diff --git a/pkg/usecase/cmdargs.go b/pkg/usecase/cmdargs.go
new file mode 100644
index 0000000..d5e8f6e
--- /dev/null
+++ b/pkg/usecase/cmdargs.go
@@ -0,0 +1,28 @@
+package usecase
+
+import "cursor-api-proxy/internal/config"
+
+func BuildAgentFixedArgs(cfg config.BridgeConfig, workspaceDir, model string, stream bool) []string {
+	args := []string{"--print"}
+	if cfg.ApproveMcps {
+		args = append(args, "--approve-mcps")
+	}
+	if cfg.Force {
+		args = append(args, "--force")
+	}
+	if cfg.ChatOnlyWorkspace {
+		args = append(args, "--trust")
+	}
+	args = append(args, "--workspace", workspaceDir)
+	args = append(args, "--model", model)
+	if stream {
+		args = append(args, "--stream-partial-output", "--output-format", "stream-json")
+	} else {
+		args = append(args, "--output-format", "text")
+	}
+	return args
+}
+
+func BuildAgentCmdArgs(cfg config.BridgeConfig, workspaceDir, model, prompt string, stream bool) []string {
+	return append(BuildAgentFixedArgs(cfg, workspaceDir, model, stream), prompt)
+}
diff --git a/pkg/usecase/maxmode.go b/pkg/usecase/maxmode.go
new file mode 100644
index 0000000..291113b
--- /dev/null
+++ b/pkg/usecase/maxmode.go
@@ -0,0 +1,85 @@
+package usecase
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"runtime"
+)
+
+func getCandidates(agentScriptPath, configDirOverride string) []string {
+	if configDirOverride != "" {
+		return []string{filepath.Join(configDirOverride, "cli-config.json")}
+	}
+
+	var result []string
+
+	if dir := os.Getenv("CURSOR_CONFIG_DIR"); dir != "" {
+		result = append(result, filepath.Join(dir, "cli-config.json"))
+	}
+
+	if agentScriptPath != "" {
+		agentDir := filepath.Dir(agentScriptPath)
+		result = append(result, filepath.Join(agentDir, "..", "data", "config", "cli-config.json"))
+	}
+
+	home := os.Getenv("HOME")
+	if home == "" {
+		home = os.Getenv("USERPROFILE")
+	}
+
+	switch runtime.GOOS {
+	case "windows":
+		local := os.Getenv("LOCALAPPDATA")
+		if local == "" {
+			local = filepath.Join(home, "AppData", "Local")
+		}
+		result = append(result, filepath.Join(local, "cursor-agent", "cli-config.json"))
+	case "darwin":
+		result = append(result, filepath.Join(home, "Library", "Application Support", "cursor-agent", "cli-config.json"))
+	default:
+		xdg := os.Getenv("XDG_CONFIG_HOME")
+		if xdg == "" {
+			xdg = filepath.Join(home, ".config")
+		}
+		result = append(result, filepath.Join(xdg, "cursor-agent", "cli-config.json"))
+	}
+
+	return result
+}
+
+func RunMaxModePreflight(agentScriptPath, configDirOverride string) {
+	for _, candidate := range getCandidates(agentScriptPath, configDirOverride) {
+		data, err := os.ReadFile(candidate)
+		if err != nil {
+			continue
+		}
+
+		// Strip BOM if present
+		if len(data) >= 3 && data[0] == 0xEF && data[1] == 0xBB && data[2] == 0xBF {
+			data = data[3:]
+		}
+
+		var raw map[string]interface{}
+		if err := json.Unmarshal(data, &raw); err != nil {
+			continue
+		}
+		if raw == nil || len(raw) <= 1 {
+			continue
+		}
+
+		raw["maxMode"] = true
+		if model, ok := raw["model"].(map[string]interface{}); ok {
+			model["maxMode"] = true
+		}
+
+		out, err := json.MarshalIndent(raw, "", "  ")
+		if err != nil {
+			continue
+		}
+		if err := os.WriteFile(candidate, out, 0644); err != nil {
+			continue
+		}
+		return
+	}
+}
diff --git a/pkg/usecase/runner.go b/pkg/usecase/runner.go
new file mode 100644
index 0000000..ee4b093
--- /dev/null
+++ b/pkg/usecase/runner.go
@@ -0,0 +1,72 @@
+package usecase
+
+import (
+	"context"
+	"cursor-api-proxy/internal/config"
+	"cursor-api-proxy/pkg/infrastructure/process"
+	"os"
+	"path/filepath"
+)
+
+func init() {
+	process.MaxModeFn = RunMaxModePreflight
+}
+
+func cacheTokenForAccount(configDir string) {
+	if configDir == "" {
+		return
+	}
+	token := ReadKeychainToken()
+	if token != "" {
+		WriteCachedToken(configDir, token)
+	}
+}
+
+func AccountsDir() string {
+	home := os.Getenv("HOME")
+	if home == "" {
+		home = os.Getenv("USERPROFILE")
+	}
+	return filepath.Join(home, ".cursor-api-proxy", "accounts")
+}
+
+func RunAgentSync(cfg config.BridgeConfig, workspaceDir string, cmdArgs []string, tempDir, configDir string, ctx context.Context) (process.RunResult, error) {
+	opts := process.RunOptions{
+		Cwd:       workspaceDir,
+		TimeoutMs: cfg.TimeoutMs,
+		MaxMode:   cfg.MaxMode,
+		ConfigDir: configDir,
+		Ctx:       ctx,
+	}
+
+	result, err := process.Run(cfg.AgentBin, cmdArgs, opts)
+
+	cacheTokenForAccount(configDir)
+	if tempDir != "" {
+		os.RemoveAll(tempDir)
+	}
+
+	return result, err
+}
+
+func RunAgentStreamWithContext(cfg config.BridgeConfig, workspaceDir string, cmdArgs []string, onLine func(string), tempDir, configDir string, ctx context.Context) (process.StreamResult, error) {
+	opts := process.RunStreamingOptions{
+		RunOptions: process.RunOptions{
+			Cwd:       workspaceDir,
+			TimeoutMs: cfg.TimeoutMs,
+			MaxMode:   cfg.MaxMode,
+			ConfigDir: configDir,
+			Ctx:       ctx,
+		},
+		OnLine: onLine,
+	}
+
+	result, err := process.RunStreaming(cfg.AgentBin, cmdArgs, opts)
+
+	cacheTokenForAccount(configDir)
+	if tempDir != "" {
+		os.RemoveAll(tempDir)
+	}
+
+	return result, err
+}
diff --git a/pkg/usecase/sanitizer.go b/pkg/usecase/sanitizer.go
new file mode 100644
index 0000000..661df80
--- /dev/null
+++ b/pkg/usecase/sanitizer.go
@@ -0,0 +1,95 @@
+package usecase
+
+import "regexp"
+
+type rule struct {
+	pattern     *regexp.Regexp
+	replacement string
+}
+
+var rules = []rule{
+	{regexp.MustCompile(`(?i)x-anthropic-billing-header:[^\n]*\n?`), ""},
+	{regexp.MustCompile(`(?i)\bcc_version=[^\s;,\n]+[;,]?\s*`), ""},
+	{regexp.MustCompile(`(?i)\bcc_entrypoint=[^\s;,\n]+[;,]?\s*`), ""},
+	{regexp.MustCompile(`(?i)\bcch=[a-f0-9]+[;,]?\s*`), ""},
+	{regexp.MustCompile(`\bClaude Code\b`), "Cursor"},
+	{regexp.MustCompile(`(?i)Anthropic['']s official CLI for Claude`), "Cursor AI assistant"},
+	{regexp.MustCompile(`\bAnthropic\b`), "Cursor"},
+	{regexp.MustCompile(`(?i)anthropic\.com`), "cursor.com"},
+	{regexp.MustCompile(`(?i)claude\.ai`), "cursor.sh"},
+	{regexp.MustCompile(`^[;,\s]+`), ""},
+}
+
+func SanitizeText(text string) string {
+	for _, r := range rules {
+		text = r.pattern.ReplaceAllString(text, r.replacement)
+	}
+	return text
+}
+
+func SanitizeMessages(messages []interface{}) []interface{} {
+	result := make([]interface{}, len(messages))
+	for i, raw := range messages {
+		if raw == nil {
+			result[i] = raw
+			continue
+		}
+		m, ok := raw.(map[string]interface{})
+		if !ok {
+			result[i] = raw
+			continue
+		}
+		newMsg := make(map[string]interface{}, len(m))
+		for k, v := range m {
+			newMsg[k] = v
+		}
+		switch c := m["content"].(type) {
+		case string:
+			newMsg["content"] = SanitizeText(c)
+		case []interface{}:
+			newParts := make([]interface{}, len(c))
+			for j, p := range c {
+				if pm, ok := p.(map[string]interface{}); ok && pm["type"] == "text" {
+					if t, ok := pm["text"].(string); ok {
+						newPart := make(map[string]interface{}, len(pm))
+						for k, v := range pm {
+							newPart[k] = v
+						}
+						newPart["text"] = SanitizeText(t)
+						newParts[j] = newPart
+						continue
+					}
+				}
+				newParts[j] = p
+			}
+			newMsg["content"] = newParts
+		}
+		result[i] = newMsg
+	}
+	return result
+}
+
+func SanitizeSystem(system interface{}) interface{} {
+	switch v := system.(type) {
+	case string:
+		return SanitizeText(v)
+	case []interface{}:
+		result := make([]interface{}, len(v))
+		for i, p := range v {
+			if pm, ok := p.(map[string]interface{}); ok && pm["type"] == "text" {
+				if t, ok := pm["text"].(string); ok {
+					newPart := make(map[string]interface{}, len(pm))
+					for k, val := range pm {
+						newPart[k] = val
+					}
+					newPart["text"] = SanitizeText(t)
+					result[i] = newPart
+					continue
+				}
+			}
+			result[i] = p
+		}
+		return result
+	}
+	return system
+}
diff --git a/pkg/usecase/sanitizer_test.go b/pkg/usecase/sanitizer_test.go
new file mode 100644
index 0000000..393b510
--- /dev/null
+++ b/pkg/usecase/sanitizer_test.go
@@ -0,0 +1,60 @@
+package usecase
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestSanitizeTextAnthropicBilling(t *testing.T) {
+	input := "x-anthropic-billing-header: abc123\nHello"
+	got := SanitizeText(input)
+	if strings.Contains(got, "x-anthropic-billing-header") {
+		t.Errorf("billing header not removed: %q", got)
+	}
+}
+
+func TestSanitizeTextClaudeCode(t *testing.T) {
+	input := "I am Claude Code assistant"
+	got := SanitizeText(input)
+	if strings.Contains(got, "Claude Code") {
+		t.Errorf("'Claude Code' not replaced: %q", got)
+	}
+	if !strings.Contains(got, "Cursor") {
+		t.Errorf("'Cursor' not present in output: %q", got)
+	}
+}
+
+func TestSanitizeTextAnthropic(t *testing.T) {
+	input := "Powered by Anthropic's technology and anthropic.com"
+	got := SanitizeText(input)
+	if strings.Contains(got, "Anthropic") {
+		t.Errorf("'Anthropic' not replaced: %q", got)
+	}
+	if strings.Contains(got, "anthropic.com") {
+		t.Errorf("'anthropic.com' not replaced: %q", got)
+	}
+}
+
+func TestSanitizeTextNoChange(t *testing.T) {
+	input := "Hello, this is a normal message about cursor."
+	got := SanitizeText(input)
+	if got != input {
+		t.Errorf("unexpected change: %q -> %q", input, got)
+	}
+}
+
+func TestSanitizeMessages(t *testing.T) {
+	messages := []interface{}{
+		map[string]interface{}{"role": "user", "content": "Ask Claude Code something"},
+		map[string]interface{}{"role": "system", "content": "Use Anthropic's tools"},
+	}
+	result := SanitizeMessages(messages)
+
+	for _, raw := range result {
+		m := raw.(map[string]interface{})
+		c := m["content"].(string)
+		if strings.Contains(c, "Claude Code") || strings.Contains(c, "Anthropic") {
+			t.Errorf("found unsanitized content: %q", c)
+		}
+	}
+}
diff --git a/pkg/usecase/token.go b/pkg/usecase/token.go
new file mode 100644
index 0000000..6dce4c6
--- /dev/null
+++ b/pkg/usecase/token.go
@@ -0,0 +1,36 @@
+package usecase
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+const tokenFile = ".cursor-token"
+
+func ReadCachedToken(configDir string) string {
+	p := filepath.Join(configDir, tokenFile)
+	data, err := os.ReadFile(p)
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(string(data))
+}
+
+func WriteCachedToken(configDir, token string) {
+	p := filepath.Join(configDir, tokenFile)
+	_ = os.WriteFile(p, []byte(token), 0600)
+}
+
+func ReadKeychainToken() string {
+	if runtime.GOOS != "darwin" {
+		return ""
+	}
+	out, err := exec.Command("security", "find-generic-password", "-s", "cursor-access-token", "-w").Output()
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(string(out))
+}
diff --git a/pkg/usecase/toolcall.go b/pkg/usecase/toolcall.go
new file mode 100644
index 0000000..37f3677
--- /dev/null
+++ b/pkg/usecase/toolcall.go
@@ -0,0 +1,154 @@
+package usecase
+
+import (
+	"encoding/json"
+	"regexp"
+	"strings"
+)
+
+type ToolCall struct {
+	Name      string
+	Arguments string // JSON string
+}
+
+type ParsedResponse struct {
+	TextContent string
+	ToolCalls   []ToolCall
+}
+
+func (p *ParsedResponse) HasToolCalls() bool {
+	return len(p.ToolCalls) > 0
+}
+
+// Modified regex to handle nested JSON
+var toolCallTagRe = regexp.MustCompile(`(?s)行政法规\s*(\{(?:[^{}]|\{[^{}]*\})*\})\s*ugalakh`)
+var antmlFunctionCallsRe = regexp.MustCompile(`(?s)<function_calls>\s*(.*?)\s*</function_calls>`)
+var antmlInvokeRe = regexp.MustCompile(`(?s)<invoke\s+name="([^"]+)">\s*(.*?)\s*</invoke>`)
+var antmlParamRe = regexp.MustCompile(`(?s)<parameter\s+name="([^"]+)">(.*?)</parameter>`)
+
+func ExtractToolCalls(text string, toolNames map[string]bool) *ParsedResponse {
+	result := &ParsedResponse{}
+
+	if locs := toolCallTagRe.FindAllStringSubmatchIndex(text, -1); len(locs) > 0 {
+		var calls []ToolCall
+		var textParts []string
+		last := 0
+		for _, loc := range locs {
+			if loc[0] > last {
+				textParts = append(textParts, text[last:loc[0]])
+			}
+			jsonStr := text[loc[2]:loc[3]]
+			if tc := parseToolCallJSON(jsonStr, toolNames); tc != nil {
+				calls = append(calls, *tc)
+			} else {
+				textParts = append(textParts, text[loc[0]:loc[1]])
+			}
+			last = loc[1]
+		}
+		if last < len(text) {
+			textParts = append(textParts, text[last:])
+		}
+		if len(calls) > 0 {
+			result.TextContent = strings.TrimSpace(strings.Join(textParts, ""))
+			result.ToolCalls = calls
+			return result
+		}
+	}
+
+	if locs := antmlFunctionCallsRe.FindAllStringSubmatchIndex(text, -1); len(locs) > 0 {
+		var calls []ToolCall
+		var textParts []string
+		last := 0
+		for _, loc := range locs {
+			if loc[0] > last {
+				textParts = append(textParts, text[last:loc[0]])
+			}
+			block := text[loc[2]:loc[3]]
+			invokes := antmlInvokeRe.FindAllStringSubmatch(block, -1)
+			for _, inv := range invokes {
+				name := inv[1]
+				if toolNames != nil && len(toolNames) > 0 && !toolNames[name] {
+					continue
+				}
+				body := inv[2]
+				args := map[string]interface{}{}
+				params := antmlParamRe.FindAllStringSubmatch(body, -1)
+				for _, p := range params {
+					paramName := p[1]
+					paramValue := strings.TrimSpace(p[2])
+					var jsonVal interface{}
+					if err := json.Unmarshal([]byte(paramValue), &jsonVal); err == nil {
+						args[paramName] = jsonVal
+					} else {
+						args[paramName] = paramValue
+					}
+				}
+				argsJSON, _ := json.Marshal(args)
+				calls = append(calls, ToolCall{Name: name, Arguments: string(argsJSON)})
+			}
+			last = loc[1]
+		}
+		if last < len(text) {
+			textParts = append(textParts, text[last:])
+		}
+		if len(calls) > 0 {
+			result.TextContent = strings.TrimSpace(strings.Join(textParts, ""))
+			result.ToolCalls = calls
+			return result
+		}
+	}
+
+	result.TextContent = text
+	return result
+}
+
+func parseToolCallJSON(jsonStr string, toolNames map[string]bool) *ToolCall {
+	var raw map[string]interface{}
+	if err := json.Unmarshal([]byte(jsonStr), &raw); err != nil {
+		return nil
+	}
+	name, _ := raw["name"].(string)
+	if name == "" {
+		return nil
+	}
+	if toolNames != nil && len(toolNames) > 0 && !toolNames[name] {
+		return nil
+	}
+	var argsStr string
+	switch a := raw["arguments"].(type) {
+	case string:
+		argsStr = a
+	case map[string]interface{}, []interface{}:
+		b, _ := json.Marshal(a)
+		argsStr = string(b)
+	default:
+		if p, ok := raw["parameters"]; ok {
+			b, _ := json.Marshal(p)
+			argsStr = string(b)
+		} else {
+			argsStr = "{}"
+		}
+	}
+	return &ToolCall{Name: name, Arguments: argsStr}
+}
+
+func CollectToolNames(tools []interface{}) map[string]bool {
+	names := map[string]bool{}
+	for _, t := range tools {
+		m, ok := t.(map[string]interface{})
+		if !ok {
+			continue
+		}
+		if m["type"] == "function" {
+			if fn, ok := m["function"].(map[string]interface{}); ok {
+				if name, ok := fn["name"].(string); ok {
+					names[name] = true
+				}
+			}
+		}
+		if name, ok := m["name"].(string); ok {
+			names[name] = true
+		}
+	}
+	return names
+}