René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"\"Error: WARNING: Cache entry deserialization failed, entry ignored\" turns builds red","articleBody":"\u003c!--- Please direct any generic questions related to actions to our support community forum at https://github.community/c/code-to-cloud/github-actions/41 ---\u003e\n\u003c!--- Before opening up a new bug report, please make sure to check for similar existing issues --\u003e\n\n**Description:**\nWhen using `actions/setup-python@v6`, sometimes the build output will include the warning \"WARNING: Cache entry deserialization failed, entry ignored.\" Something then treats this as an error and stylizes it as \"Error: WARNING: Cache entry deserialization failed, entry ignored.\" This results in a \"red\" annotation even though the build succeeded.\n\n**Action version:**\n6\n\n**Platform:**\n- [ ] Ubuntu\n- [x] macOS\n- [ ] Windows\n\nI have only seen this on `macos-26` (ARM). I'm running my builds on multiple Ubuntu versions, multiple Windows versions, and `macos15-intel`, `macos-26`, and `macos-26-intel`, but I have only ever seen this problem on `macos-26`. It's possible it could occur on other platforms as well, but it happens every run with `macos-26`.\n\n**Runner type:**\n- [x] Hosted\n- [ ] Self-hosted\n\n**Tools version:**\nThis is occurring on Python 3.10. I am also testing on 3.12 and 3.14, both on `macos-26`, but this occurs only on Python 3.10. It's possible it could occur on other versions as well, but it happens every run with 3.10.\n\n**Repro steps:**  \nAdd this to your workflow using `macos-26`:\n```\n      - name: Installing Python 3.10\n        uses: actions/setup-python@v6\n        with:\n          python-version: \"3.10\"\n          cache: \"pip\"\n```\n\nYou can view an example of the problem here: https://github.com/OddSource/ifaddrs4u/actions/runs/26189279490\n\nHere's the raw log output from that example: https://productionresultssa6.blob.core.windows.net/actions-results/dfb8936d-094e-4cd2-9f35-3410202f148e/workflow-job-run-9d4e464c-c0b6-5d27-8a60-7be7d2ac21f9/logs/job/job-logs.txt?rsct=text%2Fplain\u0026se=2026-05-20T21%3A43%3A19Z\u0026sig=ycaulFWWEQHuTLznY37a1StspVeKesa34TcByAGL3Mw%3D\u0026ske=2026-05-21T00%3A53%3A48Z\u0026skoid=ca7593d4-ee42-46cd-af88-8b886a2f84eb\u0026sks=b\u0026skt=2026-05-20T20%3A53%3A48Z\u0026sktid=398a6654-997b-47e9-b12b-9515b896b4de\u0026skv=2025-11-05\u0026sp=r\u0026spr=https\u0026sr=b\u0026st=2026-05-20T21%3A33%3A14Z\u0026sv=2025-11-05\n\nAnd the workflow in question is here: https://github.com/OddSource/ifaddrs4u/blob/main/.github/workflows/matrix-gh-runers.yml\n\n**Expected behavior:**\nFor the action, when used as documented with supported options values, to not cause output that GitHub Actions treats as an error unless something actually went wrong.\n\n**Actual behavior:**\nThe action succeeds, but results in \"error\" output that causes red annotations on the builds.","author":{"url":"https://github.com/beamerblvd","@type":"Person","name":"beamerblvd"},"datePublished":"2026-05-20T21:19:41.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/1317/setup-python/issues/1317"}