Windows strict sandbox: clear refusal messages and a switch that remembers it was on

What

A sandbox is a fenced-off area where commands run with limited access to your computer. On Windows, Claude Code has a strict sandbox mode in which no command may run outside it. Two pieces changed:

• Refusal messages: when strict sandbox mode is on and a command cannot run inside the sandbox, Claude Code now builds a specific message such as 'The command did not run. Strict sandbox mode is on, so no command may run outside the sandbox'. It says what went wrong: the sandbox was switched off, was not set up, failed to start, or an exclusion was not honoured. It also tells Claude not to work around it. For Bash, the shell tool, this also depends on the CLAUDE_CODE_NANKEEN_KESTREL environment variable or the tengu_nifty_ripple server switch.
• The switch remembers being on: the Windows-only check on the CLAUDE_CODE_NANKEEN_KESTREL environment variable or the tengu_nankeen_kestrel server switch now records that it has been on once either returns true. Before, it simply returned the current value. The server switch falls back to off.

The flag server returned tengu_nankeen_kestrel as off for this site's account and for an anonymous visitor, but no reading has been taken under this release yet. Nothing has been read about tengu_nifty_ripple.

Why

Windows users in strict sandbox mode get an explanation of why a command did not run instead of a generic failure, and Claude is told not to try to get around the sandbox. Remembering that the switch was on lets later steps in the same session know the feature was used, even if it has since turned off.