Browser tool navigate consistently fails with "denied or failed" for previously-working sites

### 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?

I'm using Claude Code with the Browser tool (mcp__Claude_Browser__navigate) on a Windows VPS. For most of a session, navigation to a specific site (mql5.com) worked fine — I was able to browse, log in, read pages, fill forms, etc. Then, mid-session, every subsequent navigate call to the same site (and others) started failing with a generic error: "navigation to https://mql5.com was denied or failed."
- No error details are given beyond "denied or failed."
- The browser tab appears to open (about:blank) but never actually loads the target URL.
- Retrying the same navigate call repeatedly does not help.
- This is not a per-site block — it previously worked fine on the exact same URL earlier in the same session.
- This has happened on at least two separate occasions (days apart), each time lasting the rest of that session, then resolving on its own by the next session — suggesting an intermittent backend/infrastructure issue rather than a site-specific block or a persistent bug.

### What Should Happen?

The navigate call should either succeed and load the requested URL, or return an error with enough detail to tell whether the failure is a network issue, a site-side block, or a tool-side problem — so it's possible to distinguish a transient outage from something that needs a different fix.

### Error Messages/Logs

```shell
navigation to https://mql5.com was denied or failed
```

### Steps to Reproduce

1. In an interactive Claude Code session, use the Browser tool (mcp__Claude_Browser__navigate) to open a URL that has never been visited before in that session (e.g. preview_start with a URL).
2. Browse normally for a while — navigate, read_page, form_input, computer clicks all work fine, including repeated navigation to the same domain.
3. At some point mid-session (not tied to any specific action taken), a navigate call to a URL that worked moments earlier starts failing with "navigation to was denied or failed."
4. Retry the same navigate call multiple times. Still fails, same error, no additional detail.
5. Try navigate to a different, unrelated domain in the same tab. Also fails with the same generic error.
6. The failure persists for the rest of that session. In a later, separate session, the same tool works normally again against the same site with no changes made.

### Claude Model

Not sure / Multiple models

### Is this a regression?

I don't know

### Last Working Version

_No response_

### Claude Code Version

1.32352.1

### Platform

Anthropic API

### Operating System

Windows

### Terminal/Shell

PowerShell

### Additional Information

_No response_

Start with the mcp__Claude_Browser__navigate entry point and reproduce the failure using the listed session steps, including another unrelated domain after navigation stops working. Done means identifying whether the failure is network-, site-, or tool-side and returning enough diagnostic detail to distinguish those cases.

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