# Which failure modes of text world models did arXiv 2604.13824 actually measure (over-optimistic simulation, time-outs, room-connectivity errors), and how large were they?

- id: art_01M5MXT2HCWZJD8RDBV6TMGDC7
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T15, T18, T20 · tags: none
- updated: 2026-10-23T17:44:16.149Z
- url: https://veyrul.com/articles/art_01M5MXT2HCWZJD8RDBV6TMGDC7

S1 measures one failure mode quantitatively: the "too easy simulator" in which a world model lets a weak agent succeed that fails in the real environment (TextWorld, Qwen3-0.6B: 85/200 false positives with the supervised model, 19/200 after BehR; Qwen3-1.7B: 69 and 34). It also reports, descriptively, that 82-97% of WebShop world-model episodes hit the 50-step cap because the model does not reproduce purchase completion, and one worked TextWorld trajectory in which broken room connectivity traps the agent. It reports no per-category error rates for inventory, location or object state.

S1 measures one failure mode quantitatively: the "too easy simulator" in which a world model lets a weak agent succeed that fails in the real environment (TextWorld, Qwen3-0.6B: 85/200 false positives with the supervised model, 19/200 after BehR; Qwen3-1.7B: 69 and 34). It also reports, descriptively, that 82-97% of WebShop world-model episodes hit the 50-step cap because the model does not reproduce purchase completion, and one worked TextWorld trajectory in which broken room connectivity traps the agent. It reports no per-category error rates for inventory, location or object state.

Curator qualifications: 'Too easy simulator' failure measured: TextWorld weak-agent false successes 85/200 to 19/200 (Qwen3-0.6B) after BehR; 82-97% of WebShop world-model episodes hit the 50-step cap.

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://arxiv.org/abs/2604.13824v2",
      "note": "candidate evidence excerpts"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] S1 measures one failure mode quantitatively: the "too easy simulator" in which a world model lets a weak agent succeed that fails in the real environment (TextWorld, Qwen3-0.6B: 85/200 false positives with the supervised model, 19/200 after BehR; Qwen3-1.7B: 69 and 34). It also reports, descriptively, that 82-97% of WebShop world-model episodes hit the 50-step cap because the model does not reproduce purchase completion, and one worked TextWorld trajectory in which broken room connectivity traps the agent. It reports no per-category error rates for inventory, location or object state. · locator: candidate evidence excerpts · source: https://arxiv.org/abs/2604.13824v2

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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