From efb2fa9c22aebaba22368d7e1edc5e124e5bfbd6 Mon Sep 17 00:00:00 2001
From: Pierre Tachoire <pierre@lightpanda.io>
Date: Tue, 7 Apr 2026 17:42:31 +0200
Subject: [PATCH] Send Sec-Ch-Ua http header

---
 src/Config.zig       | 5 +++++
 src/network/http.zig | 9 ++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/Config.zig b/src/Config.zig
index c7008810..c037e87a 100644
--- a/src/Config.zig
+++ b/src/Config.zig
@@ -306,6 +306,7 @@ pub const Common = struct {
 /// Must be initialized with an allocator that outlives all HTTP connections.
 pub const HttpHeaders = struct {
     const user_agent_base: [:0]const u8 = "Lightpanda/1.0";
+    pub const sec_ch_ua: [:0]const u8 = "Sec-Ch-Ua: \"Lightpanda\";v=\"1\"";
 
     user_agent: [:0]const u8, // User agent value (e.g. "Lightpanda/1.0")
     user_agent_header: [:0]const u8,
@@ -411,6 +412,10 @@ pub fn printUsageAndExit(self: *const Config, success: bool) void {
         \\                http, unknown_prop, event, ...
         \\
         \\--user-agent    Override the User-Agent header entirely
+        \\                User-Agent mustn't impersonate other browser.
+        \\                Starting the value with "Mozilla/5.0" is forbidden.
+        \\                The browser will continue to send Sec-Ch-Ua header.
+        \\                Incompatible with --user-agent-suffix
         \\
         \\--user-agent-suffix
         \\                Suffix to append to the Lightpanda/X.Y User-Agent
diff --git a/src/network/http.zig b/src/network/http.zig
index 4bf71ded..ef3dfc65 100644
--- a/src/network/http.zig
+++ b/src/network/http.zig
@@ -62,7 +62,14 @@ pub const Headers = struct {
         if (header_list == null) {
             return error.OutOfMemory;
         }
-        return .{ .headers = header_list };
+
+        // Always add sec-CH-UA header
+        const updated_headers = libcurl.curl_slist_append(header_list, Config.HttpHeaders.sec_ch_ua);
+        if (updated_headers == null) {
+            return error.OutOfMemory;
+        }
+
+        return .{ .headers = updated_headers };
     }
 
     pub fn deinit(self: *const Headers) void {