fix(evals): build /run.sh with printf so legacy builder works#2779
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The Dockerfile.template used a BuildKit heredoc (`RUN cat <<-'EOF' >/run.sh`). With the legacy builder it parses as `RUN cat >/run.sh` — empty stdin, 0-byte file. Every eval container then dies with `exec /run.sh: exec format error`, emits no events, and the run ends with Total Cost=$0 / Errors=N/N. Replace the heredoc with a single `RUN printf … > /run.sh && chmod +x`. Same resulting file, works on both legacy builder and BuildKit.
melmennaoui
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May 13, 2026
docker-agent
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Assessment: 🟢 APPROVE
This is a clean, well-scoped fix. The heredoc → printf replacement correctly addresses the legacy builder compatibility issue described in the PR. No bugs were found in the changed code.
Summary of changes reviewed:
pkg/evaluation/Dockerfile.template: Replaces a BuildKit-only heredoc with a POSIX-compatibleprintfcommand to write/run.sh, ensuring the file is populated correctly when the legacy builder is used.
The fix is byte-identical in output to the original heredoc under BuildKit, and the added chmod +x is a safe no-op on a file that was already executable under the heredoc approach.
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Summary
pkg/evaluation/Dockerfile.templateused a BuildKit heredoc to write/run.sh:Heredocs require BuildKit. When the build runs against the legacy builder, this is parsed as just
RUN cat >/run.sh—catreads from empty stdin and produces a zero-byte/run.sh. The subsequent heredoc body lines are treated as standalone Dockerfile instructions; Docker is lenient and the build "succeeds" with/run.shempty but executable.Replaced with a single
printfthat works on both legacy and BuildKit builders:Resulting
/run.shis byte-identical to what the heredoc produces under BuildKit.