In the previous closed-source version of Symfony CLI, the first time I run it, I saw this dialog to allow/deny incoming requests in the macOS firewall:

After allowing it, I added the binary to the list of applications which are allowed incoming requests and that's it. I never saw that firewall dialog again.

With the new open source version, I see the same firewall dialog whenever I run symfony proxy:start and symfony serve -d. I've tried adding the Symfony CLI binary to the list of allowed apps (both the real binary at e.g. /opt/homebrew/Cellar/symfony-cli/5.4.2/bin/symfony and the link to the binary at e.g. /opt/homebrew/bin/symfony) and I update this whenever I upgrade the Symfony CLI version, but it doesn't work.

Today I was really tired of this issue and I looked for other solutions. I found this explanation for the problem --> https://superuser.com/a/912663 and this solution for it --> https://superuser.com/a/1438094

Running the following command solved the problem for me:

sudo codesign --force --deep --sign - /opt/homebrew/Cellar/symfony-cli/5.4.2/bin/symfony

Just sharing this here in case others have the same problem or in case we can do something in this project to improve the situation. Thanks!