diff --git a/Package.swift b/Package.swift
index 1255b1c..16be457 100644
--- a/Package.swift
+++ b/Package.swift
@@ -17,7 +17,7 @@ let package = Package(
         .library(name: "NetworkServer",   targets: ["NetworkServer"]),
     ],
     dependencies: [
-        .package(url: "https://github.com/luizmb/FP.git", from: "1.7.0"),
+        .package(url: "https://github.com/luizmb/FP.git", from: "1.8.1"),
         .package(url: "https://github.com/apple/swift-nio.git", from: "2.65.0"),
         .package(url: "https://github.com/swiftlang/swift-docc-plugin", from: "1.4.0"),
     ],
diff --git a/Sources/HTMLTemplating/TemplateEngine.swift b/Sources/HTMLTemplating/TemplateEngine.swift
index 87d86a8..0a696a1 100644
--- a/Sources/HTMLTemplating/TemplateEngine.swift
+++ b/Sources/HTMLTemplating/TemplateEngine.swift
@@ -62,7 +62,7 @@ public struct HTMLEnvironment {
 
 public typealias Context = [String: TemplateValue]
 
-public indirect enum TemplateValue {
+public indirect enum TemplateValue: Sendable {
     case string(String)
     case list([Context])
     case bool(Bool)
diff --git a/Sources/NetworkClient/RequestPublisher+Applicative.swift b/Sources/NetworkClient/RequestPublisher+Applicative.swift
index 9f2ba3d..b25f59b 100644
--- a/Sources/NetworkClient/RequestPublisher+Applicative.swift
+++ b/Sources/NetworkClient/RequestPublisher+Applicative.swift
@@ -6,7 +6,7 @@ import Foundation
 
 public extension RequestPublisher {
     /// Lifts a pure value into `RequestPublisher`, ignoring the `URLRequest`.
-    static func pure(_ value: A) -> RequestPublisher<A> {
+    static func pure(_ value: A) -> RequestPublisher<A> where A: Sendable {
         RequestPublisher { _ in
             Just(value).setFailureType(to: HTTPError.self).eraseToAnyPublisher()
         }
@@ -14,7 +14,7 @@ public extension RequestPublisher {
 
     /// Applies a request-dependent function to a request-dependent value.
     /// Both are run against the same `URLRequest` and zipped.
-    static func apply<B>(_ f: RequestPublisher<(A) -> B>, _ r: RequestPublisher<A>) -> RequestPublisher<B> {
+    static func apply<B>(_ f: RequestPublisher<@Sendable (A) -> B>, _ r: RequestPublisher<A>) -> RequestPublisher<B> {
         RequestPublisher<B> { request in
             f.run(request)
                 .zip(r.run(request))
diff --git a/Sources/NetworkClient/RequestPublisher+ApplicativeOperators.swift b/Sources/NetworkClient/RequestPublisher+ApplicativeOperators.swift
index a0aa8d3..0d2f489 100644
--- a/Sources/NetworkClient/RequestPublisher+ApplicativeOperators.swift
+++ b/Sources/NetworkClient/RequestPublisher+ApplicativeOperators.swift
@@ -6,7 +6,7 @@ import FP
 // MARK: - RequestPublisher Applicative Operators
 
 // (<*>) :: RequestPublisher<(a -> b)> -> RequestPublisher<a> -> RequestPublisher<b>
-public func <*> <A, B>(_ f: RequestPublisher<(A) -> B>, _ r: RequestPublisher<A>) -> RequestPublisher<B> {
+public func <*> <A, B>(_ f: RequestPublisher<@Sendable (A) -> B>, _ r: RequestPublisher<A>) -> RequestPublisher<B> {
     RequestPublisher.apply(f, r)
 }
 
diff --git a/Sources/NetworkClient/RequestPublisher+Functor.swift b/Sources/NetworkClient/RequestPublisher+Functor.swift
index 60c81e7..e96063b 100644
--- a/Sources/NetworkClient/RequestPublisher+Functor.swift
+++ b/Sources/NetworkClient/RequestPublisher+Functor.swift
@@ -6,22 +6,22 @@ import Foundation
 
 public extension RequestPublisher {
     /// Transforms the output value; the same `URLRequest` is threaded through unchanged.
-    func map<B>(_ f: @escaping (A) -> B) -> RequestPublisher<B> {
+    func map<B: Sendable>(_ f: @escaping @Sendable (A) -> B) -> RequestPublisher<B> {
         RequestPublisher<B> { request in run(request).map(f).eraseToAnyPublisher() }
     }
 
     /// Curried fmap for point-free composition.
-    static func fmap<B>(_ f: @escaping (A) -> B) -> (RequestPublisher<A>) -> RequestPublisher<B> {
+    static func fmap<B: Sendable>(_ f: @escaping @Sendable (A) -> B) -> @Sendable (RequestPublisher<A>) -> RequestPublisher<B> {
         { $0.map(f) }
     }
 
     /// Replaces the output with a constant value.
-    func replace<B>(with value: B) -> RequestPublisher<B> {
-        map { _ in value }
+    func replace<B: Sendable>(with value: B) -> RequestPublisher<B> {
+        map { @Sendable _ in value }
     }
 
     /// Maps the failure side of the underlying publisher.
-    func mapError(_ f: @escaping (HTTPError) -> HTTPError) -> RequestPublisher<A> {
+    func mapError(_ f: @escaping @Sendable (HTTPError) -> HTTPError) -> RequestPublisher<A> {
         RequestPublisher { request in run(request).mapError(f).eraseToAnyPublisher() }
     }
 }
diff --git a/Sources/NetworkClient/RequestPublisher+FunctorOperators.swift b/Sources/NetworkClient/RequestPublisher+FunctorOperators.swift
index 05e36e8..8a4e8aa 100644
--- a/Sources/NetworkClient/RequestPublisher+FunctorOperators.swift
+++ b/Sources/NetworkClient/RequestPublisher+FunctorOperators.swift
@@ -6,23 +6,23 @@ import FP
 // MARK: - RequestPublisher Functor Operators
 
 // (<$>) :: (a -> b) -> RequestPublisher<a> -> RequestPublisher<b>
-public func <£> <A, B>(_ f: @escaping (A) -> B, _ r: RequestPublisher<A>) -> RequestPublisher<B> {
+public func <£> <A, B: Sendable>(_ f: @escaping @Sendable (A) -> B, _ r: RequestPublisher<A>) -> RequestPublisher<B> {
     r.map(f)
 }
 
 // (<&>) :: RequestPublisher<a> -> (a -> b) -> RequestPublisher<b>
-public func <&> <A, B>(_ r: RequestPublisher<A>, _ f: @escaping (A) -> B) -> RequestPublisher<B> {
+public func <&> <A, B: Sendable>(_ r: RequestPublisher<A>, _ f: @escaping @Sendable (A) -> B) -> RequestPublisher<B> {
     r.map(f)
 }
 
 // ($>) :: RequestPublisher<a> -> b -> RequestPublisher<b>
 // swiftlint:disable:next identifier_name
-public func £> <A, B>(_ r: RequestPublisher<A>, _ value: B) -> RequestPublisher<B> {
+public func £> <A, B: Sendable>(_ r: RequestPublisher<A>, _ value: B) -> RequestPublisher<B> {
     r.replace(with: value)
 }
 
 // (<$) :: b -> RequestPublisher<a> -> RequestPublisher<b>
-public func <£ <A, B>(_ value: B, _ r: RequestPublisher<A>) -> RequestPublisher<B> {
+public func <£ <A, B: Sendable>(_ value: B, _ r: RequestPublisher<A>) -> RequestPublisher<B> {
     r £> value
 }
 #endif
diff --git a/Sources/NetworkClient/RequestPublisher+Monad.swift b/Sources/NetworkClient/RequestPublisher+Monad.swift
index 02016e1..b1aac40 100644
--- a/Sources/NetworkClient/RequestPublisher+Monad.swift
+++ b/Sources/NetworkClient/RequestPublisher+Monad.swift
@@ -7,7 +7,7 @@ import Foundation
 public extension RequestPublisher {
     /// Chains two `RequestPublisher`s, threading the same `URLRequest` through both
     /// (Reader + Publisher monad stack).
-    func flatMap<B>(_ f: @escaping (A) -> RequestPublisher<B>) -> RequestPublisher<B> {
+    func flatMap<B>(_ f: @escaping @Sendable (A) -> RequestPublisher<B>) -> RequestPublisher<B> {
         RequestPublisher<B> { request in
             self.run(request)
                 .flatMap { a in f(a).run(request) }
@@ -16,7 +16,7 @@ public extension RequestPublisher {
     }
 
     /// Curried bind for point-free composition.
-    static func bind<B>(_ f: @escaping (A) -> RequestPublisher<B>) -> (RequestPublisher<A>) -> RequestPublisher<B> {
+    static func bind<B>(_ f: @escaping @Sendable (A) -> RequestPublisher<B>) -> @Sendable (RequestPublisher<A>) -> RequestPublisher<B> {
         { $0.flatMap(f) }
     }
 
@@ -32,23 +32,23 @@ public extension RequestPublisher {
 
     /// Kleisli composition (left-to-right): `(X -> m A) >=> (A -> m B) = X -> m B`.
     static func kleisli<X, B>(
-        _ f: @escaping (X) -> RequestPublisher<A>,
-        _ g: @escaping (A) -> RequestPublisher<B>
-    ) -> (X) -> RequestPublisher<B> {
+        _ f: @escaping @Sendable (X) -> RequestPublisher<A>,
+        _ g: @escaping @Sendable (A) -> RequestPublisher<B>
+    ) -> @Sendable (X) -> RequestPublisher<B> {
         { x in f(x).flatMap(g) }
     }
 
     /// Kleisli composition (right-to-left).
     static func kleisliBack<X, B>(
-        _ g: @escaping (A) -> RequestPublisher<B>,
-        _ f: @escaping (X) -> RequestPublisher<A>
-    ) -> (X) -> RequestPublisher<B> {
+        _ g: @escaping @Sendable (A) -> RequestPublisher<B>,
+        _ f: @escaping @Sendable (X) -> RequestPublisher<A>
+    ) -> @Sendable (X) -> RequestPublisher<B> {
         RequestPublisher.kleisli(f, g)
     }
 
     /// Recovers from failure by running an alternative `RequestPublisher`
     /// against the same `URLRequest`.
-    func flatMapError(_ f: @escaping (HTTPError) -> RequestPublisher<A>) -> RequestPublisher<A> {
+    func flatMapError(_ f: @escaping @Sendable (HTTPError) -> RequestPublisher<A>) -> RequestPublisher<A> {
         RequestPublisher { request in
             self.run(request)
                 .catch { error in f(error).run(request) }
diff --git a/Sources/NetworkClient/RequestPublisher+MonadOperators.swift b/Sources/NetworkClient/RequestPublisher+MonadOperators.swift
index 4291cd1..f121331 100644
--- a/Sources/NetworkClient/RequestPublisher+MonadOperators.swift
+++ b/Sources/NetworkClient/RequestPublisher+MonadOperators.swift
@@ -6,28 +6,28 @@ import FP
 // MARK: - RequestPublisher Monad Operators
 
 // (>>-) :: RequestPublisher<a> -> (a -> RequestPublisher<b>) -> RequestPublisher<b>
-public func >>- <A, B>(_ r: RequestPublisher<A>, _ f: @escaping (A) -> RequestPublisher<B>) -> RequestPublisher<B> {
+public func >>- <A, B>(_ r: RequestPublisher<A>, _ f: @escaping @Sendable (A) -> RequestPublisher<B>) -> RequestPublisher<B> {
     r.flatMap(f)
 }
 
 // (-<<) :: (a -> RequestPublisher<b>) -> RequestPublisher<a> -> RequestPublisher<b>
-public func -<< <A, B>(_ f: @escaping (A) -> RequestPublisher<B>, _ r: RequestPublisher<A>) -> RequestPublisher<B> {
+public func -<< <A, B>(_ f: @escaping @Sendable (A) -> RequestPublisher<B>, _ r: RequestPublisher<A>) -> RequestPublisher<B> {
     r.flatMap(f)
 }
 
 // (>=>) :: (x -> RequestPublisher<a>) -> (a -> RequestPublisher<b>) -> x -> RequestPublisher<b>
 public func >=> <X, A, B>(
-    _ f: @escaping (X) -> RequestPublisher<A>,
-    _ g: @escaping (A) -> RequestPublisher<B>
-) -> (X) -> RequestPublisher<B> {
+    _ f: @escaping @Sendable (X) -> RequestPublisher<A>,
+    _ g: @escaping @Sendable (A) -> RequestPublisher<B>
+) -> @Sendable (X) -> RequestPublisher<B> {
     RequestPublisher.kleisli(f, g)
 }
 
 // (<=<) :: (a -> RequestPublisher<b>) -> (x -> RequestPublisher<a>) -> x -> RequestPublisher<b>
 public func <=< <X, A, B>(
-    _ g: @escaping (A) -> RequestPublisher<B>,
-    _ f: @escaping (X) -> RequestPublisher<A>
-) -> (X) -> RequestPublisher<B> {
+    _ g: @escaping @Sendable (A) -> RequestPublisher<B>,
+    _ f: @escaping @Sendable (X) -> RequestPublisher<A>
+) -> @Sendable (X) -> RequestPublisher<B> {
     RequestPublisher.kleisliBack(g, f)
 }
 #endif
diff --git a/Sources/NetworkClient/RequestPublisher.swift b/Sources/NetworkClient/RequestPublisher.swift
index 8aba61e..b50b5e4 100644
--- a/Sources/NetworkClient/RequestPublisher.swift
+++ b/Sources/NetworkClient/RequestPublisher.swift
@@ -8,9 +8,9 @@ import FP
 /// Combines the Reader monad (threading the same `URLRequest` through a chain)
 /// with the Publisher monad (async response streaming with typed errors).
 public struct RequestPublisher<A>: FunctionWrapper {
-    public let run: (URLRequest) -> AnyPublisher<A, HTTPError>
+    public let run: @Sendable (URLRequest) -> AnyPublisher<A, HTTPError>
 
-    public init(_ fn: @escaping (URLRequest) -> AnyPublisher<A, HTTPError>) {
+    public init(_ fn: @escaping @Sendable (URLRequest) -> AnyPublisher<A, HTTPError>) {
         run = fn
     }
 
diff --git a/Tests/NetworkClientTests/NetworkClientTests.swift b/Tests/NetworkClientTests/NetworkClientTests.swift
index d4397f8..a644dee 100644
--- a/Tests/NetworkClientTests/NetworkClientTests.swift
+++ b/Tests/NetworkClientTests/NetworkClientTests.swift
@@ -44,7 +44,7 @@ private func firstResult<O, E: Error>(of publisher: AnyPublisher<O, E>) -> Resul
 
 // MARK: - RequestPublisher builders
 
-private func just<A>(_ value: A) -> RequestPublisher<A> {
+private func just<A: Sendable>(_ value: A) -> RequestPublisher<A> {
     RequestPublisher { _ in Just(value).setFailureType(to: HTTPError.self).eraseToAnyPublisher() }
 }
 
@@ -284,17 +284,17 @@ struct RequestPublisherFunctorTests {
 @Suite("RequestPublisher — Applicative")
 struct RequestPublisherApplicativeTests {
     @Test func apply_combinesFunctionAndValue() {
-        let f = RequestPublisher<(Int) -> String>.pure(String.init)
+        let f = RequestPublisher<@Sendable (Int) -> String>.pure(String.init)
         #expect(run(RequestPublisher.apply(f, just(42)))?.successValue == "42")
     }
 
     @Test func apply_propagatesLeftFailure() {
-        let f = fail(.badStatus(500, Data())) as RequestPublisher<(Int) -> Int>
+        let f = fail(.badStatus(500, Data())) as RequestPublisher<@Sendable (Int) -> Int>
         #expect(run(RequestPublisher.apply(f, just(1)))?.isFailure == true)
     }
 
     @Test func apply_propagatesRightFailure() {
-        let f = just { (n: Int) in n + 1 }
+        let f = just({ @Sendable (n: Int) in n + 1 } as @Sendable (Int) -> Int)
         let a = fail(.badStatus(500, Data())) as RequestPublisher<Int>
         #expect(run(RequestPublisher.apply(f, a))?.isFailure == true)
     }
@@ -326,14 +326,14 @@ struct RequestPublisherMonadTests {
     }
 
     @Test func kleisli_composes() {
-        let f: (String) -> RequestPublisher<Int> = { s in just(s.count) }
-        let g: (Int) -> RequestPublisher<String> = { n in just("\(n)") }
+        let f: @Sendable (String) -> RequestPublisher<Int> = { s in just(s.count) }
+        let g: @Sendable (Int) -> RequestPublisher<String> = { n in just("\(n)") }
         #expect(run(RequestPublisher.kleisli(f, g)("hello"))?.successValue == "5")
     }
 
     @Test func kleisliBack_composes() {
-        let f: (String) -> RequestPublisher<Int> = { s in just(s.count) }
-        let g: (Int) -> RequestPublisher<String> = { n in just("\(n)") }
+        let f: @Sendable (String) -> RequestPublisher<Int> = { s in just(s.count) }
+        let g: @Sendable (Int) -> RequestPublisher<String> = { n in just("\(n)") }
         #expect(run(RequestPublisher.kleisliBack(g, f)("hello"))?.successValue == "5")
     }
 
@@ -356,7 +356,7 @@ struct RequestPublisherOperatorTests {
     @Test func replaceLeftOp() { #expect(run("r" <£ just(5))?.successValue == "r") }
 
     @Test func applyOp() {
-        let f = just { (n: Int) in n + 1 }
+        let f = just({ @Sendable (n: Int) in n + 1 } as @Sendable (Int) -> Int)
         #expect(run(f <*> just(41))?.successValue == 42)
     }
     @Test func seqRightOp() { #expect(run(just(1) *> just("k"))?.successValue == "k") }
@@ -366,13 +366,13 @@ struct RequestPublisherOperatorTests {
     @Test func flippedBindOp() { #expect(run({ n in just(n * n) } -<< just(3))?.successValue == 9) }
 
     @Test func kleisliOp() {
-        let f: (Int) -> RequestPublisher<Int> = { n in just(n + 1) }
-        let g: (Int) -> RequestPublisher<String> = { n in just("\(n)") }
+        let f: @Sendable (Int) -> RequestPublisher<Int> = { n in just(n + 1) }
+        let g: @Sendable (Int) -> RequestPublisher<String> = { n in just("\(n)") }
         #expect(run((f >=> g)(41))?.successValue == "42")
     }
     @Test func kleisliBackOp() {
-        let f: (Int) -> RequestPublisher<Int> = { n in just(n + 1) }
-        let g: (Int) -> RequestPublisher<String> = { n in just("\(n)") }
+        let f: @Sendable (Int) -> RequestPublisher<Int> = { n in just(n + 1) }
+        let g: @Sendable (Int) -> RequestPublisher<String> = { n in just("\(n)") }
         #expect(run((g <=< f)(41))?.successValue == "42")
     }
 }