start-proxy selects an AMD64 binary on Linux ARM64

[debanjanbasu]

Problem

The CodeQL CLI now has native Linux ARM64 support in beta, but the managed private-registry proxy still selects and downloads an AMD64 executable on Linux ARM64. This prevents the proxy from running natively even when CodeQL analysis itself can run.

This report concerns the proxy artifact and architecture selection, not generic CodeQL CLI ARM64 support, registry credentials, custom CA certificates, or outbound network access.

Source and public release evidence

Source inspected on September 25, 2026: fa8392b7e54a5d74a53270a4aa7defa307aa415c.

• getProxyPackage() selects by process.platform only. Every Linux host receives update-job-proxy-linux64.tar.gz; process.arch is not checked.
• getDownloadUrl() looks for that filename in the CodeQL bundle release, then falls back to the hard-coded v2.22.0 release.
• The v2.27.0 release contains a native codeql-bundle-linux-arm64 CLI bundle, but the proxy assets are only linux64, osx64, and win64.
• Fresh inspection of both Linux proxy archives below found ELF e_machine=62 (EM_X86_64), not 183 (EM_AARCH64). Downloaded archive hashes match the digests returned by the GitHub Releases API.

Proxy release	ELF architecture	Archive SHA-256
v2.27.0	AMD64 / e_machine=62	77197411d8fe7c6d157f694e2e4edd6b94bf7d9d10c667864cd6a113c31f97b2
v2.22.0 fallback	AMD64 / e_machine=62	caed6d4ad41849570f6c62f784f20f9414a82738b120f464d7fcad1640f7900b

Public-only reproduction

This inspects public artifacts without executing them, extracting them to disk, accessing a private registry, or requiring credentials. It can run on any host with curl and Python 3; the affected execution platform is native Linux ARM64 without x86 emulation.

for version in 2.27.0 2.22.0; do
  curl --fail --silent --show-error --location \
    "https://github.com/github/codeql-action/releases/download/codeql-bundle-v${version}/update-job-proxy-linux64.tar.gz" \
    -o "proxy-v${version}.tar.gz" || exit 1
done

python3 - <<'PY'
import tarfile
from pathlib import Path

for version in ("2.27.0", "2.22.0"):
    with tarfile.open(f"proxy-v{version}.tar.gz", "r:gz") as archive:
        members = [
            member for member in archive.getmembers()
            if member.isfile() and Path(member.name).name == "update-job-proxy"
        ]
        assert len(members) == 1
        header = archive.extractfile(members[0]).read(64)
        assert header[:4] == b"\x7fELF"
        assert header[5] in (1, 2)
        byteorder = "little" if header[5] == 1 else "big"
        machine = int.from_bytes(header[18:20], byteorder)
        print(f"{version}: ELF e_machine={machine} (62=AMD64, 183=AArch64)")
PY

Actual output:

2.27.0: ELF e_machine=62 (62=AMD64, 183=AArch64)
2.22.0: ELF e_machine=62 (62=AMD64, 183=AArch64)

Native-run observation and impact

A September 21, 2026 managed CodeQL run on native Linux ARM64, Ubuntu 26.04.1, with CLI 2.27.0 uploaded analyses successfully, but its local registry-proxy connection tests failed with ECONNREFUSED; proxy cleanup reported ESRCH. This earlier runtime observation is separate from the fresh public-artifact inspection above; no new managed scan was triggered for this report.

Successful analysis upload therefore did not establish successful private-dependency resolution. The architecture mismatch can be verified independently of that runner OS version and of any particular private registry. An x64 runner remains the workaround for this proxy path.

Expected behavior

Select a native Linux ARM64 proxy artifact when process.arch === "arm64", including an architecture-compatible fallback. Until such an artifact is available, fail early with an explicit unsupported-architecture diagnostic rather than attempting to start the AMD64 executable. Tests should cover Linux x64 and arm64 selection and fallback behavior.

Could the maintainers confirm whether private-registry proxy support is intended to be part of Linux ARM64 CodeQL support, or whether this remains an unsupported combination that should be documented explicitly?

Related, but distinct

#3530 and #3531 address proxy startup retries and false-success/readiness reporting. They may explain why a dead proxy is not surfaced clearly, but they do not add an ARM64 proxy artifact or change architecture selection. This report tracks that architecture gap separately.

[mbg]

Hi @debanjanbasu,

Thanks for reporting this. I can confirm that this isn't supported yet, but this isn't only a limitation in start-proxy's download logic. There are currently no arm64 binaries being built for the proxy, and none are bundled with CodeQL releases, so just changing start-proxy won't resolve this. We will look into getting this resolved.