Web mode regression after v1.17.12: streaming stops after switching directories/checkouts, then session hits Message not found #36256

Description

Since v1.17.13, web mode quite often stops receiving live session updates in the browser. After that, the UI later crashes with errors like:

Error: Message not found: msg_f4be06c0900106RdI4GCBB3n6r

and the response payload is:

{
"body": {
"name": "NotFoundError",
"data": {
"message": "Message not found: msg_f4be06c0900106RdI4GCBB3n6r"
}
},
"status": 404
}

I do not see this on v1.17.12.

A detail that seems important: I often work with multiple separate checkouts of the same repository in different folders. These are not actual git worktrees, just independent clones/checkouts. Switching between them seems to make this bug much easier to trigger.

Plugins

none

OpenCode version

Good: v1.17.12 Bad: v1.17.13 Bad: v1.17.14

Steps to reproduce

1. Start OpenCode in web mode.
2. Open and use multiple project directories.
3. Use a setup where the same repo exists in multiple different folders as separate checkouts.
4. Switch between those directories/sessions a few times while responses are streaming or shortly after active session work.
5. At some point, the visible session stops updating live.
6. Later the UI throws NotFoundError: Message not found: msg_*.

Screenshot and/or share link

Operating System

Ubuntu 24.04, Debian 13/4

Terminal

No response