fix(config): prevent default ModelList from overriding user config

When users provide a partial config (e.g., only model_name and api_key
without api_base), Go's JSON parser was reusing default ModelList values
at the same index position, causing wrong api_base to be used.

This fix:
1. Sets ModelList to nil in DefaultConfig() to avoid inheriting defaults
2. Adds GetDefaultModelList() function for first-time users
3. Applies default model list only when both ModelList and legacy providers
   are empty (new user scenario)

Closes #680

pkg/config/config.go

@@ -617,6 +617,12 @@ func LoadConfig(path string) (*Config, error) {
 		cfg.ModelList = ConvertProvidersToModelList(cfg)
 	}
 
+	// If model_list is still empty and no legacy providers, use default model list
+	// This ensures new users get a working config template on first run
+	if len(cfg.ModelList) == 0 && !cfg.HasProvidersConfig() {
+		cfg.ModelList = GetDefaultModelList()
+	}
+
 	// Validate model_list for uniqueness and required fields
 	if err := cfg.ValidateModelList(); err != nil {
 		return nil, err

pkg/config/defaults.go

@@ -134,7 +134,73 @@ func DefaultConfig() *Config {
 		Providers: ProvidersConfig{
 			OpenAI: OpenAIProviderConfig{WebSearch: true},
 		},
-		ModelList: []ModelConfig{
+		// NOTE: ModelList is intentionally nil here to avoid inheriting default values
+		// when users provide partial config. The actual default model list is applied
+		// in LoadConfig when both ModelList and legacy providers are empty.
+		ModelList: nil,
+		Gateway: GatewayConfig{
+			Host: "127.0.0.1",
+			Port: 18790,
+		},
+		Tools: ToolsConfig{
+			MediaCleanup: MediaCleanupConfig{
+				Enabled:  true,
+				MaxAge:   30,
+				Interval: 5,
+			},
+			Web: WebToolsConfig{
+				Proxy: "",
+				Brave: BraveConfig{
+					Enabled:    false,
+					APIKey:     "",
+					MaxResults: 5,
+				},
+				DuckDuckGo: DuckDuckGoConfig{
+					Enabled:    true,
+					MaxResults: 5,
+				},
+				Perplexity: PerplexityConfig{
+					Enabled:    false,
+					APIKey:     "",
+					MaxResults: 5,
+				},
+			},
+			Cron: CronToolsConfig{
+				ExecTimeoutMinutes: 5,
+			},
+			Exec: ExecConfig{
+				EnableDenyPatterns: true,
+			},
+			Skills: SkillsToolsConfig{
+				Registries: SkillsRegistriesConfig{
+					ClawHub: ClawHubRegistryConfig{
+						Enabled: true,
+						BaseURL: "https://clawhub.ai",
+					},
+				},
+				MaxConcurrentSearches: 2,
+				SearchCache: SearchCacheConfig{
+					MaxSize:    50,
+					TTLSeconds: 300,
+				},
+			},
+		},
+		Heartbeat: HeartbeatConfig{
+			Enabled:  true,
+			Interval: 30,
+		},
+		Devices: DevicesConfig{
+			Enabled:    false,
+			MonitorUSB: true,
+		},
+	}
+}
+
+// GetDefaultModelList returns the default model list template for first-time users.
+// This is separate from DefaultConfig to avoid the JSON parser inheriting default values
+// when users provide partial configuration (issue #680).
+func GetDefaultModelList() []ModelConfig {
+	return []ModelConfig{
 		// ============================================
 		// Add your API key to the model you want to use
 		// ============================================
@@ -287,61 +353,5 @@ func DefaultConfig() *Config {
 			APIBase:   "http://localhost:8000/v1",
 			APIKey:    "",
 		},
-		},
-		Gateway: GatewayConfig{
-			Host: "127.0.0.1",
-			Port: 18790,
-		},
-		Tools: ToolsConfig{
-			MediaCleanup: MediaCleanupConfig{
-				Enabled:  true,
-				MaxAge:   30,
-				Interval: 5,
-			},
-			Web: WebToolsConfig{
-				Proxy: "",
-				Brave: BraveConfig{
-					Enabled:    false,
-					APIKey:     "",
-					MaxResults: 5,
-				},
-				DuckDuckGo: DuckDuckGoConfig{
-					Enabled:    true,
-					MaxResults: 5,
-				},
-				Perplexity: PerplexityConfig{
-					Enabled:    false,
-					APIKey:     "",
-					MaxResults: 5,
-				},
-			},
-			Cron: CronToolsConfig{
-				ExecTimeoutMinutes: 5,
-			},
-			Exec: ExecConfig{
-				EnableDenyPatterns: true,
-			},
-			Skills: SkillsToolsConfig{
-				Registries: SkillsRegistriesConfig{
-					ClawHub: ClawHubRegistryConfig{
-						Enabled: true,
-						BaseURL: "https://clawhub.ai",
-					},
-				},
-				MaxConcurrentSearches: 2,
-				SearchCache: SearchCacheConfig{
-					MaxSize:    50,
-					TTLSeconds: 300,
-				},
-			},
-		},
-		Heartbeat: HeartbeatConfig{
-			Enabled:  true,
-			Interval: 30,
-		},
-		Devices: DevicesConfig{
-			Enabled:    false,
-			MonitorUSB: true,
-		},
 	}
 }