Claude in Chrome extension won't connect to any Cowork session (cloud or local) — "Sign-in unavailable, must be opened from claude.com"

Summary: The Claude in Chrome extension will not connect to any Cowork session as of today. Every browser action returns "Browser extension is not connected," and trying to connect/sign in the extension shows: "Sign-in unavailable — This page must be opened from claude.com. Close this window and sign in there." This has worked reliably for months and started failing today.

Environment:

Windows desktop, Google Chrome
Claude extension v1.0.85, toggled On, Site access "On all sites," all permissions granted
Reproduced in BOTH a cloud/web Cowork session (claude.ai/cowork/…) and a brand-new task started in the Claude desktop app (on-computer)

What happens:

Cowork reports "Claude in Chrome extension isn't connected" / "Browser extension is not connected" on every browser action (tab context, navigate, etc.)
Attempting to connect the extension shows "Sign-in unavailable — This page must be opened from claude.com."
The Cowork session URL includes ?reason=elevated_auth&auth_kind=untrusted
"Require trusted devices" is ON in Cowork settings

Steps tried (all failed):

Logged out and back into claude.ai
Verified extension is On, current version, on all sites
Started a fresh task in the desktop app (local/on-computer), not just the cloud session — same failure
Retried the connection multiple times

Key isolation detail: In the same sessions, file/device access to my computer works fine, and reading public web pages works fine — so the failure is specifically the Chrome extension connection, not the device link or network.

Impact: Cowork cannot perform any Google Business Profile or live WordPress work, since both depend on the browser extension.