# Cylc7 vs Cylc8- Who is still using Cylc7, and why? **URL:** \ **Category:** Atmosphere\ **Tags:** cylc, access-am3, access-ram3\ **Created:** [2 October 2026 00:12 UTC](https://forum.access-hive.org.au/t/cylc7-vs-cylc8-who-is-still-using-cylc7-and-why/7052 "2026-10-02T00:12:41Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![lachlanswhyborn](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/lachlanswhyborn/32/1837_2.png) [@lachlanswhyborn](https://forum.access-hive.org.au/u/lachlanswhyborn)\ **Post date:** [2 October 2026 00:12 UTC](https://forum.access-hive.org.au/t/cylc7-vs-cylc8-who-is-still-using-cylc7-and-why/7052/1 "2026-10-02T00:12:41Z")
Hi to all Cylc users out there, We are approaching the end of life for Cylc7 support, although we don’t have a date in mind yet. The primary reason for this is that the new NCI machine **will not** support Cylc7, so there is a very hard deadline for the transition. At the moment, both the AM3 and rAM3 configurations run as expected with Cylc8 using Cylc7 compatibility mode (nothing is required on your part- Cylc8 does this automatically). This compatibility will be retired, and I believe has been in more recent Cylc releases. This means breaking compatibility with Cylc7 is inevitable. To this end, I want information from those still using Cylc7. First, I want a gauge of how many people are still running with Cylc7. Second, for those who are still using Cylc7, what are the reasons you continue to use it over Cylc8? What can ACCESS-NRI provide to help you make the change to Cylc8? ---
**Author:** ![sonyafiddes](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/sonyafiddes/32/603_2.png) [@sonyafiddes](https://forum.access-hive.org.au/u/sonyafiddes)\ **Post date:** [4 October 2026 23:13 UTC](https://forum.access-hive.org.au/t/cylc7-vs-cylc8-who-is-still-using-cylc7-and-why/7052/2 "2026-10-04T23:13:05Z")
Hi Lachlan, Those of use using the UM RNS (pre-rAM3) are using cylc7. My current runs of rAM3 are also using cylc7 as that is the default (from memory?). @alanah.chapman has been running ACCESS-AM2 with cylc7, but I think she may have finished her simulations for now? @Matt_Woodhouse and @ZhangchengPei may also have some legacy UM RNS runs that also use cylc7. FYI for the community (and @bethanwhite @paocorrales - I just saw some of your responses on cumulus) - the Atmosphere WG will ask for a tutorial in our next meeting of how to transition to cylc8 🙂 I also like the cylc7 gui - I don’t tend to run via the ARE, so havent tried the cylc8 gui yet and the cylc 8 tui is not as good at letting me know with big red dots when something fails 😆 Otherwise its just a time thing - when a new project starts I’ll use cylc8, but likely for exisitng ones I won’t do it until I absoultly have to (or hope that the project is finished before then). ---
**Author:** ![griff](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/griff/32/332_2.png) [@griff](https://forum.access-hive.org.au/u/griff)\ **Post date:** [5 October 2026 00:08 UTC](https://forum.access-hive.org.au/t/cylc7-vs-cylc8-who-is-still-using-cylc7-and-why/7052/3 "2026-10-05T00:08:05Z")
Users of UKMO suites running ‘stuff’ will have a need for Cylc7. This may diminish as the UKMO ports things to Cylc8, but there will be older suites for a little while. Our Team’s current work may not require the use of older suites, but it has not been ruled out as a possible requirement. ---
**Author:** ![alanah.chapman](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/alanah.chapman/32/4377_2.png) [@alanah.chapman](https://forum.access-hive.org.au/u/alanah.chapman)\ **Post date:** [5 October 2026 00:45 UTC](https://forum.access-hive.org.au/t/cylc7-vs-cylc8-who-is-still-using-cylc7-and-why/7052/4 "2026-10-05T00:45:08Z")
Hi Lachlan, As Sonya says above, I have been running ACCESS-AM2 with cylc7 (I don’t know whether it could have worked with cylc8?) - but I have finished all my simulations with ACCESS-AM2. Going forward I plan to use a configuration of rAM3- so I assume that means I will be moving to cylc8. As to why cylc7, I learnt to run simulations from the 21CW documentation ([Introduction to Rose/Cylc — 21st Century Weather Software Wiki](https://21centuryweather.github.io/21st-Century-Weather-Software-Wiki/rose-cylc/rose-cylc-intro.html)) which uses cylc7 as I think that was written in the early cylc8 days and people hadn’t transitioned yet… A cylc8 tutorial would be great! ---
**Author:** ![lachlanswhyborn](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/lachlanswhyborn/32/1837_2.png) [@lachlanswhyborn](https://forum.access-hive.org.au/u/lachlanswhyborn)\ **Post date:** [5 October 2026 02:13 UTC](https://forum.access-hive.org.au/t/cylc7-vs-cylc8-who-is-still-using-cylc7-and-why/7052/5 "2026-10-05T02:13:40Z")
Appreciate the feedback. Unfortunately, once Gadi’s new machine is online, it will be out of our hands- Cylc7 is written in Python2, and my understanding is that Python2 will not be supported on the new machine. We do have [AM3 training](https://access-am3-configs.access-hive.org.au/training/CWLCM-2026/#start-the-experiment) which uses Cylc8, and we will certainly write similar documentation for rAM3. The Cylc developers have provided a [summary of the major changes](https://cylc.github.io/cylc-doc/stable/html/7-to-8/summary.html) and a [cheat sheet](https://cylc.github.io/cylc-doc/stable/html/7-to-8/cheat-sheet.html) for the transition. I’ve successfully run a fair few Cylc7 suites with Cylc8 without any changes, using the automatic compatibility mode, but the Cylc developers are planning to phase out compatibility mode as well (although we are likely to maintain Cylc7 compatible versions for quite a while). ---
**Author:** ![chenhui.jin](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/chenhui.jin/32/2550_2.png) [@chenhui.jin](https://forum.access-hive.org.au/u/chenhui.jin)\ **Post date:** [5 October 2026 03:09 UTC](https://forum.access-hive.org.au/t/cylc7-vs-cylc8-who-is-still-using-cylc7-and-why/7052/6 "2026-10-05T03:09:10Z")
Hi Lachlan, I’m still using cylc 7 for my ACCESS-rAM3 simulations. I agree with Sonya, the Cylc 7 GUI is functional and easy to use. I’ve also tried running ACCESS-AM3 with Cylc 8, but so far, I’ve found its GUI and TUI less intuitive than the Cylc 7 GUI. I may just need more time to become familiar with Cylc 8. Training sessions or online documentation would be very welcome to help Cylc 7 users make the transition more easily.