diff --git a/Sources/ApolloCodegenLib/ApolloCodegen.swift b/Sources/ApolloCodegenLib/ApolloCodegen.swift
index 7768b69c15..bfcf62e2d4 100644
--- a/Sources/ApolloCodegenLib/ApolloCodegen.swift
+++ b/Sources/ApolloCodegenLib/ApolloCodegen.swift
@@ -22,6 +22,7 @@ public class ApolloCodegen {
     case invalidSchemaName(_ name: String, message: String)
     case targetNameConflict(name: String)
     case typeNameConflict(name: String, conflictingName: String, containingObject: String)
+    case failedToComputeOperationIdentifier(type: String, name: String, error: Swift.Error)
 
     public var errorDescription: String? {
       switch self {
@@ -64,6 +65,8 @@ public class ApolloCodegen {
         Recommend using a field alias for one of these fields to resolve this conflict. \
         For more info see: https://www.apollographql.com/docs/ios/troubleshooting/codegen-troubleshooting#typenameconflict
         """
+      case let .failedToComputeOperationIdentifier(type, name, error):
+        return "Received failure while computing operation identifier for \(type) named '\(name)', Error: \(error.localizedDescription)"
       }
     }
   }
@@ -91,6 +94,9 @@ public class ApolloCodegen {
     
   }
 
+  /// A `nil` result is treated as a cancellation, and the default operationIdentifier is used
+  public typealias ComputeOperationIdentifier = (any IROperation, @escaping (Result<String, Swift.Error>?) -> Void) -> Void
+
   /// Executes the code generation engine with a specified configuration.
   ///
   /// - Parameters:
@@ -103,16 +109,18 @@ public class ApolloCodegen {
   public static func build(
     with configuration: ApolloCodegenConfiguration,
     withRootURL rootURL: URL? = nil,
-    itemsToGenerate: ItemsToGenerate = [.code]
+    itemsToGenerate: ItemsToGenerate = [.code],
+    computeOperationIdentifier: ComputeOperationIdentifier? = nil
   ) throws {
-    try build(with: configuration, rootURL: rootURL, itemsToGenerate: itemsToGenerate)
+    try build(with: configuration, rootURL: rootURL, itemsToGenerate: itemsToGenerate, computeOperationIdentifier: computeOperationIdentifier)
   }
 
   internal static func build(
     with configuration: ApolloCodegenConfiguration,
     rootURL: URL? = nil,
     fileManager: ApolloFileManager = .default,
-    itemsToGenerate: ItemsToGenerate
+    itemsToGenerate: ItemsToGenerate,
+    computeOperationIdentifier: ComputeOperationIdentifier? = nil
   ) throws {
 
     let configContext = ConfigurationContext(
@@ -131,29 +139,34 @@ public class ApolloCodegen {
 
     let ir = IR(compilationResult: compilationResult)
 
-    var existingGeneratedFilePaths: Set<String>?
-
-    if itemsToGenerate.contains(.code) && configuration.options.pruneGeneratedFiles {
-      existingGeneratedFilePaths = try findExistingGeneratedFilePaths(
+    let generate: () throws -> Void = {
+      try generateFiles(
+        compilationResult: compilationResult,
+        ir: ir,
         config: configContext,
-        fileManager: fileManager
+        fileManager: fileManager,
+        itemsToGenerate: itemsToGenerate,
+        computeOperationIdentifier: computeOperationIdentifier
       )
     }
 
-    try generateFiles(
-      compilationResult: compilationResult,
-      ir: ir,
-      config: configContext,
-      fileManager: fileManager,
-      itemsToGenerate: itemsToGenerate
-    )
-
-    if var existingGeneratedFilePaths {
+    let generateWithPruning: () throws -> Void = {
+      var existingGeneratedFilePaths = try findExistingGeneratedFilePaths(
+        config: configContext,
+        fileManager: fileManager
+      )
+      try generate()
       try deleteExtraneousGeneratedFiles(
         from: &existingGeneratedFilePaths,
         afterCodeGenerationUsing: fileManager
       )
     }
+
+    if itemsToGenerate.contains(.code) && configuration.options.pruneGeneratedFiles {
+      try generateWithPruning()
+    } else {
+      try generate()
+    }
   }
 
   // MARK: Internal
@@ -412,7 +425,8 @@ public class ApolloCodegen {
     ir: IR,
     config: ConfigurationContext,
     fileManager: ApolloFileManager = .default,
-    itemsToGenerate: ItemsToGenerate
+    itemsToGenerate: ItemsToGenerate,
+    computeOperationIdentifier: ComputeOperationIdentifier? = nil
   ) throws {
 
     if itemsToGenerate.contains(.code) {
@@ -431,9 +445,40 @@ public class ApolloCodegen {
       operationIDsFileGenerator = OperationManifestFileGenerator(config: config)
     }
 
-    for operation in compilationResult.operations {
+    let irOperations = compilationResult.operations.map { ir.build(operation: $0) }
+    var results = [Result<String, Swift.Error>?](repeating: nil, count: irOperations.count)
+
+    if let computeOperationIdentifier {
+      let dispatchGroup = DispatchGroup()
+      DispatchQueue.concurrentPerform(iterations: irOperations.count) { index in
+        let irOperation = irOperations[index]
+        var sources: [String] = [irOperation.definition.source.convertedToSingleLine()]
+        for fragment in irOperation.referencedFragments {
+          sources.append(fragment.definition.source.convertedToSingleLine())
+        }
+        dispatchGroup.enter()
+        computeOperationIdentifier(irOperation) { result in
+          results[index] = result
+          dispatchGroup.leave()
+        }
+      }
+      dispatchGroup.wait()
+    }
+
+    for (index, irOperation) in irOperations.enumerated() {
       try autoreleasepool {
-        let irOperation = ir.build(operation: operation)
+        if let result = results[index] {
+          switch result {
+          case .success(let operationIdentifier):
+            irOperation.operationIdentifier = operationIdentifier
+          case .failure(let error):
+            throw Error.failedToComputeOperationIdentifier(
+              type: irOperation.definition.operationType.rawValue,
+              name: irOperation.definition.name,
+              error: error
+            )
+          }
+        }
 
         if itemsToGenerate.contains(.code) {
           try validateTypeConflicts(for: irOperation.rootField.selectionSet, with: config, in: irOperation.definition.name)
@@ -611,4 +656,24 @@ public class ApolloCodegen {
 
 }
 
+public protocol IROperation: AnyObject {
+  var filePath: String { get }
+  var name: String { get }
+  var source: String { get }
+  var type: CompilationResult.OperationType { get }
+}
+
+extension IR.Operation: IROperation {
+  public var filePath: String { definition.filePath }
+  public var name: String { definition.name }
+  public var source: String {
+    var sources: [String] = [definition.source.convertedToSingleLine()]
+    for fragment in referencedFragments {
+      sources.append(fragment.definition.source.convertedToSingleLine())
+    }
+    return sources.joined(separator: "\n")
+  }
+  public var type: CompilationResult.OperationType { definition.operationType }
+}
+
 #endif
diff --git a/Sources/ApolloCodegenLib/ApolloSchemaDownloader.swift b/Sources/ApolloCodegenLib/ApolloSchemaDownloader.swift
index 295198d64e..491d9f04dd 100644
--- a/Sources/ApolloCodegenLib/ApolloSchemaDownloader.swift
+++ b/Sources/ApolloCodegenLib/ApolloSchemaDownloader.swift
@@ -46,11 +46,13 @@ public struct ApolloSchemaDownloader {
   ///   - configuration: The `ApolloSchemaDownloadConfiguration` used to download the schema.
   ///   - rootURL: The root `URL` to resolve relative `URL`s in the configuration's paths against.
   ///     If `nil`, the current working directory of the executing process will be used.
+  ///   - session: The network session to use for the download. If `nil` the `URLSession.Shared` will be used by default.
   /// - Returns: Output from a successful fetch or throws an error.
   /// - Throws: Any error which occurs during the fetch.
   public static func fetch(
     configuration: ApolloSchemaDownloadConfiguration,
-    withRootURL rootURL: URL? = nil
+    withRootURL rootURL: URL? = nil,
+    session: NetworkSession? = nil
   ) throws {
     try ApolloFileManager.default.createContainingDirectoryIfNeeded(
       forPath: configuration.outputPath
@@ -63,14 +65,16 @@ public struct ApolloSchemaDownloader {
         httpMethod: httpMethod,
         includeDeprecatedInputValues: includeDeprecatedInputValues,
         configuration: configuration,
-        withRootURL: rootURL
+        withRootURL: rootURL,
+        session: session
       )
 
     case .apolloRegistry(let settings):
       try self.downloadFrom(
         registry: settings,
         configuration: configuration,
-        withRootURL: rootURL
+        withRootURL: rootURL,
+        session: session
       )
     }
   }
@@ -136,7 +140,8 @@ public struct ApolloSchemaDownloader {
   static func downloadFrom(
     registry: ApolloSchemaDownloadConfiguration.DownloadMethod.ApolloRegistrySettings,
     configuration: ApolloSchemaDownloadConfiguration,
-    withRootURL rootURL: URL?
+    withRootURL rootURL: URL?,
+    session: NetworkSession? = nil
   ) throws {
     CodegenLogger.log("Downloading schema from registry", logLevel: .debug)
 
@@ -145,7 +150,7 @@ public struct ApolloSchemaDownloader {
       .parentFolderURL()
       .appendingPathComponent("registry_response.json")
 
-    try URLDownloader().downloadSynchronously(
+    try URLDownloader(session: session).downloadSynchronously(
       urlRequest,
       to: jsonOutputURL,
       timeout: configuration.downloadTimeout
@@ -339,7 +344,8 @@ public struct ApolloSchemaDownloader {
     httpMethod: ApolloSchemaDownloadConfiguration.DownloadMethod.HTTPMethod,
     includeDeprecatedInputValues: Bool,
     configuration: ApolloSchemaDownloadConfiguration,
-    withRootURL: URL?
+    withRootURL: URL?,
+    session: NetworkSession? = nil
   ) throws {
 
     CodegenLogger.log("Downloading schema via introspection from \(endpoint)", logLevel: .debug)
@@ -361,8 +367,7 @@ public struct ApolloSchemaDownloader {
       }
     }()
 
-    
-    try URLDownloader().downloadSynchronously(
+    try URLDownloader(session: session).downloadSynchronously(
       urlRequest,
       to: jsonOutputURL,
       timeout: configuration.downloadTimeout
diff --git a/Sources/ApolloCodegenLib/Frontend/CompilationResult.swift b/Sources/ApolloCodegenLib/Frontend/CompilationResult.swift
index 335ed22799..fb6d9aedc0 100644
--- a/Sources/ApolloCodegenLib/Frontend/CompilationResult.swift
+++ b/Sources/ApolloCodegenLib/Frontend/CompilationResult.swift
@@ -1,7 +1,7 @@
 import JavaScriptCore
 
 /// The output of the frontend compiler.
-public class CompilationResult: JavaScriptObject {
+public final class CompilationResult: JavaScriptObject {
   private enum Constants {
     static let LocalCacheMutationDirectiveName = "apollo_client_ios_localCacheMutation"
   }
@@ -15,7 +15,7 @@ public class CompilationResult: JavaScriptObject {
 
   lazy var schemaDocumentation: String? = self["schemaDocumentation"]
   
-  public class RootTypeDefinition: JavaScriptObject {
+  public final class RootTypeDefinition: JavaScriptObject {
     lazy var queryType: GraphQLNamedType = self["queryType"]
     
     lazy var mutationType: GraphQLNamedType? = self["mutationType"]
@@ -23,7 +23,7 @@ public class CompilationResult: JavaScriptObject {
     lazy var subscriptionType: GraphQLNamedType? = self["subscriptionType"]
   }
   
-  public class OperationDefinition: JavaScriptObject, Hashable {
+  public final class OperationDefinition: JavaScriptObject, Hashable {
     lazy var name: String = self["name"]
     
     lazy var operationType: OperationType = self["operationType"]
@@ -94,7 +94,7 @@ public class CompilationResult: JavaScriptObject {
     }
   }
   
-  public class VariableDefinition: JavaScriptObject {
+  public final class VariableDefinition: JavaScriptObject {
     lazy var name: String = self["name"]
     
     lazy var type: GraphQLType = self["type"]
@@ -102,7 +102,7 @@ public class CompilationResult: JavaScriptObject {
     lazy var defaultValue: GraphQLValue? = self["defaultValue"]
   }
   
-  public class FragmentDefinition: JavaScriptObject, Hashable {
+  public final class FragmentDefinition: JavaScriptObject, Hashable {
     lazy var name: String = self["name"]
     
     lazy var type: GraphQLCompositeType = self["typeCondition"]
@@ -132,7 +132,7 @@ public class CompilationResult: JavaScriptObject {
     }
   }
   
-  public class SelectionSet: JavaScriptWrapper, Hashable, CustomDebugStringConvertible {
+  public final class SelectionSet: JavaScriptWrapper, Hashable, CustomDebugStringConvertible {
     lazy var parentType: GraphQLCompositeType = self["parentType"]
     
     lazy var selections: [Selection] = self["selections"]
@@ -165,7 +165,7 @@ public class CompilationResult: JavaScriptObject {
     }
   }
 
-  public class InlineFragment: JavaScriptObject, Hashable {
+  public final class InlineFragment: JavaScriptObject, Hashable {
     lazy var selectionSet: SelectionSet = self["selectionSet"]
 
     lazy var inclusionConditions: [InclusionCondition]? = self["inclusionConditions"]
@@ -187,7 +187,7 @@ public class CompilationResult: JavaScriptObject {
 
   /// Represents an individual selection that includes a named fragment in a selection set.
   /// (ie. `...FragmentName`)
-  public class FragmentSpread: JavaScriptObject, Hashable {
+  public final class FragmentSpread: JavaScriptObject, Hashable {
     lazy var fragment: FragmentDefinition = self["fragment"]
 
     lazy var inclusionConditions: [InclusionCondition]? = self["inclusionConditions"]
@@ -253,7 +253,7 @@ public class CompilationResult: JavaScriptObject {
     }
   }
   
-  public class Field: JavaScriptWrapper, Hashable, CustomDebugStringConvertible {
+  public final class Field: JavaScriptWrapper, Hashable, CustomDebugStringConvertible {
     lazy var name: String = self["name"]!
     
     lazy var alias: String? = self["alias"]
@@ -330,7 +330,7 @@ public class CompilationResult: JavaScriptObject {
     }
   }
   
-  public class Argument: JavaScriptObject, Hashable {
+  public final class Argument: JavaScriptObject, Hashable {
     lazy var name: String = self["name"]
 
     lazy var type: GraphQLType = self["type"]
@@ -352,7 +352,7 @@ public class CompilationResult: JavaScriptObject {
     }
   }
 
-  public class Directive: JavaScriptObject, Hashable {
+  public final class Directive: JavaScriptObject, Hashable {
     lazy var name: String = self["name"]
 
     lazy var arguments: [Argument]? = self["arguments"]
diff --git a/Sources/ApolloCodegenLib/IR/IR.swift b/Sources/ApolloCodegenLib/IR/IR.swift
index b19724aae3..ebeb8fd584 100644
--- a/Sources/ApolloCodegenLib/IR/IR.swift
+++ b/Sources/ApolloCodegenLib/IR/IR.swift
@@ -1,7 +1,7 @@
 import OrderedCollections
 import CryptoKit
 
-class IR {
+final class IR {
 
   let compilationResult: CompilationResult
 
@@ -85,7 +85,7 @@ class IR {
   ///
   /// Multiple `SelectionSet`s may select fields on the same `Entity`. All `SelectionSet`s that will
   /// be selected on the same object share the same `Entity`.
-  class Entity {
+  final class Entity {
 
     /// Represents the location within a GraphQL definition (operation or fragment) of an `Entity`.
     struct Location: Hashable {
@@ -170,7 +170,7 @@ class IR {
     }
   }
 
-  class Operation {
+  final class Operation {
     let definition: CompilationResult.OperationDefinition
 
     /// The root field of the operation. This field must be the root query, mutation, or
@@ -218,7 +218,7 @@ class IR {
     }
   }
 
-  class NamedFragment: Hashable, CustomDebugStringConvertible {
+  final class NamedFragment: Hashable, CustomDebugStringConvertible {
     let definition: CompilationResult.FragmentDefinition
     let rootField: EntityField
 
@@ -264,7 +264,7 @@ class IR {
 
   /// Represents an Inline Fragment that has been "spread into" another SelectionSet using the
   /// spread operator (`...`).
-  class InlineFragmentSpread: Hashable, CustomDebugStringConvertible {
+  final class InlineFragmentSpread: Hashable, CustomDebugStringConvertible {
     /// The `SelectionSet` representing the inline fragment that has been "spread into" its
     /// enclosing operation/fragment.
     let selectionSet: SelectionSet
@@ -310,7 +310,7 @@ class IR {
   ///
   /// While a `NamedFragment` can be shared between operations, a `NamedFragmentSpread` represents a
   /// `NamedFragment` included in a specific operation.
-  class NamedFragmentSpread: Hashable, CustomDebugStringConvertible {
+  final class NamedFragmentSpread: Hashable, CustomDebugStringConvertible {
 
     /// The `NamedFragment` that this fragment refers to.
     ///
diff --git a/Sources/ApolloCodegenLib/URLDownloader.swift b/Sources/ApolloCodegenLib/URLDownloader.swift
index 63303a5b58..b47e9665f3 100644
--- a/Sources/ApolloCodegenLib/URLDownloader.swift
+++ b/Sources/ApolloCodegenLib/URLDownloader.swift
@@ -1,7 +1,7 @@
 import Foundation
 
 /// A protocol to abstract the underlying network provider.
-protocol NetworkSession {
+public protocol NetworkSession {
 
   /// Load data via the abstracted network provider
   ///
@@ -18,7 +18,7 @@ protocol NetworkSession {
 }
 
 extension URLSession: NetworkSession {
-  func loadData(
+  public func loadData(
     with urlRequest: URLRequest,
     completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void
   ) -> URLSessionDataTask? {
@@ -63,8 +63,8 @@ class URLDownloader {
   /// - Parameters:
   ///   - session: The NetworkSession conforming instance used for downloads, defaults to the
   ///   shared URLSession singleton object.
-  init(session: NetworkSession = URLSession.shared) {
-    self.session = session
+  init(session: NetworkSession? = nil) {
+    self.session = session ?? URLSession.shared
   }
   
   /// Downloads the contents of a given URL synchronously to the given output URL
diff --git a/Sources/CodegenCLI/Commands/FetchSchema.swift b/Sources/CodegenCLI/Commands/FetchSchema.swift
index 061f223f96..93521dc4d0 100644
--- a/Sources/CodegenCLI/Commands/FetchSchema.swift
+++ b/Sources/CodegenCLI/Commands/FetchSchema.swift
@@ -48,7 +48,8 @@ public struct FetchSchema: ParsableCommand {
 
     try schemaDownloadProvider.fetch(
       configuration: schemaDownload,
-      withRootURL: rootOutputURL(for: inputs)
+      withRootURL: rootOutputURL(for: inputs),
+      session: nil
     )
   }
 }
diff --git a/Sources/CodegenCLI/Commands/Generate.swift b/Sources/CodegenCLI/Commands/Generate.swift
index 270c9a08d9..f3912f7278 100644
--- a/Sources/CodegenCLI/Commands/Generate.swift
+++ b/Sources/CodegenCLI/Commands/Generate.swift
@@ -77,7 +77,8 @@ public struct Generate: ParsableCommand {
     try codegenProvider.build(
       with: configuration,
       withRootURL: rootOutputURL(for: inputs),
-      itemsToGenerate: itemsToGenerate
+      itemsToGenerate: itemsToGenerate,
+      computeOperationIdentifier: nil
     )
   }
 
@@ -85,6 +86,6 @@ public struct Generate: ParsableCommand {
     configuration: ApolloSchemaDownloadConfiguration,
     schemaDownloadProvider: SchemaDownloadProvider.Type
   ) throws {
-    try schemaDownloadProvider.fetch(configuration: configuration, withRootURL: rootOutputURL(for: inputs))
+    try schemaDownloadProvider.fetch(configuration: configuration, withRootURL: rootOutputURL(for: inputs), session: nil)
   }
 }
diff --git a/Sources/CodegenCLI/Commands/GenerateOperationManifest.swift b/Sources/CodegenCLI/Commands/GenerateOperationManifest.swift
index 2b695766cc..77f62a3460 100644
--- a/Sources/CodegenCLI/Commands/GenerateOperationManifest.swift
+++ b/Sources/CodegenCLI/Commands/GenerateOperationManifest.swift
@@ -44,7 +44,8 @@ public struct GenerateOperationManifest: ParsableCommand {
     try codegenProvider.build(
       with: configuration,
       withRootURL: rootOutputURL(for: inputs),
-      itemsToGenerate: [.operationManifest]
+      itemsToGenerate: [.operationManifest],
+      computeOperationIdentifier: nil
     )
   }
 
diff --git a/Sources/CodegenCLI/Protocols/CodegenProvider.swift b/Sources/CodegenCLI/Protocols/CodegenProvider.swift
index 96ad36a103..7deace8994 100644
--- a/Sources/CodegenCLI/Protocols/CodegenProvider.swift
+++ b/Sources/CodegenCLI/Protocols/CodegenProvider.swift
@@ -6,7 +6,8 @@ public protocol CodegenProvider {
   static func build(
     with configuration: ApolloCodegenConfiguration,
     withRootURL rootURL: URL?,
-    itemsToGenerate: ApolloCodegen.ItemsToGenerate
+    itemsToGenerate: ApolloCodegen.ItemsToGenerate,
+    computeOperationIdentifier: ApolloCodegen.ComputeOperationIdentifier?
   ) throws
 }
 
diff --git a/Sources/CodegenCLI/Protocols/SchemaDownloadProvider.swift b/Sources/CodegenCLI/Protocols/SchemaDownloadProvider.swift
index edb7debb4c..17f75f6a8a 100644
--- a/Sources/CodegenCLI/Protocols/SchemaDownloadProvider.swift
+++ b/Sources/CodegenCLI/Protocols/SchemaDownloadProvider.swift
@@ -5,7 +5,8 @@ import ApolloCodegenLib
 public protocol SchemaDownloadProvider {
   static func fetch(
     configuration: ApolloSchemaDownloadConfiguration,
-    withRootURL rootURL: URL?
+    withRootURL rootURL: URL?,
+    session: NetworkSession?
   ) throws
 }
 
diff --git a/Tests/CodegenCLITests/Support/MockApolloCodegen.swift b/Tests/CodegenCLITests/Support/MockApolloCodegen.swift
index 24592d7ba6..fd29f2e603 100644
--- a/Tests/CodegenCLITests/Support/MockApolloCodegen.swift
+++ b/Tests/CodegenCLITests/Support/MockApolloCodegen.swift
@@ -8,7 +8,8 @@ class MockApolloCodegen: CodegenProvider {
   static func build(
     with configuration: ApolloCodegenConfiguration,
     withRootURL rootURL: URL?,
-    itemsToGenerate: ApolloCodegen.ItemsToGenerate
+    itemsToGenerate: ApolloCodegen.ItemsToGenerate,
+    computeOperationIdentifier: ApolloCodegen.ComputeOperationIdentifier? = nil
   ) throws {
     guard let handler = buildHandler else {
       fatalError("You must set buildHandler before calling \(#function)!")
diff --git a/Tests/CodegenCLITests/Support/MockApolloSchemaDownloader.swift b/Tests/CodegenCLITests/Support/MockApolloSchemaDownloader.swift
index 593adcdd88..eab9b157cf 100644
--- a/Tests/CodegenCLITests/Support/MockApolloSchemaDownloader.swift
+++ b/Tests/CodegenCLITests/Support/MockApolloSchemaDownloader.swift
@@ -7,7 +7,8 @@ class MockApolloSchemaDownloader: SchemaDownloadProvider {
 
   static func fetch(
     configuration: ApolloSchemaDownloadConfiguration,
-    withRootURL rootURL: URL?
+    withRootURL rootURL: URL?,
+    session: NetworkSession?
   ) throws {
     guard let handler = fetchHandler else {
       fatalError("You must set fetchHandler before calling \(#function)!")