Besa adds exact-action admission gates for MCP tool calls with signed capability grants
MostHat2980 · reddit · 2026-09-27
The author released Besa, a free MIT-licensed TypeScript project probing a narrower authorization boundary for agents: not who may reach a system, but whether an already-authenticated agent may execute this exact action on this exact resource, under these constraints, right now.
- Besa validates a canonical action envelope immediately before the handler, verifying a signed capability bound to the action hash, agent, tool, operation, resource, request hash, constraints, expiry, and nonce; withBesaMcp additionally binds the tool name and actual MCP arguments
- A deny never invokes the handler; allowed calls produce signed evidence linking action, capability, and result hash
- Stated limits: no replacement for IAM/OAuth/cloud authorization, v1.1.1 is unaudited, the in-memory replay store is process-local, and signed evidence only proves what a trusted recorder signed
The author asks whether exact-action admission and independently verifiable evidence should exist as a separate protocol layer or fold into IAM/MCP/cloud infrastructure.
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