[Hackathon] stellarminds-ai: capsule-emit trust layer — verifiable, anchored records for NANDA agents

[StevenMih]

What this adds

capsule-emit-nanda — a drop-in NANDA trust plugin backed by the Agent Action Capsule spec (IETF draft). Every corroborated receipt triggers a capsule_emit.emit() call, sealing the reputation event to a tamper-evident ledger that any third party can independently verify — with zero changes to existing NANDA agent code.

A companion demo (StripeCapsuledPayments) shows the same capsule pattern applied to payment events.

How it works

NANDA scenario  →  ctx.plugins.get("trust").report(agent, evidence)
                →  CapsuleEmitTrust.report()
                →  capsule_emit.emit(action, operator, agent_input, agent_output, anchor=True)
                →  anchored to https://anchor.agentactioncapsule.org/v1/digest (live public log)
                →  capsule sealed to local JSONL ledger
                →  agent-action-capsule verify --store capsule_ledger.jsonl  ✔

Three gates before a receipt contributes to reputation:

1. Valid — Ed25519 issuer signature verifies
2. Corroborated — distinct counterparty co-signed the same interaction
3. Anchored — a capsule was emitted and is present in the ledger

Gate 3 is the novel contribution: an agent whose interactions are never anchored gets zero reputation score even if their receipts are individually valid and corroborated. The capsule ledger is the authoritative, externally-auditable record.

Installable package

pip install -e examples/capsule-emit

# scenario.yaml
layers:
  trust: capsule_emit

Smoke tests

$ pytest examples/capsule-emit/tests/ -v
tests/test_smoke.py::test_trust_report_and_score  PASSED
tests/test_smoke.py::test_sandbox_pay             PASSED

Both plugins instantiate cleanly, exercise a happy path each, and sandbox mode runs without any Stripe credentials.

Files changed

Path	Role
examples/capsule-emit/capsule_emit_nanda/trust.py	CapsuleEmitTrust — NANDA Trust protocol implementation
examples/capsule-emit/capsule_emit_nanda/payments.py	StripeCapsuledPayments — standalone payment demo
examples/capsule-emit/pyproject.toml	Installable package config, entry-points
examples/capsule-emit/README.md	Plugin docs
examples/capsule-emit/tests/test_smoke.py	Smoke tests
examples/stripe-capsule-payment/README.md	Stripe demo docs with protocol-conformance caveats

Demo clarifications

• StripeCapsuledPayments is a standalone demo, not a conforming NANDA Payments protocol implementation. The NANDA Payments protocol requires pay(to, amount, ref) -> Receipt; this class uses a different signature. @runtime_checkable only checks method names, so an isinstance check will falsely pass — documented in the module docstring.
• On the real-Stripe path, payee is not enforced at the Stripe level (no destination/transfer_data) — the capsule commits to the payer/payee pair by digest, but the charge does not route to the payee.