ObjectDisposedException - IServiceProvider disposed while tool handler execution. #1269
Description
Describe the bug
Sometimes I get ObjectDisposedException from DI services like the IServiceProvider itself or DbContext
inside the tool call handler.
It looks like OpenAI closes the connection for too-long-running tools,
and instead of canceling the CancellationToken, the service scope gets disposed.
Or the scope gets disposed of without waiting for the handler to cancel cleanly.
To Reproduce
Steps to reproduce the behavior:
- Setup: Stateless, Http Transport
- Call a long-running tool
- Close the connection to simulate a read-timeout.
Note
I use it with OpenAI
OpenAI requires statelessness and closes the connection after some timeout.
services.AddMcpServer(options => options.ScopeRequests = true)
.WithHttpTransport(options => {
options.Stateless = true;
})
.AddAuthorizationFilters()
.WithToolsFromAssemblyFixed(toolAssembly)
.AddCallToolFilter(next => (context, token) => ToolCallErrorHandler(next, context, token));
// ...
app.MapMcp("/mcp").RequireAuthorization("mcp");
static async ValueTask<CallToolResult> ToolCallErrorHandler(McpRequestHandler<CallToolRequestParams, CallToolResult> next, RequestContext<CallToolRequestParams> context, CancellationToken cancellationToken)
{
try {
return await next(context, cancellationToken);
}
catch (Exception ex) {
if (x is not OperationCanceledException) {
// Error here inside `GetRequiredService` - the `ex` error is also an ObjectDisposedException with origin in DbContext.SaveChanges()
context.Services!.GetRequiredService<ILogger<McpFeatureAttribute>>()
.LogCritical(ex, "MCP Error {tool}: {message}", context.Params?.Name, ex.Message);
}
return new CallToolResult {
Content = [new TextContentBlock { Text = $"Error: {ex.Message}" }],
IsError = true
};
}
}Expected behavior
I expect the handler to either complete or cancel through CancellationToken before the service scope is disposed.
Logs
ERROR ModelContextProtocol.Server.McpServer "{ToolName}" threw an unhandled exception.
System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'IServiceProvider'.
at Microsoft.Extensions.DependencyInjection.ServiceLookup.ThrowHelper.ThrowObjectDisposedException()
at ModelContextProtocol.Server.RequestServiceProvider`1.GetService(Type serviceType)
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
at Nomos.Web.Features.Mcp.Abstructions.McpFeatureInstaller.ToolCallErrorHandler(McpRequestHandler`2 next, RequestContext`1 context, CancellationToken cancellationToken) in /src/Nomos.Web/Features/Mcp/Abstructions/McpFeatureInstaller.cs:line 42
at ModelContextProtocol.AspNetCore.AuthorizationFilterSetup.<>c__DisplayClass7_0.<<ConfigureCallToolFilter>b__1>d.MoveNext()
--- End of stack trace from previous location ---
at ModelContextProtocol.Server.McpServerImpl.<>c__DisplayClass51_2.<<ConfigureTools>b__5>d.MoveNext()Additional context
Add any other context about the problem here.