LinkedIn post · Sep 1, 2026, 7:32 PM UTC

Fable 5.1 (and Mythos 5.1) just released

Engagement on LinkedIn, as of 2026-10-19

Source: LinkedIn activity page (reactions, comments, reposts) and LinkedIn creator analytics export (impressions, engagements).

Same price as Fable 5, cache reads 75% cheaper

Stronger long-horizon agentic coding, research, and document/spreadsheet/slide work

Improved grounding digs into primary sources (e.g., earnings transcripts) instead of secondary coverage

Fable 5.1 = public version with cyber/bio safety fallbacks; Mythos 5.1 = same model, full capabilities, Project Glasswing only

Beats Fable 5 and Opus 5 on a hard browser-agent benchmark (82% vs 74% vs 57%)

First published on LinkedIn on Sep 1, 2026, 7:32 PM UTC (original). Kept here in full so it stays available.