Delayed Supervision for Test-Time Language Models
Organizations: MIT CSAIL
Abstract
Test-time language models adapt a compact memory while processing the input sequence. This perspective encompasses nonlinear fast-weight learning in LaCT, associative delta-rule updates in DeltaNet, and generalized delta-rule state updates in RWKV-7. Training these models to predict the next token does not explicitly require a fact to remain accessible after many subsequent memory updates. We study delayed supervision for this test-time memory: during post-training, ask a simulator-grounded question only after a long interval of unrelated events, and supervise its answer alongside ordinary next-token prediction. Questions are evaluated on disposable branches, so their answers never enter the continuing event stream. The construction distinguishes retention from revision: a retained fact must remain valid throughout the delay, whereas a revised fact must be answered with its latest value. We evaluate this approach on LaCT-760M and plain DeltaNet-1.3B using TextWorld training trajectories and shared BABILong and RULER evaluation panels, and include a separately reported RWKV-7 comparison. Relative to event-only training, delayed QA improves BABILong by 5.48 percentage points for LaCT and 1.32 points for DeltaNet, and single-needle RULER by 1.45 and 3.27 points, respectively. The RWKV-7 comparison reports gains of 4.60 and 7.00 points on its own panels. These results support delayed semantic supervision as a practical outer training objective for usable test-time memory, while leaving open how much of the benefit derives specifically from delay rather than general question-answering and answer-termination supervision.
Figures & tables
| Backbone | Training | BABILong | RULER single-needle |
|---|---|---|---|
| LaCT | Original | 21.48 | 85.21 |
| NTP | 25.60 | 87.39 | |
| Delayed QA | 31.08 | 88.85 | |
| DeltaNet | Original | 18.68 | 80.36 |
| NTP | 21.16 | 80.24 | |
| Delayed QA | 22.48 | 83.52 |
| Task | Length | Original | NTP | Delayed QA |
|---|---|---|---|---|
| Multi-value retrieval | 2K | 36.00 | 40.00 | 37.00 |
| Variable tracking | 2K | 12.80 | 6.80 | 13.20 |
| Common-word extraction | 2K | 19.20 | 13.40 | 12.80 |
| Frequent-word extraction | 2K | 25.33 | 21.33 | 39.33 |
| Multi-value retrieval | 4K | 18.50 | 20.00 | 14.50 |
| Variable tracking | 4K | 18.00 | 8.00 | 22.40 |
Appendix figures & tables2 assets
Supplementary material from the paper’s appendix.
Appendix
| Setting | LaCT | DeltaNet | RWKV-7 |
|---|---|---|---|
| Parameters | 760M | 1.3B | 1.5B |
| World exposures | 1,024 | 1,024 | 64 |
| Effective batch (worlds) | 8 | 8 | 4 |
| Outer updates | 128 | 128 | 16 |
| QA branches / world | 12 | 8 | 2 |
| Event coefficient | 0.5 | 1 | 1 |
| Benchmark | Length | NTP | Delayed QA |
|---|---|---|---|
| BABILong | 8K | 24.00 | 29.20 |
| BABILong | 16K | 21.20 | 25.20 |
| RULER single-needle | 8K | 84.33 | 93.33 |
| RULER single-needle | 16K | 53.33 | 58.33 |
Language Model Post-Training
Language model post-training adapts pretrained models to follow instructions, reason, use tools, and meet task-specific or human-defined goals.
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