* Studio: log transformers version-switching decisions and stop swallowing MLX activation failures
Two logging gaps in dynamic transformers version switching (issue #6103):
1. get_transformers_tier returned a tier with no trace of why. Add an
info log at each decision point naming the model and the trigger
(which substring matched, or which config check fired), so a model
landing on the wrong tier is diagnosable.
2. The MLX fast-path in run_training_process activated the transformers
version inside a bare 'except Exception: pass', silently swallowing
failures while the non-MLX path reports them. A missing or broken
version venv (e.g. Gemma-4 needing 5.5.0) left no trace and only a
confusing downstream crash. Extract a small _activate_transformers_version_or_warn
helper that logs a warning on failure while keeping the non-fatal
fall-through, and call it from the MLX path.
Adds tier-selection logging tests and helper warn/silent tests.
* Studio: clarify path-prepend log, warn on venv version mismatch, log per-package install progress
Completes the remaining logging items of #6103 in studio/backend/utils/transformers_version.py:
- activate_transformers_for_subprocess: the early "Activated transformers X.X.X" line was misleading because at that point only the venv directory has been prepended to sys.path, not imported. It now says it prepended the venv to sys.path and notes the loaded version is confirmed later by "Subprocess loaded transformers ...".
- _venv_dir_is_valid: a detected version mismatch is logged at warning instead of info, since it immediately triggers a full venv wipe and reinstall that should be visible in the logs.
- _ensure_venv_dir: log each package as it starts installing with an N/M progress counter, so a slow runtime install is not mistaken for a hang (pip/uv output is piped and only surfaced on error).
Adds tests covering all three behaviours; pre-existing unused imports are left untouched.
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* Studio: make tier log-capture tests independent of import order
The new issue #6103 caplog assertions in test_transformers_version.py
relied on the module-level sys.modules.setdefault("loggers", stub)
winning the import race. In a full backend pytest run another module
(for example test_log_filter_no_truncation, collected earlier) imports
the real loggers first, so the setdefault is a no-op and
transformers_version.logger becomes a structlog/stdout logger that
caplog cannot capture -- the tier, activation, venv-mismatch and
install-progress log assertions then fail even though the line was
emitted.
Bind a real stdlib logger to transformers_version.logger for the
duration of each test via an autouse fixture, so the module logs through
logging and caplog captures them regardless of collection order.
* Studio: log local checkpoint tier decisions and warn on MLX inference activation
- get_transformers_tier: the local config.json fast path returned a tier
without logging it, so local checkpoints stayed opaque while HF ids were
traceable. Log each decision there too, with a caplog regression test.
- inference worker: the MLX path swallowed _activate_transformers_version
failures with a bare except, the same gap issue #6103 fixed for training.
Warn instead, keeping the non-fatal fall-through.
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Co-authored-by: Daniel Han <michaelhan2050@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
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