Enable A2A streaming capability by default

Wrap FastA2A agent card generation so Agent Zero advertises streaming support on A2A endpoints by default.

Add focused regression coverage for the agent-card capability rewrite and proxy wiring, and update the helper DOX profile for the new wrapper.

helpers/fasta2a_server.py

@@ -2,11 +2,13 @@
 import asyncio
 import uuid
 import atexit
+import json
 from typing import Any, List
 import contextlib
 import threading
 
 from helpers import settings, projects
+from starlette.responses import Response as StarletteResponse
 from starlette.requests import Request
 
 # Local imports
@@ -61,6 +63,27 @@ except ImportError:  # pragma: no cover – library not installed
 _PRINTER = PrintStyle(italic=True, font_color="purple", padding=False)
 
 
+def _enable_streaming_capability(agent_card_body: bytes) -> bytes:
+    """Return an agent-card JSON body with A2A streaming enabled."""
+    agent_card = json.loads(agent_card_body)
+    capabilities = agent_card.get("capabilities")
+    if not isinstance(capabilities, dict):
+        capabilities = {}
+        agent_card["capabilities"] = capabilities
+    capabilities["streaming"] = True
+    return json.dumps(agent_card, separators=(",", ":"), ensure_ascii=False).encode("utf-8")
+
+
+class AgentZeroFastA2A(FastA2A):  # type: ignore[misc]
+    """FastA2A app with Agent Zero defaults layered over library defaults."""
+
+    async def _agent_card_endpoint(self, request: Request) -> StarletteResponse:
+        response = await super()._agent_card_endpoint(request)
+        body = _enable_streaming_capability(response.body)
+        self._agent_card_json_schema = body
+        return StarletteResponse(content=body, media_type="application/json")
+
+
 class AgentZeroWorker(Worker):  # type: ignore[misc]
     """Agent Zero implementation of FastA2A Worker."""
 
@@ -242,7 +265,7 @@ class DynamicA2AProxy:
             }
 
             # Create new FastA2A app with proper thread safety
-            new_app = FastA2A(  # type: ignore
+            new_app = AgentZeroFastA2A(  # type: ignore
                 storage=storage,
                 broker=broker,
                 name="Agent Zero",

helpers/fasta2a_server.py.dox.md

@@ -11,6 +11,8 @@
 - `fasta2a_server.py` owns the runtime implementation.
 - `fasta2a_server.py.dox.md` owns durable notes about responsibilities, contracts, side effects, and verification for that implementation.
 - Classes:
+- `AgentZeroFastA2A` (`FastA2A`)
+  - `async _agent_card_endpoint(self, request: Request) -> StarletteResponse`
 - `AgentZeroWorker` (`Worker`)
   - `async run_task(self, params: Any) -> None`
   - `async cancel_task(self, params: Any) -> None`
@@ -20,6 +22,7 @@
   - `get_instance()`
   - `reconfigure(self, token: str)`
 - Top-level functions:
+- `_enable_streaming_capability(agent_card_body: bytes) -> bytes`: Ensure the generated A2A agent card advertises streaming support.
 - `is_available()`: Check if FastA2A is available and properly configured.
 - `get_proxy()`: Get the FastA2A proxy instance.
 - Notable constants/configuration names: `_PRINTER`.
@@ -28,12 +31,13 @@
 
 - Helper modules own reusable framework APIs and must preserve public callers unless all callers, tests, and docs are updated together.
 - Update this file whenever public functions, classes, persistence behavior, path/security assumptions, side effects, or cross-module contracts change.
+- Agent Zero wraps `FastA2A` with `AgentZeroFastA2A` so the generated agent card sets `capabilities.streaming` to `true` by default.
 - Observed side-effect areas: filesystem writes, filesystem deletion, settings/state persistence, secret handling, scheduler state.
-- Imported dependency areas include: `agent`, `asyncio`, `atexit`, `contextlib`, `helpers`, `helpers.persist_chat`, `helpers.print_style`, `initialize`, `starlette.requests`, `threading`, `typing`, `uuid`.
+- Imported dependency areas include: `agent`, `asyncio`, `atexit`, `contextlib`, `helpers`, `helpers.persist_chat`, `helpers.print_style`, `initialize`, `json`, `starlette.requests`, `starlette.responses`, `threading`, `typing`, `uuid`.
 
 ## Key Concepts
 
-- Important called helpers/classes observed in the source: `PrintStyle`, `DynamicA2AProxy.get_instance`, `super.__init__`, `join`, `UserMessage`, `threading.Lock`, `atexit.register`, `self._configure`, `settings.get_settings`, `path.startswith`, `self._convert_message`, `initialize_agent`, `AgentContext`, `context.log.log`, `context.communicate`, `context.reset`, `AgentContext.remove`, `remove_chat`, `self.storage.update_task`, `self._register_shutdown`.
+- Important called helpers/classes observed in the source: `PrintStyle`, `DynamicA2AProxy.get_instance`, `json.loads`, `json.dumps`, `super.__init__`, `super._agent_card_endpoint`, `join`, `UserMessage`, `threading.Lock`, `atexit.register`, `self._configure`, `settings.get_settings`, `path.startswith`, `self._convert_message`, `initialize_agent`, `AgentContext`, `context.log.log`, `context.communicate`, `context.reset`, `AgentContext.remove`, `remove_chat`, `self.storage.update_task`, `self._register_shutdown`.
 - Keep request/response, tool, or helper semantics documented here at the same time as source changes.
 
 ## Work Guidance
@@ -45,7 +49,8 @@
 ## Verification
 
 - Run targeted tests for changed helper behavior; run security regressions for auth, filesystem, WebSocket, tunnel, upload, or secret-handling helpers.
-- No direct test reference was found by name search; choose the nearest behavioral test or perform a focused smoke check.
+- Related tests:
+  - `tests/test_fasta2a_server.py`
 
 ## Child DOX Index
 

tests/test_fasta2a_server.py

@@ -0,0 +1,102 @@
+from __future__ import annotations
+
+import importlib
+import json
+import sys
+import types
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+if str(ROOT) not in sys.path:
+    sys.path.insert(0, str(ROOT))
+
+
+def _load_fasta2a_server(monkeypatch):
+    settings_stub = types.ModuleType("helpers.settings")
+    settings_stub.get_settings = lambda: {
+        "a2a_server_enabled": True,
+        "mcp_server_token": "test-token",
+    }
+    monkeypatch.setitem(sys.modules, "helpers.settings", settings_stub)
+
+    projects_stub = types.ModuleType("helpers.projects")
+    projects_stub.activate_project = lambda *args, **kwargs: None
+    monkeypatch.setitem(sys.modules, "helpers.projects", projects_stub)
+
+    print_style_stub = types.ModuleType("helpers.print_style")
+
+    class _PrintStyle:
+        def __init__(self, *args, **kwargs):
+            pass
+
+        def print(self, *args, **kwargs):
+            pass
+
+    print_style_stub.PrintStyle = _PrintStyle
+    monkeypatch.setitem(sys.modules, "helpers.print_style", print_style_stub)
+
+    starlette_stub = types.ModuleType("starlette")
+    starlette_responses_stub = types.ModuleType("starlette.responses")
+
+    class _Response:
+        def __init__(self, content=b"", media_type=None, *args, **kwargs):
+            self.body = content if isinstance(content, bytes) else str(content).encode()
+            self.media_type = media_type
+
+    starlette_responses_stub.Response = _Response
+    starlette_requests_stub = types.ModuleType("starlette.requests")
+    starlette_requests_stub.Request = object
+    monkeypatch.setitem(sys.modules, "starlette", starlette_stub)
+    monkeypatch.setitem(sys.modules, "starlette.responses", starlette_responses_stub)
+    monkeypatch.setitem(sys.modules, "starlette.requests", starlette_requests_stub)
+
+    agent_stub = types.ModuleType("agent")
+    agent_stub.AgentContext = type(
+        "AgentContext",
+        (),
+        {"remove": staticmethod(lambda *args, **kwargs: None)},
+    )
+    agent_stub.UserMessage = lambda **kwargs: types.SimpleNamespace(**kwargs)
+    agent_stub.AgentContextType = types.SimpleNamespace(BACKGROUND="background")
+    monkeypatch.setitem(sys.modules, "agent", agent_stub)
+
+    initialize_stub = types.ModuleType("initialize")
+    initialize_stub.initialize_agent = lambda: {}
+    monkeypatch.setitem(sys.modules, "initialize", initialize_stub)
+
+    persist_chat_stub = types.ModuleType("helpers.persist_chat")
+    persist_chat_stub.remove_chat = lambda *args, **kwargs: None
+    monkeypatch.setitem(sys.modules, "helpers.persist_chat", persist_chat_stub)
+
+    sys.modules.pop("helpers.fasta2a_server", None)
+    return importlib.import_module("helpers.fasta2a_server")
+
+
+def test_a2a_agent_card_streaming_capability_is_enabled_by_default(monkeypatch):
+    module = _load_fasta2a_server(monkeypatch)
+
+    updated = module._enable_streaming_capability(
+        b'{"name":"Agent Zero","capabilities":{"streaming":false,"pushNotifications":false}}'
+    )
+
+    agent_card = json.loads(updated)
+    assert agent_card["capabilities"]["streaming"] is True
+    assert agent_card["capabilities"]["pushNotifications"] is False
+
+
+def test_a2a_agent_card_streaming_capability_creates_missing_block(monkeypatch):
+    module = _load_fasta2a_server(monkeypatch)
+
+    updated = module._enable_streaming_capability(b'{"name":"Agent Zero"}')
+
+    assert json.loads(updated)["capabilities"] == {"streaming": True}
+
+
+def test_a2a_proxy_uses_streaming_enabled_fast_a2a_wrapper(monkeypatch):
+    module = _load_fasta2a_server(monkeypatch)
+    proxy = object.__new__(module.DynamicA2AProxy)
+
+    proxy._configure()
+
+    assert isinstance(proxy.app, module.AgentZeroFastA2A)