pr: 136703
summary: Disable cross-cluster functionality for `_fleet/_fleet_msearch`
area: Search
type: breaking
issues: []
breaking:
  title: Disable cross-cluster functionality for `_fleet/_fleet_msearch`
  area: Search
  details: |-
    This endpoint is largely used for local searches only and is not compatible with true cross-cluster searches where
    arbitrary number of indices and remotes can be specified. Although it is meant to accept an index parameter that
    denotes a single searchable target, such a limitation can be bypassed through various means.

    Keeping in view this endpoint's stated intent and future scope, cross-cluster functionality is being explicitly disabled.
  impact: |-
    This endpoint will no longer accept remote indices. Should one be provided, a top-level error is returned with
    an appropriate explanation.
  notable: false
