Status: Research snapshot / migration aid
Scope: Clarify current viewer state across three layers:

1. declared/selected IDs in ViewerRegistry,
2. runtime wiring via mod providers,
3. actual pane rendering behavior today.

During the migration, viewer IDs can appear implemented when they are only declared. This note tracks the real state so planning and issue scoping can use one source.

Viewer ID	Registry default mapping	Runtime provider wiring (Verso/mod path)	Render mode mapping	Actually rendered in pane today	Notes
viewer:webview	Yes	Yes	CompositedTexture	Yes (composited runtime path)	Canonical default web viewer ID.
viewer:wry	Declared in docs/runtime policies	Depends on mod wiring/feature flags	NativeOverlay	Partially platform/path-dependent	Not universally active in all runs.
viewer:plaintext	Yes	Core/default	EmbeddedEgui	Yes	Implemented in tile behavior text path.
viewer:markdown	Yes	Core/default	EmbeddedEgui	Yes	Implemented via markdown embedded render path.
viewer:pdf	Yes	Often remapped by Verso to viewer:webview for routing	EmbeddedEgui (policy)	Not embedded as dedicated pane renderer in current path	Present in selection/mode mapping; dedicated embed path not active in node pane behavior.
viewer:csv	Yes	Selection/runtime tests present	EmbeddedEgui (policy)	Not embedded as dedicated pane renderer in current path	Routing exists; dedicated CSV pane renderer not active.
viewer:settings	Yes (graphshell://settings)	Core/default	EmbeddedEgui (policy)	Routed to settings intents/surfaces (not generic node embed)	Special internal route.
viewer:metadata	Core-seed/default fallback in seed mode	Core/default	EmbeddedEgui (policy)	Limited/indirect path	Used as safe non-web fallback identity in seed contexts.
viewer:image	Documented target	Not yet active in default registry mapping	Intended embedded mode	Not yet	Planned in universal content model work.
viewer:directory	Documented target	Not yet active in default registry mapping	Intended embedded mode	Not yet	Planned in universal content model work.
viewer:audio	Documented target	Not yet active in default registry mapping	Intended embedded mode	Not yet	Planned in universal content model work.

• Stable today: viewer:webview, viewer:plaintext, viewer:markdown.
• Declared but not fully pane-embedded in the active path: viewer:pdf, viewer:csv, and additional documented targets.
• Special route: viewer:settings resolves into settings intents rather than a generic content pane implementation.

Use this matrix when defining work items as:

• Selection complete, render missing,
• Render mode mapped, provider wiring partial,
• Fully operational.

This avoids mixing declaration-level readiness with runtime completeness.