Cross-Package Features (CPF-001)

Use this skill when implementing a feature that touches multiple Harmony packages (e.g., core, capabilities, blueprints, apps/console).

When to Use

• •Adding a new capability and exposing it to MCP + Console catalog/palette
• •Adding or extending workflow/HITL infrastructure and wiring UI + handlers
• •Adding a new GoldenContext domain and surfacing it across telemetry + UI
• •Any change that requires coordinated exports/barrels across packages

Implementation Order (recommended)

1. •

   Types + schemas first

   • •Define stable types/schemas at the lowest layer that owns the contract.
   • •Prefer Zod schemas where the boundary is untrusted (OCS/TCS-001).
2. •

   Core next

   • •Add shared types/logic to packages/core (avoid app-specific dependencies).
   • •If needed by Temporal workflow bundles, export from the workflow-only entrypoint (packages/core/src/wcs/workflow.ts).
3. •

   Capabilities

   • •Implement the capability in packages/capabilities/src/... and register it in packages/capabilities/src/registry.ts (deterministic, by metadata.id).
   • •Ensure NIS-001 + CDM-001 metadata is complete: metadata.id, metadata.domain, metadata.tags.
4. •

   Blueprint activities / orchestration

   • •Add/extend blueprint activities in packages/blueprints/src/activities/... (WCS-001).
   • •Prefer driving behavior through capabilities rather than adding bespoke side-effect code.
5. •

   Server integration handlers

   • •Add HTTP handlers under packages/apps/console/server/... (e.g., Slack interactive callbacks).
   • •Keep handlers thin: verify → parse → call workflow/capability → map response.
6. •

   Client UI

   • •Add pages/components last so they can rely on stable APIs and schemas.
   • •Ensure discovery metadata is surfaced consistently (domain/subdomain/tags).

Export & Registry Hygiene

• •Prefer updating existing barrels rather than creating new ones:
  • •packages/core/src/index.ts (Node-safe core exports)
  • •packages/core/src/wcs/workflow.ts (workflow-bundle-safe exports)
• •Registry keys MUST equal canonical IDs (NIS-001).
• •Ordering MUST be stable (sort by metadata.id) to keep catalogs deterministic (CDM-001).

Test Strategy (TDD-aligned)

• •Unit tests at the lowest layer that owns behavior
• •Contract tests for capabilities (TCS-001): schemas vs aiHints.exampleInput/exampleOutput
• •Integration tests at package boundaries (HTTP handler, workflow gate) only after unit/contract coverage exists

References

• •references/cross-package-features.md
• •packages/core/src/index.ts
• •packages/core/src/wcs/workflow.ts
• •packages/capabilities/src/registry.ts