.
For Rust developers there is an embedded mode, the aws-emulator-embedded crate, that runs inside the test process. Each instance keeps its own state, so tests do not share buckets, tables, or queues and can run in parallel.
The pitch leans heavily on coding agents. AWS demonstrated Kiro creating a DynamoDB table, writing an item, and reading it back against the local endpoint. An agent that iterates dozens of times is cheaper and less risky when each attempt hits a laptop instead of a Region.
Fidelity is the hard part, and it is where earlier tools like LocalStack have long had to prove themselves. AWS builds the emulator from the same API models the SDKs use, so requests and errors have the right shape. Shape is not behavior, though, which is why the company says it also runs fidelity tests: short SDK programs that run a workflow, such as storing, reading, and deleting an object, and assert how AWS behaves. Each is verified against real AWS. How many services and workflows those tests cover is the number that will decide whether a passing local test means much.