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fix: disable InMemoryMcpTaskStore to avoid ObjectDisposedException (upstream SDK bug)#411

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jongalloway merged 2 commits intomainfrom
fix/disable-task-store-di-scope-bug
Mar 18, 2026
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fix: disable InMemoryMcpTaskStore to avoid ObjectDisposedException (upstream SDK bug)#411
jongalloway merged 2 commits intomainfrom
fix/disable-task-store-di-scope-bug

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@jongalloway jongalloway commented Mar 18, 2026

Problem

MCP SDK v1.1.0's ExecuteToolAsTaskAsync disposes the request-scoped IServiceProvider before the background task resolves services, causing ObjectDisposedException on every tool call when InMemoryMcpTaskStore is registered — not just dotnet_project, but also dotnet_solution and any other tool the client invokes.

System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'IServiceProvider'.
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ThrowHelper.ThrowObjectDisposedException()
   at McpServerBuilderExtensions.CreateTarget(IServiceProvider services, Type type)
   at McpServerImpl.ExecuteToolAsTaskAsync...

Root Cause

This is an upstream SDK bug: modelcontextprotocol/csharp-sdk#1430

Fix

Comment out InMemoryMcpTaskStore registration. Without a task store, the SDK runs all tools synchronously inline — reliable and compatible with all clients.

  • Program.cs: commented-out registration with TODO and upstream link
  • DotNetCliTools.Misc.cs: AsyncTasks = false in ServerCapabilities
  • McpConformanceTests.cs: task lifecycle tests replaced with graceful degradation tests
  • ServerCapabilitiesTests.cs: updated assertions

TaskSupport = ToolTaskSupport.Optional is kept on dotnet_project so it's ready to activate when the upstream fix ships.

Tracking issue: #410

Testing

55/55 conformance + capabilities tests pass.

@jongalloway
fix: disable InMemoryMcpTaskStore to avoid ObjectDisposedException
8964287 
MCP SDK v1.1.0's ExecuteToolAsTaskAsync disposes the request-scoped
IServiceProvider before the background task resolves services, causing
ObjectDisposedException on every tool call when a task store is registered.

Comment out InMemoryMcpTaskStore registration until the upstream SDK
fixes the DI scope lifetime issue.

Upstream: modelcontextprotocol/csharp-sdk#1430

TaskSupport = Optional is kept on dotnet_project so the attribute is
ready to activate when the store is re-enabled.
@jongalloway jongalloway requested a review from Copilot March 18, 2026 02:55
Copilot AI reviewed Mar 18, 2026
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Pull request overview

Disables MCP Task support in the .NET MCP server as a workaround for an upstream MCP SDK v1.1.0 DI scope disposal bug that triggers ObjectDisposedException during tool execution.

Changes:

  • Commented out InMemoryMcpTaskStore registration to force synchronous tool execution.
  • Updated dotnet_server_capabilities to report supports.asyncTasks = false.
  • Adjusted conformance/capabilities tests to validate graceful degradation (no tasks capability advertised) and updated assertions.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File Description
DotNetMcp/Program.cs Disables task store registration with TODO + upstream issue reference.
DotNetMcp/Tools/Cli/DotNetCliTools.Misc.cs Reports AsyncTasks = false in server capabilities output.
DotNetMcp.Tests/Server/McpConformanceTests.cs Replaces task lifecycle tests with degradation/synchronous execution checks.
DotNetMcp.Tests/Server/ServerCapabilitiesTests.cs Updates assertions to expect asyncTasks to be false.

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DotNetMcp/Tools/Cli/DotNetCliTools.Misc.cs Outdated
Comment on lines +72 to +74
Telemetry = true, // SDK v0.6+ supports request duration logging and OpenTelemetry semantic conventions
Metrics = true, // In-memory per-tool metrics via MCP message filter (dotnet_server_metrics tool)
AsyncTasks = true, // MCP Task support enabled: long-running operations (build, test, publish) can run as async tasks
AsyncTasks = false, // Disabled: MCP SDK DI scope bug (https://github.com/modelcontextprotocol/csharp-sdk/issues/1430)
DotNetMcp.Tests/Server/McpConformanceTests.cs Outdated
Comment on lines +744 to +746
// Assert - the tool attribute declares TaskSupport = Optional so it's ready when
// task support is enabled via Features:EnableTaskSupport. Without a task store
// registered, the SDK runs it synchronously inline (graceful degradation).
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jongalloway commented Mar 18, 2026

@copilot

@jongalloway
fix: derive AsyncTasks from IMcpTaskStore DI registration; fix mislea…
5117fca 
…ding comment

Co-authored-by: jongalloway <68539+jongalloway@users.noreply.github.com>
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Copilot AI commented Mar 18, 2026

@copilot

Addressed both review comments in commit 5117fca:

  1. DotNetCliTools.Misc.cs – Added optional IMcpTaskStore? parameter to the DotNetCliTools constructor and stored it in _taskStore. AsyncTasks is now derived at runtime from _taskStore != null, so dotnet_server_capabilities always reflects the actual DI configuration and can't drift when the task store is re-enabled.

  2. McpConformanceTests.cs – Replaced the non-existent "Features:EnableTaskSupport" reference with a direct mention of un-commenting the IMcpTaskStore registration in Program.cs and the upstream SDK issue link.

All 55 conformance + capabilities tests continue to pass.

@jongalloway jongalloway merged commit d282b1c into main Mar 18, 2026
4 checks passed
@jongalloway jongalloway deleted the fix/disable-task-store-di-scope-bug branch March 18, 2026 03:15
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