FastContext 1.0 4B RL
microsoft/FastContext-1.0-4B-RL
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Released
14 Jun 2026
License: mit · microsoft/FastContext-1.0-4B-RL
AI summary
● machine-written
Microsoft releases FastContext 1.0 4B RL, a 4B coding agent subagent
FastContext-1.0-4B-RL is a 4 billion parameter model developed by Microsoft for repository exploration in coding agents. It reduces token consumption by up to 60% and improves end-to-end resolution rates by up to 5.5% through parallel tool calls and focused context provision. The model supports 262K token context and uses reinforcement learning refinement based on Qwen3-4B-Instruct.
What's new
- 4B parameter model optimized for repository exploration in coding agents
- Supports 262K token context window for extended code navigation
- Reduces main-agent token consumption by up to 60% on benchmark tasks
- Improved end-to-end resolution rates up to +5.5% when integrated with main agents
- Uses GRPO-based reinforcement learning for search and citation generation
Best for
Building or enhancing LLM-powered coding agents requiring efficient repository navigationReducing token consumption in multi-agent coding systemsFast code exploration and information extraction from large repositoriesImproving accuracy of main coding agents through focused context provision
Source: https://huggingface.co/microsoft/FastContext-1.0-4B-RL