From 25d1c18a3f5c42bdaf246d4104f13ea2a2eb4929 Mon Sep 17 00:00:00 2001
From: Luis Pater <webmaster@idotorg.org>
Date: Thu, 2 Apr 2026 11:03:11 +0800
Subject: [PATCH] fix: scope experimental cch signing to billing header

---
 go.mod                                      |  2 +-
 internal/runtime/executor/claude_signing.go | 25 +++++++++++++++++----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/go.mod b/go.mod
index 9213f736..7ad363a7 100644
--- a/go.mod
+++ b/go.mod
@@ -81,7 +81,7 @@ require (
 	github.com/muesli/cancelreader v0.2.2 // indirect
 	github.com/muesli/termenv v0.16.0 // indirect
 	github.com/pelletier/go-toml/v2 v2.2.2 // indirect
-	github.com/pierrec/xxHash v0.1.5 // indirect
+	github.com/pierrec/xxHash v0.1.5
 	github.com/pjbgf/sha1cd v0.5.0 // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
 	github.com/rs/xid v1.5.0 // indirect
diff --git a/internal/runtime/executor/claude_signing.go b/internal/runtime/executor/claude_signing.go
index c52aef49..697a6882 100644
--- a/internal/runtime/executor/claude_signing.go
+++ b/internal/runtime/executor/claude_signing.go
@@ -8,19 +8,36 @@ import (
 	xxHash64 "github.com/pierrec/xxHash/xxHash64"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
 	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
+	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
 )
 
 const claudeCCHSeed uint64 = 0x6E52736AC806831E
 
-var claudeBillingHeaderPlaceholderPattern = regexp.MustCompile(`(x-anthropic-billing-header:[^"]*?\bcch=)(00000)(;)`)
+var claudeBillingHeaderCCHPattern = regexp.MustCompile(`\bcch=([0-9a-f]{5});`)
 
 func signAnthropicMessagesBody(body []byte) []byte {
-	if !claudeBillingHeaderPlaceholderPattern.Match(body) {
+	billingHeader := gjson.GetBytes(body, "system.0.text").String()
+	if !strings.HasPrefix(billingHeader, "x-anthropic-billing-header:") {
+		return body
+	}
+	if !claudeBillingHeaderCCHPattern.MatchString(billingHeader) {
 		return body
 	}
 
-	cch := fmt.Sprintf("%05x", xxHash64.Checksum(body, claudeCCHSeed)&0xFFFFF)
-	return claudeBillingHeaderPlaceholderPattern.ReplaceAll(body, []byte("${1}"+cch+"${3}"))
+	unsignedBillingHeader := claudeBillingHeaderCCHPattern.ReplaceAllString(billingHeader, "cch=00000;")
+	unsignedBody, err := sjson.SetBytes(body, "system.0.text", unsignedBillingHeader)
+	if err != nil {
+		return body
+	}
+
+	cch := fmt.Sprintf("%05x", xxHash64.Checksum(unsignedBody, claudeCCHSeed)&0xFFFFF)
+	signedBillingHeader := claudeBillingHeaderCCHPattern.ReplaceAllString(unsignedBillingHeader, "cch="+cch+";")
+	signedBody, err := sjson.SetBytes(unsignedBody, "system.0.text", signedBillingHeader)
+	if err != nil {
+		return unsignedBody
+	}
+	return signedBody
 }
 
 func resolveClaudeKeyConfig(cfg *config.Config, auth *cliproxyauth.Auth) *config.ClaudeKey {