Plan First, Act Later: Streaming Reasoning for Executable Memory in Robot Control
Organizations: Peking University · PKU-FirstMoveAI Lab · JD Logistics · University of California, Berkeley ·
Abstract
Long-horizon robot manipulation requires a robot to remember task-relevant information beyond its short observation window. Existing memory-augmented policies typically retrieve relevant information from history and reason over it at execution time, placing a heavy reasoning burden on the high-level model. To address this challenge, we propose PAL (Plan first, Act Later), a hierarchical memory framework for vision-language robot manipulation. It maintains a short-term visual buffer, a semantic-event memory, and an executable subtask\_list. A high-level vision-language model (VLM) converts streaming visual observations into the subtask\_list. At execution time, the VLM selects the currently relevant subtask from the subtask\_list and passes it to a low-level vision-language-action (VLA) policy. To teach the model what to write to memory and when to update it, we introduce a two-stage data generation procedure that first expands sparse update supervision and then uses self-labeling with task-grounded verification to generate training data that better match the state distribution encountered during execution. We evaluate our approach on memory-dependent benchmarks and real-world manipulation tasks. On RoboMME, PAL achieves a 56.05% success rate, outperforming the strongest baseline, FrameSamp-Modul, at 44.51%. In real-world experiments across four manipulation tasks, \pal{} reaches 60.83% overall success, surpassing MemER (45.00%) and FrameSamp-Modul (28.33%). These results show that proactively writing future-relevant subtasks into hierarchical memory improves long-horizon visual reasoning and robot control. Code and videos can be found on our website: https://qinghangliu.github.io/pal-webpage/
Figures & tables
| Method | Short-video | Long-video | In-context | Episode-start | AVG |
| Baselines | |||||
| 10.67 | 28.45 | 11.72 | 36.15 | ||
| EventVLA | 27.60 | 19.00 | 32.50 | 21.33 | |
| FrameSamp-Modul | 41.87 | 46.00 | 27.05 | 72.96 | |
| MemER | 37.52 | 28.00 | 41.00 | 65.11 | |
| GPT-6-astra + VLA | 31.71 | 66.00 | 28.00 | 56.67 | |
| PatternLock | RouteStick | VideoPlaceOrder | VideoPlaceButton | |||||
|---|---|---|---|---|---|---|---|---|
| Variant | Update freq. | Final acc. | Update freq. | Final acc. | Update freq. | Final acc. | Update freq. | Final acc. |
| Sparse Label | 2.68 | 22.00% | 3.34 | 50.00% | 0.00 | 0.00% | 0.00 | 0.00% |
| (-14.6%) | (-8.7%) | (-100.0%) | (-100.0%) | |||||
| Stage 1 Only | 4.32 | 24.00% | 5.28 | 30.00% | 1.34 | 18.00% | 1.38 | 18.00% |
| (+37.6%) | (+44.3%) | (+34.0%) | (+38.0%) | |||||
| Update Gate | 3.10 | 78.00% | 3.66 | 82.00% | 1.00 | 80.00% | 1.00 | 78.00% |
| Method | PatternLock | PickXtimes | VideoPlaceOrder | VideoUnmask | Overall |
|---|---|---|---|---|---|
| FrameSamp-Modul | 30.00 10.00 | 40.00 30.00 | 13.33 5.77 | 30.00 0.00 | 28.33 3.82 |
| MemER | 33.33 5.77 | 0.00 0.00 | 46.67 30.55 | 100.00 0.00 | 45.00 6.61 |
| Ours | 40.00 0.00 | 53.33 15.28 | 50.00 0.00 | 100.00 0.00 | 60.83 3.82 |
Appendix figures & tables8 assets
Supplementary material from the paper’s appendix.
Appendix
| Configurations | Values |
|---|---|
| Network Architecture | |
| Base VLM | Qwen3-VL-4B-Instruct |
| Low-level policy | Pretrained MemER VLA |
| Action chunk length | |
| Fine-tuning | LoRA on language-model linear layers |
| Frozen modules | Vision tower and aligner |
| Method | Short-video | Long-video | In-context | Episode-start | AVG | ||||||||||||
| Video Umsk | Video Repick | Video UmskS | Pattern Lock | Route Stick | Move Cube | Insert Peg | Video PlcBtn | Video PlcOrd | Button Umsk | Button UmskS | Pick HighL | Stop Cube | Pick Xtimes | Bin Fill | Swing Xtimes | ||
| Baselines | |||||||||||||||||
| 20.44 | 0.44 | 18.67 | 2.89 | 4.67 | 26.00 | 1.56 | 31.11 | 25.78 | 22.22 | 6.67 | 11.33 | 6.67 | 42.89 | 30.00 | 35.56 | 17.93 | |
| EventVLA | 66.00 | 30.00 | 17.60 | 4.00 | 27.60 | 44.00 | 4.00 | 22.00 | 16.00 | 60.00 | 12.00 | 12.00 | 46.00 | 48.00 | 6.00 | 10.00 | 26.57 |
| FrameSamp-Modul | 32.67 | 30.44 | 24.44 | 53.56 | 66.67 | 77.78 | 7.56 | 60.00 | 32.00 | 25.11 | 18.22 | 22.89 | 42.00 | 87.33 | 39.56 | 92.00 | 44.51 |
| MemER | 81.33 | 25.33 | 38.00 | 16.67 | 12.00 | 82.67 | 6.67 | 30.00 | 26.00 | 72.00 | 21.33 | 70.67 | 0.00 | 79.33 | 56.67 | 59.33 | 42.38 |
| Configurations | Values |
|---|---|
| Conditioning-video sampling | Every timesteps |
| Execution action chunk | |
| VLM query | Once per action chunk |
| Visual buffer input | uniformly sampled frames |
| Policy seeds |
| Task | Level 1 | Level 2 | Level 3 | Level 4 |
| PickXtimes | 2 successful picks | 3 successful picks | 4 successful picks | – |
| VideoPlaceOrder | 2 placements | 3 placements | 4 placements | 5 placements |
| PatternLock | 1 movement | 2 movements | 3 movements | 4 movements |
| VideoUnmask | No difficulty levels | |||
Memory-Augmented VLMs
Memory-augmented vision-language models use persistent or retrieved context to improve reasoning across long inputs and interactions.
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