[BUG] Input redirection broken in Bash tool

Human summary

Claude tries to run ./program < file.txt in its Bash tool, but the tool fails to pass the file contents in. Probably sandboxing issue.

bash -c "./program < file.txt" works, and cat file.txt | ./program works too.

It'd be okay if it knew not to use <, but since it expects it to work it costs a lot of tokens due to being given a bum steer by the confusion.

Machine generated spew follows:

Environment

• Platform (select one):
• [x] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: 1.0.38 (Claude Code)
• Operating System: Linux 6.11.0-28-generic (Ubuntu 24.04.2 LTS)
• Terminal: gnome terminal -> tmux -> bash

Bug Description

The Bash tool does not handle input redirection (<) correctly. Commands using stdin redirection produce no output, while the same commands work correctly with pipes. This affects standard Unix workflows and Makefile patterns.

Steps to Reproduce

1. Create a test file: echo 'test content' > test.txt
2. Create a simple C program that reads from stdin:

``c
#include <stdio.h>
int main() {
char buffer[256];
while (fgets(buffer, sizeof(buffer), stdin)) {
printf("%s", buffer);
}
return 0;
}
``

1. Compile: gcc -o test_program test.c
2. Run with input redirection: ./test_program < test.txt
3. Observe no output
4. Run with pipe: cat test.txt | ./test_program
5. Observe correct output

Expected Behavior

• ./test_program < test.txt should output the contents of test.txt
• Process substitution <() should work in Makefiles without requiring bash -c
• Standard input redirection should work as in a normal bash shell

Actual Behavior

• Input redirection (<) produces no output - the program reads 0 bytes from stdin
• Process substitution <() fails with "Syntax error: '(' unexpected"
• The same commands work only when:
• Using pipes instead: cat file | ./program
• Explicitly wrapped in bash: bash -c './program < file'

Additional Context

• The Bash tool reports it's running bash 5.2.21(1)-release
• File descriptor redirection also fails: exec 3< file && cat <&3
• This breaks common Unix patterns and makes it difficult to run standard Makefiles
• The issue appears to be a sandboxing/security restriction rather than a shell issue