OpenAIAnthropicGooglexAIPerplexity
← Back to all updatesPublished ·Anthropic• Minor
Claude Fable 5 and Claude Mythos 5 use the tokenizer introduced with Claude Opus 4.7.
The read
The same text produces roughly 30% more tokens than before Claude Opus 4.7, so prompt measurement matters.
The frame
Use the token counting API with model claude-fable-5 to measure prompts under the new tokenizer.
Primary source
Anthropic →Keep reading
See what Nova3 builds →Related updates
- Jul 26, 2026OpenAI updated GPT-5.5 Instant to improve conversational quality in decision, advice, planning, research, and shopping tasks.
- Jul 25, 2026Enterprise and Edu users can find skills under Plugins, on the Skills tab in the Plugin Directory.
- Jul 25, 2026Anthropic removed modelcard language for Claude Fable 5 and Claude Mythos 5.
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