The first entry is always the pin's source. Overall confidence is a weighted average of how firmly each reference supports the start and end times used above; a reference counts half as much for every 180 days older than the newest.
No official date: September 21 is the day Polymarket's[2] per-day market prices highest, at 31% on its outcome row (the page header reads 30.5%), with September 22 at 25% and September 24 at 15%, and “No release by September 30” at 22%. The figures are the chance on each row, not the Buy Yes or Buy No prices in cents beside them.
Polymarket's[1] daily market is where the September 21 date comes from: it priced that day at about 45%, ahead of September 22 (18%) and September 24 (14%), with 24.5% on no release by September 30.
CellCog traces the "Opus 5.1" name to the claude-marshmallow-eap and claude-melon-eap strings seen around August 21-24, and notes "there is no announcement, model card, API identifier, pricing page, or benchmark."
CometAPI applies the roughly 2-3 week gap from the Honeycomb early-access build to Opus 5 and says "a public release could arrive in the coming weeks," while stressing the dates remain unverified.
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