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Such models are typically accepted when they reach high transition accuracy on sampled trajectories. We argue this is the wrong notion of adequacy for planning.\n  We show four things. (1) An LLM-synthesized CWM can pass a sampling gate at 100% transition accuracy and be $\\geq 98\\%$ state-accurate on the planner's own search distribution, yet lose systematically at play, because the $<1\\%$ it gets wrong is exactly the pivotal dynamics; the play cost of the omitted rule is $0.091$ (seed-clustered 95% CI $[0.065,0.117]$, $n=4800$). We call this the verified-vs-correct gap, and confirm it end-to-end through the synthesis pipeline. (2) The harm follows a quantitative law, $\\mathrm{danger}=\\mathrm{play\\_cost}\\times(1-\\mathrm{rarity})^N$, whose $(1-\\mathrm{rarity})^N$ gate-miss factor is proven exact ","title":"When a Verified World Model Still Loses: Play-Adequacy vs Prediction-Accuracy in LLM-Synthesized Code World Models","url":"https://arxiv.org/abs/2607.14169","vendor":"arxiv_cs_ai"},"summary":"arXiv:2607.14169v1 Announce Type: new \nAbstract: Large language models can synthesize a game's rules as executable code - a Code World Model (CWM) - which a classical planner then searches over. Such models are typically accepted when they reach high transition accuracy on sampled trajectories. We argue this is the wrong notion of adequacy for planning.\n  We show four things. (1) An LLM-synthesized CWM can pass a sampling gate at 100% transition accuracy and be $\\geq 98\\%$ state-accurate on the planner's own search distribution, yet lose systematically at play, because the $<1\\%$ it gets wrong is exactly the pivotal dynamics; the play cost of the omitted rule is $0.091$ (seed-clustered 95% CI $[0.065,0.117]$, $n=4800$). We call this the verified-vs-correct gap, and confirm it end-to-end through the synthesis pipeline. (2) The harm follows a quantitative law, $\\mathrm{danger}=\\mathrm{play\\_cost}\\times(1-\\mathrm{rarity})^N$, whose $(1-\\mathrm{rarity})^N$ gate-miss factor is proven exact ","title":"When a Verified World Model Still Loses: Play-Adequacy vs Prediction-Accuracy in LLM-Synthesized Code World Models","vendor":"arxiv_cs_ai"},"confidence":{"method":"deterministic"},"decision":"POSITIVE","issued_at":"2026-07-17T04:43:38Z","notes":"Spider vendor_press (news) news.vendor_press.v1","object":{"captured_by":"crovia.spider.vendor_press","primary_source_url":"https://arxiv.org/abs/2607.14169"},"predecessors":[],"schema":"crovia.axiom.v1","signature":"ed25519:421034958e77ee81a9bd9607d86dd975b36c287f8337c8fb1c3a1e8d6e2a6bcaef92dc07bacc17a368767299fa4ce1c5afea8ef7b9605f81bdbc73919e40f000","signer":"crovia.substrate","subject":{"observed_at":"2026-07-17T04:43:38Z","source_collector":"spider:vendor_press","target_id":"https://arxiv.org/abs/2607.14169"},"tsa":{"authority":"crovia.substrate.bootstrap","rfc3161_token":"{\"kind\":\"crovia.bootstrap.tsa\",\"source_jsonl\":\"/opt/crovia/spider/data/news/vendor_press_v1.jsonl\",\"source_seal_merkle_root\":\"spider_vendor_press_v1\",\"upgrade_path\":\"Sessione H \\u2014 OpenTimestamps weekly anchor\"}"},"zk_mode":"clear","zk_proof":null},"ledger":{"leaf_hash":"3b3bc7089629af7ca088fdc7059f3d7cfb24bba8a1f19f14d38c3dfcce79ed1e","leaf_index":322985,"ledger_path":"/opt/crovia/substrate/axiom_ledger.jsonl"},"merkle_proof":{"hash_alg":"sha256","leaf_prefix":"0x00","node_prefix":"0x01","odd_leaf_rule":"duplicate_last","path":[{"sibling":"c2737ed808e33c7cf53594b5515c42dcd28b084145386e39505c45e0a1553f86","side":"left"},{"sibling":"7e0c2af0930ec7cc9500559c4d0c4c3879f6c0f626377a0dcd0e83b5958eed1c","side":"right"},{"sibling":"35ce649311bbac3733e637a136201d04e2a7dbcf9c2a1a04f67269af20fbfdcc","side":"right"},{"sibling":"140bff0bb142b135e7285df8f900105d1946ee17090bedd3876628f5b9652527","side":"left"},{"sibling":"76fabdab88dea699652b847d6e666f62d270aa954c3a931bc4eb8587ebb2b548","side":"right"},{"sibling":"fef12197c3728f06d870239e723f414c7df9e8e044582778e065e3251b39c7ec","side":"left"},{"sibling":"e20baa8791119aeca771591615d2b5dda42707944e22980f8722d64fe8a20f4c","side":"right"},{"sibling":"5944e6d0988d989a4ae4330320fe2633624339ee8db50eaa0d3fe8981ac982cf","side":"left"},{"sibling":"e90a96bd60cc2aad32b2969366989aa5d4e0c71aeb240044c7778cca7188dc3f","side":"left"},{"sibling":"d7e66b08e4f129ea3ff266d25de4f974fe1f0d56e2fae2a6d3ae1e1565007da9","side":"right"},{"sibling":"05a09763743cdc09fc45cf454e4e3ea4a0d1cd74f9c8162b2a57e2c873160908","side":"left"},{"sibling":"de3120ef2488b8a791a686b47257da4e612256abdfcdda7519265e7edd47d041","side":"left"},{"sibling":"e86f56a4883492da5b5e7b0201324c52946e865e69b99ebb532f41fe3c658ee4","side":"right"},{"sibling":"34d85f6ad6cc7dfa79d90e2b9ff99a561bcdc75b0301bbbd3e83861f54535c1e","side":"left"},{"sibling":"f302542c38ba7c3aab7c9280dd60259ecec777dca6e6f71b6f0729b0b8791b72","side":"left"},{"sibling":"d8b9143917b539c543cf4448cec00131f8b807bd8004979c54ebe09798748c66","side":"left"},{"sibling":"9b11714124b9b951ff9450b0ee9d625a0b70b6da2cf388bd3df1475eec0b17ba","side":"right"},{"sibling":"a4523a9014d45df43e006e9210a73428c380d771f2c650a1b986910759b0cdf7","side":"right"},{"sibling":"1cecb7f447febd025aac272837c80de218aecc6485d2395a509b2a1f1b9c746e","side":"left"}]},"schema":"crovia.axiom_proof.v1","seal":{"first_collector_run_id":"","first_receipt_hash":"","jsonl_path":"/opt/crovia/substrate/axiom_ledger.jsonl","key_id":"430895f101d38164","last_collector_run_id":"","last_receipt_hash":"","leaf_count":323382,"merkle_root":"2f4d32419c80a9600aba5a480fc3fb7012ec0a695c91a1b055048e78760b65ca","public_key_hex":"cf742e26f75669dc673cb5c0786a1ae23ae8ca19c347317192ce40c28a7ff25c","run_id":"hourly_json_retrofit_20260717T053701Z","schema":"crovia.seal.v1","seal_family_version":"crovia-seal-family/1","seal_kind":"substrate_batch","sealed_at":"2026-07-17T05:38:31Z","sig_algorithm":"ed25519","signature":"495308c7bf004117807331d3f71d0b079f6bd7ed7737faa58c773b1b3e80ee84928d2d8519cc7d2b809506501aada1be6546f72c7ecda3dad5445cbb44502209","signer_version":"1.1.0"},"trust_root":{"key_id":"430895f101d38164","public_key_hex":"cf742e26f75669dc673cb5c0786a1ae23ae8ca19c347317192ce40c28a7ff25c","signature_algorithm":"ed25519","url":"/registry/canon/TRUST_ROOT.md"},"verifier":{"spec":"/registry/canon/AXIOM_RECEIPT_v1.md","url":"/v/axm_b57db51eff397d5f72a77dc777a8917e2da02e7494599ba5164f000f0b2d0d4b"}}