Dropping Mac x86_64 support?

[cburroughs]

Reference:

• [macOS] The macOS 13 Ventura based runner images will begin deprecation on September 22nd and will be fully unsupported by December 4th for GitHub and ADO actions/runner-images#13046
• [macOS] The additional macOS 15 Sonoma Intel-based image will be available in GitHub Actions actions/runner-images#13045

Currently, Pants supports x86_64 Macs by way of the macos-13 runner provided by GitHub. These were deprecated this week and will be fully unsupported by December 4th. We have the option of either kicking the can down the road with macos-15-intel, or dropping Mac x86_64 support.

My own view is that at this point it that at this point x86_64 Macs are uncommon and chasing flaky CI failures are not fun.
macos-15-intel' is also something of a surprise. In prior discussion we had expected macos-13 to be the end of the line. As a volunteer project, it doesn't make sense to support what is at this point a niche platform without ... well someone volunteering.

I also think if a Sponsor wanted to retain support that would be reasonable.

NOTE: To be able to support release branches we should make this decision before 2.30.

[benjyw]

A reasonable next step is to sound out users on Slack?

[cburroughs]

Done (https://pantsbuild.slack.com/archives/C046T6T9U/p1759166453147979)

[cburroughs]

Prior discussion at: #22479

Which includes a spiffy chart from @huonw . This is what I get when trying to run said script against yesterday's data

| release        |   darwin_arm64 |   darwin_x86_64 |   linux_aarch64 |   linux_x86_64 |
|:---------------|---------------:|----------------:|----------------:|---------------:|
| release_2.24.1 |           1553 |             169 |            7578 |         426590 |
| release_2.24.2 |           2435 |             155 |           20457 |          81072 |
| release_2.24.3 |             64 |              14 |               8 |           9630 |
| release_2.25.0 |           2920 |             212 |            5960 |         526960 |
| release_2.25.1 |           8190 |            5375 |           14421 |         119948 |
| release_2.25.2 |             54 |               6 |               2 |           3249 |
| release_2.25.3 |             12 |               5 |               3 |            186 |
| release_2.26.0 |           5078 |             367 |           56825 |         470701 |
| release_2.26.1 |            755 |              65 |             105 |          76593 |
| release_2.26.2 |            522 |              13 |           18431 |         126708 |
| release_2.27.0 |           4476 |             317 |           10577 |         310429 |
| release_2.28.0 |           1259 |              87 |            9864 |          40777 |

[benjyw]

Wait, given the previous discussion, why aren't we running CI on our macstadium x86_64 machine? That was the whole point.

[benjyw]

Blog post soliciting info: https://www.pantsbuild.org/blog/2025/10/06/winding-down-macos-intel-support

[bjkeller]

@benjyw Not to cause a panic, but what is your ideal end date?

[cburroughs]

Roughly October/the-next-release (to have time to support bugfix releases before the Dec 4 GitHub date)