# CHG-04 replacement-seam reproduction

This deterministic fixture demonstrates the argument in “Parallel
Implementations Are Not a Replacement Seam.”

It contains:

- two synthetic transports with incompatible request and response shapes;
- two adapters implementing one application-owned booking operation;
- one selector for controlled cutover;
- one contract suite run against both adapters; and
- a captured-input comparison which strips volatile remote values.

Run:

```sh
node experiment.mjs
```

All inputs, transports, identifiers, and behavior are synthetic. The fixture
does not contact a remote system or reproduce a private integration, provider,
application, or production result.