[BUG] Approved plugin install fails with HTTP 404 from Browse Plugins screen

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?

Summary

Installing approved/native plugins (Data, Finance, Legal, Customer Support, etc.) from the "Browse Plugins" screen in Claude Desktop (Cowork) fails with a generic "Failed to install plugin" toast message. The underlying error is Failed to fetch browsable plugins (HTTP 404) — the API endpoint that serves plugin metadata returns a 404 response.

Error

From ~/Library/Logs/Claude/claude.ai-web.log:

2026-02-19 13:52:02 [error] [REACT_QUERY_CLIENT] QueryClient error: Error: Error invoking remote method
'$eipc_message$_fb7e340f-ab1c-4ed6-8e7d-3658658e6168_$_claude.web_$_CustomPlugins_$_installPlugin':
Error: Failed to fetch browsable plugins (HTTP 404)

The error repeats on every install attempt. In my session, it occurred 10 times between 13:52 and 14:23 (UTC-3) on 2026-02-19.

Additional Context

• App version: Claude 1.1.3541 (update was downloaded but the error occurred on the previous version as well)
• Platform: macOS (Apple Silicon)
• Affects: All plugins in the "Approved" tab — not specific to any one plugin
• Note: This is different from the EXDEV error reported in #25444, which affects marketplace plugins added by URL. This issue affects the built-in/approved plugins in the Browse Plugins screen.
• The Browse Plugins page loads and displays all plugin cards correctly — the 404 error only occurs when attempting to install
• No relevant error is logged in main.log, cowork_vm_node.log, or coworkd.log — the error only appears in claude.ai-web.log

What Should Happen?

Expected Behavior

Clicking "Install" on an approved plugin should download and install the plugin successfully. The API endpoint used by CustomPlugins.installPlugin should return a valid response (not 404).

Error Messages/Logs

## Logs

The error only appears in `claude.ai-web.log`. Other log files (`main.log`, `cowork_vm_node.log`, `coworkd.log`) contain no mention of the plugin installation failure, which makes debugging harder for users who only check the main log.

Steps to Reproduce

Steps to Reproduce

1. Open Claude Desktop (Cowork mode)
2. Navigate to Browse Plugins ("Navegar por plugins")
3. In the Approved tab, click Install on any plugin (e.g., "Data", "Finance", "Legal")
4. A toast notification appears: "Failed to install plugin." — no additional details are shown in the UI

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude 1.1.3541

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_