Merge pull request #2328 from glifocat/wip/destinations-default-to-origin

fix: default reply destination to message origin in multi-destination groups

container/agent-runner/src/destinations.ts

@@ -120,6 +120,10 @@ function buildDestinationsSection(): string {
   lines.push('Text outside of `<message>` blocks is scratchpad — logged but not sent anywhere.');
   lines.push('Use `<internal>...</internal>` to make scratchpad intent explicit.');
   lines.push('');
+  lines.push(
+    '**Default routing**: when replying to an incoming message, address the same destination the message came `from` — every inbound `<message>` tag carries a `from="name"` attribute that names the origin destination. Only address a different destination when the request itself asks you to (e.g., "tell Laura that…").',
+  );
+  lines.push('');
   lines.push(
     'To send a message mid-response (e.g., an acknowledgment before a long task), call the `send_message` MCP tool with the `to` parameter set to a destination name.',
   );