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Merged
glen-84 merged 7 commits into from
May 12, 2026
Merged

[MCP] Make storage observer resilient to duplicates and bad documents #9673

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f35ec47
[MCP] Deduplicate tool and prompt names on load
glen-84 May 11, 2026
bb260c8
Address Copilot feedback
glen-84 May 11, 2026
361bba3
Align with OpenAPI adapter
glen-84 May 12, 2026
111cb35
Prefer valid duplicate over invalid in RebuildToolsAsync
glen-84 May 12, 2026
0cf7c6b
Address Copilot feedback: semaphore release, deterministic test wait
glen-84 May 12, 2026
b14f1e1
Move StartAsync subscription check inside semaphore lock
glen-84 May 12, 2026
54d446c
Merge branch 'main' into gai/fix-mcp-duplicate-features
glen-84 May 12, 2026
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9 changes: 9 additions & 0 deletions ...ocolate/Adapters/src/Adapters.Mcp.Abstractions/Properties/McpAdapterResources.Designer.cs
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3 changes: 3 additions & 0 deletions src/HotChocolate/Adapters/src/Adapters.Mcp.Abstractions/Properties/McpAdapterResources.resx
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Expand Up @@ -18,6 +18,9 @@
<resheader name="writer">
<value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
</resheader>
<data name="CallToolHandler_ToolInvalid" xml:space="preserve">
<value>The tool '{0}' is currently unavailable.</value>
</data>
<data name="CallToolHandler_ToolNotFound" xml:space="preserve">
<value>The tool '{0}' was not found.</value>
</data>
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15 changes: 15 additions & 0 deletions src/HotChocolate/Adapters/src/Adapters.Mcp.Core/Handlers/CallToolHandler.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,21 @@ public static async ValueTask<CallToolResult> HandleAsync(
};
}

if (!tool.HasValidDocument)
{
return new CallToolResult
{
Content =
[
new TextContentBlock
{
Text = string.Format(CallToolHandler_ToolInvalid, context.Params.Name)
}
],
IsError = true
};
}

var requestExecutor = services.GetRequiredService<IRequestExecutor>();
var rootServiceProvider = services.GetRequiredService<IRootServiceProviderAccessor>().ServiceProvider;
var httpContext = rootServiceProvider.GetRequiredService<IHttpContextAccessor>().HttpContext!;
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214 changes: 133 additions & 81 deletions src/HotChocolate/Adapters/src/Adapters.Mcp.Core/McpStorageObserver.cs
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Expand Up @@ -68,12 +68,12 @@ public async Task StartAsync(CancellationToken cancellationToken)
_promptsSubscription = _storage
.Buffer<PromptStorageEventArgs>(TimeSpan.FromMilliseconds(500), 10)
.Where(batch => batch.Count > 0)
.Subscribe(onNext: ProcessBatch);
.Subscribe(_ => HandlePromptsChangedAsync().FireAndForget());

_toolsSubscription = _storage
.Buffer<OperationToolStorageEventArgs>(TimeSpan.FromMilliseconds(500), 10)
.Where(batch => batch.Count > 0)
.Subscribe(onNext: ProcessBatch);
.Subscribe(_ => HandleToolsChangedAsync().FireAndForget());
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try
{
Expand All @@ -89,73 +89,66 @@ await Task.WhenAll(

private async Task InitializePromptsAsync(CancellationToken cancellationToken)
{
var prompts = ImmutableDictionary.CreateBuilder<string, (Prompt, ImmutableArray<PromptMessage>)>();
using var scope = _diagnosticEvents.InitializePrompts();

foreach (var promptDefinition in await _storage.GetPromptDefinitionsAsync(cancellationToken))
{
var prompt = PromptFactory.CreatePrompt(promptDefinition);
prompts.Add(promptDefinition.Name, prompt);
}

_prompts = prompts.ToImmutable();
_registry.UpdatePrompts(_prompts);
await RebuildPromptsAsync(cancellationToken);
}

private async Task InitializeToolsAsync(CancellationToken cancellationToken)
{
var tools = ImmutableDictionary.CreateBuilder<string, OperationTool>();
using var scope = _diagnosticEvents.InitializeTools();
await RebuildToolsAsync(cancellationToken);
}

foreach (var toolDefinition in await _storage.GetOperationToolDefinitionsAsync(cancellationToken))
private async Task HandlePromptsChangedAsync()
{
if (_disposed)
{
var validationResult = s_documentValidator.Validate(_schema, toolDefinition.Document);

if (validationResult.HasErrors)
{
_diagnosticEvents.ValidationErrors(validationResult.Errors);
continue;
}

tools.Add(toolDefinition.Name, _toolFactory.CreateTool(toolDefinition));
return;
}

_tools = tools.ToImmutable();
_registry.UpdateTools(_tools);
}

private void ProcessBatch(IList<PromptStorageEventArgs> eventArgs)
{
_semaphore.Wait(_ct);
try
{
await _semaphore.WaitAsync(_ct);
}
catch (OperationCanceledException)
{
return;
}
catch (ObjectDisposedException)
{
return;
}

var rebuildSucceeded = false;
try
{
foreach (var eventArg in eventArgs)
if (_disposed)
{
switch (eventArg.Type)
{
case PromptStorageEventType.Updated:
using (_diagnosticEvents.UpdatePrompts())
{
var prompt = PromptFactory.CreatePrompt(eventArg.PromptDefinition!);
_prompts = _prompts.SetItem(eventArg.Name, prompt);
break;
}

case PromptStorageEventType.Removed:
_prompts = _prompts.Remove(eventArg.Name);
break;

default:
throw new ArgumentOutOfRangeException();
}
return;
}

_registry.UpdatePrompts(_prompts);
using var scope = _diagnosticEvents.UpdatePrompts();
await RebuildPromptsAsync(_ct);
rebuildSucceeded = true;
}
catch
{
// Ignore unexpected exceptions while processing updates.
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}
finally
{
_semaphore.Release();
try
{
_semaphore.Release();
}
catch (ObjectDisposedException)
{
}
}

if (!rebuildSucceeded)
{
return;
}

foreach (var mcpServer in _mcpServers.Values)
Expand All @@ -164,47 +157,56 @@ private void ProcessBatch(IList<PromptStorageEventArgs> eventArgs)
}
}

private void ProcessBatch(IList<OperationToolStorageEventArgs> eventArgs)
private async Task HandleToolsChangedAsync()
{
_semaphore.Wait(_ct);
if (_disposed)
{
return;
}

try
{
await _semaphore.WaitAsync(_ct);
}
catch (OperationCanceledException)
{
return;
}
catch (ObjectDisposedException)
{
return;
}

var rebuildSucceeded = false;
try
{
foreach (var eventArg in eventArgs)
if (_disposed)
{
switch (eventArg.Type)
{
case OperationToolStorageEventType.Updated:
using (_diagnosticEvents.UpdateTools())
{
var validationResult =
s_documentValidator.Validate(_schema, eventArg.ToolDefinition!.Document);

if (validationResult.HasErrors)
{
_diagnosticEvents.ValidationErrors(validationResult.Errors);
continue;
}

var tool = _toolFactory.CreateTool(eventArg.ToolDefinition!);
_tools = _tools.SetItem(eventArg.Name, tool);
break;
}

case OperationToolStorageEventType.Removed:
_tools = _tools.Remove(eventArg.Name);
break;

default:
throw new ArgumentOutOfRangeException();
}
return;
}

_registry.UpdateTools(_tools);
using var scope = _diagnosticEvents.UpdateTools();
await RebuildToolsAsync(_ct);
rebuildSucceeded = true;
}
catch
{
// Ignore unexpected exceptions while processing updates.
}
finally
{
_semaphore.Release();
try
{
_semaphore.Release();
}
catch (ObjectDisposedException)
{
}
}

if (!rebuildSucceeded)
{
return;
}

foreach (var mcpServer in _mcpServers.Values)
Expand All @@ -213,6 +215,56 @@ private void ProcessBatch(IList<OperationToolStorageEventArgs> eventArgs)
}
}

private async Task RebuildPromptsAsync(CancellationToken cancellationToken)
{
var prompts = ImmutableDictionary.CreateBuilder<string, (Prompt, ImmutableArray<PromptMessage>)>();

foreach (var promptDefinition in await _storage.GetPromptDefinitionsAsync(cancellationToken))
{
// When multiple definitions share a name (e.g. across collections published to the
// same stage), the first one wins in storage iteration order.
if (prompts.ContainsKey(promptDefinition.Name))
{
continue;
}

var prompt = PromptFactory.CreatePrompt(promptDefinition);
prompts.Add(promptDefinition.Name, prompt);
}

_prompts = prompts.ToImmutable();
_registry.UpdatePrompts(_prompts);
}

private async Task RebuildToolsAsync(CancellationToken cancellationToken)
{
var tools = ImmutableDictionary.CreateBuilder<string, OperationTool>();

foreach (var toolDefinition in await _storage.GetOperationToolDefinitionsAsync(cancellationToken))
{
// When multiple definitions share a name (e.g. across collections published to the
// same stage), the first one wins in storage iteration order.
if (tools.ContainsKey(toolDefinition.Name))
{
continue;
}

var validationResult = s_documentValidator.Validate(_schema, toolDefinition.Document);

if (validationResult.HasErrors)
{
_diagnosticEvents.ValidationErrors(validationResult.Errors);
tools.Add(toolDefinition.Name, OperationToolFactory.CreateInvalidTool(toolDefinition));
continue;
}

tools.Add(toolDefinition.Name, _toolFactory.CreateTool(toolDefinition));
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}

_tools = tools.ToImmutable();
_registry.UpdateTools(_tools);
}

public void Dispose()
{
if (_disposed)
Expand Down
6 changes: 6 additions & 0 deletions src/HotChocolate/Adapters/src/Adapters.Mcp.Core/OperationTool.cs
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Expand Up @@ -14,4 +14,10 @@ internal sealed class OperationTool(DocumentNode documentNode, Tool tool)
public Resource? ViewResource { get; init; }

public string? ViewHtml { get; init; }

/// <summary>
/// True when the tool's document validates against the current schema. Invalid tools are
/// still listed (so consumers see they exist) but calls to them must be rejected.
/// </summary>
public bool HasValidDocument { get; init; } = true;
}
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