[BUG] Invalid server route when opening or creating a session in OpenCode Web

Description

When using OpenCode Web remotely in Chromium, the web UI can fail after a project has been selected. Opening an existing session or clicking New session may leave the UI unresponsive. Chromium showed:

Error: Invalid server route
    at ra (.../assets/index-<hash>.js:...)
    at get serverKey (.../assets/index-<hash>.js:...)

The OpenCode backend remains healthy and can access the selected project.

The separate directory-picker problem is already reported in #39434. This report is only about the session/browser-route error after a project is selected.

Plugins

None

OpenCode version

Current beta: 0.0.0-beta-202608031317.

Also observed with stable 1.18.11.

Steps to reproduce

1. Run opencode web in Docker with password protection enabled.
2. Mount a project directory into the container and select that project in OpenCode Web.
3. Open the web UI from another device on the private network.
4. Try to open an existing session or click New session.
5. Observe that the UI may become unresponsive and Chromium can show Invalid server route.

Screenshot and/or share link

No response

Operating System

Ubuntu Docker host; Chromium client on Windows.

Terminal

No response