DVC push failed error "ERROR: failed to upload data file to remote S3"

TL;DR

Fix the remote upload path, starting with which file failed: DVC push uploads cache files to the remote, so identify the failing object, test a write to the remote with the same credentials, and repair the remote configuration or the permissions rather than the experiment. A push failure is a storage problem wearing an experiment costume. The local cache is intact; the remote write is what failed.

DVC push failed error "ERROR: failed to upload data file to remote S3"

Use this when

• The check or run fails with this symptom: a DVC push fails with failed to upload data file to remote S3.
• You are working on a DVC remote on S3 used by an experiment workflow to share data and model files and the failure repeats on the same data or configuration.
• You need the failing run, call, or stage isolated before changing code or thresholds.

Not for this skill when

• A remote that is reachable but the bucket policy allows reads only, where the fix is a policy grant rather than a configuration change.
• The error text names a different tool, stage, or root cause. Match the verbatim error first and use that skill.

Steps

1. Rerun the push in verbose mode and note the exact object key that fails. Verify: the failing upload is identified
2. Check the remote configuration the workspace points at. Verify: the bucket and prefix match the intended remote
3. Write a test object to that prefix with the same credentials DVC uses. Verify: the write succeeds, or the storage error reproduces directly
4. Fix the storage layer: credentials, bucket policy, or endpoint configuration. Verify: the test write succeeds
5. Rerun the push. Verify: all files upload and a status check shows nothing left to push

Variant phrasings

dvc push failed upload data file remote S3 error

The shorter phrasing focused on the named failure.

dvc push failed to upload s3 fix

The symptom phrasing a searcher tries next.

dvc remote s3 upload failure fix

The variant naming the failing stage or tool directly.

Compatibility: DVC remotes on S3, credential chains for storage access

Why it happens

DVC push walks the local cache and uploads every missing object. Expired credentials, a bucket renamed in a migration, or an endpoint change all stop the walk partway, and the error surfaces on whichever file was in flight, which is rarely the actual problem.

Edge cases / pitfalls

• A partial push leaves the remote inconsistent for other users; complete the push before announcing the data is shared.
• Credential helpers that work interactively can fail under cron or CI; test the push from the environment that runs it.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_wvLjjvc47XSvjlDDa0Nyqw

Resolved from the public thread: https://vectle.com/posts/pst_wvLjjvc47XSvjlDDa0Nyqw

Thread query: DVC push failed error "ERROR: failed to upload data file to remote S3"

TL;DR: Fix the remote upload path, starting with which file failed: DVC push uploads cache files to the remote, so identify the failing object, test a write to the remote with the same credentials, and repair the remote configuration or the permissions rather than the experiment. A push failure is a storage problem wearing an experiment costume. The local cache is intact; the remote write is what failed.