feat(transports): add HTTP/WebSocket transport support

Cargo.toml

@@ -4,6 +4,7 @@ members = [
     "src/agent-client-protocol-conductor",
     "src/agent-client-protocol-cookbook",
     "src/agent-client-protocol-derive",
+    "src/agent-client-protocol-http",
     "src/agent-client-protocol-rmcp",
     "src/agent-client-protocol-test",
     "src/agent-client-protocol-trace-viewer",
@@ -23,6 +24,7 @@ homepage = "https://github.com/agentclientprotocol/rust-sdk"
 agent-client-protocol = { path = "src/agent-client-protocol", version = "0.11.1" }
 agent-client-protocol-conductor = { path = "src/agent-client-protocol-conductor", version = "0.11.1" }
 agent-client-protocol-derive = { path = "src/agent-client-protocol-derive", version = "0.11.0" }
+agent-client-protocol-http = { path = "src/agent-client-protocol-http", version = "0.11.1" }
 agent-client-protocol-rmcp = { path = "src/agent-client-protocol-rmcp", version = "0.11.1" }
 agent-client-protocol-test = { path = "src/agent-client-protocol-test" }
 agent-client-protocol-trace-viewer = { path = "src/agent-client-protocol-trace-viewer", version = "0.11.0" }
@@ -57,6 +59,9 @@ clap = { version = "4.5", features = ["derive"] }
 
 # HTTP
 axum = "0.8"
+reqwest = { version = "0.12", default-features = false, features = ["rustls-tls", "json"] }
+eventsource-stream = "0.2"
+url = "2.5"
 async-process = "2"
 async-stream = "0.3.6"
 blocking = "1"

md/SUMMARY.md

@@ -7,6 +7,10 @@
 - [Design Overview](./design.md)
 - [Protocol Reference](./protocol.md)
 
+# Transports
+
+- [HTTP / WebSocket Transport](./http-transport.md)
+
 # Conductor (agent-client-protocol-conductor)
 
 - [Conductor Design](./conductor.md)

md/http-transport.md

@@ -0,0 +1,36 @@
+# HTTP / WebSocket Transport
+
+`agent-client-protocol-http` exposes ACP agents over one `/acp` endpoint.
+
+- `POST /acp` with `initialize` creates a connection and returns `Acp-Connection-Id`.
+- Later `POST /acp` requests include `Acp-Connection-Id`; session-scoped requests also include `Acp-Session-Id` or `params.sessionId`.
+- `GET /acp` with `Accept: text/event-stream` streams agent messages over SSE.
+- `GET /acp` with a WebSocket upgrade uses text frames for JSON-RPC messages.
+- `DELETE /acp` tears down the connection.
+
+## Server
+
+```rust
+use agent_client_protocol_http::AcpHttpServer;
+
+let app = AcpHttpServer::new(|| my_agent()).into_router();
+let listener = tokio::net::TcpListener::bind("127.0.0.1:8080").await?;
+axum::serve(listener, app).await?;
+```
+
+## Client
+
+```rust
+use agent_client_protocol_http::HttpClient;
+
+let transport = HttpClient::new("http://127.0.0.1:8080")?;
+my_client().connect_to(transport).await?;
+```
+
+The same `HttpClient` also speaks WebSocket — pass a `ws://` or `wss://` URL
+and it will open a single bidirectional connection instead of using POST + SSE:
+
+```rust
+let transport = HttpClient::new("ws://127.0.0.1:8080")?;
+my_client().connect_to(transport).await?;
+```

md/introduction.md

@@ -22,6 +22,7 @@ The `agent-client-protocol` crate includes a [`concepts`](https://docs.rs/agent-
 src/
 ├── agent-client-protocol/              # Core protocol SDK
 ├── agent-client-protocol-tokio/        # Tokio utilities (process spawning)
+├── agent-client-protocol-http/         # HTTP/SSE/WebSocket transport
 ├── agent-client-protocol-rmcp/         # Integration with rmcp crate
 ├── agent-client-protocol-cookbook/     # Usage patterns (rendered as rustdoc)
 ├── agent-client-protocol-derive/       # Proc macros
@@ -37,11 +38,13 @@ src/
 graph TD
     acp[agent-client-protocol<br/>Core SDK]
     tokio[agent-client-protocol-tokio<br/>Process spawning]
+    http[agent-client-protocol-http<br/>HTTP/SSE/WebSocket transport]
     rmcp[agent-client-protocol-rmcp<br/>rmcp integration]
     conductor[agent-client-protocol-conductor<br/>Proxy orchestration]
     cookbook[agent-client-protocol-cookbook<br/>Usage patterns]
 
     tokio --> acp
+    http --> acp
     rmcp --> acp
     conductor --> acp
     conductor --> tokio

src/agent-client-protocol-http/CHANGELOG.md

@@ -0,0 +1,6 @@
+# Changelog
+
+## [Unreleased]
+
+### Added
+- HTTP/SSE/WebSocket transport for ACP agents

src/agent-client-protocol-http/Cargo.toml

@@ -0,0 +1,44 @@
+[package]
+name = "agent-client-protocol-http"
+version = "0.11.1"
+edition.workspace = true
+authors.workspace = true
+license.workspace = true
+repository.workspace = true
+homepage.workspace = true
+description = "HTTP and WebSocket transport for the Agent Client Protocol (ACP)"
+keywords = ["acp", "agent", "protocol", "http", "websocket"]
+categories = ["development-tools", "web-programming::http-server"]
+
+[dependencies]
+agent-client-protocol.workspace = true
+jsonrpcmsg.workspace = true
+
+futures.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+tokio = { workspace = true, features = ["sync", "rt", "macros", "time"] }
+tokio-util.workspace = true
+tracing.workspace = true
+thiserror.workspace = true
+
+# Server
+axum = { workspace = true, features = ["ws", "macros"] }
+tower-http = { version = "0.6", features = ["cors"] }
+async-stream = { workspace = true }
+uuid = { workspace = true }
+
+# Client
+reqwest = { workspace = true, features = ["stream"] }
+eventsource-stream = { workspace = true }
+url = { workspace = true }
+tokio-tungstenite = "0.29"
+
+[dev-dependencies]
+agent-client-protocol = { workspace = true }
+agent-client-protocol-test.workspace = true
+tokio = { workspace = true, features = ["full"] }
+tracing-subscriber.workspace = true
+
+[lints]
+workspace = true

src/agent-client-protocol-http/README.md

@@ -0,0 +1,8 @@
+# agent-client-protocol-http
+
+HTTP/WebSocket transport for ACP agents.
+
+- **Server**: `AcpHttpServer` exposes agents over HTTP + SSE with optional WebSocket upgrade
+- **Client**: `HttpClient` connects to remote agents over HTTP + SSE
+
+See the [documentation](https://docs.rs/agent-client-protocol-http) for usage examples.