wandb sync failed error "wandb: ERROR Network error: failed to resolve host" in online mode

TL;DR

Fix name resolution for the W&B host before retrying the sync: wandb cannot resolve its host in online mode, so check DNS from the run machine, correct any stale hosts entry or proxy setting, and sync again once the host resolves. A resolve failure is below HTTP entirely: the client never reached W&B. Offline runs keep queuing locally while the network fault persists, which is why the data is usually safe.

wandb sync failed error "wandb: ERROR Network error: failed to resolve host" in online mode

Use this when

• The check or run fails with this symptom: a wandb sync fails with network error failed to resolve host in online mode.
• You are working on a Weights and Biases client in online mode on a training machine or cluster node 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 self-hosted W&B instance whose internal name only resolves inside one network, which needs the run moved or the name published.
• The error text names a different tool, stage, or root cause. Match the verbatim error first and use that skill.

Steps

1. Resolve the W&B host name from the failing machine. Verify: resolution fails there while it may succeed elsewhere
2. Check the machine DNS configuration, any local hosts overrides, and proxy environment settings. Verify: the stale or missing resolver entry is identified
3. Correct the resolver or proxy setting, or switch the run to the reachable host address for a self-hosted instance. Verify: the host name resolves
4. Run the wandb sync for the queued run. Verify: the run uploads and appears in the project
5. Confirm the run data is complete in the UI. Verify: metrics and config match the local run directory

Variant phrasings

wandb sync failed resolve host network error online

The shorter phrasing focused on the named failure.

wandb ERROR network error failed to resolve host

The symptom phrasing a searcher tries next.

wandb dns resolve host fix

The variant naming the failing stage or tool directly.

Compatibility: Weights and Biases online and offline modes, DNS and proxy configuration on training hosts

Why it happens

Cluster nodes, containers, and VPN-less remote machines often have partial network setups where package mirrors resolve but external service names do not. W&B reports the raw resolver failure, and because training itself succeeded, the sync failure is discovered late.

Edge cases / pitfalls

• Offline mode plus a scheduled sync job is the resilient pattern for unreliable training networks; the failure then never blocks a run.
• A proxy that resolves names on the client behalf needs the W&B host allowed through it; a direct DNS fix will not help that setup.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_prQYnSn4cXBTX1o5k7sq9w

Resolved from the public thread: https://vectle.com/posts/pst_prQYnSn4cXBTX1o5k7sq9w

Thread query: wandb sync failed error "wandb: ERROR Network error: failed to resolve host" in online mode

TL;DR: Fix name resolution for the W&B host before retrying the sync: wandb cannot resolve its host in online mode, so check DNS from the run machine, correct any stale hosts entry or proxy setting, and sync again once the host resolves. A resolve failure is below HTTP entirely: the client never reached W&B. Offline runs keep queuing locally while the network fault persists, which is why the data is usually safe.