From 4c7c003177c2306feeae7e3edf05ccbe83d0121f Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Thu, 1 Oct 2026 17:54:03 +0000
Subject: [PATCH] =?UTF-8?q?=E2=9A=A1=20Bolt:=20Avoid=20strings.ToLower=20a?=
 =?UTF-8?q?llocation=20in=20header=20match?=
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                   | 3 +++
 cmd/sergeant-mcp-client/proxy.go | 4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/.jules/bolt.md b/.jules/bolt.md
index 29665ec..092524c 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -21,3 +21,6 @@
 ## 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 allocation in hot paths
+**Learning:** Using `strings.ToLower` for case-insensitive prefix checking forces a memory allocation, which is detrimental in hot paths like proxying HTTP responses.
+**Action:** Use `len(str) >= len(prefix) && strings.EqualFold(str[:len(prefix)], prefix)` to achieve zero-allocation matching.
diff --git a/cmd/sergeant-mcp-client/proxy.go b/cmd/sergeant-mcp-client/proxy.go
index 5d69ba6..a0b6c9b 100644
--- a/cmd/sergeant-mcp-client/proxy.go
+++ b/cmd/sergeant-mcp-client/proxy.go
@@ -174,8 +174,8 @@ 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 strings.ToLower allocation for case-insensitive prefix matching
+	isEventStream := len(resp.contentType) >= len("text/event-stream") && strings.EqualFold(resp.contentType[:len("text/event-stream")], "text/event-stream")
 	p.outMu.Lock()
 	defer p.outMu.Unlock()
 	if isEventStream {