Echo-LoRA: Parameter-Efficient Fine-Tuning via Cross-Layer Representation Injection
Existing LoRA-based methods are constrained to single-layer weight updates, limiting their ability to leverage intermediate representations from deep networks and thereby hindering the performance of parameter-efficient fine-tuning. This work proposes Echo-LoRA, which introduces a cross-layer representation injection mechanism: sample-specific echo representations are generated by aggregating hidden states at deep layer boundaries and then injected into shallow LoRA or DoRA modules via a lightweight projection and gating network. During training, answer masking, masked distillation, and stochastic routing are jointly employed to stabilize the auxiliary pathway and reduce the training–inference discrepancy; notably, the auxiliary structure can be entirely removed at inference time, incurring no additional overhead. Evaluated on eight commonsense reasoning benchmarks, Echo-LoRA achieves an average improvement of 5.7 percentage points over LoRA (3.0 points under unified reimplementation) and gains 2.7 points when combined with DoRA.