STV_ADR_012: Browser-local opt-in view snapshots

Status: accepted. Date: 2026-10-28. Type/scope: software persistence. Decision owner: project owner through CR019 concept-review delegation. Supersedes: partially STV_ADR_010: Separate persistent details from hover inspection only for its unconditional no-serialization/reload-clearing policy. Superseded by: none.

Decision

Use the browser Web Storage localStorage API, synchronous guarded getItem, setItem and removeItem, with versioned JSON and independent view keys. STATE validates data against the current published graph; RENDER owns UI/wiring, LAYOUT owns validated placement and INSPECT owns ordered card reopening. See Store opt-in snapshots inde... (STV_SWR_073), Validate and reconstruct re... (STV_SWR_074), Restore presentation withou... (STV_SWR_075) and Internal interfaces and model contract. No dependency, account or server is added.

Alternatives and consequences

Cookies send state to the server and impose small payload limits. Session storage would not meet browser-restart retention. IndexedDB offers asynchronous storage but adds transactions for a bounded 200-node snapshot. Native localStorage is sufficient; reads/writes can throw and must remain recoverable. Store identifiers, exploration, geometry and transform only, never rendered HTML or hidden content. Storage is local and may be cleared by the user/browser. file URL support varies; unsupported storage produces an explanation while offline exploration works.

Platform evidence: Web Storage API and Window.localStorage documentation: https://developer.mozilla.org/en-US/docs/Web/API/Window/localStorage . Product-specific validation, isolation and recovery remain STV responsibilities. Real browser file/HTTP feasibility and failure injection are implementation gates.

Verification

Validate and store remember... (STV_TC_SW_056) and Remember and restore a real... (STV_TC_SY_070) define snapshot and real-host criteria. No runtime result is implied by this decision.

Affected components: Exploration state engine (STV_SWE_STATE), Accessible view and viewport (STV_SWE_RENDER), Semantic rank layout (STV_SWE_LAYOUT), Hover, persistent details a... (STV_SWE_INSPECT). Scoped review and acceptance are recorded in CR019 scoped concept review, round 16.