Execute Python code with full system access. Returns {success, output, result, error}. Use for: data processing, file operations, API calls, system automation, any Python task. Prefer over js_exec unless JS-specific features needed. UNLOCKED: all imports (os, subprocess, requests, pathlib), file I/O, network access. Persistent state via module-level variables across calls. Limits: 30s timeout (PYTHON_EXEC_TIMEOUT env), 100k chars, 2k lines, 20k AST nodes.

Full shell filesystem access (UNSANDBOXED, 50MB read limit). Use for all file operations. Doesn't encounter race conditions with file watchers. grep contains all the functionality of bash + powershell filesystem search. Auto-fixes code fences and smart quotes on write. Actions: read, write, edit, delete, copy, move, mkdir, rmdir, list, tree, search, grep, stat, diff, hash, touch, head, tail, duplicates. edit: [{old_text, new_text}]. grep: regex search in directories. diff: compare files/strings. hash: SHA256/MD5 checksums. duplicates: find duplicate files by hash.

Execute shell commands. Returns {success, output, exit_code, duration_seconds}. Use for: git, npm, pip, system commands, anything requiring shell. UNRESTRICTED - full privileges, no sandboxing. Windows: cmd.exe, Unix: bash. Timeout: 120s default, 600s max. Background: run_in_background=true returns task_id. Use bg_status/bg_kill/bg_list to manage. For file ops prefer fs; for Python prefer python_exec.

Execute JavaScript code in a full Node.js environment. Returns an object with keys: success (bool), output (combined stdout/stderr), stdout, stderr, exitCode, and outputTruncated (bool if output exceeded 100KB). Use this tool when: (1) manipulating JSON data where JavaScript's native handling is cleaner than Python, (2) testing algorithms where JS syntax is preferred, (3) using npm packages not available in Python, (4) working with Node.js-specific APIs. Do NOT use this tool when: (1) generating visualizations - Node.js has no DOM, canvas, or browser APIs (use python_exec with matplotlib instead), (2) the task is equally achievable in Python (prefer python_exec for consistency). The tool provides persistent state across calls via a state object that is automatically loaded from and saved to .shell0_js_state.json in the working directory. Assign values to state.myKey to persist them between invocations. Limitations: 30-second default timeout (configurable up to 600s), 100K character source limit, 2000 line limit, 100KB output cap. On timeout the process is killed. Syntax errors return in stderr with line numbers. Requires Node.js on PATH.