How Platform Extensions work

Audience: Builders and operators on HUMΛN HumanOS.
Canon: kb/155 · ADR docs/architecture/platform-extensions-adr.md

What you get

Platform Extensions add org-scoped surfaces without forking core apps:

1. Command Plane (CP) — cp_extension sections (dashboards, artifact lists, metrics, alerts, learning hooks, or sandboxed iframes).
2. Companion — companion_module modes, sidebar panels, tools, and composer quick actions.

Three marketplace modes

Mode	Meaning
Standalone extension	marketplace_assets.asset_type = extension, manifest humanos.extension.v1. Installs CP + optional Companion surfaces only.
Bundled extension	An agent/connector/workflow manifest includes cp_extension / companion_module; installs with that asset.
Bundle	humanos.bundle.v1 composes agents, connectors, extensions, workflows in install_order.

Security model (short)

• Server-driven (default): Only registered section types run in the host — schema validation is the main gate.
• Sandboxed iframe: Strict sandbox, hash-before-load, humanos-extension-protocol-v1 postMessage — requires manual review for marketplace certification. See docs/architecture/platform-extension-vetting-checklist.md.

Where to go next

• Building CP UI: docs/guides/building-first-cp-extension.md
• Companion: docs/guides/companion-modules-author-experience.md
• Composing assets: docs/guides/building-a-bundle.md