20. core.load_vars

core.load_vars loads a host-resolved vars document into the caller component through explicit capture.

A vars document is a valid KDL v2 document whose concrete format is host-defined.

The term vars here refers to a literal data document convention, not to a distinct KAL variable scope.

KAL defines the semantic requirements only:

• the resolved document must parse as valid KDL v2
• the resolved document must represent literal data only
• the resolved document must not contain KAL components, operators, guards, capture blocks, or workflow-control constructs
• the resolved document must be mapped by the host into an object-shaped capture domain
• analyzable top-level keys from that host-mapped object-shaped capture domain become named capture sources

The source field contains a host-resolved data-document reference.

KAL defines only the semantic requirement:

the reference must resolve to exactly one valid KDL v2 vars document

The concrete reference form and resolution mechanism are host-defined.

KDL v2 does not require KAL to use one universal top-level node convention for vars documents in this specification.

The concrete document shape, root-node convention, and host-side mapping from KDL v2 surface syntax to that object-shaped capture domain are host-defined.

Rules:

• values in vars documents are literal-only
• workflow logic is not allowed in vars documents
• loaded keys should be analyzable from the host-mapped capture domain
• values are never imported implicitly into caller scope
• named capture sources correspond to top-level keys in the host-mapped capture domain
• _ captures the whole host-mapped capture domain object
• capture destinations follow the normal writable-destination rules
• type validation applies to declared destination types when present
• missing captured keys fail validation when analyzable
• otherwise, missing captured keys fail when evaluated
• successful capture writes follow normal component body execution order

Validation of key existence for named captures is defined against the host-mapped capture domain, not directly against raw KDL surface structure.

Example:

core.load_vars "Load environment vars" {
  source "environment-vars"

  capture {
    api_url -> locals.api_url
    retries -> locals.retries
  }
}

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