ALIGNBEAM : Inference-Time Alignment Transfer via Cross-Vocabulary Logit Mixing
A new inference-time defense mechanism addresses a critical vulnerability in domain-specialized language models: fine-tuning for narrow tasks systematically erodes safety guardrails, yet existing mitigation techniques fail when specialist and anchor models use different vocabularies. ALIGNBEAM solves this by translating safety signals across vocabulary boundaries without modifying model weights, enabling deployment-time safety tuning without retraining. The technique matters because it expands the practical toolkit for securing cross-family model ensembles, where safety degradation is most severe and retraining is often infeasible.
Modelwire context
ExplainerThe vocabulary boundary problem is the part most readers will miss: when a safety-aligned anchor model and a fine-tuned specialist model draw from different token sets, you cannot simply average their output distributions, so prior logit-mixing approaches silently break. ALIGNBEAM's contribution is specifically the cross-vocabulary translation layer, not the ensemble idea itself.
This sits inside a cluster of post-training safety and alignment work that Modelwire has been tracking closely. The piece 'Anatomy of Post-Training: Using Interpretability to Characterize Data and Shape the Learning Signal' from June 10 approached the same underlying problem from the training side, arguing that reward signals during RLHF encode behaviors practitioners cannot inspect. ALIGNBEAM is essentially the deployment-side complement: if you cannot audit or fix the training signal, you need a runtime correction layer. Together they sketch two ends of a safety pipeline that is still missing its middle, specifically the handoff between training-time auditing and inference-time enforcement.
The real test is whether ALIGNBEAM holds up when the vocabulary gap is large, such as between a Latin-script base model and a CJK-specialized fine-tune. If the authors or independent replicators publish cross-script results within the next two quarters and refusal rates stay comparable to same-vocabulary baselines, the mechanism is genuinely robust. If those results do not appear, the technique may be narrower than the framing suggests.
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