From 69f772b92478895e7fee4815950ceedb46be7788 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Mon, 28 Sep 2026 18:13:26 +0000
Subject: [PATCH] =?UTF-8?q?=E2=9A=A1=20Bolt:=20Zero-allocation=20case-inse?=
 =?UTF-8?q?nsitive=20prefix=20matching?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: callmeradical <822382+callmeradical@users.noreply.github.com>
---
 .jules/bolt.md                   | 4 ++++
 cmd/sergeant-mcp-client/proxy.go | 5 +++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/.jules/bolt.md b/.jules/bolt.md
index 29665ec..b326912 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -21,3 +21,7 @@
 ## 2024-10-25 - Avoid mime.ParseMediaType for exact header matching
 **Learning:** Using `mime.ParseMediaType` for exact or prefix header matching in hot paths introduces unnecessary memory allocations.
 **Action:** When substituting with `strings.HasPrefix`, explicitly handle case-insensitivity (e.g., via `strings.ToLower`) to maintain HTTP standard compliance while preventing heavy parsing allocations.
+
+## 2024-10-25 - Avoid strings.ToLower for case-insensitive prefix matching
+**Learning:** Using `strings.ToLower` for case-insensitive prefix matching forces a memory allocation. In hot paths, this creates unnecessary garbage collection overhead.
+**Action:** Use `len(str) >= len(prefix) && strings.EqualFold(str[:len(prefix)], prefix)` to achieve zero-allocation case-insensitive matching.
diff --git a/cmd/sergeant-mcp-client/proxy.go b/cmd/sergeant-mcp-client/proxy.go
index 5d69ba6..1c2a805 100644
--- a/cmd/sergeant-mcp-client/proxy.go
+++ b/cmd/sergeant-mcp-client/proxy.go
@@ -174,8 +174,9 @@ func (p *proxy) writeResponse(resp *response) {
 		return
 	}
 
-	// Performance optimization: Avoid mime.ParseMediaType allocation for exact header matching
-	isEventStream := strings.HasPrefix(strings.ToLower(resp.contentType), "text/event-stream")
+	// Performance optimization: Avoid mime.ParseMediaType and strings.ToLower allocations for prefix header matching
+	prefix := "text/event-stream"
+	isEventStream := len(resp.contentType) >= len(prefix) && strings.EqualFold(resp.contentType[:len(prefix)], prefix)
 	p.outMu.Lock()
 	defer p.outMu.Unlock()
 	if isEventStream {