OpenAIAnthropicGooglexAIPerplexity
← Back to all updatesPublished ·Anthropic• Minor
Anthropic launched Claude Fable 5 and Claude Mythos 5 with 1M context by default.
The read
The operator change is 1M context, 128k output, and adaptive thinking by default in the new Claude models.
The frame
Fable 5 is widely released, Mythos 5 sits inside Project Glasswing, so access differs by model.
Primary source
Anthropic →Keep reading
See what Nova3 builds →Related updates
- Jun 12, 2026Anthropic publicly documented stop_details on refusal responses, with category and explanation fields for routing.
- Jun 12, 2026Claude Opus 4.8 defaults the effort parameter to high across all surfaces.
- Jun 12, 2026Claude Opus 4.8 lowers prompt caching’s minimum cacheable prompt length to 1,024 tokens versus Opus 4.7.
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