[BUG] Claude in Chrome MCP: every action denied on one domain (polat.docuware.cloud) while sibling domain works; no prompt, no local setting

No source file or test is named. Start by reproducing the identical browser_batch calls on the working sibling domain and polat.docuware.cloud, then trace the extension permissions and MCP action path; done means the blocked domain either works under the stated access settings or exposes a visible, user-controllable permission decision.

Summary

Claude in Chrome (extension 1.0.94), driven from Claude Code inside the Claude desktop app (Windows 11), refuses every MCP action on one specific domain (polat.docuware.cloud) while the same tools, same tab group, same session and same minute work without any restriction on a sibling domain of the same SaaS (sap-b1-goldenimage.docuware.cloud). No permission prompt is shown anywhere; there is no local setting that lists or unblocks the domain.

Related (all closed "not planned", no workaround): #92229, #58464, #74696.

Environment

• Windows 11 Pro 10.0.26200, Google Chrome (current), Claude in Chrome extension 1.0.94, Claude desktop app (Code tab), model claude-opus-5
• Chrome → Extensions → Claude → Site access: "On all sites"
• Extension options page (chrome-extension://…/options.html#permissions) → "Your approved sites": empty ("No websites approved yet") — and the sibling domain still works with this empty list
• Side panel open, "Automatic approval enabled"
• Both domains are DocuWare Cloud tenants (same product, same vendor, HTTPS, user logged in as org admin in both)

Reproduction (one browser_batch call, two tabs, identical tool)

[navigate]      https://sap-b1-goldenimage.docuware.cloud/DocuWare/Settings/Hub/FileCabinets  -> OK
[get_page_text] tab (goldenimage)  -> "Konfigurationen … m.neffe.admin … Neffe Consulting SAP B1 Golden Image"
[get_page_text] tab (polat)        -> Permission denied for reading page content on this domain

Every tool was tried on the Polat tab (tab is inside the session's tab group, URL https://polat.docuware.cloud/DocuWare/Settings/Hub/FileCabinets, page fully loaded, user logged in):

Tried without effect: Chrome fully restarted; tab manually placed into the MCP tab group (three times, tab IDs 288441674 / 288441704 / 288441716); URL typed manually by the user (workaround from #92229); side panel opened so a "New permissions required" prompt could show (none appears); extension permissions page checked (empty list, nothing to unblock).

Expected

Either the action succeeds (the extension has "On all sites" and the user is logged in), or a visible, user-controllable per-site permission prompt/list decides — and the desktop app/MCP tools use the same source of truth as the extension's own "approved sites".

Impact

The domain is a customer system we administer; the identical workflow on the sibling tenant ran for hours the same day. Because the block is invisible and undocumented there is no way for the user to fix it — the only workaround is not using Claude in Chrome for that domain.