HandoffProbe is a local-first open-source security testing CLI for AI agent handoffs across protocol, tool and execution boundaries. It focuses on failures that can emerge when individually valid components are composed: permission widening, identity or tenant continuity problems, replay, malformed payloads, manipulated tool output and data being reinterpreted as instructions.

HandoffProbe tests the handoff itself — the trust boundary between components — with deterministic, reproducible attack cases.

v0.2.0 is now publicly available with exactly 22 stable security tests for the A2A 1.0 → MCP 2026-07-28 baseline. It can run locally, through npm, or as a reusable GitHub Action in CI.