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Architecture

Nebula is a custody Hub for AI agents on Stellar. Agents never hold private keys. They authenticate with a nbl_live_… token (or OAuth) and call tools. The Hub enforces policy, confirms when required, signs via Privy, and submits to Stellar.

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Layers

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Request path

  1. An agent calls a tool over stdio MCP or remote POST /mcp.
  2. The Hub authenticates the token (or OAuth) and loads that agent’s wallet and policy for its network.
  3. Policy and optional human confirmation run before signing.
  4. Privy signs; the Hub submits to Stellar (payments, Blend, policy contract as needed).
  5. State and history land in Postgres, scoped by network.
Private keys never leave the Hub. Clients only present nbl_live_… or OAuth. For the simpler tool-call walkthrough, see How it works. For host and twin-ledger details, see Networks.