[BUG] WSL/WSLg: image paste fails because wl-paste returns BMP into a .png path

Claude actually found:
Confirmed the root cause. Look at the BMP header from your clipboard screenshot:

PC bitmap, Windows 3.x format, 124 x 78 x 32, 3 compression, image size 38688...

3 compression = BI_BITFIELDS. WSLg only ever forwards Windows→Linux clipboard images as image/bmp (confirmed above — wl-paste -l offers only image/bmp, no image/png), and Windows encodes them with BI_BITFIELDS compression. Claude Code's clipboard-image decoder doesn't handle that BMP variant, so it grabs the bytes, fails to decode, and silently drops it — same failure whether triggered by Ctrl+V or Alt+V, since both funnel into the same decode step.

This used to work before I updated claude this morning - but I also updated wsl2 at the same time so I am not sure if it is claude regression or wsl2 changed BMP format.

Confirming this on Claude Code 2.1.263 / WSL2 (Ubuntu, WSLg) — same root cause as above: wl-paste -l only ever offers image/bmp, and the BMP is BI_BITFIELDS-compressed, which the downstream decoder rejects.

This is a client-side workaround only, to unblock people until Claude Code fixes the decoding/format-selection upstream — it doesn't touch Claude Code itself. Here's a workaround that fixes it a different way: instead of wrapping wl-paste, a small background daemon watches the actual Wayland clipboard and republishes the image as a real image/png entry whenever a BMP-only image lands on it (via ImageMagick, convert/magick handles BI_BITFIELDS fine). Once that PNG entry exists, Claude Code's existing wl-paste --type image/png path just works — no changes needed on the Claude Code side, and normal text copy/paste is untouched.

Note: wl-paste --watch doesn't work under WSLg (Watch mode requires a compositor that supports the wlroots data-control protocol), so this polls once a second instead.

Requirements: sudo apt-get install -y wl-clipboard imagemagick

~/.local/bin/wsl-clip-image-bridge-tick.sh (one poll tick):

#!/usr/bin/env bash
# One tick of the clipboard bridge. WSLg forwards Windows clipboard images
# as BI_BITFIELDS-compressed BMP, which Claude Code's image-paste decoder
# can't read. This converts to PNG and republishes on the clipboard.
set -euo pipefail

STATE_DIR="${XDG_RUNTIME_DIR:-/tmp}/wsl-clip-image-bridge"
LAST_HASH_FILE="$STATE_DIR/last.hash"
mkdir -p "$STATE_DIR"

types=$(wl-paste -l 2>/dev/null || true)

case "$types" in
  *image/bmp*)
    if echo "$types" | grep -q "image/png"; then
      exit 0
    fi
    bmp="$(mktemp --suffix=.bmp)"
    png="$(mktemp --suffix=.png)"
    trap 'rm -f "$bmp" "$png"' EXIT

    wl-paste -t image/bmp > "$bmp" 2>/dev/null || exit 0

    hash=$(sha256sum "$bmp" | cut -d' ' -f1)
    if [ "$hash" = "$(cat "$LAST_HASH_FILE" 2>/dev/null || true)" ]; then
      exit 0
    fi
    echo "$hash" > "$LAST_HASH_FILE"

    if magick "$bmp" "$png" 2>/dev/null; then
      wl-copy -t image/png < "$png"
    fi
    ;;
esac

~/.local/bin/wsl-clip-image-bridge.sh (poll loop):

#!/usr/bin/env bash
# wl-paste --watch needs the wlroots data-control protocol, which WSLg's
# compositor doesn't implement, so we poll instead.
set -euo pipefail
TICK="$(dirname "$0")/wsl-clip-image-bridge-tick.sh"
while true; do
    "$TICK" || true
    sleep 1
done

chmod +x ~/.local/bin/wsl-clip-image-bridge.sh ~/.local/bin/wsl-clip-image-bridge-tick.sh

Autostart — add to ~/.bashrc (or ~/.zshrc):

if command -v wl-paste >/dev/null 2>&1 && ! pgrep -f wsl-clip-image-bridge.sh >/dev/null 2>&1; then
    nohup "$HOME/.local/bin/wsl-clip-image-bridge.sh" >/tmp/wsl-clip-image-bridge.log 2>&1 &
    disown
fi

Open a new shell (or run that block manually once) and normal ctrl+v/alt+v paste starts working immediately — confirmed working here. Obviously just a stopgap; the real fix belongs in Claude Code's BMP decoding (or preferring the PowerShell PNG path on WSL, as suggested above).

Follow-up for anyone who applied the wsl-clip-image-bridge workaround above: once a Claude Code release actually fixes this upstream (BMP decoding or the PowerShell PNG path), here's how to remove it cleanly. It's safe to leave running indefinitely too (it's a no-op once Claude Code stops needing it), but tidy to remove.

1. Stop the running daemon:

pkill -f wsl-clip-image-bridge.sh

2. Remove the autostart block from ~/.bashrc. It's the block that starts with the comment # WSLg only forwards Windows clipboard images... and ends with the closing fi right after the nohup .../wsl-clip-image-bridge.sh ... line — delete these exact lines (7 lines total):

# WSLg only forwards Windows clipboard images as BI_BITFIELDS BMP, which
# Claude Code's image-paste decoder can't read (Ctrl+V/Alt+V show
# "Pasting..." but nothing attaches). This bridges each clipboard image to
# a plain image/png entry. Safe to run on every shell: no-ops if already
# running.
if command -v wl-paste >/dev/null 2>&1 && ! pgrep -f wsl-clip-image-bridge.sh >/dev/null 2>&1; then
    nohup "$HOME/.local/bin/wsl-clip-image-bridge.sh" >/tmp/wsl-clip-image-bridge.log 2>&1 &
    disown
fi

(If you added it to ~/.zshrc instead, remove the same block from there.)

3. Delete the scripts and leftover state:

rm -f ~/.local/bin/wsl-clip-image-bridge.sh ~/.local/bin/wsl-clip-image-bridge-tick.sh
rm -f /tmp/wsl-clip-image-bridge.log
rm -rf "${XDG_RUNTIME_DIR:-/tmp}/wsl-clip-image-bridge"

That's it — no other state or config is touched by this workaround, so those three steps fully remove it. wl-clipboard and imagemagick (installed as prerequisites) are safe to leave installed or remove with your package manager if you don't need them for anything else.