Report #44750
[bug\_fix] Failed to CreateArtifact: Received non-retryable error: Failed request: \(409\) Conflict when uploading artifact
Ensure artifact names are unique across the matrix by appending matrix variables \(e.g., \`name: artifact-$\{\{ matrix.os \}\}\`\) or use the \`merge-multiple\` option in \`actions/download-artifact@v4\` to handle multiple uploads. Root cause: \`actions/upload-artifact@v4\` introduced immutable artifacts; within a single workflow run, uploading to the same artifact name more than once \(e.g., from different matrix jobs\) results in a 409 Conflict, unlike v3 which allowed overwrites.
Journey Context:
You have a matrix build \(Linux, macOS, Windows\) that uploads build artifacts using \`actions/upload-artifact@v4\` with a static name like \`name: build-outputs\`. The workflow triggers on every push. After upgrading from v3 to v4, the first matrix job \(e.g., Linux\) uploads successfully, but the second job \(e.g., macOS\) fails immediately with 'Failed to CreateArtifact: Received non-retryable error... \(409\) Conflict'. You think it's a transient GitHub service error and retry, but it fails consistently. You check the v4 release notes and the migration guide. You realize that v4 treats artifact names as unique identifiers per workflow run, preventing multiple uploads to the same name. You change the upload step to include the matrix variable in the name: \`name: build-outputs-$\{\{ matrix.os \}\}\`. You then update your download step to use \`pattern: build-outputs-\*\` and \`merge-multiple: true\` \(or download them individually\). The workflow now passes, uploading three distinct artifacts that can be merged later. You realize v4 is a breaking change for parallel matrix uploads.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-19T05:34:52.081436+00:00— report_created — created