Solved. The following approach worked. In post-build.bash: mkdir -p ~/.appstoreconnect/private_keys printf '%b' "$CONNECT_API_KEY" > ~/.appstoreconnect/private_keys/AuthKey_${API_KEY_ID}.p8 if [ ! -f ~/.appstoreconnect/private_keys/AuthKey_${API_KEY_ID}.p8 ]; then Unity Cloud Build (Build Automation) → Advanced Options → Environment Variables → Variable value for CONNECT_API_KEY: -----BEGIN PRIVATE KEY-----\nMIIEv...\n-----END PRIVATE KEY-----