fix(subagents): use model override for tools and middleware (#2641)

* fix(subagents): use model override for tools and middleware

* fix(config): resolve effective subagent model

* fix(subagents): defer app config loading

* fix(subagents): fully defer config.yaml load in executor __init__

The previous attempt only relocated the explicit get_app_config() call,
but left resolve_subagent_model_name(...) running eagerly in __init__.
That helper has its own internal get_app_config() fallback, which still
fired when both app_config and parent_model were None and
config.model == "inherit" — exactly the path unit tests hit, breaking
21 tests in CI with FileNotFoundError: config.yaml.

Skip the eager resolve in __init__ when it would require loading the
config file, and defer to _create_agent (which already has the
app_config or get_app_config() fallback).

backend/tests/test_tool_error_handling_middleware.py

@@ -9,11 +9,20 @@ from deerflow.agents.middlewares.tool_error_handling_middleware import (
     ToolErrorHandlingMiddleware,
     build_subagent_runtime_middlewares,
 )
+from deerflow.agents.middlewares.view_image_middleware import ViewImageMiddleware
 from deerflow.config.app_config import AppConfig, CircuitBreakerConfig
 from deerflow.config.guardrails_config import GuardrailsConfig
+from deerflow.config.model_config import ModelConfig
 from deerflow.config.sandbox_config import SandboxConfig
 
 
+def _request(name: str = "web_search", tool_call_id: str | None = "tc-1"):
+    tool_call = {"name": name}
+    if tool_call_id is not None:
+        tool_call["id"] = tool_call_id
+    return SimpleNamespace(tool_call=tool_call)
+
+
 def _module(name: str, **attrs):
     module = ModuleType(name)
     for key, value in attrs.items():
@@ -21,19 +30,62 @@ def _module(name: str, **attrs):
     return module
 
 
-def _make_app_config() -> AppConfig:
+def _make_app_config(*, supports_vision: bool = False) -> AppConfig:
     return AppConfig(
+        models=[
+            ModelConfig(
+                name="test-model",
+                display_name="test-model",
+                description=None,
+                use="langchain_openai:ChatOpenAI",
+                model="test-model",
+                supports_vision=supports_vision,
+            )
+        ],
         sandbox=SandboxConfig(use="test"),
         guardrails=GuardrailsConfig(enabled=False),
         circuit_breaker=CircuitBreakerConfig(failure_threshold=7, recovery_timeout_sec=11),
     )
 
 
-def _request(name: str = "web_search", tool_call_id: str | None = "tc-1"):
-    tool_call = {"name": name}
-    if tool_call_id is not None:
-        tool_call["id"] = tool_call_id
-    return SimpleNamespace(tool_call=tool_call)
+def _stub_runtime_middleware_imports(monkeypatch: pytest.MonkeyPatch) -> None:
+    class FakeMiddleware:
+        def __init__(self, *args, **kwargs):
+            self.args = args
+            self.kwargs = kwargs
+
+    class FakeLLMErrorHandlingMiddleware:
+        def __init__(self, *, app_config):
+            self.app_config = app_config
+
+    monkeypatch.setitem(
+        sys.modules,
+        "deerflow.agents.middlewares.llm_error_handling_middleware",
+        _module(
+            "deerflow.agents.middlewares.llm_error_handling_middleware",
+            LLMErrorHandlingMiddleware=FakeLLMErrorHandlingMiddleware,
+        ),
+    )
+    monkeypatch.setitem(
+        sys.modules,
+        "deerflow.agents.middlewares.thread_data_middleware",
+        _module("deerflow.agents.middlewares.thread_data_middleware", ThreadDataMiddleware=FakeMiddleware),
+    )
+    monkeypatch.setitem(
+        sys.modules,
+        "deerflow.sandbox.middleware",
+        _module("deerflow.sandbox.middleware", SandboxMiddleware=FakeMiddleware),
+    )
+    monkeypatch.setitem(
+        sys.modules,
+        "deerflow.agents.middlewares.dangling_tool_call_middleware",
+        _module("deerflow.agents.middlewares.dangling_tool_call_middleware", DanglingToolCallMiddleware=FakeMiddleware),
+    )
+    monkeypatch.setitem(
+        sys.modules,
+        "deerflow.agents.middlewares.sandbox_audit_middleware",
+        _module("deerflow.agents.middlewares.sandbox_audit_middleware", SandboxAuditMiddleware=FakeMiddleware),
+    )
 
 
 def test_build_subagent_runtime_middlewares_threads_app_config_to_llm_middleware(monkeypatch: pytest.MonkeyPatch):
@@ -166,3 +218,30 @@ async def test_awrap_tool_call_reraises_graph_interrupt():
 
     with pytest.raises(GraphInterrupt):
         await middleware.awrap_tool_call(req, _interrupt)
+
+
+def test_subagent_runtime_middlewares_include_view_image_for_vision_model(monkeypatch):
+    app_config = _make_app_config(supports_vision=True)
+    _stub_runtime_middleware_imports(monkeypatch)
+
+    middlewares = build_subagent_runtime_middlewares(app_config=app_config, model_name="test-model")
+
+    assert any(isinstance(middleware, ViewImageMiddleware) for middleware in middlewares)
+
+
+def test_subagent_runtime_middlewares_include_view_image_for_default_vision_model(monkeypatch):
+    app_config = _make_app_config(supports_vision=True)
+    _stub_runtime_middleware_imports(monkeypatch)
+
+    middlewares = build_subagent_runtime_middlewares(app_config=app_config, model_name=None)
+
+    assert any(isinstance(middleware, ViewImageMiddleware) for middleware in middlewares)
+
+
+def test_subagent_runtime_middlewares_skip_view_image_for_text_model(monkeypatch):
+    app_config = _make_app_config(supports_vision=False)
+    _stub_runtime_middleware_imports(monkeypatch)
+
+    middlewares = build_subagent_runtime_middlewares(app_config=app_config, model_name="test-model")
+
+    assert not any(isinstance(middleware, ViewImageMiddleware) for middleware in middlewares)