diff --git a/Sources/Haystack/API/HisItem.swift b/Sources/Haystack/API/HisItem.swift
index 5f7741c..f542b2b 100644
--- a/Sources/Haystack/API/HisItem.swift
+++ b/Sources/Haystack/API/HisItem.swift
@@ -1,5 +1,5 @@
 /// A timestamp/value pair.
-public struct HisItem {
+public struct HisItem: Sendable {
     public let ts: DateTime
     public let val: any Val
 
diff --git a/Sources/Haystack/API/HisReadRange.swift b/Sources/Haystack/API/HisReadRange.swift
index 6814515..f35c3a6 100644
--- a/Sources/Haystack/API/HisReadRange.swift
+++ b/Sources/Haystack/API/HisReadRange.swift
@@ -1,7 +1,7 @@
 import Foundation
 
 /// Query-able DateTime ranges, which support relative and absolute values.
-public enum HisReadRange {
+public enum HisReadRange: Sendable {
     case today
     case yesterday
     case date(Haystack.Date)
diff --git a/Sources/Haystack/DateTime.swift b/Sources/Haystack/DateTime.swift
index 0d78428..cfa2303 100644
--- a/Sources/Haystack/DateTime.swift
+++ b/Sources/Haystack/DateTime.swift
@@ -191,7 +191,7 @@ public struct DateTime: Val {
     }
 }
 
-var calendar = Calendar(identifier: .gregorian)
+let calendar = Calendar(identifier: .gregorian)
 
 // DateTime + Codable
 extension DateTime {
diff --git a/Sources/Haystack/IO/ZincTokenizer.swift b/Sources/Haystack/IO/ZincTokenizer.swift
index 2b225c9..312da10 100644
--- a/Sources/Haystack/IO/ZincTokenizer.swift
+++ b/Sources/Haystack/IO/ZincTokenizer.swift
@@ -18,7 +18,7 @@ class ZincTokenizer {
         try consume()
     }
 
-    public convenience init(_ string: String) throws {
+    convenience init(_ string: String) throws {
         guard let data = string.data(using: .utf8) else {
             throw ZincTokenizerError.inputIsNotUtf8
         }
diff --git a/Sources/Haystack/Val.swift b/Sources/Haystack/Val.swift
index e5d1ab6..6359983 100644
--- a/Sources/Haystack/Val.swift
+++ b/Sources/Haystack/Val.swift
@@ -24,7 +24,7 @@ extension Val {
     }
 }
 
-public enum ValType: String, CaseIterable {
+public enum ValType: String, CaseIterable, Sendable {
     case Bool
     case Coord
     case Date
diff --git a/Sources/HaystackClient/Client.swift b/Sources/HaystackClient/Client.swift
index 509d766..d04e085 100644
--- a/Sources/HaystackClient/Client.swift
+++ b/Sources/HaystackClient/Client.swift
@@ -22,7 +22,7 @@ public class Client: API {
     let fetcher: Fetcher
 
     /// Set when `open` is called.
-    private var authToken: String? = nil
+    private var authToken: String?
 
     private let jsonEncoder = JSONEncoder()
     private let jsonDecoder = JSONDecoder()
diff --git a/Sources/HaystackServer/HaystackServer.swift b/Sources/HaystackServer/HaystackServer.swift
index 69f4db9..8152d03 100644
--- a/Sources/HaystackServer/HaystackServer.swift
+++ b/Sources/HaystackServer/HaystackServer.swift
@@ -3,22 +3,22 @@ import Haystack
 
 /// A HaystackServer is a server that implements the Haystack API.
 /// It translates API calls into operations on the underlying data stores.
-public class HaystackServer: API {
+public final class HaystackServer: API, Sendable {
     let recordStore: RecordStore
     let historyStore: HistoryStore
     let watchStore: WatchStore
 
-    let onInvokeAction: (Haystack.Ref, String, [String: any Haystack.Val]) async throws -> Haystack.Grid
-    let onEval: (String) async throws -> Haystack.Grid
+    let onInvokeAction: @Sendable (Haystack.Ref, String, [String: any Haystack.Val]) async throws -> Haystack.Grid
+    let onEval: @Sendable (String) async throws -> Haystack.Grid
 
     public init(
         recordStore: RecordStore,
         historyStore: HistoryStore,
         watchStore: WatchStore,
-        onInvokeAction: @escaping (Haystack.Ref, String, [String: any Haystack.Val]) async throws -> Haystack.Grid = { _, _, _ in
+        onInvokeAction: @escaping @Sendable (Haystack.Ref, String, [String: any Haystack.Val]) async throws -> Haystack.Grid = { _, _, _ in
             GridBuilder().toGrid()
         },
-        onEval: @escaping (String) async throws -> Haystack.Grid = { _ in
+        onEval: @escaping @Sendable (String) async throws -> Haystack.Grid = { _ in
             GridBuilder().toGrid()
         }
     ) {
diff --git a/Sources/HaystackServer/Stores/HistoryStore.swift b/Sources/HaystackServer/Stores/HistoryStore.swift
index 2f2fea4..7dbb47a 100644
--- a/Sources/HaystackServer/Stores/HistoryStore.swift
+++ b/Sources/HaystackServer/Stores/HistoryStore.swift
@@ -1,7 +1,7 @@
 import Haystack
 
 /// Defines a storage system that allows reading and writing of Haystack history data.
-public protocol HistoryStore {
+public protocol HistoryStore: Sendable {
     /// Reads history data for a given ID and time range.
     func hisRead(id: Haystack.Ref, range: Haystack.HisReadRange) async throws -> [Haystack.Dict]
 
diff --git a/Sources/HaystackServer/Stores/RecordStore.swift b/Sources/HaystackServer/Stores/RecordStore.swift
index fad76d4..24d63c3 100644
--- a/Sources/HaystackServer/Stores/RecordStore.swift
+++ b/Sources/HaystackServer/Stores/RecordStore.swift
@@ -1,7 +1,7 @@
 import Haystack
 
 /// Defines a storage system that allows reading and writing of Haystack records.
-public protocol RecordStore {
+public protocol RecordStore: Sendable {
     /// Reads records from the store based on a list of IDs.
     func read(ids: [Haystack.Ref]) async throws -> [Haystack.Dict]
 
@@ -12,7 +12,7 @@ public protocol RecordStore {
     func commitAll(diffs: [RecordDiff]) async throws -> [RecordDiff]
 }
 
-public struct RecordDiff {
+public struct RecordDiff: Sendable {
     public init(
         id: Haystack.Ref,
         old: Haystack.Dict?,
diff --git a/Sources/HaystackServer/Stores/WatchStore.swift b/Sources/HaystackServer/Stores/WatchStore.swift
index 08f4df3..753eab5 100644
--- a/Sources/HaystackServer/Stores/WatchStore.swift
+++ b/Sources/HaystackServer/Stores/WatchStore.swift
@@ -2,7 +2,7 @@ import Foundation
 import Haystack
 
 /// Defines a storage system that allows stateful storage of system watches.
-public protocol WatchStore {
+public protocol WatchStore: Sendable {
     func read(watchId: String) async throws -> WatchResponse
     func create(ids: [Haystack.Ref], lease: Haystack.Number?) async throws -> String
     func addIds(watchId: String, ids: [Haystack.Ref]) async throws
@@ -11,7 +11,7 @@ public protocol WatchStore {
     func delete(watchId: String) async throws
 }
 
-public struct WatchResponse {
+public struct WatchResponse: Sendable {
     public let ids: [Haystack.Ref]
     public let lease: Haystack.Number
     public let lastReported: Foundation.Date?
diff --git a/Sources/HaystackServerVapor/Application+Haystack.swift b/Sources/HaystackServerVapor/Application+Haystack.swift
new file mode 100644
index 0000000..18a2777
--- /dev/null
+++ b/Sources/HaystackServerVapor/Application+Haystack.swift
@@ -0,0 +1,26 @@
+import Haystack
+import Vapor
+
+extension Application {
+    struct HaystackServerKey: StorageKey {
+        typealias Value = API & Sendable
+    }
+
+    public var haystack: (API & Sendable)? {
+        get {
+            storage[HaystackServerKey.self]
+        }
+        set {
+            storage[HaystackServerKey.self] = newValue
+        }
+    }
+}
+
+extension Request {
+    func haystack() throws -> any API {
+        guard let haystack = application.haystack else {
+            fatalError("HaystackServer is not configured in the Vapor application.")
+        }
+        return haystack
+    }
+}
diff --git a/Sources/HaystackServerVapor/HaystackRouteCollection.swift b/Sources/HaystackServerVapor/HaystackRouteCollection.swift
index 4f2498e..2f52068 100644
--- a/Sources/HaystackServerVapor/HaystackRouteCollection.swift
+++ b/Sources/HaystackServerVapor/HaystackRouteCollection.swift
@@ -3,19 +3,14 @@ import Vapor
 
 /// A route collection that exposes Haystack API endpoints.
 public struct HaystackRouteCollection: RouteCollection {
-    /// This instance defines all Haystack API processing that is done server-side.
-    let delegate: any API
-
-    public init(delegate: any API) {
-        self.delegate = delegate
-    }
+    public init() {}
 
     public func boot(routes: any Vapor.RoutesBuilder) throws {
         /// Closes the current authentication session.
         ///
         /// https://project-haystack.org/doc/docHaystack/Ops#close
-        routes.post("close") { _ in
-            try await delegate.close()
+        routes.post("close") { request in
+            try await request.haystack().close()
             return ""
         }
 
@@ -23,14 +18,14 @@ public struct HaystackRouteCollection: RouteCollection {
         ///
         /// https://project-haystack.org/doc/docHaystack/Ops#about
         routes.get("about") { request in
-            try await request.respond(with: delegate.about())
+            try await request.respond(with: request.haystack().about())
         }
 
         /// Queries basic information about the server
         ///
         /// https://project-haystack.org/doc/docHaystack/Ops#about
         routes.post("about") { request in
-            try await request.respond(with: delegate.about())
+            try await request.respond(with: request.haystack().about())
         }
 
         /// Queries def dicts from the current namespace
@@ -48,7 +43,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.defs(filter: filter, limit: limit)
+                with: request.haystack().defs(filter: filter, limit: limit)
             )
         }
 
@@ -67,7 +62,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.defs(filter: filter, limit: limit)
+                with: request.haystack().defs(filter: filter, limit: limit)
             )
         }
 
@@ -86,7 +81,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.libs(filter: filter, limit: limit)
+                with: request.haystack().libs(filter: filter, limit: limit)
             )
         }
 
@@ -105,7 +100,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.libs(filter: filter, limit: limit)
+                with: request.haystack().libs(filter: filter, limit: limit)
             )
         }
 
@@ -124,7 +119,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.libs(filter: filter, limit: limit)
+                with: request.haystack().libs(filter: filter, limit: limit)
             )
         }
 
@@ -143,7 +138,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.ops(filter: filter, limit: limit)
+                with: request.haystack().ops(filter: filter, limit: limit)
             )
         }
 
@@ -162,7 +157,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.filetypes(filter: filter, limit: limit)
+                with: request.haystack().filetypes(filter: filter, limit: limit)
             )
         }
 
@@ -181,7 +176,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.filetypes(filter: filter, limit: limit)
+                with: request.haystack().filetypes(filter: filter, limit: limit)
             )
         }
 
@@ -208,10 +203,10 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             if let ids = ids {
-                return try await request.respond(with: delegate.read(ids: ids))
+                return try await request.respond(with: request.haystack().read(ids: ids))
             } else if let filter = filter {
                 return try await request.respond(
-                    with: delegate.read(filter: filter, limit: limit)
+                    with: request.haystack().read(filter: filter, limit: limit)
                 )
             } else {
                 throw Abort(.badRequest, reason: "Read request must have either 'id' or 'filter'")
@@ -241,10 +236,10 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             if let ids = ids {
-                return try await request.respond(with: delegate.read(ids: ids))
+                return try await request.respond(with: request.haystack().read(ids: ids))
             } else if let filter = filter {
                 return try await request.respond(
-                    with: delegate.read(filter: filter, limit: limit)
+                    with: request.haystack().read(filter: filter, limit: limit)
                 )
             } else {
                 throw Abort(.badRequest, reason: "Read request must have either 'id' or 'filter'")
@@ -264,7 +259,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.nav(navId: navId)
+                with: request.haystack().nav(navId: navId)
             )
         }
 
@@ -281,7 +276,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.nav(navId: navId)
+                with: request.haystack().nav(navId: navId)
             )
         }
 
@@ -300,7 +295,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.hisRead(
+                with: request.haystack().hisRead(
                     id: id,
                     range: range
                 )
@@ -325,7 +320,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.hisRead(
+                with: request.haystack().hisRead(
                     id: id,
                     range: range
                 )
@@ -351,7 +346,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.hisWrite(id: id, items: items)
+                with: request.haystack().hisWrite(id: id, items: items)
             )
         }
 
@@ -375,7 +370,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
             guard let level = level else {
                 return try await request.respond(
-                    with: delegate.pointWriteStatus(id: id)
+                    with: request.haystack().pointWriteStatus(id: id)
                 )
             }
 
@@ -391,7 +386,7 @@ public struct HaystackRouteCollection: RouteCollection {
                 throw Abort(.badRequest, reason: error.localizedDescription)
             }
             return try await request.respond(
-                with: delegate.pointWrite(
+                with: request.haystack().pointWrite(
                     id: id,
                     level: level,
                     val: val,
@@ -424,7 +419,7 @@ public struct HaystackRouteCollection: RouteCollection {
 
             if let watchDis = watchDis {
                 return try await request.respond(
-                    with: delegate.watchSubCreate(
+                    with: request.haystack().watchSubCreate(
                         watchDis: watchDis,
                         lease: lease,
                         ids: ids
@@ -434,7 +429,7 @@ public struct HaystackRouteCollection: RouteCollection {
 
             if let watchId = watchId {
                 return try await request.respond(
-                    with: delegate.watchSubAdd(
+                    with: request.haystack().watchSubAdd(
                         watchId: watchId,
                         lease: lease,
                         ids: ids
@@ -460,7 +455,7 @@ public struct HaystackRouteCollection: RouteCollection {
 
             if grid.meta.has("close") {
                 return try await request.respond(
-                    with: delegate.watchUnsubDelete(
+                    with: request.haystack().watchUnsubDelete(
                         watchId: watchId
                     )
                 )
@@ -475,7 +470,7 @@ public struct HaystackRouteCollection: RouteCollection {
                 }
 
                 return try await request.respond(
-                    with: delegate.watchUnsubRemove(
+                    with: request.haystack().watchUnsubRemove(
                         watchId: watchId,
                         ids: ids
                     )
@@ -498,7 +493,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.watchPoll(
+                with: request.haystack().watchPoll(
                     watchId: watchId,
                     refresh: refresh
                 )
@@ -524,7 +519,7 @@ public struct HaystackRouteCollection: RouteCollection {
             }
 
             return try await request.respond(
-                with: delegate.invokeAction(
+                with: request.haystack().invokeAction(
                     id: id,
                     action: action,
                     args: args
@@ -547,7 +542,7 @@ public struct HaystackRouteCollection: RouteCollection {
                 throw Abort(.badRequest, reason: error.localizedDescription)
             }
 
-            return try await request.respond(with: delegate.eval(expression: expr))
+            return try await request.respond(with: request.haystack().eval(expression: expr))
         }
     }
 }
diff --git a/Tests/HaystackClientNIOIntegrationTests/HaystackClientNIOIntegrationTests.swift b/Tests/HaystackClientNIOIntegrationTests/HaystackClientNIOIntegrationTests.swift
index d1b96d8..49615f9 100644
--- a/Tests/HaystackClientNIOIntegrationTests/HaystackClientNIOIntegrationTests.swift
+++ b/Tests/HaystackClientNIOIntegrationTests/HaystackClientNIOIntegrationTests.swift
@@ -24,7 +24,7 @@ final class HaystackClientNIOIntegrationTests: XCTestCase {
 
     override func tearDown() async throws {
         try await client.close()
-        try httpClient.syncShutdown()
+        try await httpClient.shutdown()
     }
 
     func testCloseAndOpen() async throws {
diff --git a/Tests/HaystackServerTests/HaystackServerTests.swift b/Tests/HaystackServerTests/HaystackServerTests.swift
index f207ee9..da4a126 100644
--- a/Tests/HaystackServerTests/HaystackServerTests.swift
+++ b/Tests/HaystackServerTests/HaystackServerTests.swift
@@ -504,7 +504,7 @@ final class HaystackServerTests: XCTestCase {
 /// This is a super inefficient record store based on an in-memory list of Diffs
 ///
 /// Any change automatically updates the `mod` DateTime tag on the record
-class InMemoryRecordStore: RecordStore {
+actor InMemoryRecordStore: RecordStore {
     var recs: [Haystack.Ref: Haystack.Dict] = [:]
 
     init() {}
@@ -564,7 +564,7 @@ class InMemoryRecordStore: RecordStore {
 }
 
 /// This is a super inefficient history store based on an in-memory list of histories
-class InMemoryHistoryStore: HistoryStore {
+actor InMemoryHistoryStore: HistoryStore {
     /// Maps Refs to histories. These histories are not assumed to be ordered in time (for simplicity).
     var histories: [Ref: [HisItem]]
 
@@ -604,7 +604,7 @@ class InMemoryHistoryStore: HistoryStore {
 }
 
 /// This is a super inefficient history store based on an in-memory list of histories
-class InMemoryWatchStore: WatchStore {
+actor InMemoryWatchStore: WatchStore {
     /// Maps watch IDs to a list of Refs. This is used to track which records are being watched.
     var watches: [String: Watch] = [:]
 
@@ -659,7 +659,7 @@ class InMemoryWatchStore: WatchStore {
         watches[watchId] = nil
     }
 
-    public struct Watch: Hashable {
+    struct Watch: Hashable {
         let id: String
         var ids: [Haystack.Ref]
         let lease: Haystack.Number
diff --git a/Tests/HaystackServerVaporTests/HaystackServerVaporTests.swift b/Tests/HaystackServerVaporTests/HaystackServerVaporTests.swift
index 795d928..bde2fb2 100644
--- a/Tests/HaystackServerVaporTests/HaystackServerVaporTests.swift
+++ b/Tests/HaystackServerVaporTests/HaystackServerVaporTests.swift
@@ -6,7 +6,8 @@ import XCTVapor
 final class HaystackServerVaporTests: XCTestCase {
     func testGet() throws {
         let app = Application(.testing)
-        try app.register(collection: HaystackRouteCollection(delegate: HaystackAPIMock()))
+        app.haystack = HaystackAPIMock()
+        try app.register(collection: HaystackRouteCollection())
         defer { app.shutdown() }
 
         let responseGrid = try GridBuilder()
@@ -50,7 +51,8 @@ final class HaystackServerVaporTests: XCTestCase {
 
     func testGetBadQuery() throws {
         let app = Application(.testing)
-        try app.register(collection: HaystackRouteCollection(delegate: HaystackAPIMock()))
+        app.haystack = HaystackAPIMock()
+        try app.register(collection: HaystackRouteCollection())
         defer { app.shutdown() }
 
         try app.test(
@@ -63,7 +65,8 @@ final class HaystackServerVaporTests: XCTestCase {
 
     func testPost() throws {
         let app = Application(.testing)
-        try app.register(collection: HaystackRouteCollection(delegate: HaystackAPIMock()))
+        app.haystack = HaystackAPIMock()
+        try app.register(collection: HaystackRouteCollection())
         defer { app.shutdown() }
 
         let requestGrid = try GridBuilder()
@@ -121,7 +124,8 @@ final class HaystackServerVaporTests: XCTestCase {
 
     func testPostBadQuery() throws {
         let app = Application(.testing)
-        try app.register(collection: HaystackRouteCollection(delegate: HaystackAPIMock()))
+        app.haystack = HaystackAPIMock()
+        try app.register(collection: HaystackRouteCollection())
         defer { app.shutdown() }
 
         let requestGrid = try GridBuilder()
@@ -156,7 +160,7 @@ final class HaystackServerVaporTests: XCTestCase {
     }
 }
 
-struct HaystackAPIMock: Haystack.API {
+struct HaystackAPIMock: Haystack.API, Sendable {
     func close() async throws {}
 
     func about() async throws -> Haystack.Grid {