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Legacy navigation, optimism, and failure isolation

Historical 0.62 contract

Use Interaction and API by task for the current 1.0 API.

These bounded contracts are available on 1.0 and were introduced in phase 0.62. They cover navigation, optimistic edits, localized failures, and state identity. The server remains authoritative and ordinary HTML/HTMX navigation remains the fallback.

Use hedron_core.navigation.NavigationMachine for one target's generation-safe lifecycle. A response may commit only when its NavigationIdentity still matches the pending generation and target. NavigationPolicy keeps retention, focus, scroll, and prefetch limits explicit.

FastAPI/Starlette responses can expose the identity with hedron.navigation.apply_navigation_headers. The browser adapter is the opt-in hedron_elements/static/navigation-062.mjs asset; mark links with data-hedron-navigation="enhance" and a declared data-hedron-target. If the target, request, script, or transition is unavailable, the link falls back to ordinary navigation.

Prefetch is progressive and disabled unless explicitly enabled. It permits only policy-approved safe methods and same-origin URLs, applies bounded concurrency/bytes/cache behavior, and grants no authority.

Optimistic mutations

OptimisticMutation.from_reversible_toggle, from_scalar_edit, and the existing cell-edit adapter are the approved 0.62 inventory. Every new adapter requires a base revision and idempotency key, and must be confirmable, rollback-capable, and conflict-safe. Authorization, tenant, payment, secret, destructive, and other uninventoried actions stay server-confirmed.

An uncertain response uses the explicit unknown state and must be reconciled with a refetch. It is never treated as success or silently rolled back.

Failure and identity boundaries

FailureBoundary localizes retryable errors to a declared target and propagates missing fallback, fatal, or policy-defined shared-shell failures. IdentityRegistry requires one declared writer, matching targets and schemas, and bounded JSON-compatible state transfer.

See the 0.62 acceptance packet for the locked risk inventory, diagnostics, browser disposition, and release gates.