diff --git a/Cargo.lock b/Cargo.lock
index 1434b7acdf4..bb1c97b392e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2670,6 +2670,8 @@ dependencies = [
  "error-stack",
  "futures",
  "graph",
+ "harpc-codec",
+ "harpc-server",
  "hash-codec",
  "hash-graph-api",
  "hash-graph-authorization",
@@ -2681,6 +2683,7 @@ dependencies = [
  "hash-temporal-client",
  "hash-tracing",
  "mimalloc",
+ "multiaddr",
  "regex",
  "reqwest",
  "tarpc",
diff --git a/apps/hash-graph/Cargo.toml b/apps/hash-graph/Cargo.toml
index 8c0cf030291..470de8a83f1 100644
--- a/apps/hash-graph/Cargo.toml
+++ b/apps/hash-graph/Cargo.toml
@@ -48,6 +48,9 @@ tokio = { workspace = true }
 tokio-postgres = { workspace = true }
 tokio-util = { workspace = true, features = ["codec"] }
 tracing = { workspace = true }
+harpc-server.workspace = true
+multiaddr.workspace = true
+harpc-codec = { workspace = true, features = ["json"] }
 
 [features]
 test-server = ["dep:hash-graph-test-server"]
diff --git a/apps/hash-graph/src/main.rs b/apps/hash-graph/src/main.rs
index 26689afafdc..5f188d4d8a1 100644
--- a/apps/hash-graph/src/main.rs
+++ b/apps/hash-graph/src/main.rs
@@ -1,4 +1,5 @@
 #![forbid(unsafe_code)]
+#![feature(async_closure)]
 #![expect(
     unreachable_pub,
     reason = "This is a binary but as we want to document this crate as well this should be a \
diff --git a/apps/hash-graph/src/subcommand/server.rs b/apps/hash-graph/src/subcommand/server.rs
index c22ccbbb425..3290483f850 100644
--- a/apps/hash-graph/src/subcommand/server.rs
+++ b/apps/hash-graph/src/subcommand/server.rs
@@ -11,16 +11,22 @@ use error_stack::{Report, ResultExt as _};
 use graph::{
     ontology::domain_validator::DomainValidator,
     store::{
-        DatabaseConnectionInfo, DatabasePoolConfig, FetchingPool, PostgresStorePool, StorePool as _,
+        DatabaseConnectionInfo, DatabasePoolConfig, FetchingPool, PostgresStorePool, StorePool,
     },
 };
-use hash_graph_api::rest::{RestRouterDependencies, rest_api_router};
+use harpc_codec::json::JsonCodec;
+use harpc_server::Server;
+use hash_graph_api::{
+    rest::{RestRouterDependencies, rest_api_router},
+    rpc::Dependencies,
+};
 use hash_graph_authorization::{
-    AuthorizationApi as _, NoAuthorization,
+    AuthorizationApi as _, AuthorizationApiPool, NoAuthorization,
     backend::{SpiceDbOpenApi, ZanzibarBackend as _},
     zanzibar::ZanzibarClient,
 };
 use hash_temporal_client::TemporalClientConfig;
+use multiaddr::{Multiaddr, Protocol};
 use regex::Regex;
 use reqwest::{Client, Url};
 use tokio::{net::TcpListener, time::timeout};
@@ -59,6 +65,38 @@ impl TryFrom<ApiAddress> for SocketAddr {
     }
 }
 
+#[derive(Debug, Clone, Parser)]
+pub struct RpcAddress {
+    /// The host the RPC client is listening at.
+    #[clap(long, default_value = "127.0.0.1", env = "HASH_GRAPH_RPC_HOST")]
+    pub rpc_host: String,
+
+    /// The port the RPC client is listening at.
+    #[clap(long, default_value_t = 25489, env = "HASH_GRAPH_RPC_PORT")]
+    pub rpc_port: u16,
+}
+
+impl fmt::Display for RpcAddress {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(fmt, "{}:{}", self.rpc_host, self.rpc_port)
+    }
+}
+
+impl TryFrom<RpcAddress> for SocketAddr {
+    type Error = Report<AddrParseError>;
+
+    fn try_from(address: RpcAddress) -> Result<Self, Report<AddrParseError>> {
+        address
+            .to_string()
+            .parse::<Self>()
+            .attach_printable(address)
+    }
+}
+
+#[expect(
+    clippy::struct_excessive_bools,
+    reason = "CLI arguments are boolean flags."
+)]
 #[derive(Debug, Parser)]
 pub struct ServerArgs {
     #[clap(flatten)]
@@ -67,10 +105,18 @@ pub struct ServerArgs {
     #[clap(flatten)]
     pub pool_config: DatabasePoolConfig,
 
-    /// The address the REST client is listening at.
+    /// The address the REST server is listening at.
     #[clap(flatten)]
     pub api_address: ApiAddress,
 
+    /// Enable the experimental RPC server.
+    #[clap(long, default_value_t = false, env = "HASH_GRAPH_RPC_ENABLED")]
+    pub rpc_enabled: bool,
+
+    /// The address the RPC server is listening at.
+    #[clap(flatten)]
+    pub rpc_address: RpcAddress,
+
     /// The address for the type fetcher RPC server is listening at.
     #[clap(flatten)]
     pub type_fetcher_address: TypeFetcherAddress,
@@ -134,6 +180,54 @@ pub struct ServerArgs {
     pub temporal_port: u16,
 }
 
+fn server_rpc<S, A>(
+    address: RpcAddress,
+    dependencies: Dependencies<S, A, ()>,
+) -> Result<(), Report<GraphError>>
+where
+    S: StorePool + Send + Sync + 'static,
+    A: AuthorizationApiPool + Send + Sync + 'static,
+{
+    let server = Server::new(harpc_server::ServerConfig::default()).change_context(GraphError)?;
+
+    let (router, task) = hash_graph_api::rpc::rpc_router(
+        Dependencies {
+            store: dependencies.store,
+            authorization_api: dependencies.authorization_api,
+            temporal_client: dependencies.temporal_client,
+            codec: JsonCodec,
+        },
+        server.events(),
+    );
+
+    tokio::spawn(task.into_future());
+
+    let socket_address: SocketAddr = SocketAddr::try_from(address).change_context(GraphError)?;
+    let mut address = Multiaddr::empty();
+    match socket_address {
+        SocketAddr::V4(v4) => {
+            address.push(Protocol::Ip4(*v4.ip()));
+            address.push(Protocol::Tcp(v4.port()));
+        }
+        SocketAddr::V6(v6) => {
+            address.push(Protocol::Ip6(*v6.ip()));
+            address.push(Protocol::Tcp(v6.port()));
+        }
+    }
+
+    #[expect(clippy::significant_drop_tightening, reason = "false positive")]
+    tokio::spawn(async move {
+        let stream = server
+            .listen(address)
+            .await
+            .expect("server should be able to listen on address");
+
+        harpc_server::serve::serve(stream, router).await;
+    });
+
+    Ok(())
+}
+
 pub async fn server(args: ServerArgs) -> Result<(), Report<GraphError>> {
     if args.healthcheck {
         return wait_healthcheck(
@@ -186,24 +280,42 @@ pub async fn server(args: ServerArgs) -> Result<(), Report<GraphError>> {
     let mut zanzibar_client = ZanzibarClient::new(spicedb_client);
     zanzibar_client.seed().await.change_context(GraphError)?;
 
-    let router = rest_api_router(RestRouterDependencies {
-        store: Arc::new(pool),
-        authorization_api: Arc::new(zanzibar_client),
-        domain_regex: DomainValidator::new(args.allowed_url_domain),
-        temporal_client: if let Some(host) = args.temporal_host {
-            Some(
-                TemporalClientConfig::new(
-                    Url::from_str(&format!("{}:{}", host, args.temporal_port))
-                        .change_context(GraphError)?,
-                )
-                .change_context(GraphError)?
-                .await
-                .change_context(GraphError)?,
+    let temporal_client_fn = async |host: Option<String>, port: u16| {
+        if let Some(host) = host {
+            TemporalClientConfig::new(
+                Url::from_str(&format!("{host}:{port}")).change_context(GraphError)?,
             )
+            .change_context(GraphError)?
+            .await
+            .map(Some)
+            .change_context(GraphError)
         } else {
-            None
-        },
-    });
+            Ok(None)
+        }
+    };
+
+    let router = {
+        let dependencies = RestRouterDependencies {
+            store: Arc::new(pool),
+            authorization_api: Arc::new(zanzibar_client),
+            domain_regex: DomainValidator::new(args.allowed_url_domain),
+            temporal_client: temporal_client_fn(args.temporal_host.clone(), args.temporal_port)
+                .await?,
+        };
+
+        if args.rpc_enabled {
+            tracing::info!("Starting RPC server...");
+
+            server_rpc(args.rpc_address, Dependencies {
+                store: Arc::clone(&dependencies.store),
+                authorization_api: Arc::clone(&dependencies.authorization_api),
+                temporal_client: temporal_client_fn(args.temporal_host, args.temporal_port).await?,
+                codec: (),
+            })?;
+        }
+
+        rest_api_router(dependencies)
+    };
 
     tracing::info!("Listening on {}", args.api_address);
     axum::serve(
diff --git a/libs/@local/graph/api/src/rpc/mod.rs b/libs/@local/graph/api/src/rpc/mod.rs
index 2508d384869..b523cbb83cb 100644
--- a/libs/@local/graph/api/src/rpc/mod.rs
+++ b/libs/@local/graph/api/src/rpc/mod.rs
@@ -71,7 +71,10 @@ pub struct Dependencies<S, A, C> {
 pub fn rpc_router<S, A, C, N>(
     dependencies: Dependencies<S, A, C>,
     notifications: N,
-) -> (Router<impl Route<RequestBody>>, Task<Account, N>)
+) -> (
+    Router<impl Route<RequestBody, ResponseBody: Send, Future: Send> + Send>,
+    Task<Account, N>,
+)
 where
     S: StorePool + Send + Sync + 'static,
     A: AuthorizationApiPool + Send + Sync + 'static,
diff --git a/libs/@local/harpc/server/src/lib.rs b/libs/@local/harpc/server/src/lib.rs
index ed068aa1d88..0a56313cb99 100644
--- a/libs/@local/harpc/server/src/lib.rs
+++ b/libs/@local/harpc/server/src/lib.rs
@@ -19,9 +19,10 @@ use core::{
 
 use error_stack::{Report, ResultExt as _};
 use futures::{Stream, StreamExt as _, stream::FusedStream};
+pub use harpc_net::{session::server::SessionConfig, transport::TransportConfig};
 use harpc_net::{
-    session::server::{EventStream, ListenStream, SessionConfig, SessionLayer, Transaction},
-    transport::{TransportConfig, TransportLayer},
+    session::server::{EventStream, ListenStream, SessionLayer, Transaction},
+    transport::TransportLayer,
 };
 use multiaddr::Multiaddr;
 use tokio_util::sync::{CancellationToken, DropGuard};