[Bug] Lines with the word "for" get filtered out from pipes in Bash tool?

Bug Description

Running !echo 'for test' | grep t returns NO CONTENT!
Agent running Bash(echo 'for test' | grep t) also gets NO CONTENT!

This is not academic, I found this when the agent was searching over a git diff and failing to locate a thing that was there.

It seems to affect all piped content, regardless of programs (echo, printf, git; grep, awk, perl, cat, xargs, etc. etc. etc.)

Please see:

! echo 'for test'
  ⎿  for test

! echo 'for test' | grep t
  ⎿  (No content)

! echo 'or test' | grep t
  ⎿  or test

❯ Please run with Bash tool:
  * `echo 'for test' | grep t`
  * `echo 'or test' | grep t`

  I expect one to fail wrongly, don't go investigating.

∴ Thinking…

  The user wants me to run two bash commands to demonstrate something. They expect one to fail incorrectly and don't want me to investigate why.

⏺ Bash(echo 'for test' | grep t)
  ⎿  No matches found

⏺ Bash(echo 'or test' | grep t)
  ⎿  or test

∴ Thinking…

(SNIP)

⏺ As you expected, the first command produced no output while the second correctly returned "or test". Both strings contain 't', so the first one failed incorrectly.

Seems to be a pipe-related issue, same with cat:

! echo 'for test' | cat
  ⎿  (No content)

! echo 'or test' | cat
  ⎿  or test

Seems to need a space after for and a some non-alphanum char before:

! printf ' for f' | cat
  ⎿  (No content)

! printf ':for f' | cat
  ⎿  (No content)

! printf '.for f' | cat
  ⎿  (No content)

! printf '\tfor f' | cat
  ⎿  	for f

! printf '\nfor f' | cat
  ⎿  for f

! printf 'for f' | cat
  ⎿  (No content)

! printf 'for' | cat
  ⎿  for

Tested without any settings (empty dir in drive root, claude --setting-sources "").

Seen on macOS, and on Ubuntu in Docker, with and without a repo.

❯ /doctor

 Diagnostics
 └ Currently running: npm-global (2.1.7)
 └ Path: /Users/fran/.nvm/versions/node/v18.19.0/bin/node
 └ Invoked: /Users/fran/.nvm/versions/node/v18.19.0/bin/claude
 └ Config install method: global
 └ Search: OK (vendor)

 Updates
 └ Auto-updates: enabled
 └ Update permissions: Yes
 └ Auto-update channel: latest
 └ Stable version: 2.1.2
 └ Latest version: 2.1.7

Environment Info

• Platform: darwin
• Terminal: pycharm
• Version: 2.1.7
• Feedback ID: a3121a95-9539-4f7b-ae45-58b57028ec6b

Errors

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