refactor: restructure codebase to internal/ directory with modular architecture

- Move all source files to internal/{app,backend,config,executor,logger,parser,utils}
- Integrate third-party libraries: zerolog, goccy/go-json, gopsutil, cobra/viper
- Add comprehensive unit tests for utils package (94.3% coverage)
- Add performance benchmarks for string operations
- Fix error display: cleanup warnings no longer pollute Recent Errors
- Add GitHub Actions CI workflow
- Add Makefile for build automation
- Add README documentation

Generated with SWE-Agent.ai

Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

codeagent-wrapper/internal/backend/backend.go

@@ -0,0 +1,33 @@
+package backend
+
+import config "codeagent-wrapper/internal/config"
+
+// Backend defines the contract for invoking different AI CLI backends.
+// Each backend is responsible for supplying the executable command and
+// building the argument list based on the wrapper config.
+type Backend interface {
+	Name() string
+	BuildArgs(cfg *config.Config, targetArg string) []string
+	Command() string
+	Env(baseURL, apiKey string) map[string]string
+}
+
+var (
+	logWarnFn  = func(string) {}
+	logErrorFn = func(string) {}
+)
+
+// SetLogFuncs configures optional logging hooks used by some backends.
+// Callers can safely pass nil to disable the hook.
+func SetLogFuncs(warnFn, errorFn func(string)) {
+	if warnFn != nil {
+		logWarnFn = warnFn
+	} else {
+		logWarnFn = func(string) {}
+	}
+	if errorFn != nil {
+		logErrorFn = errorFn
+	} else {
+		logErrorFn = func(string) {}
+	}
+}

codeagent-wrapper/internal/backend/backend_test.go

@@ -0,0 +1,322 @@
+package backend
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+
+	config "codeagent-wrapper/internal/config"
+)
+
+func TestClaudeBuildArgs_ModesAndPermissions(t *testing.T) {
+	backend := ClaudeBackend{}
+
+	t.Run("new mode omits skip-permissions when env disabled", func(t *testing.T) {
+		t.Setenv("CODEAGENT_SKIP_PERMISSIONS", "false")
+		cfg := &config.Config{Mode: "new", WorkDir: "/repo"}
+		got := backend.BuildArgs(cfg, "todo")
+		want := []string{"-p", "--setting-sources", "", "--output-format", "stream-json", "--verbose", "todo"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("new mode includes skip-permissions by default", func(t *testing.T) {
+		cfg := &config.Config{Mode: "new", SkipPermissions: false}
+		got := backend.BuildArgs(cfg, "-")
+		want := []string{"-p", "--dangerously-skip-permissions", "--setting-sources", "", "--output-format", "stream-json", "--verbose", "-"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("resume mode includes session id", func(t *testing.T) {
+		t.Setenv("CODEAGENT_SKIP_PERMISSIONS", "false")
+		cfg := &config.Config{Mode: "resume", SessionID: "sid-123", WorkDir: "/ignored"}
+		got := backend.BuildArgs(cfg, "resume-task")
+		want := []string{"-p", "--setting-sources", "", "-r", "sid-123", "--output-format", "stream-json", "--verbose", "resume-task"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("resume mode without session still returns base flags", func(t *testing.T) {
+		t.Setenv("CODEAGENT_SKIP_PERMISSIONS", "false")
+		cfg := &config.Config{Mode: "resume", WorkDir: "/ignored"}
+		got := backend.BuildArgs(cfg, "follow-up")
+		want := []string{"-p", "--setting-sources", "", "--output-format", "stream-json", "--verbose", "follow-up"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("resume mode can opt-in skip permissions", func(t *testing.T) {
+		cfg := &config.Config{Mode: "resume", SessionID: "sid-123", SkipPermissions: true}
+		got := backend.BuildArgs(cfg, "resume-task")
+		want := []string{"-p", "--dangerously-skip-permissions", "--setting-sources", "", "-r", "sid-123", "--output-format", "stream-json", "--verbose", "resume-task"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("nil config returns nil", func(t *testing.T) {
+		if backend.BuildArgs(nil, "ignored") != nil {
+			t.Fatalf("nil config should return nil args")
+		}
+	})
+}
+
+func TestBackendBuildArgs_Model(t *testing.T) {
+	t.Run("claude includes --model when set", func(t *testing.T) {
+		t.Setenv("CODEAGENT_SKIP_PERMISSIONS", "false")
+		backend := ClaudeBackend{}
+		cfg := &config.Config{Mode: "new", Model: "opus"}
+		got := backend.BuildArgs(cfg, "todo")
+		want := []string{"-p", "--setting-sources", "", "--model", "opus", "--output-format", "stream-json", "--verbose", "todo"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("gemini includes -m when set", func(t *testing.T) {
+		backend := GeminiBackend{}
+		cfg := &config.Config{Mode: "new", Model: "gemini-3-pro-preview"}
+		got := backend.BuildArgs(cfg, "task")
+		want := []string{"-o", "stream-json", "-y", "-m", "gemini-3-pro-preview", "task"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("codex includes --model when set", func(t *testing.T) {
+		const key = "CODEX_BYPASS_SANDBOX"
+		t.Setenv(key, "false")
+
+		backend := CodexBackend{}
+		cfg := &config.Config{Mode: "new", WorkDir: "/tmp", Model: "o3"}
+		got := backend.BuildArgs(cfg, "task")
+		want := []string{"e", "--model", "o3", "--skip-git-repo-check", "-C", "/tmp", "--json", "task"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+}
+
+func TestClaudeBuildArgs_GeminiAndCodexModes(t *testing.T) {
+	t.Run("gemini new mode defaults workdir", func(t *testing.T) {
+		backend := GeminiBackend{}
+		cfg := &config.Config{Mode: "new", WorkDir: "/workspace"}
+		got := backend.BuildArgs(cfg, "task")
+		want := []string{"-o", "stream-json", "-y", "task"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("gemini resume mode uses session id", func(t *testing.T) {
+		backend := GeminiBackend{}
+		cfg := &config.Config{Mode: "resume", SessionID: "sid-999"}
+		got := backend.BuildArgs(cfg, "resume")
+		want := []string{"-o", "stream-json", "-y", "-r", "sid-999", "resume"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("gemini resume mode without session omits identifier", func(t *testing.T) {
+		backend := GeminiBackend{}
+		cfg := &config.Config{Mode: "resume"}
+		got := backend.BuildArgs(cfg, "resume")
+		want := []string{"-o", "stream-json", "-y", "resume"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("gemini nil config returns nil", func(t *testing.T) {
+		backend := GeminiBackend{}
+		if backend.BuildArgs(nil, "ignored") != nil {
+			t.Fatalf("nil config should return nil args")
+		}
+	})
+
+	t.Run("gemini stdin mode uses -p flag", func(t *testing.T) {
+		backend := GeminiBackend{}
+		cfg := &config.Config{Mode: "new"}
+		got := backend.BuildArgs(cfg, "-")
+		want := []string{"-o", "stream-json", "-y", "-p", "-"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("codex build args omits bypass flag by default", func(t *testing.T) {
+		const key = "CODEX_BYPASS_SANDBOX"
+		t.Setenv(key, "false")
+
+		backend := CodexBackend{}
+		cfg := &config.Config{Mode: "new", WorkDir: "/tmp"}
+		got := backend.BuildArgs(cfg, "task")
+		want := []string{"e", "--skip-git-repo-check", "-C", "/tmp", "--json", "task"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("codex build args includes bypass flag when enabled", func(t *testing.T) {
+		const key = "CODEX_BYPASS_SANDBOX"
+		t.Setenv(key, "true")
+
+		backend := CodexBackend{}
+		cfg := &config.Config{Mode: "new", WorkDir: "/tmp"}
+		got := backend.BuildArgs(cfg, "task")
+		want := []string{"e", "--dangerously-bypass-approvals-and-sandbox", "--skip-git-repo-check", "-C", "/tmp", "--json", "task"}
+		if !reflect.DeepEqual(got, want) {
+			t.Fatalf("got %v, want %v", got, want)
+		}
+	})
+}
+
+func TestClaudeBuildArgs_BackendMetadata(t *testing.T) {
+	tests := []struct {
+		backend Backend
+		name    string
+		command string
+	}{
+		{backend: CodexBackend{}, name: "codex", command: "codex"},
+		{backend: ClaudeBackend{}, name: "claude", command: "claude"},
+		{backend: GeminiBackend{}, name: "gemini", command: "gemini"},
+	}
+
+	for _, tt := range tests {
+		if got := tt.backend.Name(); got != tt.name {
+			t.Fatalf("Name() = %s, want %s", got, tt.name)
+		}
+		if got := tt.backend.Command(); got != tt.command {
+			t.Fatalf("Command() = %s, want %s", got, tt.command)
+		}
+	}
+}
+
+func TestLoadMinimalEnvSettings(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	t.Setenv("USERPROFILE", home)
+
+	t.Run("missing file returns empty", func(t *testing.T) {
+		if got := LoadMinimalEnvSettings(); len(got) != 0 {
+			t.Fatalf("got %v, want empty", got)
+		}
+	})
+
+	t.Run("valid env returns string map", func(t *testing.T) {
+		dir := filepath.Join(home, ".claude")
+		if err := os.MkdirAll(dir, 0o755); err != nil {
+			t.Fatalf("MkdirAll: %v", err)
+		}
+		path := filepath.Join(dir, "settings.json")
+		data := []byte(`{"env":{"ANTHROPIC_API_KEY":"secret","FOO":"bar"}}`)
+		if err := os.WriteFile(path, data, 0o600); err != nil {
+			t.Fatalf("WriteFile: %v", err)
+		}
+
+		got := LoadMinimalEnvSettings()
+		if got["ANTHROPIC_API_KEY"] != "secret" || got["FOO"] != "bar" {
+			t.Fatalf("got %v, want keys present", got)
+		}
+	})
+
+	t.Run("non-string values are ignored", func(t *testing.T) {
+		dir := filepath.Join(home, ".claude")
+		path := filepath.Join(dir, "settings.json")
+		data := []byte(`{"env":{"GOOD":"ok","BAD":123,"ALSO_BAD":true}}`)
+		if err := os.WriteFile(path, data, 0o600); err != nil {
+			t.Fatalf("WriteFile: %v", err)
+		}
+
+		got := LoadMinimalEnvSettings()
+		if got["GOOD"] != "ok" {
+			t.Fatalf("got %v, want GOOD=ok", got)
+		}
+		if _, ok := got["BAD"]; ok {
+			t.Fatalf("got %v, want BAD omitted", got)
+		}
+		if _, ok := got["ALSO_BAD"]; ok {
+			t.Fatalf("got %v, want ALSO_BAD omitted", got)
+		}
+	})
+
+	t.Run("oversized file returns empty", func(t *testing.T) {
+		dir := filepath.Join(home, ".claude")
+		path := filepath.Join(dir, "settings.json")
+		data := bytes.Repeat([]byte("a"), MaxClaudeSettingsBytes+1)
+		if err := os.WriteFile(path, data, 0o600); err != nil {
+			t.Fatalf("WriteFile: %v", err)
+		}
+		if got := LoadMinimalEnvSettings(); len(got) != 0 {
+			t.Fatalf("got %v, want empty", got)
+		}
+	})
+}
+
+func TestOpencodeBackend_BuildArgs(t *testing.T) {
+	backend := OpencodeBackend{}
+
+	t.Run("basic", func(t *testing.T) {
+		cfg := &config.Config{Mode: "new"}
+		got := backend.BuildArgs(cfg, "hello")
+		want := []string{"run", "--format", "json", "hello"}
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("with model", func(t *testing.T) {
+		cfg := &config.Config{Mode: "new", Model: "opencode/grok-code"}
+		got := backend.BuildArgs(cfg, "task")
+		want := []string{"run", "-m", "opencode/grok-code", "--format", "json", "task"}
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("resume mode", func(t *testing.T) {
+		cfg := &config.Config{Mode: "resume", SessionID: "ses_123", Model: "opencode/grok-code"}
+		got := backend.BuildArgs(cfg, "follow-up")
+		want := []string{"run", "-m", "opencode/grok-code", "-s", "ses_123", "--format", "json", "follow-up"}
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("resume without session", func(t *testing.T) {
+		cfg := &config.Config{Mode: "resume"}
+		got := backend.BuildArgs(cfg, "task")
+		want := []string{"run", "--format", "json", "task"}
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("got %v, want %v", got, want)
+		}
+	})
+
+	t.Run("stdin mode omits dash", func(t *testing.T) {
+		cfg := &config.Config{Mode: "new"}
+		got := backend.BuildArgs(cfg, "-")
+		want := []string{"run", "--format", "json"}
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("got %v, want %v", got, want)
+		}
+	})
+}
+
+func TestOpencodeBackend_Interface(t *testing.T) {
+	backend := OpencodeBackend{}
+
+	if backend.Name() != "opencode" {
+		t.Errorf("Name() = %q, want %q", backend.Name(), "opencode")
+	}
+	if backend.Command() != "opencode" {
+		t.Errorf("Command() = %q, want %q", backend.Command(), "opencode")
+	}
+}

codeagent-wrapper/internal/backend/claude.go

@@ -0,0 +1,139 @@
+package backend
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+
+	config "codeagent-wrapper/internal/config"
+
+	"github.com/goccy/go-json"
+)
+
+type ClaudeBackend struct{}
+
+func (ClaudeBackend) Name() string    { return "claude" }
+func (ClaudeBackend) Command() string { return "claude" }
+func (ClaudeBackend) Env(baseURL, apiKey string) map[string]string {
+	baseURL = strings.TrimSpace(baseURL)
+	apiKey = strings.TrimSpace(apiKey)
+	if baseURL == "" && apiKey == "" {
+		return nil
+	}
+	env := make(map[string]string, 2)
+	if baseURL != "" {
+		env["ANTHROPIC_BASE_URL"] = baseURL
+	}
+	if apiKey != "" {
+		env["ANTHROPIC_API_KEY"] = apiKey
+	}
+	return env
+}
+func (ClaudeBackend) BuildArgs(cfg *config.Config, targetArg string) []string {
+	return buildClaudeArgs(cfg, targetArg)
+}
+
+const MaxClaudeSettingsBytes = 1 << 20 // 1MB
+
+type MinimalClaudeSettings struct {
+	Env   map[string]string
+	Model string
+}
+
+// LoadMinimalClaudeSettings 从 ~/.claude/settings.json 只提取安全的最小子集：
+// - env: 只接受字符串类型的值
+// - model: 只接受字符串类型的值
+// 文件缺失/解析失败/超限都返回空。
+func LoadMinimalClaudeSettings() MinimalClaudeSettings {
+	home, err := os.UserHomeDir()
+	if err != nil || home == "" {
+		return MinimalClaudeSettings{}
+	}
+
+	claudeDir := filepath.Clean(filepath.Join(home, ".claude"))
+	settingPath := filepath.Clean(filepath.Join(claudeDir, "settings.json"))
+	rel, err := filepath.Rel(claudeDir, settingPath)
+	if err != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(os.PathSeparator)) {
+		return MinimalClaudeSettings{}
+	}
+
+	info, err := os.Stat(settingPath)
+	if err != nil || info.Size() > MaxClaudeSettingsBytes {
+		return MinimalClaudeSettings{}
+	}
+
+	data, err := os.ReadFile(settingPath) // #nosec G304 -- path is fixed under user home and validated to stay within claudeDir
+	if err != nil {
+		return MinimalClaudeSettings{}
+	}
+
+	var cfg struct {
+		Env   map[string]any `json:"env"`
+		Model any            `json:"model"`
+	}
+	if err := json.Unmarshal(data, &cfg); err != nil {
+		return MinimalClaudeSettings{}
+	}
+
+	out := MinimalClaudeSettings{}
+
+	if model, ok := cfg.Model.(string); ok {
+		out.Model = strings.TrimSpace(model)
+	}
+
+	if len(cfg.Env) == 0 {
+		return out
+	}
+
+	env := make(map[string]string, len(cfg.Env))
+	for k, v := range cfg.Env {
+		s, ok := v.(string)
+		if !ok {
+			continue
+		}
+		env[k] = s
+	}
+	if len(env) == 0 {
+		return out
+	}
+	out.Env = env
+	return out
+}
+
+func LoadMinimalEnvSettings() map[string]string {
+	settings := LoadMinimalClaudeSettings()
+	if len(settings.Env) == 0 {
+		return nil
+	}
+	return settings.Env
+}
+
+func buildClaudeArgs(cfg *config.Config, targetArg string) []string {
+	if cfg == nil {
+		return nil
+	}
+	args := []string{"-p"}
+	// Default to skip permissions unless CODEAGENT_SKIP_PERMISSIONS=false
+	if cfg.SkipPermissions || cfg.Yolo || config.EnvFlagDefaultTrue("CODEAGENT_SKIP_PERMISSIONS") {
+		args = append(args, "--dangerously-skip-permissions")
+	}
+
+	// Prevent infinite recursion: disable all setting sources (user, project, local)
+	// This ensures a clean execution environment without CLAUDE.md or skills that would trigger codeagent
+	args = append(args, "--setting-sources", "")
+
+	if model := strings.TrimSpace(cfg.Model); model != "" {
+		args = append(args, "--model", model)
+	}
+
+	if cfg.Mode == "resume" {
+		if cfg.SessionID != "" {
+			// Claude CLI uses -r <session_id> for resume.
+			args = append(args, "-r", cfg.SessionID)
+		}
+	}
+
+	args = append(args, "--output-format", "stream-json", "--verbose", targetArg)
+
+	return args
+}

codeagent-wrapper/internal/backend/codex.go

@@ -0,0 +1,79 @@
+package backend
+
+import (
+	"strings"
+
+	config "codeagent-wrapper/internal/config"
+)
+
+type CodexBackend struct{}
+
+func (CodexBackend) Name() string    { return "codex" }
+func (CodexBackend) Command() string { return "codex" }
+func (CodexBackend) Env(baseURL, apiKey string) map[string]string {
+	baseURL = strings.TrimSpace(baseURL)
+	apiKey = strings.TrimSpace(apiKey)
+	if baseURL == "" && apiKey == "" {
+		return nil
+	}
+	env := make(map[string]string, 2)
+	if baseURL != "" {
+		env["OPENAI_BASE_URL"] = baseURL
+	}
+	if apiKey != "" {
+		env["OPENAI_API_KEY"] = apiKey
+	}
+	return env
+}
+func (CodexBackend) BuildArgs(cfg *config.Config, targetArg string) []string {
+	return BuildCodexArgs(cfg, targetArg)
+}
+
+func BuildCodexArgs(cfg *config.Config, targetArg string) []string {
+	if cfg == nil {
+		panic("buildCodexArgs: nil config")
+	}
+
+	var resumeSessionID string
+	isResume := cfg.Mode == "resume"
+	if isResume {
+		resumeSessionID = strings.TrimSpace(cfg.SessionID)
+		if resumeSessionID == "" {
+			logErrorFn("invalid config: resume mode requires non-empty session_id")
+			isResume = false
+		}
+	}
+
+	args := []string{"e"}
+
+	// Default to bypass sandbox unless CODEX_BYPASS_SANDBOX=false
+	if cfg.Yolo || config.EnvFlagDefaultTrue("CODEX_BYPASS_SANDBOX") {
+		logWarnFn("YOLO mode or CODEX_BYPASS_SANDBOX enabled: running without approval/sandbox protection")
+		args = append(args, "--dangerously-bypass-approvals-and-sandbox")
+	}
+
+	if model := strings.TrimSpace(cfg.Model); model != "" {
+		args = append(args, "--model", model)
+	}
+
+	if reasoningEffort := strings.TrimSpace(cfg.ReasoningEffort); reasoningEffort != "" {
+		args = append(args, "-c", "model_reasoning_effort="+reasoningEffort)
+	}
+
+	args = append(args, "--skip-git-repo-check")
+
+	if isResume {
+		return append(args,
+			"--json",
+			"resume",
+			resumeSessionID,
+			targetArg,
+		)
+	}
+
+	return append(args,
+		"-C", cfg.WorkDir,
+		"--json",
+		targetArg,
+	)
+}

codeagent-wrapper/internal/backend/gemini.go

@@ -0,0 +1,110 @@
+package backend
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+
+	config "codeagent-wrapper/internal/config"
+)
+
+type GeminiBackend struct{}
+
+func (GeminiBackend) Name() string    { return "gemini" }
+func (GeminiBackend) Command() string { return "gemini" }
+func (GeminiBackend) Env(baseURL, apiKey string) map[string]string {
+	baseURL = strings.TrimSpace(baseURL)
+	apiKey = strings.TrimSpace(apiKey)
+	if baseURL == "" && apiKey == "" {
+		return nil
+	}
+	env := make(map[string]string, 2)
+	if baseURL != "" {
+		env["GOOGLE_GEMINI_BASE_URL"] = baseURL
+	}
+	if apiKey != "" {
+		env["GEMINI_API_KEY"] = apiKey
+	}
+	return env
+}
+func (GeminiBackend) BuildArgs(cfg *config.Config, targetArg string) []string {
+	return buildGeminiArgs(cfg, targetArg)
+}
+
+// LoadGeminiEnv loads environment variables from ~/.gemini/.env
+// Supports GEMINI_API_KEY, GEMINI_MODEL, GOOGLE_GEMINI_BASE_URL
+// Also sets GEMINI_API_KEY_AUTH_MECHANISM=bearer for third-party API compatibility
+func LoadGeminiEnv() map[string]string {
+	home, err := os.UserHomeDir()
+	if err != nil || home == "" {
+		return nil
+	}
+
+	envDir := filepath.Clean(filepath.Join(home, ".gemini"))
+	envPath := filepath.Clean(filepath.Join(envDir, ".env"))
+	rel, err := filepath.Rel(envDir, envPath)
+	if err != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(os.PathSeparator)) {
+		return nil
+	}
+
+	data, err := os.ReadFile(envPath) // #nosec G304 -- path is fixed under user home and validated to stay within envDir
+	if err != nil {
+		return nil
+	}
+
+	env := make(map[string]string)
+	for _, line := range strings.Split(string(data), "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		idx := strings.IndexByte(line, '=')
+		if idx <= 0 {
+			continue
+		}
+		key := strings.TrimSpace(line[:idx])
+		value := strings.TrimSpace(line[idx+1:])
+		if key != "" && value != "" {
+			env[key] = value
+		}
+	}
+
+	// Set bearer auth mechanism for third-party API compatibility
+	if _, ok := env["GEMINI_API_KEY"]; ok {
+		if _, hasAuth := env["GEMINI_API_KEY_AUTH_MECHANISM"]; !hasAuth {
+			env["GEMINI_API_KEY_AUTH_MECHANISM"] = "bearer"
+		}
+	}
+
+	if len(env) == 0 {
+		return nil
+	}
+	return env
+}
+
+func buildGeminiArgs(cfg *config.Config, targetArg string) []string {
+	if cfg == nil {
+		return nil
+	}
+	args := []string{"-o", "stream-json", "-y"}
+
+	if model := strings.TrimSpace(cfg.Model); model != "" {
+		args = append(args, "-m", model)
+	}
+
+	if cfg.Mode == "resume" {
+		if cfg.SessionID != "" {
+			args = append(args, "-r", cfg.SessionID)
+		}
+	}
+
+	// Use positional argument instead of deprecated -p flag.
+	// For stdin mode ("-"), use -p to read from stdin.
+	if targetArg == "-" {
+		args = append(args, "-p", targetArg)
+	} else {
+		args = append(args, targetArg)
+	}
+
+	return args
+}

codeagent-wrapper/internal/backend/opencode.go

@@ -0,0 +1,29 @@
+package backend
+
+import (
+	"strings"
+
+	config "codeagent-wrapper/internal/config"
+)
+
+type OpencodeBackend struct{}
+
+func (OpencodeBackend) Name() string                                 { return "opencode" }
+func (OpencodeBackend) Command() string                              { return "opencode" }
+func (OpencodeBackend) Env(baseURL, apiKey string) map[string]string { return nil }
+func (OpencodeBackend) BuildArgs(cfg *config.Config, targetArg string) []string {
+	args := []string{"run"}
+	if cfg != nil {
+		if model := strings.TrimSpace(cfg.Model); model != "" {
+			args = append(args, "-m", model)
+		}
+		if cfg.Mode == "resume" && cfg.SessionID != "" {
+			args = append(args, "-s", cfg.SessionID)
+		}
+	}
+	args = append(args, "--format", "json")
+	if targetArg != "-" {
+		args = append(args, targetArg)
+	}
+	return args
+}

codeagent-wrapper/internal/backend/registry.go

@@ -0,0 +1,29 @@
+package backend
+
+import (
+	"fmt"
+	"strings"
+)
+
+var registry = map[string]Backend{
+	"codex":    CodexBackend{},
+	"claude":   ClaudeBackend{},
+	"gemini":   GeminiBackend{},
+	"opencode": OpencodeBackend{},
+}
+
+// Registry exposes the available backends. Intended for internal inspection/tests.
+func Registry() map[string]Backend {
+	return registry
+}
+
+func Select(name string) (Backend, error) {
+	key := strings.ToLower(strings.TrimSpace(name))
+	if key == "" {
+		key = "codex"
+	}
+	if backend, ok := registry[key]; ok {
+		return backend, nil
+	}
+	return nil, fmt.Errorf("unsupported backend %q", name)
+}