{"event":{"id":"evt-hist-20260928-claude-sonnet55-release","dedupe_key":"frontier_model_release:2026-09-28:anthropic-introduces-claude-sonnet-5-5","event_type":"frontier_model_release","title":"Anthropic introduces Claude Sonnet 5.5","summary":"Anthropic released Claude Sonnet 5.5 on September 28, 2026. Its performance and price comparisons are company claims; the dated release is distinct from the earlier Claude Opus 5.5 milestone.","occurred_at":"2026-09-28T00:00:00.000Z","published_at":"2026-09-28T00:00:00.000Z","observed_at":"2026-10-18T06:11:00.000Z","reconstructed_at":"2026-10-18T06:11:00.000Z","ingest_type":"historical_backfill","locations":null,"status":"verified","confidence":0.92,"metadata":{"bounded_canonical_search":1,"date_precision":"day","evidence_only":1,"external_postcutoff_id":"2026-09-28-claude-sonnet-5-5","global_novelty_not_proven":1,"realized_outcomes_not_inferred":1},"created_at":"2026-10-18T06:52:23.816Z","updated_at":"2026-10-18T06:52:23.816Z"},"artifacts":[{"id":"art-hist-20260928-claude-sonnet55-release","dedupe_key":"1aeb797b721467b3e4d1768a1f6235b827beec67b98b53bc0c8644d0327beda4","canonical_url":"https://www.anthropic.com/claude-sonnet-5-5","evidence_locator":"","artifact_type":"first_party_publication","title":"Anthropic introduces Claude Sonnet 5.5","summary":"","creator_entities":[],"released_at":"2026-09-28T00:00:00.000Z","content_hash":null,"metadata":[],"created_at":"2026-10-18T06:52:23.815Z","updated_at":"2026-10-18T06:52:23.815Z","relation":"documented_by"}],"signals":[]}