refactor!: remove hardcoded default models, require explicit config

REMOVED all hardcoded default backend/model values from defaultModelsConfig.
Now ~/.codeagent/models.json is REQUIRED - missing config returns clear error
with example configuration.

BREAKING CHANGE: Users must configure ~/.codeagent/models.json before using
--agent or parallel tasks with agent: field.

Generated with SWE-Agent.ai

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

codeagent-wrapper/internal/app/bench_test.go

@@ -3,6 +3,7 @@ package wrapper
 import (
 	"bytes"
 	"os"
+	"path/filepath"
 	"testing"
 
 	config "codeagent-wrapper/internal/config"
@@ -29,6 +30,18 @@ func BenchmarkConfigParse_ParseArgs(b *testing.B) {
 	b.Setenv("HOME", home)
 	b.Setenv("USERPROFILE", home)
 
+	configDir := filepath.Join(home, ".codeagent")
+	if err := os.MkdirAll(configDir, 0o755); err != nil {
+		b.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(configDir, "models.json"), []byte(`{
+  "agents": {
+    "develop": { "backend": "codex", "model": "gpt-test" }
+  }
+}`), 0o644); err != nil {
+		b.Fatal(err)
+	}
+
 	config.ResetModelsConfigCacheForTest()
 	b.Cleanup(config.ResetModelsConfigCacheForTest)
 

codeagent-wrapper/internal/app/cli.go

@@ -254,7 +254,11 @@ func buildSingleConfig(cmd *cobra.Command, args []string, rawArgv []string, opts
 	var resolvedBackend, resolvedModel, resolvedPromptFile, resolvedReasoning string
 	if agentName != "" {
 		var resolvedYolo bool
-		resolvedBackend, resolvedModel, resolvedPromptFile, resolvedReasoning, _, _, resolvedYolo = config.ResolveAgentConfig(agentName)
+		var err error
+		resolvedBackend, resolvedModel, resolvedPromptFile, resolvedReasoning, _, _, resolvedYolo, err = config.ResolveAgentConfig(agentName)
+		if err != nil {
+			return nil, fmt.Errorf("failed to resolve agent %q: %w", agentName, err)
+		}
 		yolo = resolvedYolo
 	}
 

codeagent-wrapper/internal/app/main_test.go

@@ -1392,6 +1392,24 @@ func TestBackendParseArgs_PromptFileFlag(t *testing.T) {
 func TestBackendParseArgs_PromptFileOverridesAgent(t *testing.T) {
 	defer resetTestHooks()
 
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	t.Setenv("USERPROFILE", home)
+	t.Cleanup(config.ResetModelsConfigCacheForTest)
+	config.ResetModelsConfigCacheForTest()
+
+	configDir := filepath.Join(home, ".codeagent")
+	if err := os.MkdirAll(configDir, 0o755); err != nil {
+		t.Fatalf("MkdirAll: %v", err)
+	}
+	if err := os.WriteFile(filepath.Join(configDir, "models.json"), []byte(`{
+  "agents": {
+    "develop": { "backend": "codex", "model": "gpt-test" }
+  }
+}`), 0o644); err != nil {
+		t.Fatalf("WriteFile: %v", err)
+	}
+
 	os.Args = []string{"codeagent-wrapper", "--prompt-file", "/tmp/custom.md", "--agent", "develop", "task"}
 	cfg, err := parseArgs()
 	if err != nil {

codeagent-wrapper/internal/config/agent.go

@@ -7,8 +7,6 @@ import (
 	"strings"
 	"sync"
 
-	ilogger "codeagent-wrapper/internal/logger"
-
 	"github.com/goccy/go-json"
 )
 
@@ -35,80 +33,85 @@ type ModelsConfig struct {
 	Backends       map[string]BackendConfig    `json:"backends,omitempty"`
 }
 
-var defaultModelsConfig = ModelsConfig{
-	DefaultBackend: "opencode",
-	DefaultModel:   "opencode/grok-code",
-	Agents: map[string]AgentModelConfig{
-		"oracle":                  {Backend: "claude", Model: "claude-opus-4-5-20251101", PromptFile: "~/.claude/skills/omo/references/oracle.md", Description: "Technical advisor"},
-		"librarian":               {Backend: "claude", Model: "claude-sonnet-4-5-20250929", PromptFile: "~/.claude/skills/omo/references/librarian.md", Description: "Researcher"},
-		"explore":                 {Backend: "opencode", Model: "opencode/grok-code", PromptFile: "~/.claude/skills/omo/references/explore.md", Description: "Code search"},
-		"develop":                 {Backend: "codex", Model: "", PromptFile: "~/.claude/skills/omo/references/develop.md", Description: "Code development"},
-		"frontend-ui-ux-engineer": {Backend: "gemini", Model: "", PromptFile: "~/.claude/skills/omo/references/frontend-ui-ux-engineer.md", Description: "Frontend engineer"},
-		"document-writer":         {Backend: "gemini", Model: "", PromptFile: "~/.claude/skills/omo/references/document-writer.md", Description: "Documentation"},
+var defaultModelsConfig = ModelsConfig{}
+
+const modelsConfigTildePath = "~/.codeagent/models.json"
+
+const modelsConfigExample = `{
+  "default_backend": "codex",
+  "default_model": "gpt-4.1",
+  "backends": {
+    "codex": { "api_key": "..." },
+    "claude": { "api_key": "..." }
   },
-}
+  "agents": {
+    "develop": {
+      "backend": "codex",
+      "model": "gpt-4.1",
+      "prompt_file": "~/.codeagent/prompts/develop.md",
+      "reasoning": "high",
+      "yolo": true
+    }
+  }
+}`
 
 var (
 	modelsConfigOnce   sync.Once
 	modelsConfigCached *ModelsConfig
+	modelsConfigErr    error
 )
 
-func modelsConfig() *ModelsConfig {
+func modelsConfig() (*ModelsConfig, error) {
 	modelsConfigOnce.Do(func() {
-		modelsConfigCached = loadModelsConfig()
+		modelsConfigCached, modelsConfigErr = loadModelsConfig()
 	})
-	if modelsConfigCached == nil {
-		return &defaultModelsConfig
-	}
-	return modelsConfigCached
+	return modelsConfigCached, modelsConfigErr
 }
 
-func loadModelsConfig() *ModelsConfig {
+func modelsConfigPath() (string, error) {
 	home, err := os.UserHomeDir()
-	if err != nil {
-		ilogger.LogWarn(fmt.Sprintf("Failed to resolve home directory for models config: %v; using defaults", err))
-		return &defaultModelsConfig
+	if err != nil || strings.TrimSpace(home) == "" {
+		return "", fmt.Errorf("failed to resolve user home directory: %w", err)
 	}
 
 	configDir := filepath.Clean(filepath.Join(home, ".codeagent"))
 	configPath := filepath.Clean(filepath.Join(configDir, "models.json"))
 	rel, err := filepath.Rel(configDir, configPath)
 	if err != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(os.PathSeparator)) {
-		return &defaultModelsConfig
+		return "", fmt.Errorf("refusing to read models config outside %s: %s", configDir, configPath)
+	}
+	return configPath, nil
+}
+
+func modelsConfigHint(configPath string) string {
+	configPath = strings.TrimSpace(configPath)
+	if configPath == "" {
+		return fmt.Sprintf("Create %s with e.g.:\n%s", modelsConfigTildePath, modelsConfigExample)
+	}
+	return fmt.Sprintf("Create %s (resolved to %s) with e.g.:\n%s", modelsConfigTildePath, configPath, modelsConfigExample)
+}
+
+func loadModelsConfig() (*ModelsConfig, error) {
+	configPath, err := modelsConfigPath()
+	if err != nil {
+		return nil, fmt.Errorf("%w\n\n%s", err, modelsConfigHint(""))
 	}
 
 	data, err := os.ReadFile(configPath) // #nosec G304 -- path is fixed under user home and validated to stay within configDir
 	if err != nil {
-		if !os.IsNotExist(err) {
-			ilogger.LogWarn(fmt.Sprintf("Failed to read models config %s: %v; using defaults", configPath, err))
+		if os.IsNotExist(err) {
+			return nil, fmt.Errorf("models config not found: %s\n\n%s", configPath, modelsConfigHint(configPath))
 		}
-		return &defaultModelsConfig
+		return nil, fmt.Errorf("failed to read models config %s: %w\n\n%s", configPath, err, modelsConfigHint(configPath))
 	}
 
 	var cfg ModelsConfig
 	if err := json.Unmarshal(data, &cfg); err != nil {
-		ilogger.LogWarn(fmt.Sprintf("Failed to parse models config %s: %v; using defaults", configPath, err))
-		return &defaultModelsConfig
+		return nil, fmt.Errorf("failed to parse models config %s: %w\n\n%s", configPath, err, modelsConfigHint(configPath))
 	}
 
 	cfg.DefaultBackend = strings.TrimSpace(cfg.DefaultBackend)
-	if cfg.DefaultBackend == "" {
-		cfg.DefaultBackend = defaultModelsConfig.DefaultBackend
-	}
 	cfg.DefaultModel = strings.TrimSpace(cfg.DefaultModel)
-	if cfg.DefaultModel == "" {
-		cfg.DefaultModel = defaultModelsConfig.DefaultModel
-	}
-
-	// Merge with defaults
-	for name, agent := range defaultModelsConfig.Agents {
-		if _, exists := cfg.Agents[name]; !exists {
-			if cfg.Agents == nil {
-				cfg.Agents = make(map[string]AgentModelConfig)
-			}
-			cfg.Agents[name] = agent
-		}
-	}
 
 	// Normalize backend keys so lookups can be case-insensitive.
 	if len(cfg.Backends) > 0 {
@@ -127,7 +130,7 @@ func loadModelsConfig() *ModelsConfig {
 		}
 	}
 
-	return &cfg
+	return &cfg, nil
 }
 
 func LoadDynamicAgent(name string) (AgentModelConfig, bool) {
@@ -150,7 +153,10 @@ func LoadDynamicAgent(name string) (AgentModelConfig, bool) {
 }
 
 func ResolveBackendConfig(backendName string) (baseURL, apiKey string) {
-	cfg := modelsConfig()
+	cfg, err := modelsConfig()
+	if err != nil || cfg == nil {
+		return "", ""
+	}
 	resolved := resolveBackendConfig(cfg, backendName)
 	return strings.TrimSpace(resolved.BaseURL), strings.TrimSpace(resolved.APIKey)
 }
@@ -172,12 +178,30 @@ func resolveBackendConfig(cfg *ModelsConfig, backendName string) BackendConfig {
 	return BackendConfig{}
 }
 
-func resolveAgentConfig(agentName string) (backend, model, promptFile, reasoning, baseURL, apiKey string, yolo bool) {
-	cfg := modelsConfig()
+func resolveAgentConfig(agentName string) (backend, model, promptFile, reasoning, baseURL, apiKey string, yolo bool, err error) {
+	if err := ValidateAgentName(agentName); err != nil {
+		return "", "", "", "", "", "", false, err
+	}
+
+	cfg, err := modelsConfig()
+	if err != nil {
+		return "", "", "", "", "", "", false, err
+	}
+	if cfg == nil {
+		return "", "", "", "", "", "", false, fmt.Errorf("models config is nil\n\n%s", modelsConfigHint(""))
+	}
+
 	if agent, ok := cfg.Agents[agentName]; ok {
 		backend = strings.TrimSpace(agent.Backend)
 		if backend == "" {
-			backend = cfg.DefaultBackend
+			backend = strings.TrimSpace(cfg.DefaultBackend)
+			if backend == "" {
+				configPath, pathErr := modelsConfigPath()
+				if pathErr != nil {
+					return "", "", "", "", "", "", false, fmt.Errorf("agent %q has empty backend and default_backend is not set\n\n%s", agentName, modelsConfigHint(""))
+				}
+				return "", "", "", "", "", "", false, fmt.Errorf("agent %q has empty backend and default_backend is not set\n\n%s", agentName, modelsConfigHint(configPath))
+			}
 		}
 		backendCfg := resolveBackendConfig(cfg, backend)
 
@@ -190,31 +214,46 @@ func resolveAgentConfig(agentName string) (backend, model, promptFile, reasoning
 			apiKey = strings.TrimSpace(backendCfg.APIKey)
 		}
 
-		return backend, strings.TrimSpace(agent.Model), agent.PromptFile, agent.Reasoning, baseURL, apiKey, agent.Yolo
+		model = strings.TrimSpace(agent.Model)
+		if model == "" {
+			configPath, pathErr := modelsConfigPath()
+			if pathErr != nil {
+				return "", "", "", "", "", "", false, fmt.Errorf("agent %q has empty model; set agents.%s.model in %s\n\n%s", agentName, agentName, modelsConfigTildePath, modelsConfigHint(""))
+			}
+			return "", "", "", "", "", "", false, fmt.Errorf("agent %q has empty model; set agents.%s.model in %s\n\n%s", agentName, agentName, modelsConfigTildePath, modelsConfigHint(configPath))
+		}
+		return backend, model, agent.PromptFile, agent.Reasoning, baseURL, apiKey, agent.Yolo, nil
 	}
 
 	if dynamic, ok := LoadDynamicAgent(agentName); ok {
-		backend = cfg.DefaultBackend
-		model = cfg.DefaultModel
+		backend = strings.TrimSpace(cfg.DefaultBackend)
+		model = strings.TrimSpace(cfg.DefaultModel)
+		configPath, pathErr := modelsConfigPath()
+		if backend == "" || model == "" {
+			if pathErr != nil {
+				return "", "", "", "", "", "", false, fmt.Errorf("dynamic agent %q requires default_backend and default_model to be set in %s\n\n%s", agentName, modelsConfigTildePath, modelsConfigHint(""))
+			}
+			return "", "", "", "", "", "", false, fmt.Errorf("dynamic agent %q requires default_backend and default_model to be set in %s\n\n%s", agentName, modelsConfigTildePath, modelsConfigHint(configPath))
+		}
 		backendCfg := resolveBackendConfig(cfg, backend)
 		baseURL = strings.TrimSpace(backendCfg.BaseURL)
 		apiKey = strings.TrimSpace(backendCfg.APIKey)
-		return backend, model, dynamic.PromptFile, "", baseURL, apiKey, false
+		return backend, model, dynamic.PromptFile, "", baseURL, apiKey, false, nil
 	}
 
-	backend = cfg.DefaultBackend
-	model = cfg.DefaultModel
-	backendCfg := resolveBackendConfig(cfg, backend)
-	baseURL = strings.TrimSpace(backendCfg.BaseURL)
-	apiKey = strings.TrimSpace(backendCfg.APIKey)
-	return backend, model, "", "", baseURL, apiKey, false
+	configPath, pathErr := modelsConfigPath()
+	if pathErr != nil {
+		return "", "", "", "", "", "", false, fmt.Errorf("agent %q not found in %s\n\n%s", agentName, modelsConfigTildePath, modelsConfigHint(""))
+	}
+	return "", "", "", "", "", "", false, fmt.Errorf("agent %q not found in %s\n\n%s", agentName, modelsConfigTildePath, modelsConfigHint(configPath))
 }
 
-func ResolveAgentConfig(agentName string) (backend, model, promptFile, reasoning, baseURL, apiKey string, yolo bool) {
+func ResolveAgentConfig(agentName string) (backend, model, promptFile, reasoning, baseURL, apiKey string, yolo bool, err error) {
 	return resolveAgentConfig(agentName)
 }
 
 func ResetModelsConfigCacheForTest() {
 	modelsConfigCached = nil
+	modelsConfigErr = nil
 	modelsConfigOnce = sync.Once{}
 }

codeagent-wrapper/internal/config/agent_config_test.go

@@ -3,78 +3,43 @@ package config
 import (
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 )
 
-func TestResolveAgentConfig_Defaults(t *testing.T) {
+func TestResolveAgentConfig_NoConfig_ReturnsHelpfulError(t *testing.T) {
 	home := t.TempDir()
 	t.Setenv("HOME", home)
 	t.Setenv("USERPROFILE", home)
 	t.Cleanup(ResetModelsConfigCacheForTest)
 	ResetModelsConfigCacheForTest()
 
-	// Test that default agents resolve correctly without config file
-	tests := []struct {
-		agent          string
-		wantBackend    string
-		wantModel      string
-		wantPromptFile string
-	}{
-		{"oracle", "claude", "claude-opus-4-5-20251101", "~/.claude/skills/omo/references/oracle.md"},
-		{"librarian", "claude", "claude-sonnet-4-5-20250929", "~/.claude/skills/omo/references/librarian.md"},
-		{"explore", "opencode", "opencode/grok-code", "~/.claude/skills/omo/references/explore.md"},
-		{"frontend-ui-ux-engineer", "gemini", "", "~/.claude/skills/omo/references/frontend-ui-ux-engineer.md"},
-		{"document-writer", "gemini", "", "~/.claude/skills/omo/references/document-writer.md"},
+	_, _, _, _, _, _, _, err := ResolveAgentConfig("develop")
+	if err == nil {
+		t.Fatalf("expected error, got nil")
 	}
-
-	for _, tt := range tests {
-		t.Run(tt.agent, func(t *testing.T) {
-			backend, model, promptFile, _, _, _, _ := resolveAgentConfig(tt.agent)
-			if backend != tt.wantBackend {
-				t.Errorf("backend = %q, want %q", backend, tt.wantBackend)
+	msg := err.Error()
+	if !strings.Contains(msg, modelsConfigTildePath) {
+		t.Fatalf("error should mention %s, got: %s", modelsConfigTildePath, msg)
 	}
-			if model != tt.wantModel {
-				t.Errorf("model = %q, want %q", model, tt.wantModel)
+	if !strings.Contains(msg, filepath.Join(home, ".codeagent", "models.json")) {
+		t.Fatalf("error should mention resolved config path, got: %s", msg)
 	}
-			if promptFile != tt.wantPromptFile {
-				t.Errorf("promptFile = %q, want %q", promptFile, tt.wantPromptFile)
-			}
-		})
-	}
-}
-
-func TestResolveAgentConfig_UnknownAgent(t *testing.T) {
-	home := t.TempDir()
-	t.Setenv("HOME", home)
-	t.Setenv("USERPROFILE", home)
-	t.Cleanup(ResetModelsConfigCacheForTest)
-	ResetModelsConfigCacheForTest()
-
-	backend, model, promptFile, _, _, _, _ := resolveAgentConfig("unknown-agent")
-	if backend != "opencode" {
-		t.Errorf("unknown agent backend = %q, want %q", backend, "opencode")
-	}
-	if model != "opencode/grok-code" {
-		t.Errorf("unknown agent model = %q, want %q", model, "opencode/grok-code")
-	}
-	if promptFile != "" {
-		t.Errorf("unknown agent promptFile = %q, want empty", promptFile)
+	if !strings.Contains(msg, "\"agents\"") {
+		t.Fatalf("error should include example config, got: %s", msg)
 	}
 }
 
 func TestLoadModelsConfig_NoFile(t *testing.T) {
-	home := "/nonexistent/path/that/does/not/exist"
+	home := t.TempDir()
 	t.Setenv("HOME", home)
 	t.Setenv("USERPROFILE", home)
 	t.Cleanup(ResetModelsConfigCacheForTest)
 	ResetModelsConfigCacheForTest()
 
-	cfg := loadModelsConfig()
-	if cfg.DefaultBackend != "opencode" {
-		t.Errorf("DefaultBackend = %q, want %q", cfg.DefaultBackend, "opencode")
-	}
-	if len(cfg.Agents) != 6 {
-		t.Errorf("len(Agents) = %d, want 6", len(cfg.Agents))
+	_, err := loadModelsConfig()
+	if err == nil {
+		t.Fatalf("expected error, got nil")
 	}
 }
 
@@ -119,7 +84,10 @@ func TestLoadModelsConfig_WithFile(t *testing.T) {
 	t.Cleanup(ResetModelsConfigCacheForTest)
 	ResetModelsConfigCacheForTest()
 
-	cfg := loadModelsConfig()
+	cfg, err := loadModelsConfig()
+	if err != nil {
+		t.Fatalf("loadModelsConfig: %v", err)
+	}
 
 	if cfg.DefaultBackend != "claude" {
 		t.Errorf("DefaultBackend = %q, want %q", cfg.DefaultBackend, "claude")
@@ -140,9 +108,8 @@ func TestLoadModelsConfig_WithFile(t *testing.T) {
 		}
 	}
 
-	// Check that defaults are merged
-	if _, ok := cfg.Agents["oracle"]; !ok {
-		t.Error("default agent oracle should be merged")
+	if _, ok := cfg.Agents["oracle"]; ok {
+		t.Error("oracle should not be present without explicit config")
 	}
 
 	baseURL, apiKey := ResolveBackendConfig("claude")
@@ -153,7 +120,10 @@ func TestLoadModelsConfig_WithFile(t *testing.T) {
 		t.Errorf("ResolveBackendConfig(apiKey) = %q, want %q", apiKey, "backend-key")
 	}
 
-	backend, model, _, _, agentBaseURL, agentAPIKey, _ := ResolveAgentConfig("custom-agent")
+	backend, model, _, _, agentBaseURL, agentAPIKey, _, err := ResolveAgentConfig("custom-agent")
+	if err != nil {
+		t.Fatalf("ResolveAgentConfig(custom-agent): %v", err)
+	}
 	if backend != "codex" {
 		t.Errorf("ResolveAgentConfig(backend) = %q, want %q", backend, "codex")
 	}
@@ -183,12 +153,26 @@ func TestResolveAgentConfig_DynamicAgent(t *testing.T) {
 		t.Fatalf("WriteFile: %v", err)
 	}
 
-	backend, model, promptFile, _, _, _, _ := resolveAgentConfig("sarsh")
-	if backend != "opencode" {
-		t.Errorf("backend = %q, want %q", backend, "opencode")
+	configDir := filepath.Join(home, ".codeagent")
+	if err := os.MkdirAll(configDir, 0o755); err != nil {
+		t.Fatalf("MkdirAll: %v", err)
 	}
-	if model != "opencode/grok-code" {
-		t.Errorf("model = %q, want %q", model, "opencode/grok-code")
+	if err := os.WriteFile(filepath.Join(configDir, "models.json"), []byte(`{
+  "default_backend": "codex",
+  "default_model": "gpt-test"
+}`), 0o644); err != nil {
+		t.Fatalf("WriteFile: %v", err)
+	}
+
+	backend, model, promptFile, _, _, _, _, err := ResolveAgentConfig("sarsh")
+	if err != nil {
+		t.Fatalf("ResolveAgentConfig(sarsh): %v", err)
+	}
+	if backend != "codex" {
+		t.Errorf("backend = %q, want %q", backend, "codex")
+	}
+	if model != "gpt-test" {
+		t.Errorf("model = %q, want %q", model, "gpt-test")
 	}
 	if promptFile != "~/.codeagent/agents/sarsh.md" {
 		t.Errorf("promptFile = %q, want %q", promptFile, "~/.codeagent/agents/sarsh.md")
@@ -213,9 +197,66 @@ func TestLoadModelsConfig_InvalidJSON(t *testing.T) {
 	t.Cleanup(ResetModelsConfigCacheForTest)
 	ResetModelsConfigCacheForTest()
 
-	cfg := loadModelsConfig()
-	// Should fall back to defaults
-	if cfg.DefaultBackend != "opencode" {
-		t.Errorf("invalid JSON should fallback, got DefaultBackend = %q", cfg.DefaultBackend)
+	_, err := loadModelsConfig()
+	if err == nil {
+		t.Fatalf("expected error, got nil")
+	}
+}
+
+func TestResolveAgentConfig_UnknownAgent_ReturnsError(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	t.Setenv("USERPROFILE", home)
+	t.Cleanup(ResetModelsConfigCacheForTest)
+	ResetModelsConfigCacheForTest()
+
+	configDir := filepath.Join(home, ".codeagent")
+	if err := os.MkdirAll(configDir, 0o755); err != nil {
+		t.Fatalf("MkdirAll: %v", err)
+	}
+	if err := os.WriteFile(filepath.Join(configDir, "models.json"), []byte(`{
+  "default_backend": "codex",
+  "default_model": "gpt-test",
+  "agents": {
+    "develop": { "backend": "codex", "model": "gpt-test" }
+  }
+}`), 0o644); err != nil {
+		t.Fatalf("WriteFile: %v", err)
+	}
+
+	_, _, _, _, _, _, _, err := ResolveAgentConfig("unknown-agent")
+	if err == nil {
+		t.Fatalf("expected error, got nil")
+	}
+	if !strings.Contains(err.Error(), "unknown-agent") {
+		t.Fatalf("error should mention agent name, got: %s", err.Error())
+	}
+}
+
+func TestResolveAgentConfig_EmptyModel_ReturnsError(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	t.Setenv("USERPROFILE", home)
+	t.Cleanup(ResetModelsConfigCacheForTest)
+	ResetModelsConfigCacheForTest()
+
+	configDir := filepath.Join(home, ".codeagent")
+	if err := os.MkdirAll(configDir, 0o755); err != nil {
+		t.Fatalf("MkdirAll: %v", err)
+	}
+	if err := os.WriteFile(filepath.Join(configDir, "models.json"), []byte(`{
+  "agents": {
+    "bad-agent": { "backend": "codex", "model": " " }
+  }
+}`), 0o644); err != nil {
+		t.Fatalf("WriteFile: %v", err)
+	}
+
+	_, _, _, _, _, _, _, err := ResolveAgentConfig("bad-agent")
+	if err == nil {
+		t.Fatalf("expected error, got nil")
+	}
+	if !strings.Contains(strings.ToLower(err.Error()), "empty model") {
+		t.Fatalf("error should mention empty model, got: %s", err.Error())
 	}
 }

codeagent-wrapper/internal/executor/env_inject_test.go

@@ -46,7 +46,10 @@ func TestEnvInjectionWithAgent(t *testing.T) {
 	defer config.ResetModelsConfigCacheForTest()
 
 	// Test ResolveAgentConfig
-	agentBackend, model, _, _, baseURL, apiKey, _ := config.ResolveAgentConfig("test-agent")
+	agentBackend, model, _, _, baseURL, apiKey, _, err := config.ResolveAgentConfig("test-agent")
+	if err != nil {
+		t.Fatalf("ResolveAgentConfig: %v", err)
+	}
 	t.Logf("ResolveAgentConfig: backend=%q, model=%q, baseURL=%q, apiKey=%q",
 		agentBackend, model, baseURL, apiKey)
 
@@ -118,7 +121,10 @@ func TestEnvInjectionLogic(t *testing.T) {
 
 	// Step 2: If agent specified, get agent config
 	if agentName != "" {
-		agentBackend, _, _, _, agentBaseURL, agentAPIKey, _ := config.ResolveAgentConfig(agentName)
+		agentBackend, _, _, _, agentBaseURL, agentAPIKey, _, err := config.ResolveAgentConfig(agentName)
+		if err != nil {
+			t.Fatalf("ResolveAgentConfig(%q): %v", agentName, err)
+		}
 		t.Logf("Step 2 - ResolveAgentConfig(%q): backend=%q, baseURL=%q, apiKey=%q",
 			agentName, agentBackend, agentBaseURL, agentAPIKey)
 

codeagent-wrapper/internal/executor/executor.go

@@ -1060,11 +1060,13 @@ func RunCodexTaskWithContext(parentCtx context.Context, taskSpec TaskSpec, backe
 	if envBackend != nil {
 			baseURL, apiKey := config.ResolveBackendConfig(cfg.Backend)
 			if agentName := strings.TrimSpace(taskSpec.Agent); agentName != "" {
-			agentBackend, _, _, _, agentBaseURL, agentAPIKey, _ := config.ResolveAgentConfig(agentName)
+				agentBackend, _, _, _, agentBaseURL, agentAPIKey, _, err := config.ResolveAgentConfig(agentName)
+				if err == nil {
 					if strings.EqualFold(strings.TrimSpace(agentBackend), strings.TrimSpace(cfg.Backend)) {
 						baseURL, apiKey = agentBaseURL, agentAPIKey
 					}
 				}
+			}
 			if injected := envBackend.Env(baseURL, apiKey); len(injected) > 0 {
 				cmd.SetEnv(injected)
 			// Log injected env vars with masked API keys (to file and stderr)

codeagent-wrapper/internal/executor/parallel_config.go

@@ -96,7 +96,10 @@ func ParseParallelConfig(data []byte) (*ParallelConfig, error) {
 				if err := config.ValidateAgentName(task.Agent); err != nil {
 					return nil, fmt.Errorf("task block #%d invalid agent name: %w", taskIndex, err)
 				}
-			backend, model, promptFile, reasoning, _, _, _ := config.ResolveAgentConfig(task.Agent)
+				backend, model, promptFile, reasoning, _, _, _, err := config.ResolveAgentConfig(task.Agent)
+				if err != nil {
+					return nil, fmt.Errorf("task block #%d failed to resolve agent %q: %w", taskIndex, task.Agent, err)
+				}
 				if task.Backend == "" {
 					task.Backend = backend
 				}

skills/do/README.md

@@ -158,7 +158,7 @@ EOF
 
 ## ~/.codeagent/models.json Configuration
 
-Optional. Uses codeagent-wrapper built-in config by default. To customize:
+Required when using `agent:` in parallel tasks or `--agent`. Create `~/.codeagent/models.json` to configure agent → backend/model mappings:
 
 ```json
 {