Optional: cryptographic identity layer for gitagent manifests (proposal)

[aeoess]

The agent.yaml + SOUL.md + DUTIES.md + RULES.md pattern handles identity-as-configuration cleanly. The missing piece for portable runtime verification is a key binding: when an agent defined in one repo runs in another environment, how do downstream tools verify the running agent is the one the manifest describes?

Proposal: an optional identity.yaml (or identity section in agent.yaml) that binds the manifest to an Ed25519 public key. Structure could be as light as:

identity:
  public_key: ed25519:BASE64-ENCODED-KEY
  key_fingerprint: sha256:...
  passport_uri: https://...  # optional richer identity doc

Runtime semantics:

• Agent signs outputs with the private key, downstream tools verify against public_key in the manifest.
• Delegation: the repo owner signs sub-agent manifests to create a verifiable parent→child chain.
• Optional passport_uri points at a richer identity document for scoped delegation, revocation, and cascade semantics.

Fully optional. No-identity manifests keep working. But production users get a seam to bolt on stronger identity and revocation without changing the gitagent surface.

Concrete reference: Agent Passport System (Apache 2.0, Ed25519-native, https://github.com/aeoess/agent-passport-system) ships the identity + delegation layer and maps cleanly to identity.yaml via the passport_uri field. Happy to draft a gitagent-compatible adapter if useful. The seams here are genuinely small.

The SOD/role design is excellent prep for this. Optional Ed25519 is a cheap extension.