{"record":{"id":"89c1bcc4828cefd4","repo":"Lightning-AI/pytorch-lightning","slug":"f-trainer-barebones-true-fast-dev-run-fast-dev","errorCode":null,"errorMessage":"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.\"","messagePattern":"f\"`Trainer\\(barebones=True, fast_dev_run=(.+?)\\)` was passed\\.\" \" Development run is not meant for raw speed evaluation so it is disabled in barebones mode\\.\"","errorType":"validation","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"src/lightning/pytorch/trainer/trainer.py","lineNumber":375,"sourceCode":"                    f\"`Trainer(barebones=True, log_every_n_steps={log_every_n_steps!r})` was passed.\"\n                    \" Logging can impact raw speed so it is disabled in barebones mode.\"\n                )\n            log_every_n_steps = 0\n            if enable_model_summary:\n                raise ValueError(\n                    f\"`Trainer(barebones=True, enable_model_summary={enable_model_summary!r})` was passed.\"\n                    \" Model summary can impact raw speed so it is disabled in barebones mode.\"\n                )\n            enable_model_summary = False\n            if num_sanity_val_steps is not None and num_sanity_val_steps != 0:\n                raise ValueError(\n                    f\"`Trainer(barebones=True, num_sanity_val_steps={num_sanity_val_steps!r})` was passed.\"\n                    \" Sanity checking can impact raw speed so it is disabled in barebones mode.\"\n                )\n            num_sanity_val_steps = 0\n            # opt-ins\n            if fast_dev_run is not False and fast_dev_run != 0:\n                raise ValueError(\n                    f\"`Trainer(barebones=True, fast_dev_run={fast_dev_run!r})` was passed.\"\n                    \" Development run is not meant for raw speed evaluation so it is disabled in barebones mode.\"\n                )\n            if detect_anomaly:\n                raise ValueError(\n                    f\"`Trainer(barebones=True, detect_anomaly={detect_anomaly!r})` was passed.\"\n                    \" Anomaly detection can impact raw speed so it is disabled in barebones mode.\"\n                )\n            if profiler is not None:\n                raise ValueError(\n                    f\"`Trainer(barebones=True, profiler={profiler!r})` was passed.\"\n                    \" Profiling can impact raw speed so it is disabled in barebones mode.\"\n                )\n            deactivated = (\n                \" - Checkpointing: `Trainer(enable_checkpointing=True)`\",\n                \" - Progress bar: `Trainer(enable_progress_bar=True)`\",\n                \" - Model summary: `Trainer(enable_model_summary=True)`\",\n                \" - Logging: `Trainer(logger=True)`, `Trainer(log_every_n_steps>0)`,\"","sourceCodeStart":357,"sourceCodeEnd":393,"githubUrl":"https://github.com/Lightning-AI/pytorch-lightning/blob/9fed5c27d2a62ff0efd6c3573599921d6ff67c14/src/lightning/pytorch/trainer/trainer.py#L357-L393","documentation":"Trainer was created with barebones=True while fast_dev_run was enabled. A development run (1 batch, 1 epoch) is not meant for raw speed evaluation, so barebones mode rejects the combination.","triggerScenarios":"Trainer(barebones=True, fast_dev_run=True) or fast_dev_run=<int> (anything other than False/0).","commonSituations":"Leaving fast_dev_run=True from a debugging session while also enabling barebones=True for benchmarking.","solutions":["Remove fast_dev_run when using barebones=True","Set fast_dev_run=False","Remove barebones=True if you actually want a dev run"],"exampleFix":"// before\ntrainer = Trainer(barebones=True, fast_dev_run=True)\n// after\ntrainer = Trainer(barebones=True)","handlingStrategy":"validation","validationCode":"if cfg.get(\"barebones\") and cfg.get(\"fast_dev_run\") not in (False, 0, None):\n    cfg[\"fast_dev_run\"] = False\ntrainer = Trainer(**cfg)","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Never combine debugging flags (fast_dev_run, detect_anomaly) with benchmarking flags (barebones)","Use fast_dev_run only in smoke tests, not benchmark scripts"],"tags":["trainer","barebones","fast-dev-run","misconfiguration","pytorch-lightning"],"backgroundTag":"invalid-argument-combination","analyzedSha":"9fed5c27d2a62ff0efd6c3573599921d6ff67c14","analyzedAt":"2026-08-28T11:52:41.083Z","schemaVersion":2},"datasetVersion":"2026-08-28T16:17:29.566Z"}