PhantomEnvironments: 7B LLM Trained in Synthetic RL Environments Matches Agents 10x Its Size

CShorten30 · x · 2026-10-03

Anmol Kabra's team released PhantomEnvironments, fully synthetic RL environments that turn off-the-shelf LLMs into strong search agents.

A 7B LLM trained with RL in PhantomEnvs performs like an agent 10x its size
Environments generate at $0 cost, require no distillation, and are fully open-source
The bet: agent training is bottlenecked by RL environments, and synthetic environments are the biggest lever for scaling data
The team won a large NVIDIA GPU compute grant to continue work on synthetic data and self-improving agents
Upcoming: Snorkel AI Frontier Data Summit (Oct 8), oral at COLM's LSEI workshop and poster at LLA workshop (Oct 9)

Paper is out; code is coming soon as a hero run finishes on the new NVIDIA compute.

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