diff --git a/Cargo.lock b/Cargo.lock
index 937f67c79..b13fee326 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -344,7 +344,8 @@ dependencies = [
  "rmcp",
  "serde",
  "serde_json",
- "sse-stream",
+ "sse-stream 0.2.6",
+ "sse-stream 0.3.0",
  "thiserror 2.0.21",
  "tokio",
  "tokio-stream",
@@ -6627,7 +6628,7 @@ dependencies = [
  "schemars 1.2.2",
  "serde",
  "serde_json",
- "sse-stream",
+ "sse-stream 0.2.6",
  "thiserror 2.0.21",
  "tokio",
  "tokio-stream",
@@ -7475,6 +7476,22 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "sse-stream"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d385160fc0fba84f7b9cc8ef3263e410d0e3ca7ab4927f1356df33145ace69a4"
+dependencies = [
+ "bytes",
+ "futures-util",
+ "http-body",
+ "http-body-util",
+ "memchr",
+ "pin-project-lite",
+ "simdutf8",
+ "thiserror 2.0.21",
+]
+
 [[package]]
 name = "stable_deref_trait"
 version = "1.2.1"
diff --git a/Cargo.toml b/Cargo.toml
index 60987adc0..8a2d6e0ec 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -50,7 +50,7 @@ tokio-tungstenite = { version = "0.30.0", features = ["rustls-tls-webpki-roots"]
 
 # MCP and API clients
 rmcp = { version = "^3.5.1", default-features = false }
-sse-stream = "0.2.6"
+sse-stream = "0.3.0"
 async-openai = { version = "^0.42.0", features = ["byot", "chat-completion", "responses"] }
 reqwest = { version = "^0.13.4", default-features = false, features = ["json", "query", "rustls", "http2", "stream"] }
 oauth2 = "5.0"
diff --git a/crates/mcp-utils/Cargo.toml b/crates/mcp-utils/Cargo.toml
index 16aec25a2..3f4077d2b 100644
--- a/crates/mcp-utils/Cargo.toml
+++ b/crates/mcp-utils/Cargo.toml
@@ -36,6 +36,7 @@ client = [
     "dep:serde",
     "dep:serde_json",
     "dep:sse-stream",
+    "dep:sse-stream-rmcp",
     "dep:tokio-stream",
     "dep:utils",
     "rmcp/transport-streamable-http-client-reqwest",
@@ -60,6 +61,8 @@ reqwest = { workspace = true, optional = true }
 serde = { workspace = true, optional = true }
 serde_json = { workspace = true, optional = true }
 sse-stream = { workspace = true, optional = true }
+# rmcp 3.5's StreamableHttpClient trait uses Sse from sse-stream 0.2.x.
+sse-stream-rmcp = { package = "sse-stream", version = "0.2.6", optional = true }
 tokio-stream = { workspace = true, features = ["sync"], optional = true }
 utils = { package = "aether-utils", path = "../utils", version = "0.2.19", optional = true }
 
diff --git a/crates/mcp-utils/src/client/sigv4.rs b/crates/mcp-utils/src/client/sigv4.rs
index 1f1e85548..3d41743aa 100644
--- a/crates/mcp-utils/src/client/sigv4.rs
+++ b/crates/mcp-utils/src/client/sigv4.rs
@@ -6,7 +6,7 @@ use rmcp::transport::auth::AuthError;
 use rmcp::transport::streamable_http_client::{
     SseError, StreamableHttpClient, StreamableHttpError, StreamableHttpPostResponse,
 };
-use sse_stream::Sse;
+use sse_stream_rmcp::Sse;
 use std::collections::HashMap;
 use std::sync::Arc;