Update Token Counting for Claude Fable 5 to Prevent Budget Overruns
Recalculate your prompt costs for 30% higher token density.
Update your token counting scripts to use the 'claude-fable-5' model parameter to account for the new tokenizer's 30% increased token production.
The Scenario
You are preparing a massive codebase or document set for a 1M token context window and need to ensure your prompts won't be truncated or over-budget.
Before & after
Developers traditionally estimate token counts using rough character-to-token ratios or older tokenizer versions. This manual estimation often takes 10-15 minutes of testing and can result in unexpected costs due to a 30% increase in token density.
Use the token counting API with the model parameter set to 'claude-fable-5'. This takes seconds to execute and provides precise billing and context management data.
The Prompt
I am using the new Claude Fable 5 model. Please help me estimate the token count for the following text using the updated tokenizer logic: [PASTE_YOUR_TEXT_HERE]
Claude Fable 5 and Mythos 5 use a newer tokenizer that produces roughly 30% more tokens for the same text compared to older models. Precise counting is essential to avoid hitting the 1M token context limit or exceeding budgets.
Source
Claude Platform - Claude API Docs"Use the token counting API with model: "claude-fable-5" to measure your prompts under the new tokenizer."