# Ansible Release 12 introduces breaking changes to Jinja2 filters, conditions, macros, and undefined-variable tests

DevFeed: [Ansible Release 12 introduces breaking changes to Jinja2 filters, conditions, macros, and undefined-variable tests](<https://devfeed.tech/articles/ansible-release-12-the-windows-vista-moment-11274.md>)

Original publisher: [Read original article](<https://blog.ipspace.net/2025/11/ansible-12-different/>)

Published: 2025-11-03T06:44:00Z

Content type: opinion

Language: en

Sources: [ipSpace.net blog](<https://devfeed.tech/sources/ipspace-net-blog.md>)

Topics: [Ansible](<https://devfeed.tech/topics/ansible.md>), [releases](<https://devfeed.tech/topics/releases.md>), [configuration](<https://devfeed.tech/topics/configuration.md>)

Tags: [ansible](<https://devfeed.tech/tags/ansible.md>), [configuration](<https://devfeed.tech/tags/configuration.md>), [errors](<https://devfeed.tech/tags/errors.md>), [expression](<https://devfeed.tech/tags/expression.md>), [release](<https://devfeed.tech/tags/release.md>)

## AI overview

An opinion article examines breaking behavior changes in Ansible release 12, including stricter when-condition results, changed Jinja2 macro return values, and errors for tests involving undefined variables. The author describes compatibility problems encountered while updating netlab templates.

## Source excerpt

My first encounter with Ansible release 12 wasn't exactly encouraging. We were using a few Ansible Jinja2 filters (ipaddr and hwaddr) in internal netlab templates, and all of a sudden those templates started crashing due to some weird behavior of attributes starting with underscore. We implemented don't use Ansible release 12 as a quick workaround, but postponing painful things is never a good solution(see also: visiting a dentist), so I decided to try to make netlab work with Ansible release 12. What a mistake to make. Read more ...