Claude Code thinking mode

In recent versions, Claude Code has changed how thinking mode works compared to the version in Claude Code in Action.

From https://github.com/anthropics/claude-code/issues/9072#issuecomment-3648376741:

• Only ultrathink is the special keyword that enables thinking on a per-request basis. Phrases like “think”, “think hard”, “think more” don’t have any impact on the allocated thinking token budget.
• If you need fine-grained control over the token budget (vs. just allocating all 31,999 tokens to the thinking budget), you can set the MAX_THINKING_TOKENS environment variable. This setting takes priority over ultrathink, so if you set a lower MAX_THINKING_TOKENS threshold, ultrathink doesn’t override it.

From https://code.claude.com/docs/en/common-workflows#use-extended-thinking-thinking-mode:

• Sonnet 4.5 and Opus 4.5 have thinking enabled by default. All other models have thinking disabled by default.
• When thinking is enabled (via /config or ultrathink), Claude can use up to 31,999 tokens from your output budget for internal reasoning.
• Note that ultrathink both allocates the thinking budget AND semantically signals to Claude to reason more thoroughly, which may result in deeper thinking than necessary for your task.

• #claude