diff --git a/Cargo.lock b/Cargo.lock
index 5ce990b2..d5d28877 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4763,9 +4763,9 @@ dependencies = [
 
 [[package]]
 name = "unleash-yggdrasil"
-version = "0.16.1"
+version = "0.17.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "34dd3238d299dd71e59ed901b67e5d371d8c3e66ae1945fe31da7d876feb613f"
+checksum = "b8c059a19bd116c26bdc3b2acccb09ac2f9142615db9505606b367d120d455f4"
 dependencies = [
  "chrono",
  "convert_case 0.6.0",
diff --git a/server/Cargo.toml b/server/Cargo.toml
index 7e5a88cc..e9a75c61 100644
--- a/server/Cargo.toml
+++ b/server/Cargo.toml
@@ -96,7 +96,7 @@ tracing = { version = "0.1.41", features = ["log"] }
 tracing-subscriber = { version = "0.3.19", features = ["json", "env-filter"] }
 ulid = "1.1.4"
 unleash-types = { version = "0.15.5", features = ["openapi", "hashes"] }
-unleash-yggdrasil = { version = "0.16.1" }
+unleash-yggdrasil = { version = "0.17.0" }
 utoipa = { version = "5.3.1", features = ["actix_extras", "chrono"] }
 utoipa-swagger-ui = { version = "9.0.0", features = ["actix-web"] }
 [dev-dependencies]
diff --git a/server/src/builder.rs b/server/src/builder.rs
index 23c36d1b..6a6e0395 100644
--- a/server/src/builder.rs
+++ b/server/src/builder.rs
@@ -8,7 +8,7 @@ use dashmap::DashMap;
 use reqwest::Url;
 use tracing::{debug, error, warn};
 use unleash_types::client_features::ClientFeatures;
-use unleash_yggdrasil::EngineState;
+use unleash_yggdrasil::{EngineState, UpdateMessage};
 
 use crate::cli::RedisMode;
 use crate::feature_cache::FeatureCache;
@@ -70,7 +70,7 @@ async fn hydrate_from_persistent_storage(cache: CacheContainer, storage: Arc<dyn
         features_cache.insert(key.clone(), features.clone());
         let mut engine_state = EngineState::default();
 
-        let warnings = engine_state.take_state(features);
+        let warnings = engine_state.take_state(UpdateMessage::FullResponse(features));
         if let Some(warnings) = warnings {
             warn!("Failed to hydrate features for {key:?}: {warnings:?}");
         }
diff --git a/server/src/http/refresher/delta_refresher.rs b/server/src/http/refresher/delta_refresher.rs
index 6194cd97..a934f402 100644
--- a/server/src/http/refresher/delta_refresher.rs
+++ b/server/src/http/refresher/delta_refresher.rs
@@ -1,12 +1,17 @@
+use std::time::Duration;
+use eventsource_client::Client;
 use actix_web::http::header::EntityTag;
 use reqwest::StatusCode;
+use futures::TryStreamExt;
 use tracing::{debug, info, warn};
 use unleash_types::client_features::{ClientFeaturesDelta};
 use unleash_yggdrasil::EngineState;
 
 use crate::error::{EdgeError, FeatureError};
+use crate::http::headers::{UNLEASH_APPNAME_HEADER, UNLEASH_CLIENT_SPEC_HEADER, UNLEASH_INSTANCE_ID_HEADER};
 use crate::types::{ClientFeaturesDeltaResponse, ClientFeaturesRequest, EdgeToken, TokenRefresh};
 use crate::http::refresher::feature_refresher::FeatureRefresher;
+use crate::http::unleash_client::ClientMetaInformation;
 use crate::tokens::cache_key;
 
 impl FeatureRefresher {
@@ -19,7 +24,7 @@ impl FeatureRefresher {
         let updated_len = delta.events.len();
 
         debug!(
-            "Got updated client features delta. Updating features with {etag:?}, events count {updated_len}"
+            "Got updated client features delta. Updating features with etag {etag:?}, events count {updated_len}"
         );
 
         let key = cache_key(refresh_token);
@@ -110,6 +115,117 @@ impl FeatureRefresher {
             }
         }
     }
+
+    pub async fn start_streaming_delta_background_task(
+        &self,
+        client_meta_information: ClientMetaInformation,
+        custom_headers: Vec<(String, String)>,
+    ) -> anyhow::Result<()> {
+        use anyhow::Context;
+
+        let refreshes = self.get_tokens_due_for_refresh();
+        for refresh in refreshes {
+            let token = refresh.token.clone();
+            let streaming_url = self.unleash_client.urls.client_features_stream_url.as_str();
+
+            let mut es_client_builder = eventsource_client::ClientBuilder::for_url(streaming_url)
+                .context("Failed to create EventSource client for streaming")?
+                .header("Authorization", &token.token)?
+                .header(UNLEASH_APPNAME_HEADER, &client_meta_information.app_name)?
+                .header(
+                    UNLEASH_INSTANCE_ID_HEADER,
+                    &client_meta_information.instance_id,
+                )?
+                .header(
+                    UNLEASH_CLIENT_SPEC_HEADER,
+                    unleash_yggdrasil::SUPPORTED_SPEC_VERSION,
+                )?;
+
+            for (key, value) in custom_headers.clone() {
+                es_client_builder = es_client_builder.header(&key, &value)?;
+            }
+
+            let es_client = es_client_builder
+                .reconnect(
+                    eventsource_client::ReconnectOptions::reconnect(true)
+                        .retry_initial(true)
+                        .delay(Duration::from_secs(5))
+                        .delay_max(Duration::from_secs(30))
+                        .backoff_factor(2)
+                        .build(),
+                )
+                .build();
+
+            let refresher = self.clone();
+
+            tokio::spawn(async move {
+                let mut stream = es_client
+                    .stream()
+                    .map_ok(move |sse| {
+                        let token = token.clone();
+                        let refresher = refresher.clone();
+                        async move {
+                            match sse {
+                                // The first time we're connecting to Unleash.
+                                eventsource_client::SSE::Event(event)
+                                if event.event_type == "unleash-connected" =>
+                                    {
+                                        debug!(
+                                        "Connected to unleash! Populating my flag cache now.",
+                                    );
+
+                                        match serde_json::from_str(&event.data) {
+                                            Ok(delta) => { refresher.handle_client_features_delta_updated(&token, delta, None).await; }
+                                            Err(e) => { warn!("Could not parse features response to internal representation: {e:?}");
+                                            }
+                                        }
+                                    }
+                                // Unleash has updated features for us.
+                                eventsource_client::SSE::Event(event)
+                                if event.event_type == "unleash-updated" =>
+                                    {
+                                        debug!(
+                                        "Got an unleash updated event. Updating cache.",
+                                    );
+
+                                        match serde_json::from_str(&event.data) {
+                                            Ok(delta) => { refresher.handle_client_features_delta_updated(&token, delta, None).await; }
+                                            Err(e) => { warn!("Could not parse features response to internal representation: {e:?}");
+                                            }
+                                        }
+                                    }
+                                eventsource_client::SSE::Event(event) => {
+                                    info!(
+                                        "Got an SSE event that I wasn't expecting: {:#?}",
+                                        event
+                                    );
+                                }
+                                eventsource_client::SSE::Connected(_) => {
+                                    debug!("SSE Connection established");
+                                }
+                                eventsource_client::SSE::Comment(_) => {
+                                    // purposefully left blank.
+                                },
+                            }
+                        }
+                    })
+                    .map_err(|e| warn!("Error in SSE stream: {:?}", e));
+
+                loop {
+                    match stream.try_next().await {
+                        Ok(Some(handler)) => handler.await,
+                        Ok(None) => {
+                            info!("SSE stream ended? Handler was None, anyway. Reconnecting.");
+                        }
+                        Err(e) => {
+                            info!("SSE stream error: {e:?}. Reconnecting");
+                        }
+                    }
+                }
+            });
+        }
+        Ok(())
+    }
 }
 
 #[cfg(test)]
@@ -277,4 +393,6 @@ mod tests {
         })
             .await
     }
+
+
 }
diff --git a/server/src/http/refresher/feature_refresher.rs b/server/src/http/refresher/feature_refresher.rs
index 406d1f69..d643d321 100644
--- a/server/src/http/refresher/feature_refresher.rs
+++ b/server/src/http/refresher/feature_refresher.rs
@@ -11,7 +11,7 @@ use reqwest::StatusCode;
 use tracing::{debug, info, warn};
 use unleash_types::client_features::{ClientFeatures, DeltaEvent};
 use unleash_types::client_metrics::{ClientApplication, MetricsMetadata};
-use unleash_yggdrasil::EngineState;
+use unleash_yggdrasil::{EngineState, UpdateMessage};
 
 use crate::error::{EdgeError, FeatureError};
 use crate::feature_cache::FeatureCache;
@@ -495,7 +495,7 @@ impl FeatureRefresher {
                         .and_modify(|engine| {
                             if let Some(f) = self.features_cache.get(&key) {
                                 let mut new_state = EngineState::default();
-                                let warnings = new_state.take_state(f.clone());
+                                let warnings = new_state.take_state(UpdateMessage::FullResponse(f.clone()));
                                 if let Some(warnings) = warnings {
                                     warn!("The following toggle failed to compile and will be defaulted to off: {warnings:?}");
                                 };
@@ -506,7 +506,7 @@ impl FeatureRefresher {
                         .or_insert_with(|| {
                             let mut new_state = EngineState::default();
 
-                            let warnings = new_state.take_state(features);
+                            let warnings = new_state.take_state(UpdateMessage::FullResponse(features));
                             if let Some(warnings) = warnings {
                                 warn!("The following toggle failed to compile and will be defaulted to off: {warnings:?}");
                             };
@@ -623,7 +623,7 @@ mod tests {
     use dashmap::DashMap;
     use reqwest::Url;
     use unleash_types::client_features::ClientFeature;
-    use unleash_yggdrasil::EngineState;
+    use unleash_yggdrasil::{EngineState, UpdateMessage};
 
     use crate::feature_cache::{update_projects_from_feature_update, FeatureCache};
     use crate::filters::{project_filter, FeatureFilterSet};
@@ -1043,7 +1043,7 @@ mod tests {
         let example_features = features_from_disk("../examples/features.json");
         let cache_key = cache_key(&token);
         let mut engine_state = EngineState::default();
-        let warnings = engine_state.take_state(example_features.clone());
+        let warnings = engine_state.take_state(UpdateMessage::FullResponse(example_features.clone()));
         upstream_features_cache.insert(cache_key.clone(), example_features.clone());
         upstream_engine_cache.insert(cache_key.clone(), engine_state);
         let mut server = client_api_test_server(
@@ -1099,7 +1099,7 @@ mod tests {
         let example_features = features_from_disk("../examples/features.json");
         let cache_key = cache_key(&valid_token);
         let mut engine_state = EngineState::default();
-        let warnings = engine_state.take_state(example_features.clone());
+        let warnings = engine_state.take_state(UpdateMessage::FullResponse(example_features.clone()));
         upstream_features_cache.insert(cache_key.clone(), example_features.clone());
         upstream_engine_cache.insert(cache_key.clone(), engine_state);
         let server = client_api_test_server(
@@ -1144,7 +1144,7 @@ mod tests {
         let example_features = features_from_disk("../examples/hostedexample.json");
         let cache_key = cache_key(&dx_token);
         let mut engine_state = EngineState::default();
-        let warnings = engine_state.take_state(example_features.clone());
+        let warnings = engine_state.take_state(UpdateMessage::FullResponse(example_features.clone()));
         upstream_features_cache.insert(cache_key.clone(), example_features.clone());
         upstream_engine_cache.insert(cache_key.clone(), engine_state);
         let server = client_api_test_server(
@@ -1194,7 +1194,7 @@ mod tests {
         let cache_key = cache_key(&dx_token);
         upstream_features_cache.insert(cache_key.clone(), example_features.clone());
         let mut engine_state = EngineState::default();
-        let warnings = engine_state.take_state(example_features.clone());
+        let warnings = engine_state.take_state(UpdateMessage::FullResponse(example_features.clone()));
         upstream_engine_cache.insert(cache_key, engine_state);
         let server = client_api_test_server(
             upstream_token_cache,
@@ -1256,7 +1256,7 @@ mod tests {
         let cache_key = cache_key(&dx_token);
         upstream_features_cache.insert(cache_key.clone(), example_features.clone());
         let mut engine_state = EngineState::default();
-        let warnings = engine_state.take_state(example_features.clone());
+        let warnings = engine_state.take_state(UpdateMessage::FullResponse(example_features.clone()));
         upstream_engine_cache.insert(cache_key, engine_state);
         let server = client_api_test_server(
             upstream_token_cache,
@@ -1364,7 +1364,7 @@ mod tests {
         let cache_key = cache_key(&eg_token);
         upstream_features_cache.insert(cache_key.clone(), example_features.clone());
         let mut engine_state = EngineState::default();
-        let warnings = engine_state.take_state(example_features.clone());
+        let warnings = engine_state.take_state(UpdateMessage::FullResponse(example_features.clone()));
         upstream_engine_cache.insert(cache_key.clone(), engine_state);
         let server = client_api_test_server(
             upstream_token_cache,
diff --git a/server/src/main.rs b/server/src/main.rs
index 321c659c..b48e21a0 100644
--- a/server/src/main.rs
+++ b/server/src/main.rs
@@ -167,17 +167,31 @@ async fn main() -> Result<(), anyhow::Error> {
             if edge.streaming {
                 let app_name = app_name.clone();
                 let custom_headers = custom_headers.clone();
-                tokio::spawn(async move {
-                    let _ = refresher_for_background
-                        .start_streaming_features_background_task(
-                            ClientMetaInformation {
-                                app_name,
-                                instance_id,
-                            },
-                            custom_headers,
-                        )
-                        .await;
-                });
+                if edge.delta {
+                    tokio::spawn(async move {
+                        let _ = refresher_for_background
+                            .start_streaming_delta_background_task(
+                                ClientMetaInformation {
+                                    app_name,
+                                    instance_id,
+                                },
+                                custom_headers,
+                            )
+                            .await;
+                    });
+                } else {
+                    tokio::spawn(async move {
+                        let _ = refresher_for_background
+                            .start_streaming_features_background_task(
+                                ClientMetaInformation {
+                                    app_name,
+                                    instance_id,
+                                },
+                                custom_headers,
+                            )
+                            .await;
+                    });
+                }
             }
 
             let refresher = feature_refresher.clone().unwrap();
diff --git a/server/src/offline/offline_hotload.rs b/server/src/offline/offline_hotload.rs
index 95ab63da..cd77f8fa 100644
--- a/server/src/offline/offline_hotload.rs
+++ b/server/src/offline/offline_hotload.rs
@@ -14,7 +14,7 @@ use tracing::warn;
 use unleash_types::client_features::{
     ClientFeature, ClientFeatures, Strategy, Variant, WeightType,
 };
-use unleash_yggdrasil::EngineState;
+use unleash_yggdrasil::{EngineState, UpdateMessage};
 
 use crate::{cli::OfflineArgs, error::EdgeError, feature_cache::FeatureCache, types::EdgeToken};
 
@@ -69,7 +69,7 @@ pub(crate) fn load_offline_engine_cache(
         client_features.clone(),
     );
     let mut engine = EngineState::default();
-    let warnings = engine.take_state(client_features);
+    let warnings = engine.take_state(UpdateMessage::FullResponse(client_features));
     engine_cache.insert(crate::tokens::cache_key(edge_token), engine);
     if let Some(warnings) = warnings {
         warn!("The following toggle failed to compile and will be defaulted to off: {warnings:?}");