The PR workflow uses the ci-v3 RunsOn environment when the repository variable SP1_CI_RUNS_ON_ENVIRONMENT is empty.
Set this variable to legacy to select the existing runners for new ordinary jobs.
To select another RunsOn environment for ordinary PR, push, and merge-group jobs, set this variable to its environment name.
Prepare that environment before you set the variable.
The selected environment uses a 150gb:gp3:750mbps:4000iops root volume.
GPU jobs keep their instance type and AMI.
The GitHub-hosted Runner routing job validates the selection before the nine RunsOn jobs can start.
An invalid environment name or volume fails that check.
The variable affects only this workflow.
Manual runs use their runs_on_environment and runs_on_volume inputs independently of the repository variable.
An empty manual environment input selects the legacy runners.
Clear SP1_CI_RUNS_ON_ENVIRONMENT to restore the ci-v3 default for new ordinary runs.
This does not move jobs that already have runner labels or stop their instances.
Run ruby .github/scripts/check-runner-routing.rb to check the default, legacy, configured, and manual routes locally.