310250 2026-03-18 23:14:13 -0700 Web Inspector: Site Isolation: Network domain sync XHR content fallback 2026-03-18 23:14:20 -0700 1 1 1 Unclassified WebKit Web Inspector WebKit Nightly Build Unspecified Unspecified NEW InRadar P2 Normal --- 308890 1 bburg webkit-unassigned inspector-bugzilla-changes webkit-bug-importer oldest_to_newest 2191606 0 bburg 2026-03-18 23:14:13 -0700 FrameNetworkAgentProxy::didReceiveData does not have a fallback for synchronous XHR responses that exceed buffer limits or get evicted. In the legacy path, InspectorNetworkAgent checks m_loadingXHRSynchronously and falls back to base64-encoding the raw data via setResourceContent. The SI path cannot replicate this because willLoadXHRSynchronously/didLoadXHRSynchronously are not in the NetworkAgentInstrumentation interface (marked FIXME in LegacyNetworkAgent.h). Without this, sync XHR content may be missing from getResponseBody under Site Isolation. Fixing this requires adding the sync XHR hooks to NetworkAgentInstrumentation, implementing them in both LegacyNetworkAgent and FrameNetworkAgentProxy, and tracking the sync state in the proxy. Sub-bug of rdar://143782685. 2191607 1 webkit-bug-importer 2026-03-18 23:14:20 -0700 <rdar://problem/172894150>