Desktop can keep stale local MCP state until full relaunch #35285

Summary

OpenCode Desktop can get into a stale local MCP state where newly created Desktop sessions immediately fail on the first MCP tool call with a Serena MCP timeout. A full Desktop quit/relaunch clears the problem temporarily, but creating a new Desktop session does not. The same workflow does not reproduce in the OpenCode TUI.

This looks related to Desktop's persistent sidecar lifecycle and the async prompt path, rather than to Serena's startup configuration itself.

Environment

• OpenCode Desktop: 1.17.13
• OS: Windows
• MCP server: local stdio MCP (serena.exe start-mcp-server ...)
• The same MCP configuration works in the OpenCode TUI.

Observed behavior

1. Start OpenCode Desktop after a full quit/relaunch.
2. Serena MCP tool calls work initially.
3. After further Desktop usage, create a new Desktop session.
4. The first LLM-initiated Serena MCP tool call can immediately fail with a timeout.
5. Creating another new Desktop session does not fix it.
6. Fully quitting and relaunching OpenCode Desktop fixes it temporarily.
7. Running the same kind of Serena-heavy work in the TUI does not show the timeout issue.

Expected behavior

A new Desktop session should not inherit a stale/broken local MCP client state, or OpenCode should provide a way to reconnect/restart a local MCP server without fully relaunching Desktop.

Notes from code inspection

I looked for an existing issue and found related but not identical reports:

• MCP remote client has no transport-level retry on socket/connection errors #25287 covers remote MCP transport-level reconnect/retry.
• prompt_async returns 204 after startup failure, leaving empty child sessions that appear frozen #33394 and other prompt_async issues cover async prompt failure modes.

This report is specifically about Desktop + local stdio MCP + stale sidecar/MCP state.

Relevant implementation details from dev:

• Desktop starts a persistent sidecar server at app startup and keeps it alive until quit/relaunch.
  • packages/desktop/src/main/index.ts calls spawnLocalServer(...) and stores the listener in a process-level server variable.
  • packages/desktop/src/main/sidecar.ts imports virtual:opencode-server and calls Server.listen(...).
  • Creating a new Desktop session appears to create only a new conversation in the existing sidecar; it does not restart MCP clients.
• TUI has a worker/server lifecycle tied to the TUI process.
  • packages/opencode/src/cli/cmd/tui.ts starts a worker and terminates it on exit.
  • packages/opencode/src/cli/tui/worker.ts calls InstanceRuntime.disposeAllInstances() during shutdown.
  • This likely gives TUI a fresher instance/MCP lifecycle between launches.
• Desktop new-session submit uses the async prompt route.
  • packages/app/src/components/prompt-input/submit.ts creates an empty session via client.session.create() and then sends via client.session.promptAsync(...).
• The TUI main prompt path uses the normal prompt route.
  • packages/tui/src/component/prompt/index.tsx creates a session with agent/model and calls sdk.client.session.prompt(...).
• Server handlers differ:
  • packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts has prompt, which streams promptSvc.prompt(...).
  • The same file has promptAsync, which forks promptSvc.prompt(...) into a background fiber via Effect.forkIn(scope, { startImmediately: true }) and immediately returns 204 NoContent.
  • This can make Desktop accept the prompt while the actual MCP failure happens later as a session error/event.

Current workaround

Fully quit and relaunch OpenCode Desktop. Creating a new session is not sufficient because the sidecar/MCP state is reused.

Killing only the serena.exe MCP process does not seem like a complete workaround because OpenCode may mark the MCP client failed, and there does not appear to be a local MCP reconnect/restart command.

Potential fixes

Any of these would likely help:

• Add opencode mcp reconnect <name> or opencode mcp restart <name> for local MCP servers.
• Add a Desktop UI action to reconnect/restart a configured MCP server.
• Automatically reconnect/recreate a local MCP client after request timeout or connection close.
• Surface promptAsync background MCP failures more directly in Desktop.
• Refresh/reconnect failed MCP clients before sending a new Desktop session's first prompt.