From 10753f48cd820e700130b7187a43964e333b265a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=82=B5=E5=B9=BF=E8=B6=85?=
 <8617564+shao-guangchao@user.noreply.gitee.com>
Date: Sun, 9 Aug 2026 09:18:50 +0800
Subject: [PATCH] fix: ignore SSE retry: field to prevent McpTransportException

The SSE specification includes 'retry:' as a valid field for setting
the reconnection interval. However, the SseLineSubscriber treats any
unrecognized line as an error, causing McpTransportException when
MCP servers (e.g., rmcp-based servers like SurrealDB) emit retry
directives in SSE responses.

This fix adds a handler that silently ignores 'retry:' lines, matching
the existing behaviour for ':' comment lines.

Related: servers using rmcp (Rust MCP SDK) send 'retry: 3000' by
default, which triggers this error and breaks Streamable HTTP
connections to SurrealDB and other rmcp-based MCP servers.
---
 .../client/transport/ResponseSubscribers.java                | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mcp-core/src/main/java/io/modelcontextprotocol/client/transport/ResponseSubscribers.java b/mcp-core/src/main/java/io/modelcontextprotocol/client/transport/ResponseSubscribers.java
index 29dc23c35..234b8477a 100644
--- a/mcp-core/src/main/java/io/modelcontextprotocol/client/transport/ResponseSubscribers.java
+++ b/mcp-core/src/main/java/io/modelcontextprotocol/client/transport/ResponseSubscribers.java
@@ -179,6 +179,11 @@ else if (line.startsWith(":")) {
 					logger.debug("Ignoring comment line: {}", line);
 					upstream().request(1);
 				}
+				else if (line.startsWith("retry:")) {
+					// Ignore SSE retry directive — only the server controls reconnection
+					logger.debug("Ignoring retry directive: {}", line);
+					upstream().request(1);
+				}
 				else {
 					// If the response is not successful, emit an error
 					this.sink.error(new McpTransportException(