Summary

Calling the chrome MCP computer tool with action: screenshot (or zoom) and save_to_disk: true returns a screenshot ID and inline image but does not persist any bytes to disk. The tool description claims "Returns the saved path in the tool result" — no path is returned, and no file is created anywhere on the filesystem.

Environment

• Claude Code: 2.1.138
• macOS: 26.4.1 (Build 25E253)
• Chrome extension: claude-in-chrome (current as of 2026-05-10)
• Native host wrapper: ~/.claude/chrome/chrome-native-host → execs the Claude Code binary with --chrome-native-host

Reproduction

1. In Claude Code, with the chrome MCP connected, call:

   ```json { "tool": "mcp__claude-in-chrome__computer", "input": { "action": "screenshot", "tabId": 12345, "save_to_disk": true } } ```

2. Tool returns successfully:

   ``` Successfully captured screenshot (1483x812, jpeg) - ID: ss_3670cu9jg ```

   plus the inline image. No `path` field in the response text.

3. Search the entire filesystem for any file created since the call:

   ```bash touch /tmp/marker

   ... call screenshot tool ...

   find ~ -type f -newer /tmp/marker 2>/dev/null
   | grep -E '.(png|jpe?g)$'
   | grep -vE '/(node_modules|.git/|cache/|Cache/|.npm)/' find /tmp /private/tmp /var -type f -newer /tmp/marker 2>/dev/null
   | grep -E '.(png|jpe?g)$' ```

   Returns zero image files.

4. Check the chrome MCP log:

   ```bash tail -20 ~/Library/Caches/claude-cli-nodejs/<cwd-slug>/mcp-logs-claude-in-chrome/*.jsonl ```

   Records the `Calling MCP tool: computer` and `completed successfully in 1s` events, but no save event, no path, no error.

Expected

Either:

• Bytes written to a documented location (e.g. `~/Downloads/` or `$TMPDIR/claude-in-chrome/ss_xxxx.png`), AND the path included in the tool result text, OR
• The flag rejected at schema-validation time with a clear "not supported in this Claude Code version" error if the feature has been removed.

Silent acceptance + drop is the worst case — model and user both assume evidence is being persisted, but every screenshot is inline-only and dies with the conversation.

Actual impact

In a multi-hour UAT walkthrough I took ~10 screenshots, all flagged `save_to_disk: true`, and referenced their IDs (`ss_xxxx`) from markdown evidence docs under the assumption they were on disk. Discovered at end-of-session that none had landed; all evidence was inline-only and would dangle the moment the conversation closed.

This silently damages any UAT walkthrough / PR-evidence / regression-record workflow that depends on chrome MCP screenshots.

Suggested fixes (in order of preference)

1. Make `save_to_disk: true` actually save. Documented destination (e.g. `$TMPDIR/claude-in-chrome/` or `~/Downloads/`). Return the path in the tool result text.
2. If the feature is intentionally disabled in this version, reject the flag with a clear error so the model knows to use a different evidence path (e.g. a separate `download_screenshot` tool).
3. Update the tool description if the flag is genuinely not implemented yet — current wording ("Returns the saved path in the tool result") is misleading and led to silent evidence loss.

Related considerations

• `screencapture` is not a valid silent fallback because the MCP tab may not be the focused/visible window on the user's display. Documenting that chrome MCP screenshots are inline-only would change how callers structure evidence-gathering workflows.
• The existing `file_upload` and `gif_creator` tools suggest disk-IO plumbing exists for related operations — a "download current tab as PNG" tool that explicitly writes to a user-controlled path could be a cleaner fix.

How I confirmed

Marker-based `find` over entire HOME + temp dirs after a `save_to_disk: true` call returns zero image files. MCP server log records the call but no save activity.