Add multi-agent flow demo with shouter listener

Demonstrates message chaining: user -> greeter -> shouter -> user

- Add ShoutedResponse payload class (ALL CAPS response)
- Add handle_shout handler that forwards to original sender
- Update GreetingResponse to track original_sender
- Fix wrap_in_envelope to add xmlns="" to payloads
- Update organism.yaml with shouter listener
- Update tests for 2-listener configuration

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

config/organism.yaml

@@ -15,10 +15,16 @@ max_concurrent_per_agent: 5
 thread_scheduling: breadth-first
 
 listeners:
-  # The greeter listener responds to Greeting payloads
+  # The greeter receives Greeting, sends GreetingResponse to shouter
   - name: greeter
     payload_class: handlers.hello.Greeting
     handler: handlers.hello.handle_greeting
-    description: Responds with a greeting message
-    agent: false
-    broadcast: false
+    description: Receives greeting, forwards to shouter
+    agent: true
+
+  # The shouter receives GreetingResponse, sends ShoutedResponse back to user
+  - name: shouter
+    payload_class: handlers.hello.GreetingResponse
+    handler: handlers.hello.handle_shout
+    description: Shouts the greeting in ALL CAPS
+    agent: true

handlers/hello.py

@@ -1,17 +1,26 @@
 """
-hello.py — Hello World handler for testing the message pump.
+hello.py — Multi-agent hello world handlers for testing the message pump.
 
-This module provides:
-- Greeting: payload class (what the handler receives)
-- GreetingResponse: response payload (what the handler returns)
-- handle_greeting: async handler function
+This module demonstrates a multi-agent flow:
+  user -> greeter -> shouter -> user
+
+Payload classes:
+- Greeting: Initial request with a name
+- GreetingResponse: Greeter's response
+- ShoutedResponse: Shouter's ALL CAPS version
+
+Handlers:
+- handle_greeting: Receives Greeting, sends GreetingResponse to shouter
+- handle_shout: Receives GreetingResponse, sends ShoutedResponse to original sender
 
 Usage in organism.yaml:
     listeners:
       - name: greeter
         payload_class: handlers.hello.Greeting
         handler: handlers.hello.handle_greeting
-        description: Responds with a greeting message
+      - name: shouter
+        payload_class: handlers.hello.GreetingResponse
+        handler: handlers.hello.handle_shout
 """
 
 from dataclasses import dataclass
@@ -35,44 +44,82 @@ class Greeting:
 @xmlify
 @dataclass
 class GreetingResponse:
-    """Outgoing greeting response."""
+    """Greeter's response - will be forwarded to shouter."""
+    message: str
+    original_sender: str  # Track who started the conversation
+
+
+@xmlify
+@dataclass
+class ShoutedResponse:
+    """Shouter's ALL CAPS response - sent back to original sender."""
     message: str
 
 
 def wrap_in_envelope(payload_bytes: bytes, from_id: str, to_id: str, thread_id: str) -> bytes:
-    """Wrap a payload in a proper message envelope."""
+    """Wrap a payload in a proper message envelope.
+
+    Adds xmlns="" to payload to prevent it inheriting envelope namespace.
+    """
+    payload_str = payload_bytes.decode('utf-8')
+
+    # Add xmlns="" to payload root to keep it out of envelope namespace
+    if 'xmlns=' not in payload_str:
+        idx = payload_str.index('>')
+        payload_str = payload_str[:idx] + ' xmlns=""' + payload_str[idx:]
+
     return f"""<message xmlns="{ENVELOPE_NS}">
   <meta>
     <from>{from_id}</from>
     <to>{to_id}</to>
     <thread>{thread_id}</thread>
   </meta>
-  {payload_bytes.decode('utf-8')}
+  {payload_str}
 </message>""".encode('utf-8')
 
 
 async def handle_greeting(payload: Greeting, metadata: HandlerMetadata) -> bytes:
     """
-    Handle an incoming Greeting and respond with a GreetingResponse.
+    Handle an incoming Greeting and forward GreetingResponse to shouter.
 
-    Args:
-        payload: The deserialized Greeting instance
-        metadata: Contains thread_id, from_id, own_name
-
-    Returns:
-        XML bytes of the response envelope
+    Flow: user -> greeter -> shouter
     """
-    # Create response
-    response = GreetingResponse(message=f"Hello, {payload.name}!")
+    # Create response, tracking original sender for later
+    response = GreetingResponse(
+        message=f"Hello, {payload.name}!",
+        original_sender=metadata.from_id,
+    )
 
     # Serialize to XML
     response_tree = response.xml_value("GreetingResponse")
     payload_bytes = etree.tostring(response_tree, encoding='utf-8')
 
-    # Wrap in envelope - respond back to sender
+    # Forward to shouter (not back to sender)
     return wrap_in_envelope(
         payload_bytes=payload_bytes,
         from_id=metadata.own_name or "greeter",
-        to_id=metadata.from_id,  # Send back to whoever sent the greeting
+        to_id="shouter",  # Forward to shouter agent
+        thread_id=metadata.thread_id,
+    )
+
+
+async def handle_shout(payload: GreetingResponse, metadata: HandlerMetadata) -> bytes:
+    """
+    Handle GreetingResponse by shouting it back to original sender.
+
+    Flow: greeter -> shouter -> user
+    """
+    # Create ALL CAPS response
+    response = ShoutedResponse(message=payload.message.upper())
+
+    # Serialize to XML
+    response_tree = response.xml_value("ShoutedResponse")
+    payload_bytes = etree.tostring(response_tree, encoding='utf-8')
+
+    # Send back to original sender (tracked in payload)
+    return wrap_in_envelope(
+        payload_bytes=payload_bytes,
+        from_id=metadata.own_name or "shouter",
+        to_id=payload.original_sender,  # Back to whoever started the conversation
         thread_id=metadata.thread_id,
     )

tests/test_pump_integration.py

@@ -14,7 +14,7 @@ from unittest.mock import AsyncMock, patch
 
 from agentserver.message_bus import StreamPump, bootstrap, MessageState
 from agentserver.message_bus.stream_pump import ConfigLoader, ListenerConfig, OrganismConfig, Listener
-from handlers.hello import Greeting, GreetingResponse, handle_greeting, ENVELOPE_NS
+from handlers.hello import Greeting, GreetingResponse, handle_greeting, handle_shout, ENVELOPE_NS
 
 
 def make_envelope(payload_xml: str, from_id: str, to_id: str, thread_id: str) -> bytes:
@@ -50,11 +50,18 @@ class TestPumpBootstrap:
         config = ConfigLoader.load('config/organism.yaml')
 
         assert config.name == "hello-world"
-        assert len(config.listeners) == 1
+        assert len(config.listeners) == 2
+
+        # Greeter listener
         assert config.listeners[0].name == "greeter"
         assert config.listeners[0].payload_class == Greeting
         assert config.listeners[0].handler == handle_greeting
 
+        # Shouter listener
+        assert config.listeners[1].name == "shouter"
+        assert config.listeners[1].payload_class == GreetingResponse
+        assert config.listeners[1].handler == handle_shout
+
     @pytest.mark.asyncio
     async def test_bootstrap_creates_pump(self):
         """bootstrap() should create a configured pump."""
@@ -62,7 +69,9 @@ class TestPumpBootstrap:
 
         assert pump.config.name == "hello-world"
         assert "greeter.greeting" in pump.routing_table
+        assert "shouter.greetingresponse" in pump.routing_table
         assert pump.listeners["greeter"].payload_class == Greeting
+        assert pump.listeners["shouter"].payload_class == GreetingResponse
 
     @pytest.mark.asyncio
     async def test_bootstrap_generates_xsd(self):