Fix mutation convention type names with snake_case naming conventions

[michaelstaib]

• normalize mutation name placeholders in mutation conventions from snake_case to PascalCase
• apply this for generated input, payload, and error type names
• add a regression test for issue Mutation conventions + default naming convention mixup #4803 (MutationConvention_With_SnakeCase_ObjectField_NamingConvention_Uses_PascalCase_TypeNames)

Closes #4803

[github-actions]

Fusion Gateway Performance Results

Simple Composite Query

	Req/s	Err%
Constant (50 VUs)	6989.76	0.00%
Ramping (0-500-0 VUs)	7319.58	0.00%

Response Times & Query

	Min	Med	Avg	P90	P95	Max
Constant	0.58ms	5.89ms	7.01ms	10.86ms	15.64ms	177.91ms
Ramping	0.62ms	24.13ms	30.05ms	63.95ms	76.20ms	193.36ms

query TestQuery {
  topProducts(first: 5) {
    inStock
    name
    price
    shippingEstimate
    upc
    weight
    reviews {
      id
      body
      author {
        id
        username
        name
      }
    }
  }
}

---

Deep Recursion Query

	Req/s	Err%
Constant (50 VUs)	1280.34	0.00%
Ramping (0-500-0 VUs)	1351.21	0.00%

Response Times & Query

	Min	Med	Avg	P90	P95	Max
Constant	3.73ms	34.11ms	37.93ms	51.81ms	61.70ms	451.15ms
Ramping	1.91ms	133.67ms	156.96ms	338.88ms	386.88ms	657.73ms

query TestQuery {
  users {
    id
    username
    name
    reviews {
      id
      body
      product {
        inStock
        name
        price
        shippingEstimate
        upc
        weight
        reviews {
          id
          body
          author {
            id
            username
            name
            reviews {
              id
              body
              product {
                inStock
                name
                price
                shippingEstimate
                upc
                weight
              }
            }
          }
        }
      }
    }
  }
  topProducts(first: 5) {
    inStock
    name
    price
    shippingEstimate
    upc
    weight
    reviews {
      id
      body
      author {
        id
        username
        name
        reviews {
          id
          body
          product {
            inStock
            name
            price
            shippingEstimate
            upc
            weight
          }
        }
      }
    }
  }
}

---

Variable Batching Throughput

	Req/s	Err%
Constant (50 VUs)	23688.14	0.00%
Ramping (0-500-0 VUs)	18380.06	0.00%

Response Times & Query

	Min	Med	Avg	P90	P95	Max
Constant	0.08ms	1.72ms	2.06ms	3.95ms	4.79ms	43.64ms
Ramping	0.08ms	9.48ms	11.47ms	23.62ms	28.15ms	104.27ms

query TestQuery($upc: ID!, $price: Long!, $weight: Long!) {
  productByUpc(upc: $upc) {
    inStock
    shippingEstimate(weight: $weight, price: $price)
  }
}

Variables (5 sets batched per request)

[
  { "upc": "1", "price": 899, "weight": 100 },
  { "upc": "2", "price": 1299, "weight": 1000 },
  { "upc": "3", "price": 15, "weight": 20 },
  { "upc": "4", "price": 499, "weight": 100 },
  { "upc": "5", "price": 1299, "weight": 1000 }
]

---

Run 22393065855 • Commit bdcb1c0 • Wed, 25 Feb 2026 11:13:50 GMT