GitHub Actions · infra · fg-0233

upload-artifact v4 fails with 409 Conflict when matrix jobs upload to the same artifact name

Failed to CreateArtifact: Received non-retryable error: Failed request: (409) Conflict: an artifact with this name already exists on the workflow run

Verified 2026-10-15 · Confirmed by 0 builders · Trust 50/100

Cause

Artifacts created by upload-artifact v4 are immutable, so two jobs cannot write to the same name. v3 allowed it and merged the files.

Fix

Give each job a unique artifact name and merge them with download-artifact using a pattern.

Apply

- uses: actions/upload-artifact@v4
  with:
    name: results-${{ matrix.os }}
    path: out/
# later job
- uses: actions/download-artifact@v4
  with:
    pattern: results-*
    merge-multiple: true

Affects: actions/upload-artifact v4 and later

Sources

• https://github.com/actions/upload-artifact/issues/478
• https://github.com/actions/upload-artifact/blob/main/README.md

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