packages/cli/src/tui/app.tsx

@@ -13,7 +13,8 @@ import { useViewport } from './hooks/use-viewport.js';
 import { useAppMode } from './hooks/use-app-mode.js';
 import { useConversations } from './hooks/use-conversations.js';
 import { useSearch } from './hooks/use-search.js';
-import { executeHelp, executeStatus, commandRegistry } from './commands/index.js';
+import { executeHelp, executeStatus, executeHistory, commandRegistry } from './commands/index.js';
+import { fetchConversationMessages } from './gateway-api.js';
 
 export interface TuiAppProps {
   gatewayUrl: string;
@@ -133,6 +134,23 @@ export function TuiApp({
           );
           break;
         }
+        case 'history':
+        case 'hist': {
+          void executeHistory({
+            conversationId: socket.conversationId,
+            gatewayUrl,
+            sessionCookie,
+            fetchMessages: fetchConversationMessages,
+          })
+            .then((result) => {
+              socket.addSystemMessage(result);
+            })
+            .catch((err: unknown) => {
+              const msg = err instanceof Error ? err.message : String(err);
+              socket.addSystemMessage(`Failed to fetch history: ${msg}`);
+            });
+          break;
+        }
         default:
           socket.addSystemMessage(`Local command not implemented: /${parsed.command}`);
       }

packages/cli/src/tui/commands/index.ts

@@ -3,3 +3,5 @@ export { commandRegistry, CommandRegistry } from './registry.js';
 export { executeHelp } from './local/help.js';
 export { executeStatus } from './local/status.js';
 export type { StatusContext } from './local/status.js';
+export { executeHistory } from './local/history.js';
+export type { HistoryContext } from './local/history.js';

packages/cli/src/tui/commands/local/history.ts

@@ -0,0 +1,53 @@
+import type { ConversationMessage } from '../../gateway-api.js';
+
+const CONTEXT_WINDOW = 200_000;
+const CHARS_PER_TOKEN = 4;
+
+function estimateTokens(messages: ConversationMessage[]): number {
+  const totalChars = messages.reduce((sum, m) => sum + (m.content?.length ?? 0), 0);
+  return Math.round(totalChars / CHARS_PER_TOKEN);
+}
+
+export interface HistoryContext {
+  conversationId: string | undefined;
+  conversationTitle?: string | null;
+  gatewayUrl: string;
+  sessionCookie: string | undefined;
+  fetchMessages: (
+    gatewayUrl: string,
+    sessionCookie: string,
+    conversationId: string,
+  ) => Promise<ConversationMessage[]>;
+}
+
+export async function executeHistory(ctx: HistoryContext): Promise<string> {
+  const { conversationId, conversationTitle, gatewayUrl, sessionCookie, fetchMessages } = ctx;
+
+  if (!conversationId) {
+    return 'No active conversation.';
+  }
+
+  if (!sessionCookie) {
+    return 'Not authenticated — cannot fetch conversation messages.';
+  }
+
+  const messages = await fetchMessages(gatewayUrl, sessionCookie, conversationId);
+
+  const userMessages = messages.filter((m) => m.role === 'user').length;
+  const assistantMessages = messages.filter((m) => m.role === 'assistant').length;
+  const totalMessages = messages.length;
+
+  const estimatedTokens = estimateTokens(messages);
+  const contextPercent = Math.round((estimatedTokens / CONTEXT_WINDOW) * 100);
+
+  const label = conversationTitle ?? conversationId;
+
+  const lines = [
+    `Conversation: ${label}`,
+    `Messages: ${totalMessages} (${userMessages} user, ${assistantMessages} assistant)`,
+    `Estimated tokens: ~${estimatedTokens.toLocaleString()}`,
+    `Context usage: ~${contextPercent}% of ${(CONTEXT_WINDOW / 1000).toFixed(0)}K`,
+  ];
+
+  return lines.join('\n');
+}

packages/cli/src/tui/commands/registry.ts

@@ -38,6 +38,15 @@ const LOCAL_COMMANDS: CommandDef[] = [
     available: true,
     scope: 'core',
   },
+  {
+    name: 'history',
+    description: 'Show conversation message count and context usage',
+    aliases: ['hist'],
+    args: undefined,
+    execution: 'local',
+    available: true,
+    scope: 'core',
+  },
   {
     name: 'clear',
     description: 'Clear the current conversation display',
@@ -64,6 +73,7 @@ const ALIASES: Record<string, string> = {
   a: 'agent',
   s: 'status',
   h: 'help',
+  hist: 'history',
   pref: 'preferences',
 };
 

packages/cli/src/tui/gateway-api.ts

@@ -361,6 +361,31 @@ export async function deleteMission(
   }
 }
 
+// ── Conversation Message types ──
+
+export interface ConversationMessage {
+  id: string;
+  role: 'user' | 'assistant' | 'system' | 'tool';
+  content: string;
+  createdAt: string;
+}
+
+// ── Conversation Message endpoints ──
+
+export async function fetchConversationMessages(
+  gatewayUrl: string,
+  sessionCookie: string,
+  conversationId: string,
+): Promise<ConversationMessage[]> {
+  const res = await fetch(
+    `${gatewayUrl}/api/conversations/${encodeURIComponent(conversationId)}/messages`,
+    {
+      headers: headers(sessionCookie, gatewayUrl),
+    },
+  );
+  return handleResponse<ConversationMessage[]>(res, 'Failed to fetch conversation messages');
+}
+
 // ── Mission Task endpoints ──
 
 export async function fetchMissionTasks(