### Preflight Checklist - [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) and this hasn't been reported yet - [x] This is a single bug report (please file separate reports for different bugs) - [x] I am using the latest version of Claude Code ### What's Wrong? ### Routing note This is **Claude Desktop** on macOS, not Claude Code CLI/VS Code. Filing here because Desktop has no public issue tracker. Same precedent

[BUG] [Claude Desktop / macOS] Registers as default handler for .md without consent (not claude-cli://)

Status Open

Maintainer reply None cached

Workaround ✓ Mentioned in thread ↓

Activity 4 comments · opened Sep 19, 2026

Preflight Checklist

[x] I have searched existing issues and this hasn't been reported yet
[x] This is a single bug report (please file separate reports for different bugs)
[x] I am using the latest version of Claude Code

What's Wrong?

Routing note

This is Claude Desktop on macOS, not Claude Code CLI/VS Code. Filing here because Desktop has no public issue tracker. Same precedent as #93011 and other Desktop reports that bots close as "invalid."

What's wrong

Claude Desktop silently becomes the macOS default app for Markdown (.md / net.daringfireball.markdown) via Launch Services. No consent prompt. Mail attachments and Finder opens go to Claude instead of the user's prior default (e.g. TextEdit).

Support's documented fix (disableDeepLinkRegistration for claude-cli://) does not address file-type associations.

Expected

No change to OS default apps without explicit user opt-in
Or a clear Desktop setting: "Do not register as default handler for file types"

Actual

.md default became Claude Desktop (com.anthropic.claudefordesktop)
Required manual Launch Services repair to restore TextEdit
Forcing Preview for .md failed (Preview does not reliably open Markdown)

Environment

Claude Desktop (Mac) version 2.2553.1
macOS 26.6.2 (Build 25G83)
Repro: install/use Desktop → open .md from Mail/Finder → opens in Claude

#93011 (Windows Desktop reclaiming defaults on every launch; closed as not Claude Code)
#91750 (Windows Desktop registering as default for .docx/.pdf/.csv)

Requested fix

Gate all default-app / document-type registration behind a persisted opt-in. Document a Desktop setting distinct from protocol deep-link registration.

What Should Happen?

Claude Desktop should not change macOS default apps without an explicit user opt-in.

Specifically:

Installing or launching Claude Desktop must not set Claude as the default handler for Markdown (.md) or other document types.
Mail attachments and Finder double-clicks should continue to open in the user's existing default app (e.g. TextEdit for .md).
If Claude wants to offer “Open with Claude,” that should be an Open With choice or an in-app action — not a silent Launch Services default.
Ideally, Desktop Settings should include a clear toggle such as “Do not register as default handler for file types,” separate from any claude-cli:// / deep-link setting.

Error Messages/Logs

None — no error dialog was shown.

The failure mode was silent: Claude Desktop became the macOS default app for .md without a prompt or error. Mail/Finder then opened Markdown in Claude instead of TextEdit.

Optional diagnostics (if useful to the team):
- `mdls -name kMDItemContentType` on a .md file
- Launch Services default handler for `net.daringfireball.markdown` pointed at Claude Desktop (`com.anthropic.claudefordesktop`) before repair
- Claude Desktop version: 2.2553.1
- macOS: 26.6.2 (Build 25G83)

Steps to Reproduce

On macOS, note the current default app for Markdown (.md), e.g. TextEdit (Get Info → Open with, or open a .md from Finder).
Install or launch Claude Desktop (Mac app). Use it normally (no explicit “make default” action).
Quit and reopen Mail or Finder if needed.
Double-click a .md file in Finder, or open a .md email attachment.
Observe which app opens.

Expected: still opens in the prior default (e.g. TextEdit).
Actual: opens in Claude Desktop; Claude is now the Launch Services default for .md / net.daringfireball.markdown.

Also observed: Claude Desktop Info.plist claims broad document/viewer types including All Files / public.data, which facilitates claiming defaults without a user prompt.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude Desktop APP

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Additional information

There is currently no supported Claude Desktop setting to stop this.

Anthropic support pointed to disableDeepLinkRegistration / claude-cli://. That only covers a URL protocol handler. It does not stop Desktop from claiming OS file-type defaults for .md.
The only workaround we found is a manual macOS Launch Services repair (terminal / defaults database) to point Markdown back to TextEdit.
That repair does not stick as a product fix: after Claude Desktop is opened again (and/or after updates), the association can be reclaimed and .md / Mail attachments open in Claude again until the manual repair is repeated.
Related: #93011 (Windows) reports Desktop reclaiming file-type defaults on every launch, with no in-app opt-out. #91750 is similar for other document types on Windows.
Requested product fix: a persisted Desktop opt-out for file-type / default-app registration, separate from deep-link settings, defaulting to off (do not claim defaults without consent).

View original on GitHub ↗

4 Comments

mattLummus · 23 days ago

+1 very obtrusive and annoying

williamfiset · 22 days ago

+1 Super frustrating, Claude should not be changing the default settings on my computer

GET-USA · 21 days ago

I can't figure out why this isn't happening to other computers. Are you working on anything regarding deceptive AI practices?

GET-USA · 21 days ago

You have to quit Claude before opening attachments or it will default to Claude. Here is what Fin (Anthropic AI support) provided in multiple emails:

I understand you're looking for a way to prevent Claude Desktop from becoming the default handler for file attachments when the app is running on macOS.

The available sources document settings for Claude Code (the CLI tool), not Claude Desktop. The disableDeepLinkRegistration setting mentioned in the sources only controls the claude-cli:// protocol handler for Claude Code, not file-type associations for Claude Desktop.[1]<https://code.claude.com/docs/en/settings-reference>

Based on your testing, quitting Claude Desktop before opening attachments prevents it from claiming file associations. This suggests the behavior is tied to the app being running rather than persistent system-level registration.

For macOS system-level file association management, you can use Finder's "Get Info" (right-click a file → Get Info → Open with) to set default applications per file type, though this addresses the system side rather than preventing Claude Desktop's behavior.

What specific file types are you seeing Claude Desktop claim when it's running (beyond the .md, .docx, .doc, PDF, and images you mentioned earlier)?

---------------------------------------------

I understand your frustration, and I want to be clear about what happened and what options you have.

The September 2026 update (v1.44121.1) intentionally added Claude Desktop to the "Open with" menu for common file types on macOS and Windows.[1]<https://claude.com/docs/cowork/changelog> This was a product design decision, and there is currently no built-in setting within Claude Desktop to disable or opt out of this file-type registration.

What you can do:

You can continue managing your file associations at the macOS system level. macOS allows you to set default applications for specific file types through Finder (Get Info on a file, then "Open with" section). While Claude Desktop may add itself to the available options, you retain control over which application is actually set as the default for each file type.

I cannot provide guidance on third-party tools or system-level workarounds beyond standard macOS file association management, as those fall outside our support scope.

Your detailed bug report documenting the behavior across multiple file types and the operational impact has been noted. The engineering team reviews all product bug reports, though there isn't a way to track the status of specific fixes.

Please let me know if this helps or if you have any further questions.

This answer was composed by Fin AI Agent, Anthropic's AI Agent.

On Sep 22, 2026, at 10:56 AM, William Fiset @.***> wrote:

[https://avatars.githubusercontent.com/u/5898848?s=20&v=4]williamfiset left a comment (anthropics/claude-code#95567)<https://github.com/anthropics/claude-code/issues/95567#issuecomment-5779652995>

+1 Super frustrating and invasive

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