claude-code - 💡(How to fix) Fix [Bug] grep shim misdirection causes agents to bypass permission allowlist with absolute paths [1 participants]

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/rugheid/.local/share/claude/versions/2.1.128 (expected in multi-process scenarios)\n at Nq6 (/$bunfs/root/src/entrypoints/cli.js:2764:2177)\n at uGH (/$bunfs/root/src/entrypoints/cli.js:2764:1257)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-05-05T12:26:49.162Z"},{"error":"Error: Failed to fetch version from https://downloads.claude.ai/claude-code-releases/latest: timeout of 30000ms exceeded\n at yP5 (/$bunfs/root/src/entrypoints/cli.js:2762:5605)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-05-05T16:56:44.815Z"},{"error":"Error: Failed to fetch version from https://downloads.claude.ai/claude-code-releases/latest: timeout of 30000ms exceeded\n at yP5 (/$bunfs/root/src/entrypoints/cli.js:2762:5605)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-05-05T16:56:44.816Z"},{"error":"AxiosError: timeout of 5000ms exceeded\n at <anonymous> (/$bunfs/root/src/entrypoints/cli.js:120:13305)\n at emit (node:events:92:22)\n at <anonymous> (/$bunfs/root/src/entrypoints/cli.js:119:3321)\n at request (/$bunfs/root/src/entrypoints/cli.js:122:2467)\n at async As6 (/$bunfs/root/src/entrypoints/cli.js:447:4799)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-05-05T17:10:31.968Z"}]

TL;DR

The issue can be addressed by treating grep, /usr/bin/grep, and command grep as the same tool in the permission matcher to prevent agents from bypassing the intended policy.

Guidance

• Review the permission matcher configuration to ensure it handles different grep commands uniformly.
• Consider implementing an opt-out mechanism for the grep shim to prevent agents from pivoting to alternative grep commands.
• Verify that error messages are branded consistently as grep to avoid confusing agents and causing them to switch to different grep commands.
• Investigate the feasibility of updating the ugrep implementation to align more closely with GNU grep behavior and flag handling.

Notes

The provided error logs do not directly relate to the grep shim issue but indicate other problems with the application, such as lock acquisition failures and timeouts. Addressing these issues may also be necessary to ensure the overall stability of the system.

Recommendation

Apply a workaround by treating grep, /usr/bin/grep, and command grep as the same tool in the permission matcher, as this directly addresses the described issue and prevents policy bypasses.