diff --git a/Sources/Knit/ConcurrencyAttribute.swift b/Sources/Knit/ConcurrencyAttribute.swift
new file mode 100644
index 0000000..bf7ebe2
--- /dev/null
+++ b/Sources/Knit/ConcurrencyAttribute.swift
@@ -0,0 +1,16 @@
+//
+// Copyright © Block, Inc. All rights reserved.
+//
+
+/// The possible concurrency isolation for a registration.
+public enum ConcurrencyAttribute {
+    /// We do not currently have a way to forward this information through Swinject Behavior hooks
+    /// so registrations that come from behaviors will be unknown.
+    case unknown
+
+    /// The default.
+    case nonisolated
+
+    /// Corresponds to the `@MainActor` attribute.
+    case MainActor
+}
diff --git a/Sources/Knit/Module/Container+AbstractRegistration.swift b/Sources/Knit/Module/Container+AbstractRegistration.swift
index a8238e7..0545cee 100644
--- a/Sources/Knit/Module/Container+AbstractRegistration.swift
+++ b/Sources/Knit/Module/Container+AbstractRegistration.swift
@@ -12,9 +12,10 @@ extension Container {
     public func registerAbstract<Service>(
         _ serviceType: Service.Type,
         name: String? = nil,
+        concurrency: ConcurrencyAttribute = .nonisolated,
         file: String = #fileID
     ) {
-        let registration = RealAbstractRegistration<Service>(name: name, file: file)
+        let registration = RealAbstractRegistration<Service>(name: name, file: file, concurrency: concurrency)
         abstractRegistrations().abstractRegistrations.append(registration)
     }
 
@@ -26,9 +27,10 @@ extension Container {
     public func registerAbstract<Service>(
         _ serviceType: Optional<Service>.Type,
         name: String? = nil,
+        concurrency: ConcurrencyAttribute = .nonisolated,
         file: String = #fileID
     ) {
-        let registration = OptionalAbstractRegistration<Service>(name: name, file: file)
+        let registration = OptionalAbstractRegistration<Service>(name: name, file: file, concurrency: concurrency)
         abstractRegistrations().abstractRegistrations.append(registration)
     }
 
@@ -50,6 +52,7 @@ extension Container {
 internal struct RegistrationKey: Hashable, Equatable {
     let typeIdentifier: ObjectIdentifier
     let name: String?
+    let concurrency: ConcurrencyAttribute
 }
 
 /// Protocol version to allow storing generic types an array
@@ -60,6 +63,7 @@ internal protocol AbstractRegistration {
     var file: String { get }
     var name: String? { get }
     var key: RegistrationKey { get }
+    var concurrency: ConcurrencyAttribute { get }
 
     /// Register a placeholder registration to fill the unfulfilled abstract registration
     /// This placeholder cannot be resolved
@@ -89,8 +93,14 @@ fileprivate struct RealAbstractRegistration<ServiceType>: AbstractRegistration {
 
     var serviceType: ServiceType.Type { ServiceType.self }
 
+    let concurrency: ConcurrencyAttribute
+
     var key: RegistrationKey {
-        return .init(typeIdentifier: ObjectIdentifier(ServiceType.self), name: name)
+        return .init(
+            typeIdentifier: ObjectIdentifier(ServiceType.self),
+            name: name,
+            concurrency: concurrency
+        )
     }
 
     func registerPlaceholder(
@@ -113,8 +123,10 @@ fileprivate struct OptionalAbstractRegistration<ServiceType>: AbstractRegistrati
 
     var serviceType: ServiceType.Type { ServiceType.self }
 
+    let concurrency: ConcurrencyAttribute
+
     var key: RegistrationKey {
-        return .init(typeIdentifier: ObjectIdentifier(ServiceType.self), name: name)
+        return .init(typeIdentifier: ObjectIdentifier(ServiceType.self), name: name, concurrency: concurrency)
     }
 
     func registerPlaceholder(
@@ -171,12 +183,23 @@ extension Container {
             toService entry: ServiceEntry<Service>,
             withName name: String?
         ) {
-            let id = RegistrationKey(typeIdentifier: ObjectIdentifier(Type.self), name: name)
+            let id = RegistrationKey(
+                typeIdentifier: ObjectIdentifier(Type.self),
+                name: name,
+                concurrency: .unknown
+            )
             concreteRegistrations.insert(id)
         }
 
         var unfulfilledRegistrations: [any AbstractRegistration] {
-            abstractRegistrations.filter { !concreteRegistrations.contains($0.key) }
+            abstractRegistrations.filter { abstractRegistration in
+                let abstractKey = abstractRegistration.key
+                return !concreteRegistrations.contains { concreteKey in
+                    // We need to ignore the concurrency attribute currently due to Swinject limitations
+                    concreteKey.typeIdentifier == abstractKey.typeIdentifier &&
+                        concreteKey.name == abstractKey.name
+                }
+            }
         }
 
         // Throws an error if any abstract registrations have not been implemented
diff --git a/Sources/KnitCodeGen/Configuration.swift b/Sources/KnitCodeGen/Configuration.swift
index c44ddcb..e969fa5 100644
--- a/Sources/KnitCodeGen/Configuration.swift
+++ b/Sources/KnitCodeGen/Configuration.swift
@@ -13,7 +13,6 @@ public struct Configuration: Encodable, Sendable {
     public var directives: KnitDirectives
 
     public enum AssemblyType: String, Encodable, Sendable {
-        /// `Swinject.Assembly`
         case moduleAssembly = "ModuleAssembly"
         case autoInitAssembly = "AutoInitModuleAssembly"
         case abstractAssembly = "AbstractAssembly"
diff --git a/Sources/KnitCodeGen/FunctionCallRegistrationParsing.swift b/Sources/KnitCodeGen/FunctionCallRegistrationParsing.swift
index eeb97d9..633ddb3 100644
--- a/Sources/KnitCodeGen/FunctionCallRegistrationParsing.swift
+++ b/Sources/KnitCodeGen/FunctionCallRegistrationParsing.swift
@@ -285,9 +285,19 @@ private func getConcurrencyModifier(
     arguments: LabeledExprListSyntax,
     trailingClosure: ClosureExprSyntax?
 ) -> String? {
+    // Detects concrete registrations that use the explicitly named closure argument
     if arguments.contains(where: {$0.label?.text == "mainActorFactory" }) {
         return "@MainActor"
     }
+    // Detects abstract registrations
+    for arg in arguments {
+        guard arg.label?.text == "concurrency" else { continue }
+        // Corresponds to `(concurrency: .MainActor)`
+        // declName is what follows the period
+        if arg.expression.as(MemberAccessExprSyntax.self)?.declName.baseName.text == "MainActor" {
+            return "@MainActor"
+        }
+    }
     guard let signature = trailingClosure?.signature else { return nil }
     for att in signature.attributes {
         guard case let .attribute(attributeSyntax) = att else {
diff --git a/Tests/KnitCodeGenTests/RegistrationParsingTests.swift b/Tests/KnitCodeGenTests/RegistrationParsingTests.swift
index f7f136f..d7ac2a5 100644
--- a/Tests/KnitCodeGenTests/RegistrationParsingTests.swift
+++ b/Tests/KnitCodeGenTests/RegistrationParsingTests.swift
@@ -134,6 +134,16 @@ final class RegistrationParsingTests: XCTestCase {
             serviceName: "AType",
             name: "service"
         )
+
+        try assertRegistrationString(
+            """
+            container.registerAbstract(AType.self, name: "service", concurrency: .MainActor)
+            """,
+            serviceName: "AType",
+            name: "service",
+            concurrencyModifier: "@MainActor"
+        )
+
     }
 
     func testForwardedRegistration() throws {
@@ -637,6 +647,7 @@ private func assertRegistrationString(
     accessLevel: AccessLevel = .internal,
     name: String? = nil,
     isForwarded: Bool = false,
+    concurrencyModifier: String? = nil,
     file: StaticString = #filePath, line: UInt = #line
 ) throws {
     let functionCall = try XCTUnwrap(FunctionCallExprSyntax("\(raw: string)" as ExprSyntax))
@@ -651,6 +662,7 @@ private func assertRegistrationString(
     XCTAssertEqual(registration?.accessLevel, accessLevel, file: file, line: line)
     XCTAssertEqual(registration?.name, name, file: file, line: line)
     XCTAssertEqual(registration?.isForwarded, isForwarded, file: file, line: line)
+    XCTAssertEqual(registration?.concurrencyModifier, concurrencyModifier, file: file, line: line)
 }
 
 /// Assert that multiple registrations exist within the string.