User Agent handling inconsistent across SDK versions

[koren-eli]

Hi team,

I’m looking for clarification on how the AWS SDK for C++ (S3 client) handles the userAgent field across different versions.

Our use case requires appending a suffix to the existing user agent string so we can track S3 requests in logs.

• In older versions of the SDK (e.g. 1.11.100), setting clientConfig.userAgent = Aws::Client::ComputeUserAgentString() + " custom_string"; works as expected and appends the suffix.
• In newer versions (e.g. 1.11.635), the SDK appears to ignore values set in clientConfig.userAgent. I saw in this commit that appId was introduced, which appends app/{value} to the user agent. Setting clientConfig.appId = "custom_string"; works, but produces a slightly different format than other AWS SDKs.

Questions:

1. Is using appId the recommended way to append to the user agent string in modern versions of the C++ SDK?
2. Is there a supported mechanism to cleanly append a suffix (like in Python and Java) so behavior remains consistent across SDKs?
3. Are there any plans to align user-agent extension behavior across languages?

Our concern is that client applications may use different versions of the SDK, and we’d like to recommend a stable, forward-looking approach that won’t break on upgrades.

Thanks for your guidance!

[sbiscigl]

nope that looks like a regression from the earlier versions, put up a PR to fix this. it will honor the overriden UA after this change same as before. thanks for pointing it out!

[koren-eli]

Thanks!

So if I understand correctly, that leaves a gap between roughly v1.11.100 and the upcoming release with this PR where it isn’t possible to override the UA using clientConfig.userAgent. Is there a known workaround for those SDK versions to append a custom string to the UA?

[sbiscigl]

not that I know of, would be best to just pick up the bug fix once released