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The GitHub Actions spec requires runner.arch to be one of X86, X64, ARM, ARM64 (uppercase). When using -self-hosted, RUNNER_ARCH is derived from runtime.GOARCH via goArchToActionArch(). Go reports ARM64 hosts as "arm64" which was missing from the mapper, causing it to fall through and be returned verbatim in lowercase. The docker_run.go path already handled "arm64" correctly; this aligns host_environment.go with the same mapping. Fixes nektos#6181
arslanatpermission
approved these changes
Sep 18, 2026
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Summary
When running
actwith-P ubuntu-latest=-self-hostedon an ARM64 host,RUNNER_ARCHandrunner.archwere set toarm64(lowercase) instead ofARM64, violating the GitHub Actions spec which defines the valid values asX86,X64,ARM,ARM64(always uppercase).Root cause:
goArchToActionArch()inpkg/container/host_environment.gohad a mapping for"aarch64" -> "ARM64"but was missing"arm64", which is what Go'sruntime.GOARCHreturns on ARM64 hosts. The value fell through the mapper and was returned verbatim in lowercase.The Docker container path (
docker_run.go) already handled"arm64"correctly - this alignshost_environment.gowith the same mapping.Change
One line added to
goArchToActionArch()inpkg/container/host_environment.go:Fixes #6181