feat: add cache-user-id toggle for Claude cloaking

Default to generating a fresh random user_id per request instead of
reusing cached IDs. Add cache-user-id config option to opt in to the
previous caching behavior.

- Add CacheUserID field to CloakConfig
- Extract user_id cache logic to dedicated file
- Generate fresh user_id by default, cache only when enabled
- Add tests for both paths

internal/runtime/executor/claude_executor_test.go

@@ -2,9 +2,18 @@ package executor
 
 import (
 	"bytes"
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
 	"testing"
 
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
+	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
+	cliproxyexecutor "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/executor"
+	sdktranslator "github.com/router-for-me/CLIProxyAPI/v6/sdk/translator"
 	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
 )
 
 func TestApplyClaudeToolPrefix(t *testing.T) {
@@ -199,6 +208,119 @@ func TestApplyClaudeToolPrefix_NestedToolReference(t *testing.T) {
 	}
 }
 
+func TestClaudeExecutor_ReusesUserIDAcrossModelsWhenCacheEnabled(t *testing.T) {
+	resetUserIDCache()
+
+	var userIDs []string
+	var requestModels []string
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, _ := io.ReadAll(r.Body)
+		userID := gjson.GetBytes(body, "metadata.user_id").String()
+		model := gjson.GetBytes(body, "model").String()
+		userIDs = append(userIDs, userID)
+		requestModels = append(requestModels, model)
+		t.Logf("HTTP Server received request: model=%s, user_id=%s, url=%s", model, userID, r.URL.String())
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"id":"msg_1","type":"message","model":"claude-3-5-sonnet","role":"assistant","content":[{"type":"text","text":"ok"}],"usage":{"input_tokens":1,"output_tokens":1}}`))
+	}))
+	defer server.Close()
+
+	t.Logf("End-to-end test: Fake HTTP server started at %s", server.URL)
+
+	cacheEnabled := true
+	executor := NewClaudeExecutor(&config.Config{
+		ClaudeKey: []config.ClaudeKey{
+			{
+				APIKey:  "key-123",
+				BaseURL: server.URL,
+				Cloak: &config.CloakConfig{
+					CacheUserID: &cacheEnabled,
+				},
+			},
+		},
+	})
+	auth := &cliproxyauth.Auth{Attributes: map[string]string{
+		"api_key":  "key-123",
+		"base_url": server.URL,
+	}}
+
+	payload := []byte(`{"messages":[{"role":"user","content":[{"type":"text","text":"hi"}]}]}`)
+	models := []string{"claude-3-5-sonnet", "claude-3-5-haiku"}
+	for _, model := range models {
+		t.Logf("Sending request for model: %s", model)
+		modelPayload, _ := sjson.SetBytes(payload, "model", model)
+		if _, err := executor.Execute(context.Background(), auth, cliproxyexecutor.Request{
+			Model:   model,
+			Payload: modelPayload,
+		}, cliproxyexecutor.Options{
+			SourceFormat: sdktranslator.FromString("claude"),
+		}); err != nil {
+			t.Fatalf("Execute(%s) error: %v", model, err)
+		}
+	}
+
+	if len(userIDs) != 2 {
+		t.Fatalf("expected 2 requests, got %d", len(userIDs))
+	}
+	if userIDs[0] == "" || userIDs[1] == "" {
+		t.Fatal("expected user_id to be populated")
+	}
+	t.Logf("user_id[0] (model=%s): %s", requestModels[0], userIDs[0])
+	t.Logf("user_id[1] (model=%s): %s", requestModels[1], userIDs[1])
+	if userIDs[0] != userIDs[1] {
+		t.Fatalf("expected user_id to be reused across models, got %q and %q", userIDs[0], userIDs[1])
+	}
+	if !isValidUserID(userIDs[0]) {
+		t.Fatalf("user_id %q is not valid", userIDs[0])
+	}
+	t.Logf("✓ End-to-end test passed: Same user_id (%s) was used for both models", userIDs[0])
+}
+
+func TestClaudeExecutor_GeneratesNewUserIDByDefault(t *testing.T) {
+	resetUserIDCache()
+
+	var userIDs []string
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, _ := io.ReadAll(r.Body)
+		userIDs = append(userIDs, gjson.GetBytes(body, "metadata.user_id").String())
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"id":"msg_1","type":"message","model":"claude-3-5-sonnet","role":"assistant","content":[{"type":"text","text":"ok"}],"usage":{"input_tokens":1,"output_tokens":1}}`))
+	}))
+	defer server.Close()
+
+	executor := NewClaudeExecutor(&config.Config{})
+	auth := &cliproxyauth.Auth{Attributes: map[string]string{
+		"api_key":  "key-123",
+		"base_url": server.URL,
+	}}
+
+	payload := []byte(`{"messages":[{"role":"user","content":[{"type":"text","text":"hi"}]}]}`)
+
+	for i := 0; i < 2; i++ {
+		if _, err := executor.Execute(context.Background(), auth, cliproxyexecutor.Request{
+			Model:   "claude-3-5-sonnet",
+			Payload: payload,
+		}, cliproxyexecutor.Options{
+			SourceFormat: sdktranslator.FromString("claude"),
+		}); err != nil {
+			t.Fatalf("Execute call %d error: %v", i, err)
+		}
+	}
+
+	if len(userIDs) != 2 {
+		t.Fatalf("expected 2 requests, got %d", len(userIDs))
+	}
+	if userIDs[0] == "" || userIDs[1] == "" {
+		t.Fatal("expected user_id to be populated")
+	}
+	if userIDs[0] == userIDs[1] {
+		t.Fatalf("expected user_id to change when caching is not enabled, got identical values %q", userIDs[0])
+	}
+	if !isValidUserID(userIDs[0]) || !isValidUserID(userIDs[1]) {
+		t.Fatalf("user_ids should be valid, got %q and %q", userIDs[0], userIDs[1])
+	}
+}
+
 func TestStripClaudeToolPrefixFromResponse_NestedToolReference(t *testing.T) {
 	input := []byte(`{"content":[{"type":"tool_result","tool_use_id":"toolu_123","content":[{"type":"tool_reference","tool_name":"proxy_mcp__nia__manage_resource"}]}]}`)
 	out := stripClaudeToolPrefixFromResponse(input, "proxy_")