Group of 4 Under the hood
The Bash tool now understands the 'tee' command: it's sandboxed, permission-checked, and described in summaries
What
teeis now implemented as a supported shell builtin in the sandbox, piped through the existingsha*sum-style handler, and classified as awritepermission; special device targets (/dev/null,/dev/stdout,/dev/stderr,/dev/tty) are filtered out of its arguments before permission checks run.- The command path-validator now special-cases
tee: ateecall with no target paths passes immediately ("Path validation passed for tee command") instead of going through the usual working-directory restriction logic. - The basename-normalizing helper used to detect file-affecting shell commands (previously only
rm/rmdir) now also matchestee, case-insensitively and with a.exesuffix stripped. teewas added to the bash-command-summary descriptions, described as "write to files in".
Why
Previously tee wasn't recognized as a file-writing command, so it could bypass the usual write-permission and working-directory checks or produce confusing summaries; now it's treated consistently with other file-writing commands.
Names in the bundletee
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Added since
A small documentation edit on browser-use-tool touched a line naming tee after this was published.
Anthropic has trained the model to resist these prompt injections and has added an extra layer of defense. If you use the browser use tool, classifiers will automatically scan what the browser returns, such as page text or screenshots, to …agents-and-tools/tool-use/browser-use-tool see the edit
Confirmed since
Anthropic's documentation has since written up tee, on Use Claude Code on the web.
Open the session on claude.ai or the Claude mobile app to check progress or interact directly. From there you can steer Claude, provide feedback, or answer questions as in any other conversation.claude-code-on-the-web see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up tee, on Use Claude Code on the web.