Simular's Agent S4 evolves computer-use interfaces, lifting Qwen3.8-27B to 21.3% on OSWorld V2
Simular introduces Agent S4, which does not solve tasks directly but evolves a repository of computer interfaces via population-based evolution while the task agent's model and harness stay fixed. A meta-agent selects parent repositories, examines their trajectories on synthetic training tasks without success labels, writes mutated or crossed-over repositories, and evaluates them on validation tasks. With the evolved repository, Qwen3.8-27B reaches 21.3% binary success on the 108-task OSWorld V2 benchmark, versus 5.56% for the fixed-interface Qwen CUA. On ScienceBoard, the evolved repository solves 99 of 169 tasks versus 93 for the seed.
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Simular introduces Agent S4, which does not solve tasks directly but evolves a repository of computer interfaces via population-based evolution while the task agent's model and harness stay fixed. A meta-agent selects parent repositories, examines their trajectories on synthetic training tasks without success labels, writes mutated or crossed-over repositories, and evaluates them on validation tasks. With the evolved repository, Qwen3.8-27B reaches 21.3% binary success on the 108-task OSWorld V2 benchmark, versus 5.56% for the fixed-interface Qwen CUA. On ScienceBoard, the evolved repository solves 99 of 169 tasks versus 93 for the seed.
Key findings from the stored brief
- With the evolved repository, Qwen3.8-27B reaches 21.3% binary success on OSWorld V2, versus 5.56% for Qwen CUA with fixed interfaces.
- The meta-agent learns only from synthetic training tasks with no success labels; it never sees benchmark tasks or validation trajectories.
- Running with a scratch VM built three times as many new interfaces and gave the best partial score; the best binary success came from the run without it.
- On ScienceBoard, the evolved repository solves 99 of 169 tasks, compared with 93 for the seed repository.
Source claims not independently checked; results are self-reported by the company on its own benchmark runs.
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Evidence & sources
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Why this may matter
The work treats interfaces as a separate axis of improvement from the model and harness. If the reported gains hold, open models could gain substantially from better interfaces alone, and repositories could keep evolving as models and applications change.
Limits and open questions
Source claims not independently checked; results are self-reported by the company on its own benchmark runs.
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