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Agent-to-Agent (A2A) Delegation

When an orchestrator agent spawns subagents, child processes must not silently inherit unbounded power. pkg/a2a enforces cryptographic delegation envelopes and 3-step ECDH mutual authentication.

Delegation Envelope Specification

Every inter-agent task delegation is wrapped in a signed envelope:

{
  "sender_agent_id": "orchestrator-main",
  "recipient_agent_id": "subagent-researcher-1",
  "nonce": "e4c8...19b2",
  "timestamp": 1789766400,
  "mandate": {
    "role": "researcher",
    "token_budget": 20000,
    "allowed_tools": ["view_file", "read_url_content"],
    "allowed_paths": ["docs/*", "pkg/version/*"]
  },
  "signature": "ed25519:64byteSignature..."
}

Security Guarantees

  1. Replay Attack Prevention: Every message includes a unique 256-bit cryptographic nonce and a 60-second expiration timestamp. Duplicate nonces are rejected.
  2. Mandate Non-Repudiation: If a child subagent attempts an action outside the signed mandate.allowed_tools, the CEL policy engine drops the request immediately.
  3. Budget Caps: Prevents rogue subagent thrashing loops from burning API token balances.