Migrate `ubuntu-latest` Actions runners to `ubuntu-slim`

[okineadev]

I propose migrating to ubuntu-slim runners in all .github/workflows/*.yml workflows, it will be more environmentally friendly and cheaper, at least it will be cheaper for GitHub, because public projects don't have to pay for the used Actions minutes, it will also reduce carbon emissions 🍃

What workflows can be migrated?

Short answer - any that last less than 15 minutes, not compute-heavy tasks

• Auto-labelling issues
• Building and publishing packages
• Linting and formatting
• ...

I think this is ideal for TS projects, because there are no heavy tasks, and the build is just bundling and minifying the code.

How to migrate to ubuntu-slim runners?

Automatically

Use gh-slimify, it will intelligently check if workflows are suitable for migration and report problems if there are any.

Manually

Just replace ubuntu-latest with ubuntu-slim in all .github/workflows/*.yml

Next steps (optional, but recommended)

I highly recommend you to read the best practices for GitHub workflows which will significantly reduce the use of unnecessary Actions runs - https://github.com/Cambridge-ICCS/green-ci?tab=readme-ov-file#best-practices

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GitHub blog post about new 1 vCPU runners: https://github.blog/changelog/2025-10-28-1-vcpu-linux-runner-now-available-in-github-actions-in-public-preview

Pricing (tl;dr: $0.002/min): https://docs.github.com/en/billing/reference/actions-runner-pricing

GitHub-hosted runners reference: https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#standard-github-hosted-runners-for--private-repositories

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I'm new here and not sure if this is the right issue because it's not directly related to the TS ecosystem, let me know if something is wrong or I've made a mistake and we can do better 🙏

[43081j]

makes a lot of sense to me!

we could also add a basic yaml codemod to the codemods repo once its added to the manifests here

will see if anyone else has thoughts before we act though 👍

[dominikg]

on https://github.blog/changelog/2025-10-28-1-vcpu-linux-runner-now-available-in-github-actions-in-public-preview/#runner-details

These runners have one vCPU and 5 GBs RAM. When using these runners, your actions workflows execute inside of a container rather than a dedicated VM instance, enabling cost-effective, performant execution of automation tasks across GitHub. Each container provides hypervisor level 2 isolation, and the container is automatically decomissioned when a job is completed.

for security reasons i believe this shouldn't be used for jobs that have access to secrets or execute elevated actions like npm publish with oidc. Anyone has info on what hypervisor gh uses here and how they try to keep it secure?

[bluwy]

What workflows can be migrated?

Short answer - any that last less than 15 minutes, not compute-heavy tasks

• Auto-labelling issues
• Building and publishing packages
• Linting and formatting
• ...

I think this is ideal for TS projects, because there are no heavy tasks, and the build is just bundling and minifying the code.

While the github docs suggested these usecases, building, linting, formatting, minifying etc aren't inherently always cheap (or easy to compute). If the project is large or complex enough, ubuntu-latest would still be saving more time, especially since ubuntu-slim has only 1 core, multi-core tooling may run even slower then.

I think this should be evaluated in a case-by-case basis and would be hard to automate.