[bug, ci]: Cache export is not supported for the docker driver

[xingyaoww]

We should review the docker build github workflow in this repo and find the potential cause for this issue:

[stdout] Driver: docker
[stdout] 
[stdout] Nodes:
[stdout] Name:             default
[stdout] Endpoint:         default
[stdout] Status:           running
[stdout] BuildKit version: v0.20.2
[stdout] Platforms:        linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/amd64/v4, linux/386
[stdout] Labels:
[stdout]  org.mobyproject.buildkit.worker.moby.host-gateway-ip: 172.17.0.1
{"asctime": "2025-10-31 17:57:51,622", "levelname": "INFO", "name": "__main__", "filename": "build.py", "lineno": 442, "message": "[build] Cache: registry (remote/CI) + inline"}
{"asctime": "2025-10-31 17:57:51,622", "levelname": "INFO", "name": "__main__", "filename": "build.py", "lineno": 473, "message": "[build] Building target='binary' image='ghcr.io/openhands/agent-server' custom_tags='python' from base='nikolaik/python-nodejs:python3.12-nodejs22' for platforms='['linux/amd64', 'linux/arm64']'"}
{"asctime": "2025-10-31 17:57:51,622", "levelname": "INFO", "name": "__main__", "filename": "build.py", "lineno": 478, "message": "[build] Git ref='refs/heads/main' sha='efa060613c1b2bfd76dbe38bb42484bc1ee405b2' version='1.0.0a5'"}
{"asctime": "2025-10-31 17:57:51,622", "levelname": "INFO", "name": "__main__", "filename": "build.py", "lineno": 479, "message": "[build] Cache tag: buildcache-binary-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-main"}
{"asctime": "2025-10-31 17:57:51,622", "levelname": "INFO", "name": "__main__", "filename": "build.py", "lineno": 55, "message": "$ docker buildx build --file /home/runner/_work/software-agent-sdk/software-agent-sdk/openhands-agent-server/openhands/agent_server/docker/Dockerfile --target binary --build-arg BASE_IMAGE=nikolaik/python-nodejs:python3.12-nodejs22 --platform linux/amd64,linux/arm64 --push --tag ghcr.io/openhands/agent-server:efa0606-python --tag ghcr.io/openhands/agent-server:main-python --tag ghcr.io/openhands/agent-server:v1.0.0a5_nikolaik_s_python-nodejs_tag_python3.12-nodejs22_binary --cache-from type=registry,ref=ghcr.io/openhands/agent-server:buildcache-binary-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-main --cache-from type=registry,ref=ghcr.io/openhands/agent-server:buildcache-binary-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-main --cache-to type=registry,ref=ghcr.io/openhands/agent-server:buildcache-binary-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-main,mode=max /tmp/agent-build-9om56w9o/unknown-0.0.0 (cwd=/tmp/agent-build-9om56w9o/unknown-0.0.0)"}
[stderr] ERROR: Cache export is not supported for the docker driver.
[stderr] Switch to a different driver, or turn on the containerd image store, and try again.
[stderr] Learn more at https://docs.docker.com/go/build-cache-backends/
{"asctime": "2025-10-31 17:57:51,675", "levelname": "ERROR", "name": "__main__", "filename": "build.py", "lineno": 485, "message": "[build] ERROR: Build failed with exit code 1"}
{"asctime": "2025-10-31 17:57:51,675", "levelname": "ERROR", "name": "__main__", "filename": "build.py", "lineno": 486, "message": "[build] Command: docker buildx build --file /home/runner/_work/software-agent-sdk/software-agent-sdk/openhands-agent-server/openhands/agent_server/docker/Dockerfile --target binary --build-arg BASE_IMAGE=nikolaik/python-nodejs:python3.12-nodejs22 --platform linux/amd64,linux/arm64 --push --tag ghcr.io/openhands/agent-server:efa0606-python --tag ghcr.io/openhands/agent-server:main-python --tag ghcr.io/openhands/agent-server:v1.0.0a5_nikolaik_s_python-nodejs_tag_python3.12-nodejs22_binary --cache-from type=registry,ref=ghcr.io/openhands/agent-server:buildcache-binary-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-main --cache-from type=registry,ref=ghcr.io/openhands/agent-server:buildcache-binary-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-main --cache-to type=registry,ref=ghcr.io/openhands/agent-server:buildcache-binary-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-main,mode=max /tmp/agent-build-9om56w9o/unknown-0.0.0"}
{"asctime": "2025-10-31 17:57:51,675", "levelname": "ERROR", "name": "__main__", "filename": "build.py", "lineno": 487, "message": "[build] Full stdout:\n"}
{"asctime": "2025-10-31 17:57:51,675", "levelname": "ERROR", "name": "__main__", "filename": "build.py", "lineno": 488, "message": "[build] Full stderr:\nERROR: Cache export is not supported for the docker driver.\nSwitch to a different driver, or turn on the containerd image store, and try again.\nLearn more at [https://docs.docker.com/go/build-cache-backends/\n](https://docs.docker.com/go/build-cache-backends//n)"}
{"asctime": "2025-10-31 17:57:51,675", "levelname": "INFO", "name": "__main__", "filename": "build.py", "lineno": 491, "message": "[build] Cleaning /tmp/agent-build-9om56w9o/unknown-0.0.0"}
Traceback (most recent call last):
  File "/home/runner/_work/software-agent-sdk/software-agent-sdk/./openhands-agent-server/openhands/agent_server/docker/build.py", line 637, in <module>
    sys.exit(main(sys.argv[1:]))
             ^^^^^^^^^^^^^^^^^^
  File "/home/runner/_work/software-agent-sdk/software-agent-sdk/./openhands-agent-server/openhands/agent_server/docker/build.py", line 606, in main
    tags = build(opts)
           ^^^^^^^^^^^
  File "/home/runner/_work/software-agent-sdk/software-agent-sdk/./openhands-agent-server/openhands/agent_server/docker/build.py", line 482, in build
    res = _run(args, cwd=str(ctx))
          ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/_work/software-agent-sdk/software-agent-sdk/./openhands-agent-server/openhands/agent_server/docker/build.py", line 99, in _run
    raise subprocess.CalledProcessError(rc, cmd, output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command '['docker', 'buildx', 'build', '--file', '/home/runner/_work/software-agent-sdk/software-agent-sdk/openhands-agent-server/openhands/agent_server/docker/Dockerfile', '--target', 'binary', '--build-arg', 'BASE_IMAGE=nikolaik/python-nodejs:python3.12-nodejs22', '--platform', 'linux/amd64,linux/arm64', '--push', '--tag', 'ghcr.io/openhands/agent-server:efa0606-python', '--tag', 'ghcr.io/openhands/agent-server:main-python', '--tag', 'ghcr.io/openhands/agent-server:v1.0.0a5_nikolaik_s_python-nodejs_tag_python3.12-nodejs22_binary', '--cache-from', 'type=registry,ref=ghcr.io/openhands/agent-server:buildcache-binary-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-main', '--cache-from', 'type=registry,ref=ghcr.io/openhands/agent-server:buildcache-binary-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-main', '--cache-to', 'type=registry,ref=ghcr.io/openhands/agent-server:buildcache-binary-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-main,mode=max', '/tmp/agent-build-9om56w9o/unknown-0.0.0']' returned non-zero exit status 1.
/home/runner/_work/software-agent-sdk/software-agent-sdk/.venv/lib/python3.12/site-packages/litellm/llms/custom_httpx/async_client_cleanup.py:66: DeprecationWarning: There is no current event loop
  loop = asyncio.get_event_loop()

[openhands-ai]

I'm on it! xingyaoww can track my progress at all-hands.dev

[openhands-ai]

Summary

I've successfully fixed issue #982 - the Docker build failure in CI when using the default docker driver that doesn't support cache export.

✅ Changes Made

1. Fixed build.py Cache Strategy (Lines 427-459)

• Added driver detection to check if the active buildx driver supports cache export
• When push=True and driver is docker: Only use --cache-from (read-only registry cache), skip --cache-to to prevent the error
• When push=True and driver is NOT docker: Use both --cache-from and --cache-to (full registry cache with export)
• Added a helpful warning message when docker driver is detected, with instructions on how to set up docker-container builder

2. Added Comprehensive Unit Tests

• Created tests/agent_server/test_docker_build.py with 6 tests covering:
  • Driver detection functionality
  • Cache strategy behavior with docker driver (the main fix for [bug, ci]: Cache export is not supported for the docker driver #982)
  • Cache strategy behavior with docker-container driver
  • Cache strategy behavior in non-push mode
• All tests pass ✅

3. Quality Checks

• Pre-commit checks pass (ruff format, ruff lint, pycodestyle, pyright) ✅
• All unit tests pass ✅

📝 Pull Request

PR #983: #983

• Title: "Fix docker driver cache export issue in CI"
• Branch: openhands/fix-docker-driver-cache-export
• Status: Ready for review (not marked as draft as requested in instructions)
• Closes: [bug, ci]: Cache export is not supported for the docker driver #982

The fix ensures that CI builds will no longer fail with "Cache export is not supported for the docker driver" error, while maintaining full cache functionality when proper buildx drivers are configured.

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