Add logos::CallCaller, the in-process stand-in for RPC caller glue.

Generated logos_module_set_call_caller pushes onto this stack. Unit tests
that construct an impl directly skip that glue; CallCaller opens the same
stack so every C++ module can simulate a dispatch without a second
identity path in the handler.

Co-authored-by: Cursor <cursoragent@cursor.com>

cpp/logos_caller.h

@@ -286,4 +286,38 @@ LOGOS_CALLER_LOCAL inline const LogosCaller& currentCaller()
     return stack.back();
 }
 
+// RAII stand-in for the generated logos_module_set_call_caller() push.
+//
+// Production glue (plugin-qt qt-host-generator) pulls the host's
+// CallerScope document and pushes it onto THIS stack for the duration of
+// the handler. Unit tests that construct an impl directly skip that glue,
+// so they open the same stack with CallCaller. That is the supported way
+// to simulate a dispatch for ANY C++ module — not a per-module helper and
+// not a second identity path inside the handler.
+class CallCaller {
+public:
+    static CallCaller module(const std::string& name)
+    {
+        return CallCaller(std::string(R"({"kind":"module","name":")") + name + "\"}");
+    }
+    static CallCaller host() { return CallCaller(std::string(R"({"kind":"host"})")); }
+
+    explicit CallCaller(const char* json)
+        : CallCaller(std::string(json ? json : "")) {}
+
+    ~CallCaller() { detail::setCallCaller(nullptr); }
+
+    CallCaller(const CallCaller&) = delete;
+    CallCaller& operator=(const CallCaller&) = delete;
+    CallCaller(CallCaller&&) = delete;
+    CallCaller& operator=(CallCaller&&) = delete;
+
+private:
+    explicit CallCaller(std::string json) : m_json(std::move(json))
+    {
+        detail::setCallCaller(m_json.c_str());
+    }
+    std::string m_json;
+};
+
 } // namespace logos

tests/sdk/test_logos_caller.cpp

@@ -376,3 +376,18 @@ TEST_F(CallerScope, ACopyOutlivesTheDispatchThatProducedIt)
     EXPECT_TRUE(copied.isModule("chat_module"));
     EXPECT_TRUE(logos::currentCaller().isUnknown());
 }
+
+TEST_F(CallerScope, CallCallerRaiiIsTheDispatchStandIn)
+{
+    EXPECT_TRUE(logos::currentCaller().isUnknown());
+    {
+        const logos::CallCaller caller = logos::CallCaller::module("chat_module");
+        EXPECT_TRUE(logos::currentCaller().isModule("chat_module"));
+        {
+            const logos::CallCaller inner = logos::CallCaller::host();
+            EXPECT_TRUE(logos::currentCaller().isHost());
+        }
+        EXPECT_TRUE(logos::currentCaller().isModule("chat_module"));
+    }
+    EXPECT_TRUE(logos::currentCaller().isUnknown());
+}