refactor(sdk-swift): wrap relaycast engine SDK in hosted transport

CHANGELOG.md

@@ -88,7 +88,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Retry inbound webhook auth from local broker
-- Escape glob in @agent-relay/* to satisfy prettier
+- Escape glob in @agent-relay/\* to satisfy prettier
 
 ## [9.1.0] - 2026-06-24
 

packages/sdk-swift/Package.swift

@@ -1,6 +1,16 @@
 // swift-tools-version: 5.9
 import PackageDescription
 
+// The hosted-participant transport (`AgentRelaySDK`) is a thin facade over the
+// relaycast Swift engine SDK (product `Relaycast`).
+//
+// relaycast's Swift SDK lives in a subdirectory of the relaycast monorepo
+// (`packages/sdk-swift`), so it cannot be consumed as a plain git-URL SwiftPM
+// dependency on its own (git dependencies require `Package.swift` at the
+// repository root). A root-level manifest vending the `Relaycast` library was
+// added in the relaycast monorepo (AgentWorkforce/relaycast#208) and published
+// as v4.2.0; this package depends on it via that repository's git URL.
+//
 let package = Package(
     name: "AgentRelaySDK",
     platforms: [
@@ -13,9 +23,18 @@ let package = Package(
         .library(name: "AgentRelaySDK", targets: ["AgentRelaySDK"]),
         .library(name: "AgentRelayBrokerSDK", targets: ["AgentRelayBrokerSDK"])
     ],
+    dependencies: [
+        .package(
+            url: "https://github.com/AgentWorkforce/relaycast.git",
+            from: "4.2.0"
+        )
+    ],
     targets: [
         .target(
             name: "AgentRelaySDK",
+            dependencies: [
+                .product(name: "Relaycast", package: "relaycast")
+            ],
             path: "Sources/AgentRelaySDK"
         ),
         .target(

packages/sdk-swift/README.md

@@ -21,6 +21,30 @@ Add the package in Swift Package Manager:
 
 Then depend on either `AgentRelaySDK` or `AgentRelayBrokerSDK`.
 
+### `AgentRelaySDK` wraps the relaycast engine SDK
+
+`AgentRelaySDK`'s hosted transport is a thin facade over the published relaycast
+Swift engine SDK (product `Relaycast`, package `relaycast-swift`, which lives in
+the relaycast monorepo under `packages/sdk-swift`). All HTTP and realtime
+WebSocket work is delegated to relaycast; `AgentRelaySDK` keeps only the
+relay-specific glue (action-dispatch loop, `RelayChannelEvent` shape, and the
+`AsyncStream`-based public API).
+
+relaycast's Swift SDK lives in a subdirectory of the relaycast monorepo
+(`packages/sdk-swift`), so it cannot be consumed as a plain git-URL SwiftPM
+dependency on its own (git dependencies require `Package.swift` at the
+repository root). A root-level manifest that vends the `Relaycast` library is
+added to the relaycast monorepo (see
+[AgentWorkforce/relaycast#208](https://github.com/AgentWorkforce/relaycast/pull/208)),
+and this package depends on it via that repository's git URL:
+
+```swift
+.package(url: "https://github.com/AgentWorkforce/relaycast.git", from: "4.2.0")
+```
+
+The root manifest landed in relaycast#208 and was published as v4.2.0, so this
+package depends on it by version.
+
 ## Quick start
 
 ```swift