[FEATURE] Native OS file-picker dialog to attach files from the terminal (/attach) - like Claude Desktop's upload button

Feature request

A slash command or keybinding (e.g. /attach) that opens the native OS file-picker dialog (multi-select) and inserts the chosen file paths into the prompt input box, so they become part of the message the user is typing — the same experience as the upload button in Claude Desktop.

Why the existing attachment options don't cover this

Claude Code today offers three ways to reference a file, and each one breaks down for the common "attach a few screenshots" case:

• @ file mentions — require the file to be under an added working directory and require knowing/typing the filename. Screenshots have machine-generated names (Screenshot 2026-08-02 203729.png, WhatsApp Image 2026-07-26 at 10.55.14 AM (1).jpeg) that nobody remembers, so fuzzy search doesn't help; users end up opening Explorer anyway to find out what the file is even called.
• Drag & drop — requires leaving the terminal, positioning two windows, and dragging files one context switch at a time. On a laptop without a second monitor this is exactly the friction users are trying to avoid.
• Ctrl+V image paste — works for one image already on the clipboard, but not for selecting several existing files from disk.

The result: the current workflow is minimize terminal → open Explorer → find file → copy path → return → paste → repeat per file. Claude Desktop solved this years-of-UX ago with a plain upload button; the CLI has no equivalent.

Why it matters

• Screenshots are one of the highest-value inputs for a coding agent (error dialogs, UI bugs, designs to reproduce), and they are precisely the files with unguessable names living outside the project directory.
• The interruption cost is asymmetric: the user is mid-prompt, and the missing picker forces a full window/context switch at the exact moment they're formulating a question.
• Every major GUI surface of Claude (Desktop, claude.ai, VS Code extension panel) has an attach affordance; the terminal — Claude Code's primary surface — is the only one without.

What I tried (workarounds and their limits)

1. Custom slash command running a PowerShell OpenFileDialog via the ` !... ` preamble: the dialog works, but slash-command output is sent as a prompt, not inserted into the composer — so the paths can't be combined with the message the user wants to type. This is the structural gap: extensions can send prompts but cannot pre-fill the input box.
2. Global hotkey outside Claude Code: a desktop shortcut (Ctrl+Alt+P) launching a PowerShell script that opens OpenFileDialog, puts the quoted paths on the clipboard, and SendKeys-pastes them into the focused terminal. This achieves the desired UX end-to-end — but it lives entirely outside Claude Code, is per-OS, per-user setup, and fragile (focus timing, SendKeys).

That the workaround is this easy to build (one small script + a dialog) suggests the native version is low-cost relative to the friction it removes.

Proposed behavior

• /attach (or a keybinding, e.g. Ctrl+O) opens the OS-native file dialog with multi-select.
• On confirm, the selected paths are inserted at the cursor in the prompt input box (quoted, space-separated, or as @path mentions) — the user keeps typing and sends everything as one message.
• Cancel inserts nothing.
• Works regardless of whether the files are inside a working directory (read permission can still be prompted at use time, as with pasted paths today).

Environment

• Claude Code v2.1.251, Windows 11 Home (10.0.26200), Windows Terminal / PowerShell

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