WebWorld：以瀏覽器作為世界模型實現網頁程式碼的自我改進

摘要

VLM驅動的網頁代碼自我改進存在一個結構性缺陷：提出修復的模型同時也是評判修復的模型，而在該評判者視角下的視覺合理性，並不能很好地代表頁面是否真的能運作。此循環所缺少的是一個VLM無法欺騙的對手方，而瀏覽器正是這樣的對手方：它是一個確定性的、可執行的模擬器，模擬HTML工件在使用者操作下的行為，並且除了名稱之外，它就是網頁代碼的世界模型。我們提出WebWorld，這個介面讓VLM先驗可以自主地與這個「瀏覽器即世界模型」互動，並決定哪些互動會成為監督訊號。在每一輪中，VLM發出評論，規劃器將其編譯為型別化的互動契約；瀏覽器重新執行候選結果，且僅在目標進展與所有先前已驗證能力皆獲保留時，才發出驗收證明；經認證的轉變會累積成一個品質棘輪，而這是SFT輸出唯一能接觸到的東西。在匹配的訓練設定下，WebWorld-27B在HTMLBench-400上比Raw-27B提升了5.3分，在MiniAppBench-Val上提升了14.9分，並在互動式HTML生成上達到Kimi-K2.6與GPT-5.4等強大前沿系統的水準。同等規模的消融實驗顯示，瀏覽器背書的准入機制帶來了這項效益：沒有驗收證明時，匹配的9B模型提升幾乎消失殆盡。

English

VLM-driven self-improvement of web code has a structural flaw: the model that proposes the repair is the model that judges it, and visual plausibility under that judge is a poor proxy for whether the page actually works. What the loop is missing is a counterparty the VLM cannot fool, and the browser already is that counterparty: a deterministic, executable simulator of how an HTML artifact behaves under user actions, and in everything but name a world model for web code. We present WebWorld, the interface that lets a VLM prior interact with this browser-as-world-model autonomously and decides which interactions become supervision. Each round, the VLM emits a critique that the planner compiles into a typed interaction contract; the browser re-executes the candidate and issues an acceptance certificate only when both target progress and preservation of every previously verified capability hold; certified transitions accumulate as a quality ratchet that is the only thing the SFT export ever sees. Under matched training, WebWorld-27B improves Raw-27B by 5.3 points on HTMLBench-400 and 14.9 points on MiniAppBench-Val, and reaches the level of strong frontier systems such as Kimi-K2.6 and GPT-5.4 on interactive HTML generation. Equal-size ablations show that browser-backed admission carries the gain: without the certificate, the matched 9B lift nearly disappears.