Doc role: Canonical registry spec for index_registry. Status: Active / canonical Kind: Atomic registry Related docs:

• ../2026-02-22_registry_layer_plan.md (registry ecosystem and ownership model)
• SYSTEM_REGISTER.md (register hub and routing boundary)

Policy authority: This file is the canonical policy authority for index_registry semantics and boundaries. Policy in this file should be distilled from canonical specs and accepted research conclusions.

1. Local-floor policy: Local index/search capability must remain available without network providers.
2. Source-metadata policy: Query results carry explicit provider/source metadata for traceability.
3. Provider-fanout policy: Multi-provider query behavior and fallback are explicit and diagnosable.
4. Retrieval-boundary policy: Index retrieval informs surfaces/features but does not assume semantic authority ownership.

Defines search backends for local lookup, retrieval, and timeline/history queries.

In scope:

• search provider registration
• query fanout and result contracts
• history/timeline retrieval backends

Out of scope:

• command surface UX
• viewer rendering
• storage formats beyond provider contracts

This registry is a named capability surface within the Register. It should expose stable lookup and capability contracts, keep failures explicit, and avoid hidden fallback semantics.

Canonical interfaces:

• query(text) -> Iterator<Result>
• describe_backend(id) -> IndexCapability
• suggest(scope, text) -> Iterator<Suggestion>

• Index queries return structured results with explicit source metadata.
• Local search must function without network providers.
• History retrieval is a first-class index capability, not a side channel.

• federated and peer-backed providers
• result ranking policy profiles

• semantic retrieval fusion
• background index health scoring

• Registration, lookup, and fallback behavior are covered by registry contract tests.
• At least one harness or scenario path exercises the registry through real app behavior.
• Diagnostics channels emitted by this registry follow the Register diagnostics contract.
• Registry ownership remains explicit and does not collapse into widget-local or ad hoc fallback logic.