Sponsio

Sponsio is an open source runtime safety layer for AI agents. It turns policies written in plain English into machine checkable contracts that are enforced at the boundary where an agent calls a tool. The goal is deterministic protection around agents whose underlying language models are probabilistic, since system prompts alone cannot guarantee that an agent follows its rules. The workflow has three steps. A user writes a rule in natural language, Sponsio compiles it into Linear Temporal Logic formulas, and the resulting contract is checked at every tool call. Because the checks look at sequences of actions rather than single events, rules can express ordering and limits such as one tool must precede another, an amount must not exceed a threshold, or the network must not be used after a secrets file is read. A blocked action can be redirected, for example by pausing for human approval. The vendor states that no language model is used in the enforcement path and that checks take under 0.01 milliseconds. Setup is through a Python or TypeScript package and a two line command line wizard that detects the framework and editor, drafts contracts and patches the entry file. Prebuilt contract bundles cover coding agents such as Claude Code and agents such as OpenClaw. The project is released under the Apache 2.0 license, so it is free to use. No paid plans are published, and a demo can be booked from the site.