Can the version number in the SOAP api login url and version in client jar be out of sync?

Question

Our application uses the following url to login to salesforce

https://login.salesforce.com/services/Soap/u/31.0

We use the returned service endpoint for subsequent CRUD operations. Please do note that the client jar's version is 37.0.

I observed that version number in url and the version in client jar can be out of sync and still everything works fine. In our case, the client jar gets updated periodically and we have no control over it.

Through this question I want to confirm if the version in login url can be different from the client jar version, so that any future updates to client jar do not break our application, just because the version in url did not match.

Answer 1

What Salesforce says about its backward compatibility

We maintain support for each SOAP API version across releases of the platform software. SOAP API is backward compatible in that an application created to work with a given SOAP API version will continue to work with that same SOAP API version in future platform software releases.

Salesforce does not guarantee that an application written against one SOAP API version will work with future SOAP API versions: Changes in method signatures and data representations are often required as we continue to enhance SOAP API. However, we strive to keep SOAP API consistent from version to version with minimal if any changes required to port applications to newer SOAP API versions.

For example, an application written using SOAP API version 9.0 which shipped with the Winter ’07 release will continue to work with SOAP API version 9.0 on the Summer ’07 release and on future releases beyond that. However, that same application may not work with SOAP API version 10 without modifications to the application.

Making summary of all of that, it is possible, that future releases of client jar will not work with previous versions of API