Web: New session created but first message cannot be sent (Path '//session/...' is not a routable path) #12840

Description

In OpenCode Web, creating a new session succeeds, but the first message is never sent.
I only see POST /session in Network. No POST /session/{id}/message is sent afterward.
Console shows:
Uncaught (in promise) Error: Path '//session/ses_3bce84db7ffe2FH9YBwWwq0ERS' is not a routable path
at ...
at HTMLFormElement.handleSubmit (...)
This looks like a client-side routing bug (double slash route), and it interrupts the submit flow.
Actual behavior

• POST /session returns 200 OK with a valid session object.
• Then UI throws routing error Path '//session/...' is not a routable path.
• First prompt is not sent.
  Expected behavior
  After session creation, app should navigate to a valid route and send first message (POST /session/{id}/message).
  Network evidence
  POST http://127.0.0.1:4096/session response:
  {
  id: ses_3bce84db7ffe2FH9YBwWwq0ERS,
  slug: cosmic-planet,
  version: 1.1.53,
  projectID: global,
  directory: C:\Users\Administrator,
  title: New session - 2026-02-09T15:49:12.392Z,
  time: {
  created: 1770652152392,
  updated: 1770652152392
  }
  }
  Additional notes
• I did not select “new workspace / create worktree”.
• Problem seems to happen between session.create() success and route navigation, before prompt API call.

Plugins

oh-my-opencode

OpenCode version

1.1.53

Steps to reproduce

1. Open web app.
2. Go to new session view.
3. Type a message and submit.
4. Observe session creation request succeeds.
5. Observe no message request is sent.

Screenshot and/or share link

No response

Operating System

Windows

Terminal

Windows Terminal