desktop: "Message not found" 404 toast after revert + resubmit #51502

Summary

After reverting a session to an earlier user message and immediately resubmitting, the desktop client shows a "请求失败 / Message not found: msg_..." error toast. The server returns 404 for a message ID that was discarded during the revert + resubmit race. No data loss, but the error toast is confusing and looks like a failed request.

Environment

• opencode version: 2.0.18
• OS: Windows_NT 10.0.26200 (win32 x64), OpenCode Desktop app
• Terminal: n/a (desktop app)
• Shell: PowerShell 7 (portable)
• Install/channel: latest (release)
• Active plugins: @prevalentware/opencode-goal-plugin, local handoff-on-compact plugin

Reproduction

1. In OpenCode Desktop, have a session where a turn is running (assistant with tool calls).
2. Revert the session to an earlier user message (server logs session.revert.stage).
3. Resubmit the message right away.
4. Within a few seconds, an error toast appears: 请求失败 — Message not found: msg_0de12f5dc001K7Lx40bwXb7nV3.

Expected Behavior

The client should not fetch a message ID that no longer exists after a revert; no error toast should be surfaced for internal state that was already discarded.

Actual Behavior

The server returns 404 and the desktop app surfaces it as a failed-request toast. Session state remains consistent afterwards (all messages intact, subsequent turns run normally), so this appears to be a transient client/server race, not corruption.

Additional Context

Server log excerpt (~/.local/share/opencode/log/opencode.log, UTC):

timestamp=2026-09-26T14:16:15.850Z message=session.revert.stage sessionID=ses_f222edb3cffdw26p7dWwdKsPze messageID=msg_0de122002001CUFk1zuFlWhkuX
timestamp=2026-09-26T14:16:19.752Z message="Sent HTTP response" http.method=GET http.url=/api/session/ses_f222edb3cffdw26p7dWwdKsPze/message/msg_0de12f5dc001K7Lx40bwXb7nV3 http.status=404

The missing message ID (msg_0de12f5dc001...) was created ~12 ms after the resubmitted user message (msg_0de12f5d0001...) and is absent from the final message list, which suggests the client kept a reference to an assistant message that was replaced or discarded during the revert + resubmit sequence.

Frequency: observed once so far (revert followed by immediate resubmit).