[BUG] Claude Code produces no output when asked to “put response in tags”

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When using Claude Code, prompts that ask the model to “put the output in tags” sometimes result in no output at all, even though similar prompts with explicit formatting (e.g. square brackets) work correctly.

This appears to be a prompt interpretation / output suppression issue, not a user error.

What Should Happen?

Claude should return a haiku wrapped in reasonable tags (for example <haiku>...</haiku>) or ask for clarification if “tags” is ambiguous.

Actual Behavior

Claude produces no response at all (empty output).

Control Test (Works as Expected)

Prompt:

Please write a haiku about Rabbit. Put it in square brackets.

Output:

[
Soft fur, pink nose bright
Bounds through clover fields with joy
Silent paws on moss
]

Error Messages/Logs

There was not output for the prompt in CLI

Steps to Reproduce

Steps to Reproduce

• Open Claude Code in any directory

• Run the following prompt:

Please write a haiku about Rabbit. Put it in tags.

Observe that no output is produced.

Claude Model

Other

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.7 (Claude Code)

Platform

Other

Operating System

Ubuntu/Debian Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

This is the screenshot of the conversation.

<img width="724" height="713" alt="Image" src="https://github.com/user-attachments/assets/3b7222ee-9117-45a4-884e-1b8741d13aed" />