Summary & Key Takeaways ​

• ttok CLI tool for token counting has been released as version 1.0.
• The default tokenizer was switched from GPT-4 to the GPT-5/GPT-6 family.
• Experimental data suggests GPT-6 uses the same tokenizer as GPT-5 models.
• All seven GPT models (5.5, 5.6 Sol/Terra/Luna, 6 Astra/Sol/Luna) showed identical token counts on a test corpus.
• This confirms no input-count change for GPT-6 on the tested corpus.

Our Commentary ​

This is a genuinely useful piece of detective work! Simon Willison's ttok reaching 1.0 is cool, but the real gem here is the experimental confirmation about the GPT-5/6 tokenizer. We've all been wondering. It's the kind of practical, developer-focused insight that cuts through the marketing noise. I appreciate the effort to verify these details, it helps us build more predictable AI applications.