Content Quality: Compact, well-structured Briefing (469 words, within the 300-800 range). Overview, What We Know, What We Don't Know and a short Analysis are present; claims are tied to the release page that contains them.
Source Verification: All five snapshots were decompressed and read (source-0 to source-4 .html.gz); every manifest entry has status 200, no archive fallback, and suspicious_patterns null. Snapshot text was re-checked against live WebFetch of the 11.0.0 and 11.0.1 pages (identical dates and bullets), and the three uncited sibling prereleases (beta.1, rc.1, rc.2) were fetched live to confirm nothing reverted the IE11/SuspenseList removals. source-0 (11.0.0, released 30 Sep 2026 13:09 UTC): links the six prerelease notes beta.0, beta.1, beta.2, rc.0, rc.1, rc.2 (six, as the article says); nine Fixes, one Performance entry (Remove cloneNode for top-level Fragments) and four Maintenance entries, matching the article's counts; quoted fixes 'Re-attach refs when a suspended subtree reveals', 'Stop DOM nesting validation at portal boundaries' and 'Preserve the casing of camelCase custom event names' are verbatim. source-1 (11.0.0-beta.0): Breaking Changes lists 'Drop IE11 support', 'Move defaultProps into preact/compat', 'Remove automatic px suffix', 'Remove component.base', 'Remove SuspenseList' and 'Drop support for TS versions < 5.1' verbatim; 'Require initial value in useRef' is under Types, 'Switch to Object.is for hook args' under Refactors, and 'Comment denoted hydration', 'Forward ref by default', 'Add captureOwnerStack' under Features, all as stated. Note: the beta.0 page is dated 19 Aug 2025, which the article does not state, so no date error arises. source-2 (11.0.0-beta.2, 15 Jul 2026): 'Implement streamed hydration rfc' under Features, verbatim. source-3 (11.0.0-rc.0, 10 Aug 2026): 'implement use in compat', 'Support createPortal in core', 'Add useEffectEvent hook to compat' under Features; 'Leverage moveBefore rather than insertBefore when available' under Correctness; 'Compute minimal child moves with a longest increasing subsequence' under Performance; 'Bump reported React version to 19.0.0' under Maintenance, all verbatim. However, rc.0 lists FOUR Features entries (the fourth is 'Implement getServerSnapshot for useSyncExternalStore'), so the article's 'add three more Features entries' understates the list; filed as a clarification. source-4 (11.0.1, 08 Oct 2026 08:28 UTC, eight days after 11.0.0): the three Fixes, the DX entry and the Performance entry are verbatim and in the right release. All sources are first-party (github.com/preactjs, the project's own release pages, github.com is allowlisted); no independent third-party corroboration exists in the article and none is claimed, so this is a first-party-only Briefing, documented as such. No allowlist edits were needed.
Factual Accuracy: Every change is attributed to the correct release or prerelease; no change from one release is credited to another. Dates (September 30, October 8, eight-day gap) match the pages. Headline and summary: the IE11 and SuspenseList removals are stated in beta.0 notes, which the 11.0.0 notes link; the article says so openly in the Overview, and beta.1, rc.1 and rc.2 contain no reversal, so 'Stable Drops IE11 and Removes SuspenseList' is supported. Observation: the 11.0.0 page also points to preactjs.com/blog/preact-11 and the upgrade guide, which the article does not mention, and the claim that breaking changes are recorded in the earlier prerelease pages is true for those cited but the upgrade guide was not read. One minor inaccuracy: rc.0 Features count (see correction).
Overall Assessment: Accurate, carefully sourced Briefing with one small recoverable understatement. Approved with a clarification record.