[BUG] Drag & drop from the VS Code Explorer silently does nothing in Remote-WSL/SSH/Dev Containers — drop handler only accepts `file://` URIs

Summary

Shift+dragging a file from the VS Code Explorer into the Claude Code panel does nothing when the window is connected to a remote (Remote-WSL, Remote-SSH, Dev Containers). No @mention is inserted, no attachment appears, no error is shown. The same drag works in a local window.

The cause is in the webview's drop handler: it accepts only file:// URIs, but remote windows produce vscode-remote:// URIs.

Environment

• Extension: Anthropic.claude-code 2.1.261 (installed remote-side, ~/.vscode-server/extensions/anthropic.claude-code-2.1.261-linux-x64)
• VS Code: 1.136.1 (commit a44adf7f53e00964ab890f9f8758a334f1fc15bc)
• Client: Windows 11
• Remote: WSL2 (Ubuntu), kernel 6.18.40.1-microsoft-standard-WSL2
• Also present in 2.1.259 (verified), so not a recent regression

Reproduction

1. Open a folder in a Remote-WSL window (Remote-SSH and Dev Containers should behave identically).
2. Open the Claude Code panel.
3. Shift+drag any file from the VS Code Explorer onto the input.
4. The drop overlay appears, but on release nothing is inserted.

Expected: an @path/to/file mention is inserted, as happens in a local window.

Root cause

In webview/index.js, the drop handler reads VS Code's internal drag formats (resourceurls, codeeditors) and passes each URI through this helper (eG0 in 2.1.261, OJ0 in 2.1.259 — minified names change per release):

async function eG0($, J) {
  if (!$.trim()) return null;
  let Z = $.trim();
  if (!Z.startsWith("file://")) return null;          // <-- here
  if (Z = decodeURIComponent(Z.substring(7)), J && Z.startsWith(J)) {
    if (Z = Z.slice(J.length), Z.startsWith("/")) Z = Z.slice(1);
  }
  return Z;
}

In a local window the Explorer hands over file:///c%3A/Users/..., which passes. In a remote window the same file is vscode-remote://wsl%2BUbuntu/home/user/project/src/app.ts, so the guard returns null and the drop is discarded silently.

The codeeditors branch has the same problem for a different reason — it reads:

let U = q.resource.external || q.resource.fsPath;

external is the vscode-remote://… string, so it also fails the file:// check. Preferring fsPath (/home/user/project/src/app.ts) would have worked here.

Note the drag detection is scheme-agnostic, which is why the overlay still appears and the failure looks like a no-op:

function E15($) {
  return Boolean($?.includes("Files") || $?.includes("resourceurls") || $?.includes("codeeditors"));
}

Suggested fix

Normalize vscode-remote://<authority>/<path> to its path before the existing logic. Patching locally with this made drag & drop behave exactly as it does on a local window:

if (Z.startsWith("vscode-remote://")) {
  let i = Z.indexOf("/", "vscode-remote://".length);  // first "/" past the scheme = start of path
  if (i < 0) return null;
  Z = "file://" + Z.substring(i);
}

Verified against the patched build (cwd /home/user/project):

| input | output |
| --- | --- |
| vscode-remote://wsl%2BUbuntu/home/user/project/src/app.ts | src/app.ts |
| vscode-remote://wsl%2BUbuntu/home/user/notes.md (outside workspace) | /home/user/notes.md |
| file:///home/user/project/README.md | README.md (unchanged) |
| vscode-remote://badauthority | null |
| https://example.com/x | null |

Making the codeeditors branch prefer resource.fsPath over resource.external would fix that path too.

Workarounds

• Type @ and pick the file — resolved remote-side, unaffected.
• Drag from Windows Explorer instead of VS Code's Explorer — that is an OS-level drag, so it takes the dataTransfer.files branch and works.
• Right-click → Copy Relative Path, paste as text.

Related

• #21044 — same bug on Remote-SSH (Cursor), closed as not planned; it guessed at vscode-remote:// but had no code-level confirmation. This report has one.
• #25128 — drag & drop failing in the VS Code panel on macOS; may or may not be the same root cause.

if (Z.startsWith("vscode-remote://")) {
  let i = Z.indexOf("/", "vscode-remote://".length);
  if (i < 0) return null;
  Z = "file://" + Z.substring(i);
}