WarpBuild Docker "exec format error" on arm64: Fix
An "exec format error" during a WarpBuild arm64 Docker build almost always means the builder profile is missing that architecture. Here is the documented fix.
WarpBuild's Remote Docker Builders support native multi-architecture builds: per WarpBuild's docs, amd64 and arm64 run on separate builder instances rather than via QEMU emulation. When the target architecture is not enabled on the profile, the build hits an exec format error. This page explains the cause and fix from WarpBuild's docs. Confirm specifics in WarpBuild's Docker builder docs.
Why the error happens
According to WarpBuild's Docker builder docs, multi-arch builds run each architecture on a separate builder instance instead of using QEMU emulation. If you request a linux/arm64 (or multi-platform) build but the builder profile only has amd64 enabled, the arm64 image has no native builder and you get an exec format error when the wrong-architecture binary runs.
How to fix it
Per WarpBuild's docs, verify the builder profile has both linux/amd64 and linux/arm64 enabled before running a multi-platform build. Once both architectures are enabled on the profile, WarpBuild schedules each on its native builder and the exec format error goes away. Check the profile configuration in your WarpBuild dashboard or in the profile-name you pass to the action.
Avoid idle timeouts too
WarpBuild's docs also recommend invoking Warpbuilds/docker-configure immediately before your build steps to prevent idle timeouts on the remote builder. If a long setup precedes the build, the builder can time out; placing docker-configure right before the build keeps it warm. This is a separate issue from the architecture error but often shows up in the same multi-arch pipelines.
Remember the separate billing
WarpBuild's docs note that the GitHub Actions runner and the WarpBuild Remote Docker builder are billed separately, so a multi-arch build that spins up two builders plus the runner will show multiple line items. That is expected, not a bug. Verify current pricing at warpbuild.com/pricing.