fix(invoke): show full session ID and print resume command on exit (aws#904)

* fix(invoke): show full session ID and print resume command on exit

The invoke TUI truncated the session ID to 8 characters, making it
impossible to copy the full UUID needed for --session-id. Additionally,
there was no guidance on how to resume a session after exiting.

- Display full session ID in the TUI header instead of truncating
- Print a colored resume command after TUI exit (both Esc and Ctrl+C)
- Use Ink's unmount() instead of process.exit(0) for clean shutdown,
  which also fixes the update notifier not showing on Esc exit

* fix: only show resume message when a session was actually used

Author: aidandaly24

src/cli/cli.ts

@@ -224,4 +224,10 @@ export const main = async (argv: string[]) => {
 
   // Telemetry notice already printed above; only run update check here.
   await printPostCommandNotices(false, updateCheck);
+
+  const exitMessage = getExitMessage();
+  if (exitMessage) {
+    console.log(`\n${exitMessage}`);
+    clearExitMessage();
+  }
 };

src/cli/commands/invoke/command.tsx

@@ -168,10 +168,10 @@ export const registerInvoke = (program: Command) => {
             });
           } else {
             // No CLI options - interactive TUI mode (headers still passed if provided)
-            const { waitUntilExit } = render(
+            const { waitUntilExit, unmount } = render(
               <InvokeScreen
                 isInteractive={true}
-                onExit={() => process.exit(0)}
+                onExit={() => unmount()}
                 initialSessionId={cliOptions.sessionId}
                 initialUserId={cliOptions.userId}
                 initialHeaders={headers}

src/cli/tui/screens/invoke/InvokeScreen.tsx

@@ -1,5 +1,6 @@
 import { buildTraceConsoleUrl } from '../../../operations/traces';
 import { GradientText, LogLink, Panel, Screen, SelectList, TextInput } from '../../components';
+import { setExitMessage } from '../../exit-message';
 import { useInvokeFlow } from './useInvokeFlow';
 import { Box, Text, useInput, useStdout } from 'ink';
 import React, { useCallback, useEffect, useMemo, useRef, useState } from 'react';
@@ -167,6 +168,14 @@ export function InvokeScreen({
   const justCancelledRef = useRef(false);
   const mcpFetchTriggeredRef = useRef(false);
 
+  useEffect(() => {
+    if (sessionId && messages.length > 0) {
+      const cyan = '\x1b[36m';
+      const reset = '\x1b[0m';
+      setExitMessage(`To resume this session, run: ${cyan}agentcore invoke --session-id ${sessionId}${reset}`);
+    }
+  }, [sessionId, messages.length]);
+
   // Compute auth type early so hooks can reference it
   const currentAgent = config?.runtimes[selectedAgent];
   const isCustomJwt = currentAgent?.authorizerType === 'CUSTOM_JWT';
@@ -420,7 +429,7 @@ export function InvokeScreen({
       {mode !== 'select-agent' && (
         <Box>
           <Text>Session: </Text>
-          <Text color="magenta">{sessionId?.slice(0, 8) ?? 'none'}</Text>
+          <Text color="magenta">{sessionId ?? 'none'}</Text>
         </Box>
       )}
       {mode !== 'select-agent' && (