diff --git a/src/commands/model-commands.ts b/src/commands/model-commands.ts
index 6eef673..e8cf202 100644
--- a/src/commands/model-commands.ts
+++ b/src/commands/model-commands.ts
@@ -14,6 +14,7 @@ import {
   loadModelMap,
   validateModelMap,
   initModelMapFile,
+  addModelToMap,
   getExampleModelMap,
   getGlobalConfigDir,
   type ModelMapConfig,
@@ -266,28 +267,32 @@ export const modelMapCommand: Command = {
   name: 'modelmap',
   aliases: ['mm', 'models-map'],
   description: 'Show and manage model map configuration (codi-models.yaml)',
-  usage: '/modelmap [init [--global]|show|example]',
+  usage: '/modelmap [add|init|show|example] [--global]',
   taskType: 'fast',
   execute: async (args: string, context: CommandContext): Promise<string | null> => {
-    const trimmed = args.trim().toLowerCase();
+    const trimmed = args.trim();
+    const trimmedLower = trimmed.toLowerCase();
 
     // Handle help flag locally without API call
-    if (trimmed === '-h' || trimmed === '--help') {
-      console.log('\nUsage: /modelmap [init [--global]|show|example]');
+    if (trimmedLower === '-h' || trimmedLower === '--help') {
+      console.log('\nUsage: /modelmap [action] [options]');
       console.log('\nShow and manage model map configuration.');
       console.log('\nConfig locations:');
       console.log(`  Global:  ${getGlobalConfigDir()}/models.yaml`);
       console.log('  Project: ./codi-models.yaml');
       console.log('\nActions:');
-      console.log('  show          Show current model map configuration (default)');
-      console.log('  init          Create a new codi-models.yaml in current directory');
-      console.log('  init --global Create a new models.yaml in ~/.codi/');
-      console.log('  example       Show example configuration');
+      console.log('  show                    Show current model map configuration (default)');
+      console.log('  add <name> <provider> <model> [description]  Add a model alias');
+      console.log('  init                    Create a new codi-models.yaml in current directory');
+      console.log('  example                 Show example configuration');
+      console.log('\nFlags:');
+      console.log('  --global                Apply to global config (~/.codi/models.yaml)');
       console.log('\nExamples:');
-      console.log('  /modelmap              Show current configuration');
-      console.log('  /modelmap init         Create project codi-models.yaml');
-      console.log('  /modelmap init --global Create global ~/.codi/models.yaml');
-      console.log('  /modelmap example      Show example YAML');
+      console.log('  /modelmap                           Show current configuration');
+      console.log('  /modelmap add coder ollama-cloud qwen3-coder:480b-cloud');
+      console.log('  /modelmap add --global fast anthropic claude-3-5-haiku-latest');
+      console.log('  /modelmap init                      Create project codi-models.yaml');
+      console.log('  /modelmap init --global             Create global ~/.codi/models.yaml');
       console.log('\nGlobal models can be used in any project with /switch <name>');
       console.log();
       return null;
@@ -295,10 +300,37 @@ export const modelMapCommand: Command = {
 
     // Parse action and flags
     const parts = trimmed.split(/\s+/).filter(p => p);
-    const action = parts[0] || 'show';
     const isGlobal = parts.includes('--global');
+    // Remove --global from parts for easier parsing
+    const filteredParts = parts.filter(p => p.toLowerCase() !== '--global');
+    const action = (filteredParts[0] || 'show').toLowerCase();
 
     switch (action) {
+      case 'add': {
+        // Parse: add <name> <provider> <model> [description...]
+        const name = filteredParts[1];
+        const provider = filteredParts[2];
+        const model = filteredParts[3];
+        const description = filteredParts.slice(4).join(' ') || undefined;
+
+        if (!name || !provider || !model) {
+          return '__MODELMAP_ERROR__|Usage: /modelmap add <name> <provider> <model> [description]';
+        }
+
+        // Validate provider
+        const validProviders = ['anthropic', 'openai', 'ollama', 'ollama-cloud', 'runpod'];
+        if (!validProviders.includes(provider.toLowerCase())) {
+          return `__MODELMAP_ERROR__|Invalid provider "${provider}". Valid: ${validProviders.join(', ')}`;
+        }
+
+        const result = addModelToMap(name, provider.toLowerCase(), model, description, isGlobal);
+        if (result.success) {
+          const scope = isGlobal ? 'global' : 'project';
+          return `__MODELMAP_ADD__|${name}|${provider}|${model}|${result.path}|${scope}`;
+        }
+        return `__MODELMAP_ERROR__|${result.error}`;
+      }
+
       case 'init': {
         const result = initModelMapFile(process.cwd(), isGlobal);
         if (result.success) {
diff --git a/src/index.ts b/src/index.ts
index 0fcd192..e16c256 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1597,6 +1597,17 @@ function handleModelMapOutput(output: string): void {
     return;
   }
 
+  if (firstLine.startsWith('__MODELMAP_ADD__|')) {
+    const parts = firstLine.slice('__MODELMAP_ADD__|'.length).split('|');
+    const [name, provider, model, filePath, scope] = parts;
+    console.log(chalk.green(`\nAdded model "${name}" to ${scope} config`));
+    console.log(chalk.dim(`  Provider: ${provider}`));
+    console.log(chalk.dim(`  Model: ${model}`));
+    console.log(chalk.dim(`  File: ${filePath}`));
+    console.log(chalk.cyan(`\nUse with: /switch ${name}`));
+    return;
+  }
+
   if (firstLine.startsWith('__MODELMAP_INIT__|')) {
     const parts = firstLine.slice('__MODELMAP_INIT__|'.length).split('|');
     const filePath = parts[0];
diff --git a/src/model-map/index.ts b/src/model-map/index.ts
index 78dc726..a54ad15 100644
--- a/src/model-map/index.ts
+++ b/src/model-map/index.ts
@@ -21,6 +21,7 @@ export {
   watchModelMap,
   getExampleModelMap,
   initModelMap as initModelMapFile,
+  addModelToMap,
   getGlobalConfigDir,
   ModelMapValidationError,
   type ValidationResult,
diff --git a/src/model-map/loader.ts b/src/model-map/loader.ts
index ad15751..f190036 100644
--- a/src/model-map/loader.ts
+++ b/src/model-map/loader.ts
@@ -723,3 +723,91 @@ export function initModelMap(
 export function getGlobalConfigDir(): string {
   return GLOBAL_CONFIG_DIR;
 }
+
+/**
+ * Add a model to an existing model map file.
+ * Creates the file if it doesn't exist.
+ *
+ * @param name Model alias name
+ * @param provider Provider type (anthropic, openai, ollama, etc.)
+ * @param model Model ID
+ * @param description Optional description
+ * @param global If true, adds to global config (~/.codi/models.yaml)
+ * @param cwd Working directory for project config
+ */
+export function addModelToMap(
+  name: string,
+  provider: string,
+  model: string,
+  description?: string,
+  global: boolean = false,
+  cwd: string = process.cwd()
+): { success: boolean; path: string; error?: string } {
+  const targetDir = global ? GLOBAL_CONFIG_DIR : cwd;
+  const fileName = global ? GLOBAL_MODEL_MAP_FILE : MODEL_MAP_FILE;
+  const configPath = path.join(targetDir, fileName);
+
+  // Ensure directory exists for global config
+  if (global && !fs.existsSync(targetDir)) {
+    try {
+      fs.mkdirSync(targetDir, { recursive: true });
+    } catch (error) {
+      return {
+        success: false,
+        path: configPath,
+        error: `Failed to create directory: ${error instanceof Error ? error.message : String(error)}`,
+      };
+    }
+  }
+
+  // Load existing config or create new one
+  let config: ModelMapConfig;
+  if (fs.existsSync(configPath)) {
+    try {
+      const content = fs.readFileSync(configPath, 'utf-8');
+      config = yaml.load(content) as ModelMapConfig;
+      if (!config.models) config.models = {};
+    } catch (error) {
+      return {
+        success: false,
+        path: configPath,
+        error: `Failed to parse existing config: ${error instanceof Error ? error.message : String(error)}`,
+      };
+    }
+  } else {
+    // Create minimal config
+    config = {
+      version: '1',
+      models: {},
+    };
+  }
+
+  // Check if model already exists
+  if (config.models[name]) {
+    return {
+      success: false,
+      path: configPath,
+      error: `Model "${name}" already exists. Use a different name or edit the file directly.`,
+    };
+  }
+
+  // Add the model
+  config.models[name] = {
+    provider,
+    model,
+    ...(description && { description }),
+  };
+
+  // Write back
+  try {
+    const yamlContent = yaml.dump(config, { lineWidth: 100, noRefs: true });
+    fs.writeFileSync(configPath, yamlContent);
+    return { success: true, path: configPath };
+  } catch (error) {
+    return {
+      success: false,
+      path: configPath,
+      error: `Failed to write config: ${error instanceof Error ? error.message : String(error)}`,
+    };
+  }
+}