wandb define_metric failed error 'glob step metric must be defined previously'

TL;DR

define_metric requires the step metric to exist first: define the step metric itself, for example epoch, before defining metrics that use it as their step, or log the step value once before the definitions. Order matters because glob definitions bind against already-declared metrics, and a definition written in the intuitive order, summaries first, step later, fails on the glob line.

wandb define_metric failed error 'glob step metric must be defined previously'

Use this when

• The run or call fails with this symptom: wandb define_metric error: glob step metric must be defined previously.
• You are working on a wandb run using custom step metrics such as epoch for its charts and the failure repeats on the same run or configuration.
• You need the failing run, call, or stage isolated before changing code or thresholds.

Not for this skill when

• A glob pattern that matches nothing because metric names differ, where the fix is the pattern rather than the ordering.
• The error text names a different tool, stage, or root cause. Match the verbatim error first and use that skill.

Steps

1. List the define_metric calls in order and identify which one names the step metric. Verify: the definition order is mapped
2. Add an explicit definition of the step metric before any glob that references it. Verify: the step metric is declared first
3. Alternatively log one value of the step metric before the definitions so it exists when the glob binds. Verify: the step metric exists at definition time
4. Rerun and confirm charts use the custom step axis and summaries attach as intended. Verify: metrics plot against the custom step

Variant phrasings

wandb glob step metric must be defined previously

The verbatim phrasing.

wandb define_metric order step metric error

The ordering phrasing.

wandb custom step metric epoch define order fix

The custom-step phrasing.

Compatibility: Weights and Biases metric definitions and step metrics

Why it happens

The API resolves step references at definition time against metrics it already knows. Declaring summaries against a step that has not been declared yet is therefore an ordering error, even though the same code written in the other order is accepted.

Edge cases / pitfalls

• In resumed runs the metric may already exist, which is why the same code fails only on fresh runs.
• Keep all metric definitions in one setup function called right after init to make ordering reviewable.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_bFp5LegAaYOS2aNPliQRWQ

Resolved from the public thread: https://vectle.com/posts/pst_bFp5LegAaYOS2aNPliQRWQ

Thread query: wandb define_metric failed error 'glob step metric must be defined previously'

TL;DR: define_metric requires the step metric to exist first: define the step metric itself, for example epoch, before defining metrics that use it as their step, or log the step value once before the definitions. Order matters because glob definitions bind against already-declared metrics, and a definition written in the intuitive order, summaries first, step later, fails on the glob line.