Reproduce with a real same-tab history traversal in a target browser. Record the pageshow event and event.persisted; do not infer bfcache from a fast Back navigation alone.
Separate eligibility from correctness. A page can be eligible and restore stale user-visible state, or be ineligible for a legitimate reason. Use browser diagnostics before prescribing headers or event removal.
On pageshow with persisted === true, revalidate only volatile state that may have changed while the page was frozen: authentication visibility, permissions, cart/account data, connection state, and time-sensitive UI. Make the resume path idempotent so repeated restores do not duplicate listeners, observers, timers, sockets, or analytics.
Release or pause resources on the appropriate lifecycle signal and reopen them on restore when their API requires it. Do not use unload as a reliable finalization hook; mobile termination can skip it and it can affect bfcache behavior.
Register beforeunload only while there is real unsaved user data that needs a confirmation. Remove it when the dirty state clears.
Do not default to location.reload() on every persisted pageshow. A blind reload can discard drafts, repeat unsafe navigation, double instrumentation, or hide the missing resume contract. Prefer targeted reconciliation unless a fresh document load is the product's explicit safe contract.
Add a browser regression that loads state, mutates it or changes it from a second context, navigates away, goes Back, confirms whether restoration was persisted, and asserts the post-restore state and resource counts.

Quick probes

Listen once for pageshow and log persisted, current auth/data version, and active connection/listener counts.
In browser DevTools, run the bfcache eligibility test and record the blocking reason instead of guessing from source.
Traverse A -> B -> Back twice; a duplicate callback on the second cycle often exposes non-idempotent resume wiring.
Change logout/account/cart state in another tab before Back and assert that private or stale state is not exposed after restore.

Boundary with sibling skills

deeplink-hydration owns the first cold URL-to-screen reconstruction.
pwa-offline-cache-contracts owns service-worker and Cache Storage bytes.
realtime-transport-contracts owns reconnect, resume cursor, heartbeat, and event ordering. This skill owns only whether restore triggers exactly one resource reopen.
webview-bridge-pages owns native WebView renderer/app lifecycle.

PR-worthiness gate

Require a real browser history traversal plus evidence of either a persisted restore or a concrete eligibility blocker. Tie the lifecycle path to a user-visible stale/private state, duplicated or dead resource, lost work, or measurable navigation regression, then add the smallest Back/Forward test.

Reject weak findings: the mere presence of pageshow, pagehide, unload, a cache header, or a fast Back navigation; a cleanup that is already idempotent; or a hypothetical stale-state claim with no restore sequence. Do not propose no-store or unconditional reload solely to silence a bfcache diagnostic.

Output shape

Start with a disposition: confirmed, candidate/needs evidence, reject, or route. Report the navigation sequence, browser, persisted/eligibility evidence, state or resource that became wrong, sibling-skill boundary, smallest reconciliation or eligibility fix, and the Back/Forward regression that confirms the result. State explicitly when the browser did not restore from bfcache. If the report lacks persisted or eligibility evidence, label it as a candidate with an evidence gap rather than a confirmed lifecycle defect.

Sources

web.dev, Back/forward cache: https://web.dev/articles/bfcache
MDN, pageshow: https://developer.mozilla.org/en-US/docs/Web/API/Window/pageshow_event
MDN, pagehide: https://developer.mozilla.org/en-US/docs/Web/API/Window/pagehide_event
MDN, PageTransitionEvent.persisted: https://developer.mozilla.org/en-US/docs/Web/API/PageTransitionEvent/persisted
Public prior-art issue showing stale restored state and the risks of simplistic unload/reload remedies: https://github.com/undur/wonder-slim/issues/27

browser-page-lifecycle-bfcache-contracts

Browser page lifecycle and bfcache contracts

Checklist