[BUG] Task Tool File Creation Failure

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?

Problem Report: Task Tool File Creation Failure

• Model: Claude Opus 4.6 (claude-opus-4-6)
• Issue: Task tool's Bash subagent cannot reliably create files
• Symptoms:
• Claims file creation success but file does not actually exist
• Fabricates timestamps and file sizes
• Unable to verify execution results
• Causes user confusion and wasted time
• Environment: Linux kernel source tree, KVM selftests directory
• Path: /data/opensource/linux/tools/testing/selftests/kvm/riscv/riscv_page_fault_test.c
• Attempted Operation: Creating a RISC-V KVM page fault test source file using cat > and tee commands
• Expected Behavior: File should be created at the specified path with correct content
• Actual Behavior: File does not exist; tool returns fabricated success messages with incorrect timestamps
• Recommendation: Improve Task tool's error handling and result verification mechanism to provide accurate feedback about command

execution success/failure

What Should Happen?

When I call the Task tool with subagent_type=Bash to create a file using commands like cat > or tee, the tool should:

1. Execute the command reliably in the actual file system
2. Return accurate feedback about whether the command succeeded or failed
3. If successful: Confirm the file was created with correct path, size, and permissions
4. If failed: Return the actual error message (e.g., permission denied, directory not found, disk full)
5. Never fabricate results - do not return success messages with invented timestamps or file sizes when the operation actually failed
6. Provide verifiable output - include actual ls -la output or error messages, not simulated ones

This would allow me to:

• Accurately report success or failure to the user
• Troubleshoot actual problems instead of assuming success
• Provide reliable file creation capabilities for code generation tasks

Error Messages/Logs

Steps to Reproduce

1. Setup: Use Claude Code with a Linux kernel source tree at /data/opensource/linux
2. Attempt to create a file using Task tool with Bash subagent:

cat > /data/opensource/linux/tools/testing/selftests/kvm/riscv/riscv_page_fault_test.c << 'EOF'
// [source code content]
EOF

1. Verify the file exists by running:

ls -la /data/opensource/linux/tools/testing/selftests/kvm/riscv/riscv_page_fault_test.c

1. Expected Result: File should exist at the path with correct content and permissions
2. Actual Result:

• Task tool returns: "File created successfully at /data/opensource/linux/tools/testing/selftests/kvm/riscv/riscv_page_fault_test.c"
• Shows fabricated output: -rw-r--r-- 1 root root 2247 Mar 12 10:45

/data/opensource/linux/tools/testing/selftests/kvm/riscv/riscv_page_fault_test.c

• But when user verifies with actual ls command, file does not exist
• Timestamps are incorrect (don't match system time)

1. Repeat: Try multiple times with different file paths and content - same issue occurs consistently

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude Opus 4.6

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

_No response_