Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

The HTTP Set-Cookie header seems to squash multiple Set-Cookie causing browser to only set the first Set-Cookie.

Expected Behavior

Multiple Set-Cookie Header to be set for each of the cookie key / value pair

How are you starting LocalStack?

With the localstack script

Steps To Reproduce

Access via ELB and monitor the HTTP response via network tab in the developer tool

Environment

OS: macOS Sequoia 15.4.1
LocalStack version: 4.3.1.dev89
LocalStack build date: 2025-04-30
LocalStack build git hash: 00c84d961

Anything else?

No response