Files
sub2api/backend/internal/service/gateway_billing_block.go
T
eyre 219da4b9e5 feat(claude-mimicry): align Claude Code fingerprint with CLI 2.1.161
- bump impersonated CLI version 2.1.92 -> 2.1.161; derive User-Agent from
  CLICurrentVersion so the two hardcoded copies can no longer drift apart
- fix x-stainless headers to real 2.1.161 values: package-version
  0.70.0 -> 0.94.0, runtime-version v24.13.0 -> v24.3.0 (verified against
  the installed Bun-compiled binary)
- expand the disguise-path system prompt from a 2-block identity skeleton
  to a 3-block layout (billing + identity + tool-agnostic prose), matching
  real CC's multi-block shape; cache breakpoint moved to the last static
  block. Deliberately excludes # Doing tasks / # Using your tools /
  # Executing actions to avoid polluting proxied-client behavior
- stabilize the synthesized metadata.user_id session_id across conversation
  turns: derive it from (account + client discriminator + first user
  message) instead of a per-turn content/body hash. Sticky-routing
  GenerateSessionHash is intentionally left untouched; remove now-dead
  hashBodyForSessionSeed

Tests: update the 3-block system assertions in gateway_prompt_test and
gateway_anthropic_apikey_passthrough_test; add a session_id cross-turn
stability test in gateway_oauth_metadata_test.
2026-06-06 01:01:58 +08:00

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package service
import (
"crypto/sha256"
"encoding/hex"
"encoding/json"
"fmt"
"github.com/tidwall/gjson"
)
// fingerprintSalt 是计算 cc_version 后缀指纹的盐值。
//
// 来源:与 Parrot src/transform/cc_mimicry.py 的 FINGERPRINT_SALT 完全一致;
// 这是真实 Claude Code CLI 抓包推导出的常量,改动会导致 fp 与 CLI 不一致,
// 进一步触发 Anthropic 的第三方检测。
const fingerprintSalt = "59cf53e54c78"
// computeClaudeCodeFingerprint 复刻真实 Claude Code CLI 的 cc_version 指纹算法:
//
// 1. 取 messages 中第一条 role=user 的纯文本(首块 text)
// 2. 取该文本的第 4、7、20 字符(不足以 '0' 补齐)
// 3. SHA256(SALT + chars + cc_version) 取 hex 前 3 字符
//
// 算法来自 Parrot src/transform/cc_mimicry.py:compute_fingerprint,与官方 CLI 字节对齐。
// 任何偏差都会导致 cc_version=X.Y.Z.{fp} 在上游侧与真实 CLI 不一致。
func computeClaudeCodeFingerprint(body []byte, version string) string {
firstText := extractFirstUserText(body)
indices := []int{4, 7, 20}
chars := make([]byte, 0, 3)
for _, i := range indices {
if i < len(firstText) {
chars = append(chars, firstText[i])
} else {
chars = append(chars, '0')
}
}
sum := sha256.Sum256([]byte(fingerprintSalt + string(chars) + version))
return hex.EncodeToString(sum[:])[:3]
}
// extractFirstUserText 提取 messages 中第一条 user 消息的首段 text 内容。
// 兼容 string 和 []block 两种 content 格式。
func extractFirstUserText(body []byte) string {
messages := gjson.GetBytes(body, "messages")
if !messages.IsArray() {
return ""
}
first := ""
messages.ForEach(func(_, msg gjson.Result) bool {
if msg.Get("role").String() != "user" {
return true
}
content := msg.Get("content")
if content.Type == gjson.String {
first = content.String()
return false
}
if content.IsArray() {
content.ForEach(func(_, block gjson.Result) bool {
if block.Get("type").String() == "text" {
first = block.Get("text").String()
return false
}
return true
})
return false
}
return false
})
return first
}
// buildBillingAttributionBlockJSON 构造 system 数组的 billing attribution block。
//
// 形态严格对齐真实 Claude Code CLI:
//
// {"type":"text","text":"x-anthropic-billing-header: cc_version=2.1.161.{fp}; cc_entrypoint=cli; cch=00000;"}
//
// cch=00000 是签名占位符,由 signBillingHeaderCCH 在 buildUpstreamRequest 阶段
// 替换为基于完整 body 的 xxhash64 5 位十六进制摘要。
//
// 此 block 不带 cache_control(与真实 CLI 一致;cache breakpoint 由后续的
// Claude Code prompt block 承担)。
func buildBillingAttributionBlockJSON(body []byte, cliVersion string) ([]byte, error) {
if cliVersion == "" {
return nil, fmt.Errorf("cliVersion required")
}
fp := computeClaudeCodeFingerprint(body, cliVersion)
text := fmt.Sprintf(
"x-anthropic-billing-header: cc_version=%s.%s; cc_entrypoint=cli; cch=00000;",
cliVersion, fp,
)
return json.Marshal(map[string]string{
"type": "text",
"text": text,
})
}