[MCP] Fixed issue with deserialization of prompt settings

[glen-84]

Summary of the changes (Less than 80 chars)

• [MCP] Fixed issue with deserialization of prompt settings.

[Copilot]

Pull request overview

This PR fixes a deserialization issue with MCP prompt settings when using polymorphic types. The fix enables proper handling of JSON where the type discriminator property (type) appears after other properties in the JSON object, which is a known limitation in System.Text.Json's polymorphic deserialization.

Changes:

• Added AllowOutOfOrderMetadataProperties = true to McpSettingsSerializerContext to support out-of-order discriminator properties in polymorphic JSON deserialization
• Created new test project Adapters.Mcp.Core.Tests with a test validating the fix for polymorphic message content deserialization
• Updated solution files to include the new test project

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
McpSettingsSerializerContext.cs	Added AllowOutOfOrderMetadataProperties = true option to fix polymorphic deserialization when discriminator appears after data properties
McpPromptSettingsSerializerTests.cs	New test file validating that prompt settings with polymorphic content can be deserialized when the type discriminator appears after other properties
HotChocolate.Adapters.Mcp.Core.Tests.csproj	New test project configuration file following the standard patterns used in the codebase
Adapters.slnx	Updated solution file to include new test project
All.slnx	Updated master solution file to include new test project

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[github-actions]

🚀 Fusion Gateway Performance Results

Simple Composite Query

Constant Load (50 VUs)

Requests/sec	Error Rate
5763.20 req/s	0.00%

📊 Response Time Metrics

Min	Med	Max	Avg	P90	P95
0.81ms	7.16ms	165.36ms	8.52ms	13.19ms	18.61ms

Ramping Load (0→50→500→50 VUs)

Requests/sec	Error Rate
4565.93 req/s	0.00%

📊 Response Time Metrics

Min	Med	Max	Avg	P90	P95
0.80ms	37.60ms	283.17ms	48.54ms	109.94ms	126.85ms

Executed Query

fragment User on User {
  id
  username
  name
}

fragment Review on Review {
  id
  body
}

fragment Product on Product {
  inStock
  name
  price
  shippingEstimate
  upc
  weight
}

query TestQuery {
  topProducts(first: 5) {
    ...Product
    reviews {
      ...Review
      author {
        ...User
      }
    }
  }
}

Deep Recursion Query

Constant Load (50 VUs)

Requests/sec	Error Rate
268.55 req/s	0.00%

📊 Response Time Metrics

Min	Med	Max	Avg	P90	P95
12.52ms	174.89ms	571.49ms	180.53ms	227.28ms	251.15ms

Ramping Load (0→50→500→50 VUs)

Requests/sec	Error Rate
306.20 req/s	0.00%

📊 Response Time Metrics

Min	Med	Max	Avg	P90	P95
3.11ms	663.13ms	1724.68ms	690.02ms	1382.05ms	1506.15ms

Executed Query

fragment User on User {
  id
  username
  name
}

fragment Review on Review {
  id
  body
}

fragment Product on Product {
  inStock
  name
  price
  shippingEstimate
  upc
  weight
}

query TestQuery {
  users {
    ...User
    reviews {
      ...Review
      product {
        ...Product
        reviews {
          ...Review
          author {
            ...User
            reviews {
              ...Review
              product {
                ...Product
              }
            }
          }
        }
      }
    }
  }
  topProducts(first: 5) {
    ...Product
    reviews {
      ...Review
      author {
        ...User
        reviews {
          ...Review
          product {
            ...Product
          }
        }
      }
    }
  }
}

Variable Batching Throughput

Constant Load (50 VUs)

Requests/sec	Error Rate
23592.37 req/s	0.00%

📊 Response Time Metrics

Min	Med	Max	Avg	P90	P95
0.09ms	1.71ms	49.82ms	2.07ms	3.93ms	4.82ms

Ramping Load (0→50→500→50 VUs)

Requests/sec	Error Rate
18608.77 req/s	0.00%

📊 Response Time Metrics

Min	Med	Max	Avg	P90	P95
0.09ms	9.35ms	122.45ms	11.35ms	23.43ms	28.45ms

Executed Query

query TestQuery_8f7a46ce_2(
  $__fusion_1_upc: ID!
  $__fusion_2_price: Long!
  $__fusion_2_weight: Long!
) {
  productByUpc(upc: $__fusion_1_upc) {
    inStock
    shippingEstimate(weight: $__fusion_2_weight, price: $__fusion_2_price)
  }
}

Variables (5 sets batched in single request)

[
  { "__fusion_1_upc": "1", "__fusion_2_price": 899, "__fusion_2_weight": 100 },
  { "__fusion_1_upc": "2", "__fusion_2_price": 1299, "__fusion_2_weight": 1000 },
  { "__fusion_1_upc": "3", "__fusion_2_price": 15, "__fusion_2_weight": 20 },
  { "__fusion_1_upc": "4", "__fusion_2_price": 499, "__fusion_2_weight": 100 },
  { "__fusion_1_upc": "5", "__fusion_2_price": 1299, "__fusion_2_weight": 1000 }
]

No baseline data available for comparison.

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Run 21624270459 • Commit cea6215 • Tue, 03 Feb 2026 09:35:11 GMT