Claude Code v2.1.36, Opus 4.6 Fast Mode: 3 Key Takeaways
- Anthropic has released Fast mode for Opus 4.6 in Claude Code v2.1.36
- Offers faster response times with the same model quality
- Priced at $30 per input token MTok, with a 50% discount until February 16th
What is Fast Mode?
Anthropic deployed Claude Code v2.1.36 on February 7th. The key feature is Fast mode support for Opus 4.6.[GitHub Release] Fast mode isn’t a separate model. It’s the same Opus 4.6, but with API settings tweaked for speed.
You can toggle it on/off by typing /fast in the CLI. When activated, a lightning bolt icon appears next to the prompt.[Claude Code Docs]
The Trade-off: Cost vs. Speed
For under 200K tokens, it costs $30 per input MTok and $150 per output MTok. Above 200K, it increases to $60 for input and $225 for output. A 50% discount applies to all plans until February 16th.[Claude Code Docs]
Subscription plan users can only access it via Extra Usage. It’s not included in the existing usage allowance.
When Should You Use It?
It’s suitable for real-time debugging or rapid code iteration. Regular mode is better for CI/CD or batch jobs. Fast mode is separate from effort level. Fast mode only reduces latency while maintaining quality, while effort level can affect quality by reducing thinking time.[Claude Code Docs]
It’s currently in research preview, so pricing and features may change. Hope this helps!
Frequently Asked Questions (FAQ)
Q: Is Fast mode a different model?
A: No. It uses the same Opus 4.6 model. Only the API settings are different, which speeds things up. There’s no difference in model quality or features, only a reduction in response latency. The trade-off is a higher cost per token.
Q: Is the fee included in my existing subscription?
A: No. Fast mode usage is charged as Extra Usage from the start. It’s billed separately from the subscription plan’s base usage, and Extra Usage must be enabled. A 50% discount applies to all plans until February 16th.
Q: What happens if I hit the rate limit?
A: It automatically switches to regular Opus 4.6 mode. The lightning bolt icon turns gray to indicate a cooldown state. It will automatically reactivate once the cooldown is over. To turn it off manually, type /fast again.
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References
- Claude Code v2.1.36 Release – GitHub (2026-02-07)
- Speed up responses with fast mode – Claude Code Docs (2026-02-07)
- Manage costs effectively – Claude Code Docs (2026-02-07)