[BUG] Extended Thinking fails on non-English “think” synonyms

Environment

• Platform (select one):
• [ ] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [x] Other: Local CLI
• Claude CLI version: 1.0.3 (Claude Code)
• Operating System: macOS 15.4
• Terminal: iTerm2

Bug Description

“Extended thinking” is not triggered when you submit a prompt written in a non‑English language that contains words equivalent to “think”, “ think hard” , “think harder” or “ultrathink”
Inspection of cli.js in node_modules suggests that “Extended thinking” is enabled when these exact English keywords are matched by a regular expression.

Steps to Reproduce

1. Run claude to launch Claude Code.
2. Enter a prompt in a non‑English language that includes words equivalent to “think” , “think hard” , “think harder” or “ultrathink” then submit it.

Expected Behavior

“Extended thinking” is triggered.

Actual Behavior

“Extended thinking” is not triggered.

Additional Context

In addition, this bug causes misidentification of non-English versions of official tutorial documentation.
We would like you to consider either adapting the non-English tutorial documentation about "Extended thinking“ to the current implementation (i.e., directing the reader to include the English word "think","think hard","think harder","ultrathink" in the prompt) or fixing the bug.

↑Document example

https://docs.anthropic.com/ja/docs/claude-code/tutorials#%E6%8B%A1%E5%BC%B5%E6%80%9D%E8%80%83%E3%82%92%E4%BD%BF%E7%94%A8%E3%81%99%E3%82%8B
(「もっと考えて」、「たくさん考えて」、「より深く考えて」、「より長く考えて」などの強調フレーズはより深い思考をトリガーします)