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AI-generatedURLCache returnCacheDataElseLoad heuristic freshness when servers omit cache headers
Background URLCache's .returnCacheDataElseLoad policy serves a cached response if one exists, even when the entry is stale by HTTP freshness rules. When a response lacks explicit freshness headers such as Expires or Cache-Control: max-age , the cache applies an undocumented heuristic—approximately 10% of the time elapsed since the Date header—to decide wheth