Example: coverage-guard

coverage-guard shows how a contract can gate an action on a risk feed. For example, a levered staking vault could stop taking deposits. It is an example, not used by anything else. Simplified excerpt:

(define-public (check (feed <risk-feed>))
  (begin
    (asserts! (is-eq (contract-of feed) TRUSTED_FEED) ERR_UNTRUSTED_FEED)
    (let ((summary (try! (contract-call? feed get-coverage-summary)))
          (age (- burn-block-height (get updated-at summary)))
          (stale (> age (var-get max-age-blocks)))
          (thin (match (get coverage-bps summary) c (< c MIN_COVERAGE_BPS) false)))
      (ok { status: (if (or stale thin) "paused" "ok"),
            coverage-bps: (get coverage-bps summary), stale: stale,
            provenance: (get provenance summary) }))))

Paused below 2.0× coverage (MIN_COVERAGE_BPS u20000), or when the feed is older than max-age-blocks.
ok when coverage is n/a (no bonds to protect).
max-age-blocks is owner-settable because Bitcoin block rates differ between networks. The testnet deployment uses 5,300 (about two mainnet intervals at testnet's ~4-minute blocks).

Code	Meaning
`u200`	Untrusted feed
`u201`	Not the owner (`set-max-age-blocks`)
feed errors	Passed through, e.g. `u104` no data

Full source: contracts/contracts/coverage-guard.clar