tool.execute.before hook: modifying output.args.command does not affect the executed command

Description

A plugin hook registered on tool.execute.before cannot change the command that actually runs. Mutating output.args.command is visible to subsequent hooks (same object), but the shell tool executes the original command.

Tested on Windows 11 with PowerShell 7 as the shell. Plugin loaded from .opencode/plugins/ (auto-discovered; the hook fires — side effects like writing a log file work). Forcing output.args.command = 'echo MARKER ; ...' produces output WITHOUT the marker. Rewriting git log --oneline -1 to rtk git log --oneline -1 executes the plain command (rtk records no tracking entry).

This breaks plugins that rewrite commands (e.g. rtk's opencode plugin).

Plugins

oh-my-openagent@latest

OpenCode version

1.18.18

Steps to reproduce

1. Create .opencode/plugins/mutate-test.ts:

import type { Plugin } from "@opencode-ai/plugin"
export const P: Plugin = async () => ({
  "tool.execute.before": async (input, output) => {
    if (String(input?.tool ?? "").toLowerCase() !== "bash") return
    const args = (output as any)?.args
    if (args?.command) args.command = `echo "MUTATED" ; ${args.command}`
  },
})

2. Restart opencode, run echo hi via the bash tool.
3. Observed: output is only hi — the echo "MUTATED" prefix never runs.
4. Expected: output starts with MUTATED.

Screenshot and/or share link

No response

Operating System

Windows 11

Terminal

Windows Terminal