feat: add /fast toggle command for quick Opus Sonnet switching

- Add /fast slash command that toggles fast mode on/off
- Add fastMode and fastModel settings to UnifiedBotSettings
- Override model in getQueryOptions() when fast mode is active
- Switch model mid-session via Query.setModel() on active queries
- Wire settings deps to InfoCommandHandlerDeps for read/write access
- Update help system with /fast documentation
- Default fast model: claude-sonnet-4-6

Author: zebbern

claude/info-commands.ts

@@ -72,6 +72,10 @@ export const infoCommands = [
       option.setName('value')
         .setDescription('Value for the action (model name or permission mode)')
         .setRequired(false)),
+  
+  new SlashCommandBuilder()
+    .setName('fast')
+    .setDescription('Toggle fast mode — switch between default model and a fast/cheap model (Sonnet)'),
 ];
 
 // ================================
@@ -81,6 +85,10 @@ export const infoCommands = [
 export interface InfoCommandHandlerDeps {
   workDir: string;
   getQueryOptions?: () => ClaudeModelOptions;
+  /** Read current unified settings (for /fast toggle) */
+  getUnifiedSettings?: () => import("../settings/unified-settings.ts").UnifiedBotSettings;
+  /** Update unified settings (for /fast toggle) */
+  updateUnifiedSettings?: (partial: Partial<import("../settings/unified-settings.ts").UnifiedBotSettings>) => void;
 }
 
 export function createInfoCommandHandlers(deps: InfoCommandHandlerDeps) {
@@ -427,6 +435,55 @@ export function createInfoCommandHandlers(deps: InfoCommandHandlerDeps) {
           });
       }
     },
+
+    // ================================
+    // /fast — Toggle fast mode
+    // ================================
+    // deno-lint-ignore no-explicit-any
+    async onFast(ctx: any): Promise<void> {
+      if (!deps.getUnifiedSettings || !deps.updateUnifiedSettings) {
+        await ctx.reply({ content: 'Fast mode not available (settings not wired).', ephemeral: true });
+        return;
+      }
+
+      const current = deps.getUnifiedSettings();
+      const newFastMode = !current.fastMode;
+      deps.updateUnifiedSettings({ fastMode: newFastMode });
+
+      // If there's an active query, switch the model mid-session
+      const activeQuery = getActiveQuery();
+      if (activeQuery) {
+        try {
+          if (newFastMode) {
+            await setActiveModel(current.fastModel || 'claude-sonnet-4-6');
+          } else {
+            // Revert to default model (undefined = SDK default)
+            await setActiveModel(current.defaultModel || undefined);
+          }
+        } catch {
+          // Mid-session switch failed — setting still applies to next query
+        }
+      }
+
+      const modelName = newFastMode
+        ? (current.fastModel || 'claude-sonnet-4-6')
+        : (current.defaultModel || 'default (Opus)');
+      const midSessionNote = activeQuery
+        ? '\nModel switched on active session.'
+        : '';
+
+      await ctx.reply({
+        embeds: [{
+          color: newFastMode ? 0xffaa00 : 0x5865f2,
+          title: newFastMode ? '⚡ Fast Mode ON' : '🧠 Fast Mode OFF',
+          description: newFastMode
+            ? `Switched to **${modelName}** — faster responses, lower cost.${midSessionNote}`
+            : `Switched to **${modelName}** — full reasoning power.${midSessionNote}`,
+          footer: { text: 'Use /fast again to toggle back' },
+          timestamp: new Date().toISOString()
+        }]
+      });
+    },
   };
 }
 

core/command-wrappers.ts

@@ -545,6 +545,11 @@ function createInfoCommandsMap(
         await infoHandlers.onClaudeControl(ctx, action, value || undefined);
       }
     }],
+    ['fast', {
+      execute: async (ctx: InteractionContext) => {
+        await infoHandlers.onFast(ctx);
+      }
+    }],
   ]);
 }
 

core/handler-registry.ts

@@ -383,8 +383,10 @@ export function createAllHandlers(
     const s = settings.getSettings().unified;
     const opts: ClaudeModelOptions = {};
 
-    // Model
-    if (s.defaultModel) {
+    // Model — fast mode overrides default model
+    if (s.fastMode && s.fastModel) {
+      opts.model = s.fastModel;
+    } else if (s.defaultModel) {
       opts.model = s.defaultModel;
     }
 
@@ -546,6 +548,8 @@ export function createAllHandlers(
   const infoCommandHandlers = createInfoCommandHandlers({
     workDir,
     getQueryOptions,
+    getUnifiedSettings: () => settings.getSettings().unified,
+    updateUnifiedSettings: (partial) => settings.updateUnified(partial),
   });
 
   return {

help/commands.ts

@@ -783,6 +783,22 @@ export const COMMAND_HELP = {
       "Shows model capabilities and features",
       "Applies to all new conversations until changed again"
     ]
+  },
+  "fast": {
+    title: "⚡ Fast Mode Toggle",
+    description: "Toggle between the default model (Opus) and a fast/cheap model (Sonnet)",
+    usage: "/fast",
+    examples: [
+      "/fast"
+    ],
+    parameters: [],
+    notes: [
+      "Toggles fast mode on/off",
+      "Fast mode uses Sonnet for faster, cheaper responses",
+      "Works mid-session — switches model on an active query",
+      "Configure the fast model via /settings",
+      "Use /fast again to toggle back to your default model"
+    ]
   }
 };
 
@@ -861,7 +877,7 @@ export function createHelpHandlers(deps: HelpHandlerDeps) {
             fields: [
               {
                 name: "🤖 Claude Code Commands",
-                value: "`/claude` - Send prompts to Claude Code\n`/claude-enhanced` - Advanced Claude with options\n`/continue` - Continue conversation\n`/claude-cancel` - Cancel running operation",
+                value: "`/claude` - Send prompts to Claude Code\n`/claude-enhanced` - Advanced Claude with options\n`/resume` - Resume conversation\n`/claude-cancel` - Cancel running operation\n`/fast` - Toggle fast mode (Opus ↔ Sonnet)",
                 inline: false
               },
               {
@@ -881,7 +897,7 @@ export function createHelpHandlers(deps: HelpHandlerDeps) {
               },
               {
                 name: "⚙️ Advanced Settings",
-                value: "`/settings` - Unified bot settings (NEW)\n`/claude-settings` - Claude preferences\n`/output-settings` - Display settings\n`/quick-model` - Switch Claude model",
+                value: "`/settings` - Unified bot settings (NEW)\n`/claude-settings` - Claude preferences\n`/output-settings` - Display settings\n`/quick-model` - Switch Claude model\n`/fast` - Toggle fast mode",
                 inline: false
               },
               {

settings/unified-settings.ts

@@ -23,6 +23,10 @@ export interface UnifiedBotSettings {
   // Mode settings
   operationMode: 'normal' | 'plan' | 'auto-accept' | 'danger' | 'dont-ask';
 
+  // Fast mode — toggles between default model and a fast/cheap model
+  fastMode: boolean;
+  fastModel: string;
+  
   // Budget settings
   maxBudgetUsd: number | null;
 
@@ -83,6 +87,10 @@ export const UNIFIED_DEFAULT_SETTINGS: UnifiedBotSettings = {
   // Operation mode
   operationMode: 'normal',
 
+  // Fast mode — off by default, uses Sonnet as fast model
+  fastMode: false,
+  fastModel: 'claude-sonnet-4-6',
+  
   // Budget
   maxBudgetUsd: null,