Runner images do not contain the CUSTOM_ACTIONS_RESULTS_URL patch — override is a silent no-op (2.335.1, 2.336.0, 2.337.0)

[piwi3910]

Summary

Filing here because issues are disabled on falcondev-oss/github-actions-runner, and this is where the setup is documented.

CUSTOM_ACTIONS_RESULTS_URL is silently ignored by the published runner releases. The source at the release tag contains the patch, but the built artifact does not, so the override never takes effect and actions/cache continues talking to GitHub.

Verified across the three most recent releases (2.337.0, 2.336.0, 2.335.1), on linux-arm64.

Evidence

Source at the tag has it:

$ gh api repos/falcondev-oss/github-actions-runner/contents/src/Runner.Worker/Handlers/NodeScriptActionHandler.cs?ref=v2.337.0 \
    -q '.content' | base64 -d | grep -c CUSTOM_ACTIONS_RESULTS_URL
1

The published release asset does not:

$ curl -sL -o r.tar.gz https://github.com/falcondev-oss/github-actions-runner/releases/download/v2.337.0/actions-runner-linux-arm64-2.337.0.tar.gz
$ tar xzf r.tar.gz bin/Runner.Worker.dll
$ grep -ac CUSTOM_ACTIONS_RESULTS_URL bin/Runner.Worker.dll
0

Same result for v2.336.0 and v2.335.1.

The container image inherits this, because images/Dockerfile installs that tarball:

curl -f -L -o runner.tar.gz https://github.com/falcondev-oss/github-actions-runner/releases/download/v${RUNNER_VERSION}/actions-runner-${TARGETOS}-${RUNNER_ARCH}-${RUNNER_VERSION}.tar.gz

Confirmed inside a running container from ghcr.io/falcondev-oss/actions-runner:2.337.0 (digest sha256:32a63e96…, which :latest also points at):

$ grep -ac CUSTOM_ACTIONS_RESULTS_URL /home/runner/bin/Runner.Worker.dll
0

How it presents

Everything looks correct, which is what makes it costly to diagnose:

• the variable is set and readable in the runner container (printenv CUSTOM_ACTIONS_RESULTS_URL returns the URL)
• the runner registers fine and reports Current runner version: '2.337.0'
• jobs run normally and succeed
• the cache server receives zero requests — not an auth failure, not a 4xx, nothing
• actions/cache uploads to GitHub as though the override were never set

There is no warning anywhere that the variable was ignored. On a slow uplink the only symptom is that the cache step stays slow, which reads as "the cache server is misconfigured" rather than "the runner has no such feature".

Environment

• ghcr.io/falcondev-oss/actions-runner:2.337.0 / :latest, linux/arm64
• Actions Runner Controller v2 scale sets (gha-runner-scale-set 0.13.1)
• cache server 9.7.0
• actions/cache v4.3.0 (v2/Twirp cache API)

Suggested checks

The release workflow appears to build from something other than the tagged source, or to package a prebuilt upstream layout over the compiled output. A cheap regression guard would be to grep the built Runner.Worker.dll for CUSTOM_ACTIONS_RESULTS_URL in CI before publishing — the patch is the fork's entire reason to exist, so its absence should fail the release.

It would also help if the runner logged a line when the override is applied. A one-line "using custom results URL: …" at startup turns a silent no-op into something a user can see immediately.

Impact on the documented setup

The getting-started guide points users at ghcr.io/falcondev-oss/actions-runner plus CUSTOM_ACTIONS_RESULTS_URL. With the current published images that combination is a no-op, so a cache server deployed by following the docs receives nothing and every user reaches the same dead end.

[LouisHaftmann]

The patch is actually in the release. .NET stores strings in the DLL as UTF-16, so a plain grep won't find it:

python3 -c "print(open('bin/Runner.Worker.dll','rb').read().count('CUSTOM_ACTIONS_RESULTS_URL'.encode('utf-16-le')))"   # 1

So something else is going on. With ARC, make sure the env var is set on the runner container in the scale set's pod template, not on the listener. If that looks right, could you re-run with ACTIONS_STEP_DEBUG=true and share the actions/cache step log? It shows which URL the cache client is calling.

You're right that the runner shouldn't be silent about this, though. falcondev-oss/github-actions-runner#4 adds a Using custom Actions results URL: '...' line to the "Set up job" log, and it'll ship with the next runner release.