MCP: Handle notifications/cancelled to abort running requests

[evansenter]

Summary

When Claude Code sends notifications/cancelled (user hit ctrl-c), clemini ignores it and the Gemini request keeps running in the background. This wastes API tokens and can cause confusion if the abandoned task modifies files.

Current Behavior

// mcp.rs line 262-264
if request.method.starts_with("notifications/") {
    continue;  // Just ignores cancellation!
}

And tools/call spawns a task that runs independently:

tokio::spawn(async move {
    // This keeps running even after cancellation
});

Expected Behavior

When notifications/cancelled arrives:

1. Abort any running tools/call task
2. Clean up gracefully
3. The spawned task should stop (not continue burning tokens)

Implementation

In mcp.rs:

1. Store the JoinHandle from the spawned task:

let mut current_task: Option<tokio::task::JoinHandle<()>> = None;

// When spawning:
current_task = Some(tokio::spawn(async move { ... }));

2. Handle the cancellation notification:

if request.method == "notifications/cancelled" {
    if let Some(handle) = current_task.take() {
        handle.abort();
    }
    continue;
}

3. The task should handle JoinError::is_cancelled() gracefully if needed.

Testing

1. Start clemini MCP server
2. Send a long-running request (e.g., complex code generation)
3. Send notifications/cancelled
4. Verify in /tmp/clemini.log that tool calls stop after cancellation

Related

• Move off auto_functions for finer-grained ctrl-c cancellation #31 - Full Ctrl+C handling (broader refactor for REPL mode)
• This issue is scoped specifically to MCP mode cancellation