Tasfia Zaman

Author directory

2026

Entity-level unlearning is usually evaluated by what a model says: whether it stops naming the target, refuses a query, or shifts a Truth Ratio distribution. These output-level tests, however, do not show whether a subject’s internal representation has been attenuated. We introduce the Entity Representation Unlearning Framework (ERUF), a representation-aware framework that mines subject-specific activation signatures, suppresses the corresponding activation direction, and distills the behavior into LoRA parameters. Among evaluated baselines, ERUF is the only method that jointly achieves surface level suppression, internal attenuation, and utility preservation. On TOFU forget10, ERUF achieves FQ =0.99 and MU =0.62, matching reported oracle utility while approaching oracle forget quality. Across most standard foundation-model settings, ERUF maintains low leakage and low internal target activation (SMR =0.00–1.10%, EL10 <0.06, utility drift <3%). On Llama-3.1-8B, adversarial entity recovery falls from 63.89% to 20.15%, while name-agnostic recovery decreases by 72.7–77.4%. Joint surface/internal diagnostics further reveal scale-dependent behavior in reasoning-prior models that surface metrics alone would miss. We interpret these results as operational evidence of representation-level attenuation, not as a formal guarantee of irreversible deletion. Code is available in the repository.
Attention sinks assign large, largely content-independent attention to the first position. Ran-Milo et al. (2026) explain GPT-2’s sink with a parameter-level circuit: a learned query bias 𝐛Q aligns with the key projection of the first position’s effective positional encoding, whose few massive coordinates amplify the score. They infer that other architectures build sinks differently but do not measure this claim. We reproduce the original intervention effects and stress-test their causal interpretation. Baseline plus nine interventions and four structural analyses reproduce under the original evaluation, with two scope qualifications; the massive coordinates are exactly 138, 378, 447. Yet nullifying 𝐛Q leaves 44.5% of the sink, which follows an activation-dependent query route into the same first-position key. This *anchor*–*route* distinction unifies the extensions: with GPT-2 scale, the bias route fades while the activation-dependent route concentrates into fewer carrier heads; across 16 checkpoints in four families, no qualitative profile over mutually available conditions spans all families; and across five pre-training runs, anchoring recurs despite unstable coordinate identities. In GPT-2-small at 40 tokens, Swap EPE incurs about one quarter of the cross-entropy cost of Remove First PE. The stable phenomenon is an anchoring computation, not a universal parameter-level circuit, so mitigation must be validated against the target model’s wiring.