diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b93834e..ad2741e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,7 +20,7 @@ jobs:
 
       - name: Setup rust tooling
         run: |
-          rustup override set 1.83
+          rustup override set 1.85
           rustup component add rustfmt clippy
 
       - uses: ./.github/actions/ci
@@ -49,7 +49,7 @@ jobs:
 
       - name: Setup rust tooling
         run: |
-          rustup override set 1.83
+          rustup override set 1.85
           rustup component add rustfmt clippy
           rustup target add x86_64-unknown-linux-musl
 
diff --git a/.github/workflows/manual-publish.yml b/.github/workflows/manual-publish.yml
index 9f350b0..6189f32 100644
--- a/.github/workflows/manual-publish.yml
+++ b/.github/workflows/manual-publish.yml
@@ -19,7 +19,7 @@ jobs:
 
       - name: Setup rust tooling
         run: |
-          rustup override set 1.83
+          rustup override set 1.85
           rustup component add rustfmt clippy
 
       - uses: ./.github/actions/ci
diff --git a/.github/workflows/release-please.yml b/.github/workflows/release-please.yml
index 2078f4c..c6dfe21 100644
--- a/.github/workflows/release-please.yml
+++ b/.github/workflows/release-please.yml
@@ -24,7 +24,7 @@ jobs:
       - name: Setup rust tooling
         if: ${{ steps.release.outputs['launchdarkly-server-sdk--release_created'] == 'true' }}
         run: |
-          rustup override set 1.83
+          rustup override set 1.85
           rustup component add rustfmt clippy
 
       - uses: launchdarkly/gh-actions/actions/release-secrets@release-secrets-v1.2.0
diff --git a/contract-tests/Cargo.toml b/contract-tests/Cargo.toml
index 228327a..1135866 100644
--- a/contract-tests/Cargo.toml
+++ b/contract-tests/Cargo.toml
@@ -2,13 +2,15 @@
 name = "contract-tests"
 version = "0.1.0"
 edition = "2021"
-rust-version = "1.83.0"  # MSRV
+rust-version = "1.85.0"  # MSRV
 license = "Apache-2.0"
 
 [dependencies]
 actix = "0.13.0"
 actix-web = "4.2.1"
 env_logger = "0.10.0"
+# eventsource-client = { version = "0.16.0", default-features = false }
+eventsource-client = { git = "https://github.com/launchdarkly/rust-eventsource-client", branch = "feat/hyper-as-feature" }
 log = "0.4.14"
 launchdarkly-server-sdk = { path = "../launchdarkly-server-sdk/", default-features = false, features = ["event-compression"]}
 serde = { version = "1.0.132", features = ["derive"] }
@@ -17,10 +19,12 @@ futures = "0.3.12"
 hyper = { version = "0.14.19", features = ["client"] }
 hyper-rustls = { version = "0.24.1" , optional = true, features = ["http2"]}
 hyper-tls = { version = "0.5.0", optional = true }
+hyper1-tls = { package = "hyper-tls", version = "0.6.0", optional = true }
+hyper-util = { version = "0.1", features = ["client-legacy", "http1", "http2", "tokio"], optional = true }
 reqwest = { version = "0.12.4", features = ["default", "blocking", "json"] }
 async-mutex = "1.4.0"
 
 [features]
 default = ["rustls"]
-rustls = ["hyper-rustls/http1", "hyper-rustls/http2", "launchdarkly-server-sdk/rustls"]
-tls = ["hyper-tls"]
+rustls = ["hyper-rustls/http1", "hyper-rustls/http2", "launchdarkly-server-sdk/rustls", "hyper-util"]
+tls = ["hyper-tls", "hyper1-tls", "hyper-util"]
diff --git a/contract-tests/src/client_entity.rs b/contract-tests/src/client_entity.rs
index 3538178..0bcb72e 100644
--- a/contract-tests/src/client_entity.rs
+++ b/contract-tests/src/client_entity.rs
@@ -1,3 +1,4 @@
+use eventsource_client as es;
 use futures::future::FutureExt;
 use launchdarkly_server_sdk::{
     Context, ContextBuilder, MigratorBuilder, MultiContextBuilder, Reference,
@@ -20,6 +21,7 @@ use crate::command_params::{
     MigrationOperationResponse, MigrationVariationResponse, SecureModeHashResponse,
 };
 use crate::HttpsConnector;
+use crate::StreamingHttpsConnector;
 use crate::{
     command_params::{
         CommandParams, CommandResponse, EvaluateAllFlagsParams, EvaluateAllFlagsResponse,
@@ -36,6 +38,7 @@ impl ClientEntity {
     pub async fn new(
         create_instance_params: CreateInstanceParams,
         connector: HttpsConnector,
+        streaming_https_connector: StreamingHttpsConnector,
     ) -> Result<Self, BuildError> {
         let mut config_builder =
             ConfigBuilder::new(&create_instance_params.configuration.credential);
@@ -71,6 +74,8 @@ impl ClientEntity {
         }
 
         if let Some(streaming) = create_instance_params.configuration.streaming {
+            let transport =
+                es::HyperTransport::builder().build_with_connector(streaming_https_connector);
             if let Some(base_uri) = streaming.base_uri {
                 service_endpoints_builder.streaming_base_url(&base_uri);
             }
@@ -79,7 +84,7 @@ impl ClientEntity {
             if let Some(delay) = streaming.initial_retry_delay_ms {
                 streaming_builder.initial_reconnect_delay(Duration::from_millis(delay));
             }
-            streaming_builder.https_connector(connector.clone());
+            streaming_builder.transport(transport);
 
             config_builder = config_builder.data_source(&streaming_builder);
         } else if let Some(polling) = create_instance_params.configuration.polling {
@@ -98,8 +103,10 @@ impl ClientEntity {
             // If we didn't specify streaming or polling, we fall back to basic streaming. The only
             // customization we provide is the https connector to support testing multiple
             // connectors.
+            let transport =
+                es::HyperTransport::builder().build_with_connector(streaming_https_connector);
             let mut streaming_builder = StreamingDataSourceBuilder::new();
-            streaming_builder.https_connector(connector.clone());
+            streaming_builder.transport(transport);
             config_builder = config_builder.data_source(&streaming_builder);
         }
 
diff --git a/contract-tests/src/main.rs b/contract-tests/src/main.rs
index 4bd4ff2..ad400f0 100644
--- a/contract-tests/src/main.rs
+++ b/contract-tests/src/main.rs
@@ -132,6 +132,7 @@ async fn create_client(
     let client_entity = match ClientEntity::new(
         create_instance_params.into_inner(),
         app_state.https_connector.clone(),
+        app_state.streaming_https_connector.clone(),
     )
     .await
     {
@@ -206,12 +207,19 @@ struct AppState {
     counter: Mutex<u32>,
     client_entities: Mutex<HashMap<u32, ClientEntity>>,
     https_connector: HttpsConnector,
+    streaming_https_connector: StreamingHttpsConnector,
 }
 
 #[cfg(feature = "rustls")]
 type HttpsConnector = hyper_rustls::HttpsConnector<HttpConnector>;
+#[cfg(feature = "rustls")]
+type StreamingHttpsConnector = hyper_util::client::legacy::connect::HttpConnector;
+
 #[cfg(feature = "tls")]
 type HttpsConnector = hyper_tls::HttpsConnector<HttpConnector>;
+#[cfg(feature = "tls")]
+type StreamingHttpsConnector =
+    hyper1_tls::HttpsConnector<hyper_util::client::legacy::connect::HttpConnector>;
 
 #[actix_web::main]
 async fn main() -> std::io::Result<()> {
@@ -228,6 +236,8 @@ async fn main() -> std::io::Result<()> {
 
     let (tx, rx) = mpsc::channel::<()>();
 
+    #[cfg(feature = "rustls")]
+    let streaming_https_connector = hyper_util::client::legacy::connect::HttpConnector::new();
     #[cfg(feature = "rustls")]
     let connector = hyper_rustls::HttpsConnectorBuilder::new()
         .with_native_roots()
@@ -236,6 +246,8 @@ async fn main() -> std::io::Result<()> {
         .enable_http2()
         .build();
 
+    #[cfg(feature = "tls")]
+    let streaming_https_connector = hyper1_tls::HttpsConnector::new();
     #[cfg(feature = "tls")]
     let connector = hyper_tls::HttpsConnector::new();
 
@@ -243,6 +255,7 @@ async fn main() -> std::io::Result<()> {
         counter: Mutex::new(0),
         client_entities: Mutex::new(HashMap::new()),
         https_connector: connector,
+        streaming_https_connector: streaming_https_connector,
     });
 
     let server = HttpServer::new(move || {
diff --git a/launchdarkly-server-sdk/Cargo.toml b/launchdarkly-server-sdk/Cargo.toml
index fb86abf..55bae78 100644
--- a/launchdarkly-server-sdk/Cargo.toml
+++ b/launchdarkly-server-sdk/Cargo.toml
@@ -4,7 +4,7 @@ description = "LaunchDarkly Server-Side SDK"
 version = "2.6.2"
 authors = ["LaunchDarkly"]
 edition = "2021"
-rust-version = "1.83.0"  # MSRV
+rust-version = "1.85.0"  # MSRV
 license = "Apache-2.0"
 homepage = "https://docs.launchdarkly.com/sdk/server-side/rust"
 repository = "https://github.com/launchdarkly/rust-server-sdk"
@@ -20,7 +20,8 @@ features = ["event-compression"]
 chrono = "0.4.19"
 crossbeam-channel = "0.5.1"
 data-encoding = "2.3.2"
-eventsource-client = { version = "0.16.0", default-features = false }
+# eventsource-client = { version = "0.16.0", default-features = false }
+eventsource-client = { git = "https://github.com/launchdarkly/rust-eventsource-client", branch = "feat/hyper-as-feature" }
 futures = "0.3.12"
 lazy_static = "1.4.0"
 log = "0.4.14"
@@ -54,7 +55,7 @@ testing_logger = "0.1.1"
 
 [features]
 default = ["rustls"]
-rustls = ["hyper-rustls/http1", "hyper-rustls/http2", "eventsource-client/rustls"]
+rustls = ["hyper-rustls/http1", "hyper-rustls/http2", "eventsource-client/hyper-rustls"]
 event-compression = ["flate2"]
 
 [[example]]
diff --git a/launchdarkly-server-sdk/src/config.rs b/launchdarkly-server-sdk/src/config.rs
index e264bff..8e738df 100644
--- a/launchdarkly-server-sdk/src/config.rs
+++ b/launchdarkly-server-sdk/src/config.rs
@@ -6,6 +6,7 @@ use crate::events::processor_builders::{
 };
 use crate::stores::store_builders::{DataStoreFactory, InMemoryDataStoreBuilder};
 use crate::{ServiceEndpointsBuilder, StreamingDataSourceBuilder};
+use eventsource_client as es;
 
 use std::borrow::Borrow;
 
@@ -301,9 +302,9 @@ impl ConfigBuilder {
                 }
                 Some(builder) => Ok(builder),
                 #[cfg(feature = "rustls")]
-                None => Ok(Box::new(StreamingDataSourceBuilder::<
-                    hyper_rustls::HttpsConnector<hyper::client::HttpConnector>,
-                >::new())),
+                None => Ok(Box::new(
+                    StreamingDataSourceBuilder::<es::HyperTransport>::new(),
+                )),
                 #[cfg(not(feature = "rustls"))]
                 None => Err(BuildError::InvalidConfig(
                     "data source builder required when rustls is disabled".into(),
diff --git a/launchdarkly-server-sdk/src/data_source.rs b/launchdarkly-server-sdk/src/data_source.rs
index 55c786f..a533281 100644
--- a/launchdarkly-server-sdk/src/data_source.rs
+++ b/launchdarkly-server-sdk/src/data_source.rs
@@ -7,15 +7,11 @@ use crate::LAUNCHDARKLY_TAGS_HEADER;
 use es::{Client, ClientBuilder, ReconnectOptionsBuilder};
 use eventsource_client as es;
 use futures::StreamExt;
-use hyper::client::connect::Connection;
-use hyper::service::Service;
-use hyper::Uri;
 use launchdarkly_server_sdk_evaluation::{Flag, Segment};
 use parking_lot::RwLock;
 use serde::Deserialize;
 use std::sync::{Arc, Mutex, Once};
 use std::time::Duration;
-use tokio::io::{AsyncRead, AsyncWrite};
 use tokio::sync::broadcast;
 use tokio::time;
 use tokio_stream::wrappers::{BroadcastStream, IntervalStream};
@@ -73,19 +69,13 @@ pub struct StreamingDataSource {
 }
 
 impl StreamingDataSource {
-    pub fn new<C>(
+    pub fn new<T: es::HttpTransport>(
         base_url: &str,
         sdk_key: &str,
         initial_reconnect_delay: Duration,
         tags: &Option<String>,
-        connector: C,
-    ) -> std::result::Result<Self, es::Error>
-    where
-        C: Service<Uri> + Clone + Send + Sync + 'static,
-        C::Response: Connection + AsyncRead + AsyncWrite + Send + Unpin,
-        C::Future: Send + 'static,
-        C::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
-    {
+        transport: T,
+    ) -> std::result::Result<Self, es::Error> {
         let stream_url = format!("{}/all", base_url);
 
         let client_builder = ClientBuilder::for_url(&stream_url)?;
@@ -105,7 +95,7 @@ impl StreamingDataSource {
         }
 
         Ok(Self {
-            es_client: Box::new(client_builder.build_with_conn(connector)),
+            es_client: Box::new(client_builder.build_with_transport(transport)),
         })
     }
 }
@@ -385,6 +375,7 @@ mod tests {
     use super::{DataSource, PollingDataSource, StreamingDataSource};
     use crate::feature_requester_builders::HyperFeatureRequesterBuilder;
     use crate::{stores::store::InMemoryDataStore, LAUNCHDARKLY_TAGS_HEADER};
+    use eventsource_client as es;
 
     #[test_case(Some("application-id/abc:application-sha/xyz".into()), "application-id/abc:application-sha/xyz")]
     #[test_case(None, Matcher::Missing)]
@@ -411,7 +402,7 @@ mod tests {
             "sdk-key",
             Duration::from_secs(0),
             &tag,
-            HttpConnector::new(),
+            es::HyperTransport::new(),
         )
         .unwrap();
 
diff --git a/launchdarkly-server-sdk/src/data_source_builders.rs b/launchdarkly-server-sdk/src/data_source_builders.rs
index ec32390..2d1d566 100644
--- a/launchdarkly-server-sdk/src/data_source_builders.rs
+++ b/launchdarkly-server-sdk/src/data_source_builders.rs
@@ -1,6 +1,7 @@
 use super::service_endpoints;
 use crate::data_source::{DataSource, NullDataSource, PollingDataSource, StreamingDataSource};
 use crate::feature_requester_builders::{FeatureRequesterFactory, HyperFeatureRequesterBuilder};
+use eventsource_client as es;
 use hyper::{client::connect::Connection, service::Service, Uri};
 #[cfg(feature = "rustls")]
 use hyper_rustls::HttpsConnectorBuilder;
@@ -47,26 +48,25 @@ pub trait DataSourceFactory {
 /// Adjust the initial reconnect delay.
 /// ```
 /// # use launchdarkly_server_sdk::{StreamingDataSourceBuilder, ConfigBuilder};
-/// # use hyper_rustls::HttpsConnector;
-/// # use hyper::client::HttpConnector;
+/// # use eventsource_client as es;
 /// # use std::time::Duration;
 /// # fn main() {
-///     ConfigBuilder::new("sdk-key").data_source(StreamingDataSourceBuilder::<hyper_rustls::HttpsConnector<HttpConnector>>::new()
+///     ConfigBuilder::new("sdk-key").data_source(StreamingDataSourceBuilder::<es::HyperTransport>::new()
 ///         .initial_reconnect_delay(Duration::from_secs(10)));
 /// # }
 /// ```
 #[derive(Clone)]
-pub struct StreamingDataSourceBuilder<C> {
+pub struct StreamingDataSourceBuilder<T: es::HttpTransport> {
     initial_reconnect_delay: Duration,
-    connector: Option<C>,
+    transport: Option<T>,
 }
 
-impl<C> StreamingDataSourceBuilder<C> {
+impl<T: es::HttpTransport> StreamingDataSourceBuilder<T> {
     /// Create a new instance of the [StreamingDataSourceBuilder] with default values.
     pub fn new() -> Self {
         Self {
             initial_reconnect_delay: DEFAULT_INITIAL_RECONNECT_DELAY,
-            connector: None,
+            transport: None,
         }
     }
 
@@ -76,56 +76,42 @@ impl<C> StreamingDataSourceBuilder<C> {
         self
     }
 
-    /// Sets the connector for the event source client to use. This allows for re-use of a
-    /// connector between multiple client instances. This is especially useful for the
+    /// Sets the transport for the event source client to use. This allows for re-use of a
+    /// transport between multiple client instances. This is especially useful for the
     /// `sdk-test-harness` where many client instances are created throughout the test and reading
     /// the native certificates is a substantial portion of the runtime.
-    pub fn https_connector(&mut self, connector: C) -> &mut Self {
-        self.connector = Some(connector);
+    pub fn transport(&mut self, transport: T) -> &mut Self {
+        self.transport = Some(transport);
         self
     }
 }
 
-impl<C> DataSourceFactory for StreamingDataSourceBuilder<C>
-where
-    C: Service<Uri> + Clone + Send + Sync + 'static,
-    C::Response: Connection + AsyncRead + AsyncWrite + Send + Unpin,
-    C::Future: Send + 'static,
-    C::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
-{
+impl<T: es::HttpTransport> DataSourceFactory for StreamingDataSourceBuilder<T> {
     fn build(
         &self,
         endpoints: &service_endpoints::ServiceEndpoints,
         sdk_key: &str,
         tags: Option<String>,
     ) -> Result<Arc<dyn DataSource>, BuildError> {
-        let data_source_result = match &self.connector {
+        let data_source_result = match &self.transport {
             #[cfg(feature = "rustls")]
-            None => {
-                let connector = HttpsConnectorBuilder::new()
-                    .with_native_roots()
-                    .https_or_http()
-                    .enable_http1()
-                    .enable_http2()
-                    .build();
-                Ok(StreamingDataSource::new(
-                    endpoints.streaming_base_url(),
-                    sdk_key,
-                    self.initial_reconnect_delay,
-                    &tags,
-                    connector,
-                ))
-            }
+            None => Ok(StreamingDataSource::new(
+                endpoints.streaming_base_url(),
+                sdk_key,
+                self.initial_reconnect_delay,
+                &tags,
+                es::HyperTransport::new_https(),
+            )),
             #[cfg(not(feature = "rustls"))]
             None => Err(BuildError::InvalidConfig(
                 "https connector required when rustls is disabled".into(),
             )),
-            Some(connector) => Ok(StreamingDataSource::new(
+            Some(transport) => Ok(StreamingDataSource::new(
                 endpoints.streaming_base_url(),
                 sdk_key,
                 self.initial_reconnect_delay,
                 &tags,
-                connector.clone(),
+                transport.clone(),
             )),
         };
         let data_source = data_source_result?
@@ -138,7 +124,7 @@ where
     }
 }
 
-impl<C> Default for StreamingDataSourceBuilder<C> {
+impl<T: es::HttpTransport> Default for StreamingDataSourceBuilder<T> {
     fn default() -> Self {
         StreamingDataSourceBuilder::new()
     }
@@ -355,13 +341,15 @@ impl DataSourceFactory for MockDataSourceBuilder {
 
 #[cfg(test)]
 mod tests {
+    use eventsource_client::{HyperTransport, ResponseFuture};
     use hyper::client::HttpConnector;
 
     use super::*;
 
     #[test]
     fn default_stream_builder_has_correct_defaults() {
-        let builder: StreamingDataSourceBuilder<HttpConnector> = StreamingDataSourceBuilder::new();
+        let builder: StreamingDataSourceBuilder<es::HyperTransport> =
+            StreamingDataSourceBuilder::new();
 
         assert_eq!(
             builder.initial_reconnect_delay,
@@ -370,29 +358,22 @@ mod tests {
     }
 
     #[test]
-    fn stream_builder_can_use_custom_connector() {
+    fn stream_builder_can_use_custom_transport() {
         #[derive(Debug, Clone)]
-        struct TestConnector;
-        impl hyper::service::Service<hyper::Uri> for TestConnector {
-            type Response = tokio::net::TcpStream;
-            type Error = std::io::Error;
-            type Future = futures::future::BoxFuture<'static, Result<Self::Response, Self::Error>>;
-
-            fn poll_ready(
-                &mut self,
-                _cx: &mut std::task::Context<'_>,
-            ) -> std::task::Poll<Result<(), Self::Error>> {
-                std::task::Poll::Ready(Ok(()))
-            }
+        struct TestTransport;
 
-            fn call(&mut self, _req: hyper::Uri) -> Self::Future {
+        impl es::HttpTransport for TestTransport {
+            fn request(
+                &self,
+                _request: eventsource_client::Request<Option<String>>,
+            ) -> ResponseFuture {
                 // this won't be called during the test
                 unreachable!();
             }
         }
 
         let mut builder = StreamingDataSourceBuilder::new();
-        builder.https_connector(TestConnector);
+        builder.transport(TestTransport);
         assert!(builder
             .build(
                 &crate::ServiceEndpointsBuilder::new().build().unwrap(),
@@ -410,7 +391,7 @@ mod tests {
 
     #[test]
     fn initial_reconnect_delay_for_streaming_can_be_adjusted() {
-        let mut builder = StreamingDataSourceBuilder::<()>::new();
+        let mut builder = StreamingDataSourceBuilder::<HyperTransport>::new();
         builder.initial_reconnect_delay(Duration::from_secs(1234));
         assert_eq!(builder.initial_reconnect_delay, Duration::from_secs(1234));
     }