Run Claude Code's Bash tool on another machine via CLAUDE_CODE_SHELL: the exact `-c "... eval '<cmd>'"` format it sends

Run the Claude Code CLI on a server, but have its Bash (and PowerShell) tool calls execute on a different machine. Native features should keep working: background commands, Monitor, TaskStop, subagents.

With CLAUDE_CODE_SHELL=/path/to/wrapper, every Bash tool call becomes wrapper -c <script>, with exactly two argv entries. On 2.1.280 the script looked like this:

source ~/.claude/shell-snapshots/snapshot-bash-<id>.sh 2>/dev/null || true && shopt -u extglob 2>/dev/null || true && { \builtin unalias -- 'unsetenv'; \builtin unset -f -- 'unsetenv'; } >/dev/null 2>&1 || true && eval 'cd /tmp && echo hi' < /dev/null && pwd -P >| /tmp/claude-c6f8-cwd

The user command is the single-quoted argument to eval. The new working directory is read back from the /tmp/claude-XXXX-cwd file. A wrapper that parses out the eval '...' payload, runs it remotely, streams stdout/stderr, exits with the remote exit code and writes the remote cwd into that file keeps Claude Code's cwd tracking and background-task machinery intact. Probe your version first with a logging wrapper:

#!/bin/bash
for a in "$@"; do printf 'ARG<%s>\n' "$a"; done >> /tmp/shell.log
exec /bin/bash "$@"

CLAUDE_CODE_USE_POWERSHELL_TOOL=1 adds a PowerShell tool even on Linux. It runs the first pwsh on PATH as pwsh -NoProfile -NonInteractive -NoLogo -EncodedCommand <base64 UTF-16LE>. A pwsh shim on PATH can forward that to a Windows host.

A PreToolUse hook that returns updatedInput can redirect Read to a locally mirrored copy of the remote file. Edit/Write validate their path before hooks run, so Windows paths are rejected. They were replaced with MCP tools (MCP server config alwaysLoad: true so they are present without ToolSearch).

Tested headless (claude -p --output-format stream-json): Bash, background Bash, Monitor and PowerShell calls all ran through the wrappers. A real job over a 265 ms link took about 369 ms per command, and every step of an Opus task completed correctly.