Lightning-AI/pytorch-lightning · error · ValueError

f"`Trainer(barebones=True, enable_model_summary={enable_mode

Error message

f"`Trainer(barebones=True, enable_model_summary={enable_model_summary!r})` was passed." " Model summary can impact raw speed so it is disabled in barebones mode."

What it means

Trainer was created with barebones=True while enable_model_summary=True. Model summary printing adds overhead, so barebones speed-benchmark mode forbids it and fails fast in the constructor.

Source

Thrown at src/lightning/pytorch/trainer/trainer.py:362

                raise ValueError(
                    f"`Trainer(barebones=True, logger={logger!r})` was passed."
                    " Logging can impact raw speed so it is disabled in barebones mode."
                )
            logger = False
            if enable_progress_bar:
                raise ValueError(
                    f"`Trainer(barebones=True, enable_progress_bar={enable_progress_bar!r})` was passed."
                    " The progress bar can impact raw speed so it is disabled in barebones mode."
                )
            enable_progress_bar = False
            if log_every_n_steps is not None and log_every_n_steps != 0:
                raise ValueError(
                    f"`Trainer(barebones=True, log_every_n_steps={log_every_n_steps!r})` was passed."
                    " Logging can impact raw speed so it is disabled in barebones mode."
                )
            log_every_n_steps = 0
            if enable_model_summary:
                raise ValueError(
                    f"`Trainer(barebones=True, enable_model_summary={enable_model_summary!r})` was passed."
                    " Model summary can impact raw speed so it is disabled in barebones mode."
                )
            enable_model_summary = False
            if num_sanity_val_steps is not None and num_sanity_val_steps != 0:
                raise ValueError(
                    f"`Trainer(barebones=True, num_sanity_val_steps={num_sanity_val_steps!r})` was passed."
                    " Sanity checking can impact raw speed so it is disabled in barebones mode."
                )
            num_sanity_val_steps = 0
            # opt-ins
            if fast_dev_run is not False and fast_dev_run != 0:
                raise ValueError(
                    f"`Trainer(barebones=True, fast_dev_run={fast_dev_run!r})` was passed."
                    " Development run is not meant for raw speed evaluation so it is disabled in barebones mode."
                )
            if detect_anomaly:
                raise ValueError(

View on GitHub (pinned to 9fed5c27d2)

Solutions

Remove enable_model_summary when using barebones=True
Set enable_model_summary=False
Remove barebones=True if the model summary is needed

Example fix

// before
trainer = Trainer(barebones=True, enable_model_summary=True)
// after
trainer = Trainer(barebones=True)

Defensive patterns

Strategy: validation

Validate before calling

if cfg.get("barebones"):
    cfg["enable_model_summary"] = False
trainer = Trainer(**cfg)

Prevention

Set all cosmetic options to False in code before passing barebones=True
Maintain one canonical benchmark config validated in a unit test

When it happens

Trigger: Trainer(barebones=True, enable_model_summary=True).

Common situations: Reusing an existing verbose Trainer config and toggling barebones=True for benchmarking without clearing cosmetic options like model summary.

Related errors

AI-assisted analysis of Lightning-AI/pytorch-lightning@9fed5c27d2 (2026-08-28). Data as JSON: /api/errors/5afda242e0d89b5a. Report an issue: GitHub.