[BUG] Desktop extension installs silently fail on macOS Tahoe 26.5 — no error, no feedback

[mconnley]

Preflight Checklist

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

What's Wrong?

Every desktop extension install from the Directory (Settings → Extensions → Browse, or the Connectors Directory panel) silently fails. The download completes, the log emits [warn] Installing unsigned extension from ..., and then nothing happens — no error, no success, no user-facing feedback. Some extensions display a progress bar that never progresses, others just don't do anything at all. The extension never appears in the installed list.

This reproduces 100% of the time across every extension tested:

• Macos (ant.dir.gh.cursortouch.macos-mcp) — button does nothing at all
• Control your Mac (ant.dir.gh.k6l3.osascript) — shows "Installing..." progress bar indefinitely
• Kubernetes MCP Server (ant.dir.gh.flux159.mcp-server-kubernetes) — same as Macos

What Should Happen?

The extensions should install and appear in the extensions list, or a clear error message should be displayed explaining why installation failed.

Error Messages/Logs

2026-06-14 17:19:49 [info] [download:1] Starting download from https://claude.ai/api/organizations/.../dxt/extensions/ant.dir.gh.cursortouch.macos-mcp/download
2026-06-14 17:19:50 [warn] Installing unsigned extension from /var/folders/mx/.../dxt-download-1781475589938.mcpb
2026-06-14 17:20:20 [info] [download:2] Starting download from https://claude.ai/api/organizations/.../dxt/extensions/ant.dir.gh.k6l3.osascript/download
2026-06-14 17:20:20 [warn] Installing unsigned extension from /var/folders/mx/.../dxt-download-1781475620721.mcpb

Steps to Reproduce

1. Open Claude Desktop 1.12603.1 on macOS Tahoe 26.5.1
2. Go to Settings → Extensions → Browse Extensions (or use the Directory panel under Connectors)
3. Click + / Install on any extension
4. Observe: download completes, "Installing..." may briefly appear, then nothing. No extension is installed. No error is shown.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

No response

Claude Code Version

1.12603.1 (3df4fd)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Environment

• macOS: Tahoe 26.5.1 (Build 25F80)
• Hardware: Mac Studio, Apple Silicon
• Claude Desktop: 1.12603.1 (3df4fd), 2026-06-11
• Node.js: v24.12.0 (/usr/local/bin/node)
• Python: 3.14.5 (/opt/homebrew/bin/python3)

main.log — install attempts followed by silence

2026-06-14 17:19:49 [info] [download:1] Starting download from https://claude.ai/api/organizations/.../dxt/extensions/ant.dir.gh.cursortouch.macos-mcp/download
2026-06-14 17:19:50 [warn] Installing unsigned extension from /var/folders/mx/.../dxt-download-1781475589938.mcpb
2026-06-14 17:20:20 [info] [download:2] Starting download from https://claude.ai/api/organizations/.../dxt/extensions/ant.dir.gh.k6l3.osascript/download
2026-06-14 17:20:20 [warn] Installing unsigned extension from /var/folders/mx/.../dxt-download-1781475620721.mcpb

No error, no success, no subsequent log entry related to the install. The log jumps to unrelated OAuth/session activity.

Earlier session included a potentially relevant error

2026-06-14 17:12:17 [error] Failed to read version of python binary "python", failed with Error: Failed to spawn python (via disclaimer): /Applications/Claude.app/Contents/Helpers/disclaimer exited with code 127: Failed to spawn process: No such file or directory

This was resolved by symlinking python3 → python, but the extension installs continued to fail identically after the fix.

Orphaned staging directories

10 dxt-install-* directories accumulate in ~/Library/Application Support/Claude/ containing downloaded but never-unpacked package.mcpb files:

dxt-install-0GT7vL/package.mcpb  (1.2MB)
dxt-install-JI3KzH/package.mcpb  (19.9MB)
dxt-install-psDLfT/package.mcpb  (235KB)
... (7 more)

No extensions directory exists

~/Library/Application Support/Claude/extensions/ does not exist.
~/Library/Application Support/Claude/Claude Extensions/ does not exist.
Manually pre-creating these directories did not resolve the issue.

Sandbox/disclaimer helper works correctly in isolation

$ /Applications/Claude.app/Contents/Helpers/disclaimer node --version
v24.12.0
 
$ /Applications/Claude.app/Contents/Helpers/disclaimer python --version
Python 3.14.5

No macOS security blocks

log show with predicates for com.apple.security, com.apple.syspolicy, Claude, and disclaimer shows no deny/block entries during install attempts. No crash reports for disclaimer or Claude in ~/Library/Logs/DiagnosticReports/.

Extension policies are not blocking

// extensions-blocklist.json
{ "entries": [], ... }
 
// config.json (relevant field)
"dxt:allowlistEnabled:...": false

Full Disk Access granted

Full Disk Access was granted to both Claude.app and /Applications/Claude.app/Contents/Helpers/disclaimer in System Settings → Privacy & Security. System was rebooted after granting. No change in behavior.

Downloaded .mcpb files are valid

$ file /var/folders/.../dxt-download-1781475620721.mcpb
Zip archive data, at least v2.0 to extract, compression method=deflate
 
$ unzip -l /var/folders/.../dxt-download-1781475620721.mcpb | head -5
  Length      Date    Time    Name
---------  ---------- -----   ----
     1059  07-23-2025 09:27   LICENSE.md
      238  07-23-2025 09:27   README.md
   117115  07-23-2025 09:27   icon.png

Notes

This appears related to the documented pattern of macOS Tahoe 26.x tightening sandbox/privacy rules for Electron apps (#40336, #43654, #32584). The install pipeline silently swallows whatever error occurs between "Installing unsigned extension" and the actual file extraction — at minimum, the failure should be surfaced to the user.

[mconnley]

Update and Diagnostic Report

claude-diagnostic-8da4d670-20260614-2326.zip

claude-ai-web-log.txt shows every install attempt fails with:

[error] Uncaught (in promise) Error: Error invoking remote method
'..._$_Extensions_$_installDxtFromDirectory': reply was never sent

This occurs 13 times across the session, once per install attempt. The main
process receives the IPC call, starts the download, logs "Installing unsigned
extension from ...", then silently fails to complete — never sending the IPC
reply. The renderer's promise hangs until timeout.

The actual exception in the main process install handler is not logged anywhere
(main-log.txt, mcp-log.txt, mcp-server-logs.txt are all clean), suggesting an
unhandled rejection or swallowed error in the extension unpacking/installation
code path.

[shaktimaan]

It had the exact same problem.
Just as a quick fix/workaround, I renamed the MCPB to zip, unpacked it and installed it as an unpacked extension - worked

[philipjohnbasile-ta]

Seeing this too, can't install custom MCPs.

[frasim]

Same symptom on macOS Sequoia, not Tahoe — Claude Desktop 1.12603.1.

Reproducing this installing an org-directory extension (custom connector), but on macOS 15.7.7 (Sequoia, build 24G720) — not Tahoe. Since the symptom is identical with the same Desktop build 1.12603.1, this suggests the regression is in the Claude Desktop build itself, not in macOS Tahoe's sandbox.

Identical behavior to the report:

• main.log: Starting download …/dxt/extensions/<id>/download → [warn] Installing unsigned extension from …/dxt-download-*.mcpb → then nothing (no error, no spawn, no further log).
• ~/Library/Application Support/Claude/Claude Extensions/ stays empty — nothing is ever extracted.
• UI stuck on "Installing…" indefinitely; repeated attempts leave orphaned dxt-download-* temp files.
• The .mcpb is a valid zip (correct manifest.json + bundled node_modules); the same package installs and runs fine on the Linux build 1.3109.0 → macOS-build-specific.
• Org allowlist disabled, blocklist empty, no signature MDM policy set.

Reproducible 100%. Happy to share full logs.