ADR 0012: Host Extension System
- Status: Accepted
- Date: 2026-07-22
- Anchors: Extension system · Plugin system
Context
Beyond agent skills, the Career OS needs discovery sources, send channels, optional UI panels, and exporters — without forking into micro-products or cloud upsells. Plugins alone (skills) are too narrow; an open npm require of the host is too wide.
Alternatives considered:
| Option | Pros | Cons |
|---|---|---|
| Contribution points + extension-sdk | Broad but gated | More manifest surface |
| Plugins only | Simpler | Cannot cleanly add UI/discovery/send |
| Hard-code all adapters in core | Control | Blocks Horizon 4 ecosystem |
Decision
Adopt a host extension system with packages/extension-sdk and declared contribution points:
discovery.source,send.channel,agent.skill(via plugin host),ui.panel,ui.status,timeline.exporter,scheduler.jobType.
Rules:
- User enablement + visible permissions.
- Send channels use the send façade (ADR 0009).
- UI contributions use brand tokens; no streak/guilt widgets.
- Default off for third-party; first-party may ship enabled only with zero sensitive perms.
- Fail closed on missing capabilities; crash isolation from identity storage.
Consequences
Positive
- One OS feel with optional “calm rooms.”
- Clear path for official board adapters without core bloat.
- Aligns with non-goals (no surveillance extensions).
Negative / tradeoffs
- Contribution API stability matters early — version
engines.jobjitsu. - UI sandboxing complexity for
ui.panel.
Follow-ups
- Share enablement UX patterns with plugins.
- Forbid extensions that default-upload résumés to third-party clouds.
