Implement Kernel class — wire all components

[dgenio]

Summary

Implement the Kernel class that orchestrates the full request → grant → invoke → expand → explain flow.

Constructor

Kernel(
    registry: CapabilityRegistry,
    policy: PolicyEngine | None = None,       # Default: DefaultPolicyEngine
    token_provider: TokenProvider | None = None, # Default: HMACTokenProvider
    router: Router | None = None,              # Default: StaticRouter
    firewall: Firewall | None = None,          # Default: Firewall()
    handle_store: HandleStore | None = None,   # Default: HandleStore()
    trace_store: TraceStore | None = None,     # Default: TraceStore()
)

Methods

request_capabilities(goal, context_tags=None) → list[CapabilityRequest]

Delegate to registry. Deterministic.

grant_capability(request, principal, justification) → CapabilityGrant

1. Get capability from registry (raise CapabilityNotFound if missing)
2. Evaluate policy → if denied, raise PolicyDenied with denial_reason
3. Issue token with enforced_constraints
4. Return CapabilityGrant(token, enforced_constraints)

invoke(token, args, response_mode="summary") → Frame

1. Verify token (raise TokenExpired/TokenInvalid)
2. Select route via router
3. Execute via driver. If primary fails and fallbacks exist, try next. If all fail, raise last DriverError.
4. Apply redaction (based on capability sensitivity + token constraints)
5. Apply firewall transform (with budgets from capability defaults merged with token constraints)
6. Store raw data in handle store
7. Record ActionTrace
8. Return Frame

expand(handle, query) → Frame

Delegate to handle store expand. Apply budgets to result.

explain(action_id) → ActionTrace

Delegate to trace store.

Acceptance criteria

• Full happy path: request → grant → invoke → expand → explain works end-to-end
• Policy denial raises PolicyDenied with message
• Expired token raises TokenExpired
• Tampered token raises TokenInvalid
• Driver fallback: primary fails → secondary succeeds
• All drivers fail → last DriverError propagated
• Trace recorded for every invoke
• explain() returns matching trace