Shell completion commands trigger agent selection prompt

[sushichan044]

Describe the bug

Problem

When running shell completion commands like nr --completion, nr --completion-zsh, or nr --completion-bash in a directory without a lockfile, the agent selection prompt is displayed instead of the expected completion output.

Current Behavior

$ pwd
/Users/sushichan044
$ nr --completion-zsh
? Choose the agent : - Use arrow-keys. Return to submit.
o   npm
    yarn
    pnpm
    bun
    deno

Expected Behavior

Shell completion commands should output their results directly without agent detection, as they don't require a package manager agent.

Proposed Solution

Add onBeforeCommand hook that allows commands to perform agent-independent operations before agent detection occurs.
This hook is expected to be called after -v/--help processing but before getCliCommand().

Expected interface:

export interface RunOptions {
  /**
   * Called before agent detection and command execution.
   *
   * Useful for performing concrete, agent-agnostic operations such as generating shell-completion scripts.
   *
   * Call `exit()` to skip a command execution entirely.
   */
  onBeforeCommand?: (args: string[], ctx: { cwd: string, exit: () => void }) => void | Promise<void>
}

Expected usage:

runCli((agent, args, ctx) => {
  // main logic (requires agent)
  return parseNr(agent, args, ctx)
}, {
  onBeforeCommand: (args, { cwd, exit }) => {
    if (args[0] === '--completion') {
      const suggestions = getCompletionSuggestions(args, { cwd })
      console.log(suggestions.join('\n'))
      return exit()
    }

    if (args[0] === '--completion-bash') {
      console.log(rawBashCompletionScript)
      return exit()
    }
  },
})

Reproduction

https://stackblitz.com/edit/antfu-ni-nr-completion-results-agent-picker?file=README.md

System Info

System:
    OS: macOS 26.1
    CPU: (8) arm64 Apple M2
    Memory: 238.20 MB / 24.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.11.1 - /Users/sushichan044/.local/share/mise/installs/node/24.11.1/bin/node
    Yarn: 1.22.22 - /Users/sushichan044/.local/share/mise/installs/npm-corepack/0.34.4/bin/yarn
    npm: 11.6.2 - /Users/sushichan044/.local/share/mise/installs/node/24.11.1/bin/npm
    pnpm: 10.21.0 - /Users/sushichan044/.local/share/mise/installs/npm-corepack/0.34.4/bin/pnpm
    bun: 1.3.2 - /Users/sushichan044/.local/share/mise/installs/bun/1.3.2/bin/bun
    Deno: 2.5.6 - /Users/sushichan044/.local/share/mise/installs/deno/2.5.6/bin/deno
  Browsers:
    Chrome: 142.0.7444.162
    Safari: 26.1

Used Package Manager

n/a

Validations

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• Check that this is a concrete bug. For Q&A, please open a GitHub Discussion instead.
• The provided reproduction is a minimal reproducible of the bug.

Contributions

• I am willing to submit a PR to fix this issue
• I am willing to submit a PR with failing tests (actually just go ahead and do it, thanks!)