From Single-Actor Environments to Multi-Actor Event Worlds: Can LLMs Be Event World Models?
Organizations: Emory University
Abstract
World models help agents assess the consequences of their actions before acting. Many real systems, however, involve multiple actors who make their own decisions, can evolve even when the agent takes no action, and are only partially observed through event logs. We formalize these systems as event worlds and ask whether large language models can predict future observations from the log and the agent's proposed actions. We build complementary benchmarks from human Diplomacy games and real Polymarket trades. Our hierarchical framework compares prediction with and without other actors' actions, then tests multi-step rollouts, predictions for actions never taken, and usefulness to agents. Fine-tuning and more data improve prediction when all actors' recorded actions are given. With only the agent's action, models struggle when other actors strongly affect the outcome, and larger models and longer histories help little. This gap also limits multi-step prediction and agent decisions, with models overestimating plan success. Yet imagined experience and initialization from world models can still improve policy learning. Anticipating other actors' actions remains a central challenge for event world modeling.
Figures & tables
| Diplomacy | Polymarket | |
|---|---|---|
| World type | board game | market |
| Actors | 2 or 7 players | anonymous traders |
| Observation | the board | trading statistics |
| Hidden part | players’ intentions | order book, beliefs |
| Actions | move, hold, support | buy or sell |
| Horizon | one phase | one hour |
| Diplomacy | Polymarket | ||||||||
| Setting | Model | EM | EM high | EM low | F1 | Acc | Acc high | Acc low | CRPS |
| Task J (joint action) | |||||||||
| Zero-shot | GPT-6-Luna | 29.1 | 3.4 | 55.2 | 90.8 | 43.0 | 36.8 | 48.0 | 0.42 |
| GPT-6-Sol | 40.5 | 10.1 | 71.4 | 96.3 | 54.6 | 48.7 | 59.5 | 0.55 | |
| SFT | Qwen3-1.7B | 59.7 | 23.6 | 96.4 | 96.9 | 66.1 | 62.5 | 69.0 | 0.29 |
| Qwen3-8B | 65.1 | 30.8 | 100.0 | 97.7 | 65.5 | 60.5 | 69.5 | 0.29 | |
| Diplomacy | Polymarket | ||||
|---|---|---|---|---|---|
| Task | Model | F1 closed | F1 open | Acc closed | Acc direct |
| J | Qwen3-1.7B | 91.9 | 97.5 | 60.2 | 64.4 |
| Qwen3-8B | 94.1 | 97.9 | 61.2 | 63.8 | |
| GPT-6-Luna | 65.7 | 91.7 | 57.4 | 35.6 | |
| GPT-6-Sol | 83.4 | 96.4 | 57.4 | 55.6 | |
| S | Qwen3-1.7B | 55.1 | 86.0 | 55.6 | 58.6 |
| F1 | Spurious | |||
|---|---|---|---|---|
| Model | S | J | S | J |
| GPT-6-Luna | 47.7 | 30.1 | 45.9 | 89.7 |
| GPT-6-Sol | 56.5 | 57.9 | 40.4 | 83.3 |
| Qwen3-1.7B | 44.0 | 73.0 | 51.5 | 33.1 |
| Qwen3-8B | 44.3 | 77.3 | 59.6 | 29.4 |
| Training data (Qwen3-1.7B policy) | SC | Success (%) |
| Behavior policy (DipNet) | 0.24 | 61.0 |
| Real 1k | 0.58 | 47.5 |
| Imagined 1k | 0.62 | 43.0 |
| Real 1k + imagined 1k | 0.29 | 53.5 |
| Real 2k | 0.23 | 54.0 |
| Imagined 2k | 0.48 | 47.5 |
| Line of work | Main prediction or evaluation target | Relation to our study |
|---|---|---|
| Text, web, tool world models | Observations after an agent’s actions | We extend evaluation to logs with multiple actors whose future actions are unknown. |
| Visual and driving world models | Frames, scene states, or joint trajectories | Event logs can record actions and observations at irregular times. |
| Multi-agent benchmarks | Agents’ collaboration and competition | We evaluate world predictions from human game records and real market logs, then their usefulness to an agent. |
| Models of other actors | Other participants’ actions or beliefs | These predictions are one part of predicting the world’s future observations. |
| Event forecasting | Future events from records or news | Our predictions additionally condition on the agent’s proposed actions. |
| Offline model-based RL | Dynamics and policies learned from logged transitions | We examine the difficulty introduced by unknown actions of other actors. |
Appendix figures & tables20 assets
Supplementary material from the paper’s appendix.
Appendix
| Diplomacy | Polymarket | |
|---|---|---|
| clock | phase counter | physical time in seconds |
| horizon | one phase | chosen; 1 h (also 5 min, 24 h) |
| actors | 7 (or 2) players | taker wallets |
| action | one order per unit; hold if none | 0 to many orders (time, direction, size) |
| log | boards, orders, results | orders in earlier blocks |
| observation | units, centers | prices, flow, depth proxies |
| Question | Experiment | Evaluation reference | Diplomacy | Polymarket | Sec. |
| Q1: every action given | Does the model predict the next observation when every actor’s action is given? | the log | next board from all players’ orders | price move over the window from all orders | 6.1 |
| Does more data or a larger model help, and is pretraining needed? | the log | 5k to 320k transitions; 0.6B to 8B parameters; training from scratch | same | 6.1 | |
| Does the model know how much the world changes as time passes? | the log | horizons of 5 min, 1 h, and 24 h | 6.1 | ||
| Does what the model learns hold when the world shifts? | the log | two-player games, unseen in training | markets that open after the training period | 6.1 | |
| Q2: only the agent’s action | How much does knowing the other actors’ actions improve prediction? | the log | Task J vs. Task S, by interaction and when the agent issues no orders | Task J vs. Task S, including windows where the agent does nothing | 6.2 |
| Do history, predicting the other actors’ behavior, or scale close the gap? | the log | up to 10 previous phases; factored variant, its orders resolved by the engine; data and model size | up to 10 previous hours; factored variant | 6.2 |
| Seed | J | S | SF | SF+engine | Top-1 |
|---|---|---|---|---|---|
| 42 | 59.7 | 20.1 | 22.2 | 23.1 | 47.6 |
| 43 | 59.6 | 19.6 | 21.5 | 22.1 | 46.8 |
| 44 | 60.7 | 19.9 | 23.1 | 23.4 | 48.1 |
| Mean (sd) | 60.0 (0.6) | 19.8 (0.3) | 22.2 (0.8) | 22.9 (0.7) | 47.5 (0.7) |
| Setting | Model | EM | EM high | EM low | F1 | EM | EM high | EM low | F1 |
|---|---|---|---|---|---|---|---|---|---|
| Task J (joint action) | |||||||||
| Zero-shot | GPT-6-Luna | 29.1 | 3.4 | 55.2 | 90.8 | 27.8 | 3.6 | 52.4 | 89.8 |
| GPT-6-Sol | 40.5 | 10.1 | 71.4 | 96.3 | 53.3 | 18.8 | 88.3 | 96.5 | |
| Few-shot (3-shot) | GPT-6-Luna | 27.6 | 1.6 | 54.0 | 89.8 | 23.2 | 1.4 | 45.4 | 89.1 |
| GPT-6-Sol | 43.8 | 12.1 | 76.0 | 96.0 | 49.7 | 14.7 | 85.3 | 96.6 | |
| Setting | Model | Acc | Acc high | Acc low | Dir | CRPS | Acc | Acc high | Acc low | Dir | CRPS |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Task J (joint action) | |||||||||||
| Zero-shot | GPT-6-Luna | 43.0 | 36.8 | 48.0 | 56.2 | 0.42 | 45.9 | 40.6 | 50.2 | 57.2 | 0.45 |
| GPT-6-Sol | 54.6 | 48.7 | 59.5 | 56.5 | 0.55 | 55.4 | 51.3 | 58.8 | 57.6 | 0.63 | |
| Few-shot (3-shot) | GPT-6-Luna | 44.1 | 41.1 | 46.5 | 56.4 | 0.41 | 41.6 | 37.1 | 45.3 | 56.6 | 0.39 |
| GPT-6-Sol | 52.7 | 52.3 | 53.1 | 58.4 | 0.49 | 52.5 | 51.3 | 53.5 | 59.0 | 0.43 | |
| Diplomacy (EM) | Polymarket (Acc) | ||||
| Axis | Setting | J | S | J | S |
| Data (1.7B) | 5k | 48.9 (11.3) | 16.2 (0.8) | 62.0 (56.5) | 56.6 (53.2) |
| 20k | 59.7 (23.6) | 20.1 (1.6) | 66.1 (62.5) | 59.9 (55.2) | |
| 80k | 74.7 (49.8) | 23.0 (1.9) | 69.5 (66.7) | 61.8 (55.4) | |
| 320k | 88.4 (77.0) | 25.4 (1.9) | 71.6 (69.1) | 64.9 (58.9) | |
| Size (20k) | 0.6B | 57.6 (19.2) | 20.5 (1.6) | 63.3 (59.2) | 58.1 (53.8) |
| Diplomacy (EM) | Polymarket (Acc) | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Data | Initialization | J | J high | J low | J, 2p | S | J | J, later | S |
| 20k | pretrained | 59.7 | 23.6 | 96.4 | 61.1 | 20.1 | 66.1 | 67.4 | 59.9 |
| random | 32.0 | 4.6 | 59.9 | 0.3 | 10.2 | 60.8 | 59.6 | 57.8 | |
| 320k | pretrained | 88.4 | 77.0 | 100.0 | 88.4 | 25.4 | 71.6 | 74.0 | 64.9 |
| random | 66.2 | 32.9 | 100.0 | 11.0 | 24.1 | 67.5 | 65.4 | 61.7 | |
| Qwen3-1.7B | Qwen3-8B | Baseline | ||||
| Split | All | High | All | High | All | High |
| Diplomacy, Task J | ||||||
| 7p | 60.9 | 22.9 | 65.7 | 30.7 | 52.0 | 4.0 |
| 2p | 61.1 | 38.6 | 69.6 | 53.0 | 53.1 | 23.9 |
| Diplomacy, Task S | ||||||
| 7p | 19.7 | 1.2 | 19.8 | 1.2 | 7.3 | 1.5 |
| Outcome known | Acc, test later | |||
|---|---|---|---|---|
| Model | Test | Later | Task J | Task S |
| GPT-6-Luna | 81.9 | 1.6 | 43.0 46.7 | 46.1 48.5 |
| GPT-6-Sol | 68.1 | 0.0 | 54.6 57.5 | 48.5 52.6 |
| Qwen3-1.7B (SFT) | – | – | 66.1 67.4 | 59.9 61.4 |
| Qwen3-8B (SFT) | – | – | 65.5 70.7 | 60.2 63.1 |
| LightGBM | – | – | 68.8 67.1 | 61.4 61.8 |
| Diplomacy (EM) | Polymarket (Acc) | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Model | Task | |||||||||||
| Qwen3-1.7B (SFT) | J | 58.9 | 59.4 | 59.6 | 60.1 | 59.7 | 65.5 | 66.5 | 66.8 | 66.2 | 66.5 | |
| S | 19.9 | 22.2 | 21.9 | 21.1 | 20.8 | 60.5 | 60.8 | 61.9 | 61.8 | 61.1 | ||
| S, low | 38.8 | 43.6 | 42.8 | 41.2 | 40.7 | 63.8 | 63.8 | 65.0 | 64.9 | 63.7 | ||
| S, high | 1.3 | 1.2 | 1.3 | 1.2 | 1.2 | 56.5 | 57.2 | 58.0 | 58.0 | 58.0 | ||
| GPT-6-Sol | J | 40.5 | 47.4 | 53.3 | 54.5 | 51.7 | 54.6 | 56.3 | 55.4 | 54.1 | 54.8 | |
| Diplomacy (EM) | Polymarket (Acc) | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Model | J | S | SF | SF+engine | Share | J | S | SF | Share |
| GPT-6-Luna (zero-shot) | 29.1 | 6.7 | 9.3 | 17.2 | 0.24 | 43.0 | 46.1 | 47.6 | 0.06 |
| GPT-6-Sol (zero-shot) | 40.5 | 7.5 | 11.9 | 17.1 | 0.36 | 54.6 | 48.5 | 52.6 | 0.12 |
| Qwen3-1.7B (SFT) | 59.7 | 20.1 | 22.2 | 23.1 | 0.50 | 66.1 | 59.9 | 60.4 | 0.16 |
| Qwen3-8B (SFT) | 65.1 | 20.8 | 22.9 | 23.4 | 0.56 | 65.5 | 60.2 | – | 0.13 |
| DipNet policy + engine | – | – | – | 24.7 | – | – | – | – | – |
| Model | All units | Interacting | EM high |
|---|---|---|---|
| Most frequent order | 22.6 | 16.2 | 0.1 |
| GPT-6-Luna (zero-shot) | 16.8 | 10.9 | 1.5 |
| GPT-6-Sol (zero-shot) | 20.7 | 16.5 | 0.1 |
| Qwen3-1.7B (SFT, 3 seeds) | 29.6 | 25.5 | 1.9 |
| Qwen3-8B (SFT) | 30.7 | 26.6 | 1.8 |
| Qwen3-1.7B (SFT), | 36.1 | 31.9 | 1.8 |
| Task S EM | Others’ orders | ||||
|---|---|---|---|---|---|
| Model | none | messages | blank | SF | SF + msg. |
| Qwen3-1.7B, press-tuned | 18.3 | 18.2 | 17.6 | 47.0 | 47.9 |
| GPT-6-Sol | 8.9 | 11.1 | 10.2 | 31.8 | 32.9 |
| GPT-6-Luna | 6.8 | 6.9 | 7.1 | 26.3 | 26.2 |
| Retreat | Adjustment | Both | ||||
|---|---|---|---|---|---|---|
| Model | idle | acting | idle | acting | idle | acting |
| GPT-6-Luna (zero-shot) | 23.0 | 9.0 | 77.8 | 70.0 | 38.6 | 49.1 |
| GPT-6-Sol (zero-shot) | 35.8 | 17.9 | 92.4 | 91.8 | 51.9 | 66.5 |
| Qwen3-1.7B (SFT) | 45.6 | 18.7 | 80.7 | 82.5 | 55.6 | 60.6 |
| Qwen3-8B (SFT) | 47.7 | 23.9 | 85.4 | 82.5 | 58.4 | 62.4 |
| Diplomacy, 5-step chains | Polymarket, 24 hours | ||||||
|---|---|---|---|---|---|---|---|
| Task | Model | EM closed | EM open | F1 closed | F1 open | Acc closed | Acc direct |
| J | Qwen3-1.7B (SFT) | 5.6 | 65.4 | 91.9 | 97.5 | 60.2 | 64.4 |
| J | Qwen3-8B (SFT) | 13.2 | 68.8 | 94.1 | 97.9 | 61.2 | 63.8 |
| J | GPT-6-Luna | 0.0 | 42.2 | 65.7 | 91.7 | 57.4 | 35.6 |
| J | GPT-6-Sol | 0.2 | 57.2 | 83.4 | 96.4 | 57.4 | 55.6 |
| S | Qwen3-1.7B (SFT) | 0.0 | 22.0 | 55.1 | 86.0 | 55.6 | 58.6 |
| Task S form (other actors imagined) | Task J form (other actors given) | |||||||
| Model | F1 | Insensitive | Spurious | Size pred/ref | F1 | Insensitive | Spurious | Size pred/ref |
| GPT-6-Luna (zero-shot) | 47.7 | 6.0 | 45.9 | 3.4/3.9 | 30.1 | 0.1 | 89.7 | 9.5/3.9 |
| GPT-6-Sol (zero-shot) | 56.5 | 4.8 | 40.4 | 3.9/3.9 | 57.9 | 0.3 | 83.3 | 7.6/3.9 |
| Qwen3-1.7B (SFT) | 44.0 | 6.0 | 51.5 | 5.4/3.9 | 73.0 | 3.2 | 33.1 | 4.3/3.9 |
| Qwen3-8B (SFT) | 44.3 | 5.6 | 59.6 | 5.6/3.9 | 77.3 | 2.9 | 29.4 | 4.3/3.9 |
| Model | Sign | Insensitive | Magnitude | Monotonicity |
|---|---|---|---|---|
| GPT-6-Luna (zero-shot) | 93.6 | 6.9 | 1.74 | 0.20 |
| GPT-6-Sol (zero-shot) | 84.1 | 15.4 | 2.94 | 0.21 |
| Qwen3-1.7B (SFT) | 52.2 | 41.4 | 0.77 | 0.12 |
| Qwen3-8B (SFT) | 52.3 | 34.2 | 0.93 | 0.02 |
| Task | Model | WM | W2R | CR |
|---|---|---|---|---|
| J | Qwen3-1.7B (SFT) | 55.8 | 50.8 | 0.78 |
| J | Qwen3-8B (SFT) | 55.6 | 50.6 | 0.78 |
| J | GPT-6-Luna | 18.2 | 34.2 | 0.53 |
| J | GPT-6-Sol | 41.0 | 41.4 | 0.64 |
| S | Qwen3-1.7B (SFT) | 82.8 | 41.2 | 0.63 |
| S | Qwen3-8B (SFT) | 82.8 | 42.2 | 0.65 |
| Agent | Task | Real | WM | W2R | CR |
|---|---|---|---|---|---|
| Supervised | J | 65.0 | 55.8 | 50.8 | 0.78 |
| S | 65.0 | 82.8 | 41.2 | 0.63 | |
| RL | J | 67.4 | 55.6 | 50.2 | 0.74 |
| S | 67.4 | 85.2 | 46.4 | 0.69 |
| Training data | Real | Imagined | Pairs |
|---|---|---|---|
| Real 2k | 2,000 | 0 | 12,974 |
| Real 1k + imagined 1k | 1,000 | 1,000 | 12,580 |
| Imagined 2k | 0 | 2,000 | 12,271 |
LLM World Models
Large language model world models predict how environments change so agents can plan, learn, and evaluate actions before execution.
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