contracts.rules_fragment_targets

Fragment target registry orphan check.

Fails loud at startup when the fragment target registry contains entries whosefragment_blockis not defined by any page leaf template. Such registrations are inert: boosted requests hitting that HX-Target resolve to a block that does not exist, producing a runtimeBlockNotFoundError (for required targets) or silently falling back to full-page composition (for optional targets).

Relation to sibling checks:

• check_page_shell_contractsiterates each page template and reports missing required blocks per-template. High per-page fidelity but noisy when a registration is simply dead.
• This check iterates each registration and reports orphans once per target — a single high-signal issue per registry typo. It is also the only check coveringrequired=Falsetargets.

Severity tiering:

• required=True(contract-required or ad-hoc required): ERROR. Render-time would raiseBlockNotFoundErroron any boosted request matching the target id.
• required=False: WARNING. Silent render fallback keeps requests working, but the registration is almost certainly a typo or stale.

Apps can demote globally via app.override_contract_severity("fragment_target_orphan", Severity.WARNING).