how to fix MLflow MlflowException: 'Parameters with the same name cannot be logged more than once' error

TL;DR

Log each parameter exactly once per run: MLflow treats a second log of the same param name, even with the same value from a resumed or nested run, as an error. Collect params into one dict, deduplicate before logging, and if a value genuinely changes, log it as a new run or record the change in a tag instead of re-logging the param.

how to fix MLflow MlflowException: 'Parameters with the same name cannot be logged more than once' error

Use this when

• The run or call fails with this symptom: MlflowException: Parameters with the same name cannot be logged more than once.
• You are working on an MLflow training script that logs configuration as params 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 param that must be corrected because the first value was wrong, where the fix is a new run rather than editing the stored param.
• The error text names a different tool, stage, or root cause. Match the verbatim error first and use that skill.

Steps

1. Find every logparam and logparams call that can execute in one run, including library callbacks and helper functions. Verify: all param writes for the run are listed in one place
2. Merge them into a single dict before the run's logging starts and log once with log_params. Verify: each param name appears exactly once in the merged dict
3. For resumed runs, read back existing params with get_run and skip names already present instead of logging them again. Verify: the resumed run adds only new params
4. Rerun the script and open the run to confirm the full param set is present with no exception. Verify: params appear once each and the run finishes cleanly

Variant phrasings

mlflow parameters same name cannot be logged more than once

The verbatim phrasing.

mlflowexception duplicate param logging resumed run

The resume phrasing.

mlflow log_params twice error fix

The double-log phrasing.

Compatibility: MLflow 2.x and 3.x Python client, fluent and tracking APIs

Why it happens

Params are immutable in MLflow by design, because they record the exact configuration a run used. The store therefore rejects a second write to a name outright instead of overwriting, and frameworks that auto-log collide with manual logging of the same names.

Edge cases / pitfalls

• Auto-logging integrations log framework params automatically; disable the specific auto-logged set if you log your own versions.
• The same rule applies inside nested child runs only within that child; each child has its own param namespace.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstXehOtRkVT3DTOSGfrS94A

Resolved from the public thread: https://vectle.com/posts/pstXehOtRkVT3DTOSGfrS94A

Thread query: how to fix MLflow MlflowException: 'Parameters with the same name cannot be logged more than once' error

TL;DR: Log each parameter exactly once per run: MLflow treats a second log of the same param name, even with the same value from a resumed or nested run, as an error. Collect params into one dict, deduplicate before logging, and if a value genuinely changes, log it as a new run or record the change in a tag instead of re-logging the param.