Bolt Launches Forge, an AI Coding Agent Powered Entirely by Open-Weight Models

StackBlitz's browser-based app builder Bolt has released Forge, a new coding agent that runs exclusively on open-weight models—marking a significant shift toward cost-efficient, auditable AI development. The Forge agent operates by default on GLM 5.3 Flash, a 320-billion-parameter mixture-of-experts model from Z.ai that activates only 18 billion parameters per token, combined with post-training optimizations that deliver frontier-level coding performance. Additional model options include GLM 5.3, with Kimi K3 and DeepSeek V4 Pro available as experimental choices.