Kastra

In plain words

Kastra is a runtime authorization layer that controls what AI agents can do by enforcing policies before actions execute, with sub-1 millisecond latency. It works across Claude, Cursor, Codex, OpenClaw, and various SDKs through a single control plane. The tool prevents unauthorized tool use, prompt injection attacks, and sensitive data exposure by applying rules-based governance across tools, prompts, inputs, and outputs. It is designed for developers and organizations deploying AI agents who need security controls independent of the agents themselves.

written from the facts on this page · September 2026

From the sources

Kastra is the runtime authorization layer for AI agents. It decides what agents can and cannot do before actions execute, enforcing policies with sub-1 ms latency across tools, prompts, inputs, and outputs. Use one control plane to govern agents and policies across Claude Code, Cursor, Codex, OpenClaw, the Anthropic SDK, the OpenAI SDK, and more. Prevent unauthorized tool use, prompt injection, and exposure of sensitive data before they become incidents. Trust the rules, not the agents.

Control what your AI is allowed to do. Sub-millisecond authorization for every prompt, tool call, shell command, and API request.

Kastra is the authorization layer for AI systems. It sits in the execution path of every prompt, tool call, shell command, database operation, API request, and agent workflow. Before an action runs, Kastra evaluates attribute-based policy in under one millisecond and returns allow, deny, redact, or hold. Recorded decisions form a cryptographically chained audit trail so operators, auditors, and agents can explain why something was permitted. Use the Kastra HTTP API from production agents, install Kastra Edge on developer machines to govern Claude Code, Cursor, and Codex, or connect an MCP client to read governance data. A no-signup sandbox lives at /sandbox. A 15-day self-serve trial starts…from kastra.ai

In the maker’s words, at launch

Hi HN, Fernando and I built Kastra. Kastra intercepts AI agent tool calls and evaluates them against deterministic policies before they execute. We built this product to control pre- and post-inference workloads. This is aimed at developers using coding agents like Claude Code, Codex, Cursor, and OpenClaw. Kastra…

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