Input processor for removing empty toolcall list from input

src/llm/BUILD

@@ -156,13 +156,15 @@ ovms_cc_library(
             "io_processing/input_processors/chat_template_adapter.hpp",
             "io_processing/chat_template/caps.hpp",
             "io_processing/input_processors/empty_content_array_normalization_processor.hpp",
+            "io_processing/input_processors/empty_tool_calls_array_removing_processor.hpp",
             "io_processing/input_processors/raw_prompt_extractor.hpp",
             "io_processing/input_processors/text_content_normalization_processor.hpp",
             "io_processing/input_processors/tokenization_processor.hpp"],
     srcs = ["io_processing/input_processors/image_decoding_processor.cpp",
             "io_processing/input_processors/chat_template_processor.cpp",
             "io_processing/input_processors/chat_template_adapter.cpp",
             "io_processing/input_processors/empty_content_array_normalization_processor.cpp",
+            "io_processing/input_processors/empty_tool_calls_array_removing_processor.cpp",
             "io_processing/input_processors/text_content_normalization_processor.cpp",
             "io_processing/input_processors/tokenization_processor.cpp"],
     deps = [

src/llm/io_processing/input_processor.cpp

@@ -24,6 +24,7 @@
 #include "../../logging.hpp"
 #include "input_processors/chat_template_processor.hpp"
 #include "input_processors/empty_content_array_normalization_processor.hpp"
+#include "input_processors/empty_tool_calls_array_removing_processor.hpp"
 #include "input_processors/image_decoding_processor.hpp"
 #include "input_processors/chat_template_adapter.hpp"
 #include "input_processors/raw_prompt_extractor.hpp"
@@ -41,6 +42,7 @@ InputProcessor::InputProcessor(InputProcessorContext& context,
     if (isChatPath) {
         // Normalize empty content arrays to null before any content-aware processor runs.
         processors.emplace_back(std::make_unique<EmptyContentArrayNormalizationProcessor>());
+        processors.emplace_back(std::make_unique<EmptyToolCallsArrayRemovingProcessor>());
 
         // Flatten text-only content arrays for both LM and VLM. Arrays that contain
         // images (or other modalities) are left untouched for ImageDecodingProcessor.

src/llm/io_processing/input_processors/empty_tool_calls_array_removing_processor.cpp

@@ -0,0 +1,42 @@
+//*****************************************************************************
+// Copyright 2026 Intel Corporation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//*****************************************************************************
+
+#include "empty_tool_calls_array_removing_processor.hpp"
+
+#include <variant>
+
+namespace ovms {
+
+absl::Status EmptyToolCallsArrayRemovingProcessor::process(InputRequest& req) {
+    if (!std::holds_alternative<ov::genai::ChatHistory>(req.input)) {
+        return absl::Status(absl::StatusCode::kInternal,
+            "EmptyToolCallsArrayRemovingProcessor received input that is not a ChatHistory");
+    }
+    ov::genai::ChatHistory& chatHistory = std::get<ov::genai::ChatHistory>(req.input);
+    for (size_t i = 0; i < chatHistory.size(); i++) {
+        if (!chatHistory[i].contains("tool_calls")) {
+            continue;
+        }
+
+        const auto toolCalls = chatHistory[i]["tool_calls"];
+        if (toolCalls.is_array() && toolCalls.size() == 0) {
+            chatHistory[i].erase("tool_calls");
+        }
+    }
+    return absl::OkStatus();
+}
+
+}  // namespace ovms

src/llm/io_processing/input_processors/empty_tool_calls_array_removing_processor.hpp

@@ -0,0 +1,30 @@
+//*****************************************************************************
+// Copyright 2026 Intel Corporation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//*****************************************************************************
+#pragma once
+
+#include "../base_input_processor.hpp"
+
+namespace ovms {
+
+// Removes empty tool_calls arrays ("tool_calls": []) from ChatHistory messages.
+// Runs for all chat paths (LM and VLM) and must execute before ChatTemplateProcessor
+// so downstream processors and chat templates do not render an empty tool_calls list.
+class EmptyToolCallsArrayRemovingProcessor : public BaseInputProcessor {
+public:
+    absl::Status process(InputRequest& req) override;
+};
+
+}  // namespace ovms

src/test/llm/input_processing/empty_tool_calls_array_removing_processor_test.cpp

@@ -0,0 +1,73 @@
+//*****************************************************************************
+// Copyright 2026 Intel Corporation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//*****************************************************************************
+#include <string>
+
+#include <gtest/gtest.h>
+#include <openvino/genai/chat_history.hpp>
+
+#include "../../../llm/io_processing/input_processors/empty_tool_calls_array_removing_processor.hpp"
+#include "../../../llm/io_processing/input_request.hpp"
+
+using namespace ovms;
+
+// Helpers ----------------------------------------------------------------
+
+static InputRequest makeChatRequest(ov::genai::ChatHistory chatHistory) {
+    InputRequest req;
+    req.input = std::move(chatHistory);
+    return req;
+}
+
+// Tests ------------------------------------------------------------------
+
+TEST(EmptyToolCallsArrayRemovingProcessorTest, EmptyToolCallsArrayRemoved) {
+    ov::genai::ChatHistory history;
+    ov::AnyMap msg = {{"role", std::string("user")}};
+    msg["content"] = ov::genai::JsonContainer::from_json_string("\"What is the weather in Szczecin?\"");
+    msg["tool_calls"] = ov::genai::JsonContainer::from_json_string("[]");
+    history.push_back(msg);
+
+    InputRequest req = makeChatRequest(history);
+    EmptyToolCallsArrayRemovingProcessor processor;
+    const auto status = processor.process(req);
+
+    EXPECT_TRUE(status.ok());
+    const auto& result = std::get<ov::genai::ChatHistory>(req.input);
+    EXPECT_FALSE(result[0].contains("tool_calls"));
+    EXPECT_TRUE(result[0]["content"].is_string());
+    EXPECT_EQ(result[0]["content"].as_string().value_or(""), "What is the weather in Szczecin?");
+}
+
+TEST(EmptyToolCallsArrayRemovingProcessorTest, NonEmptyArrayPreserved) {
+    ov::genai::ChatHistory history;
+    ov::AnyMap msg = {{"role", std::string("assistant")}};
+    msg["tool_calls"] = ov::genai::JsonContainer::from_json_string(
+        R"([{"name":"get_weather","parameters":{"city":"Szczecin"}}])");
+
+    history.push_back(msg);
+
+    InputRequest req = makeChatRequest(history);
+    EmptyToolCallsArrayRemovingProcessor processor;
+    const auto status = processor.process(req);
+
+    EXPECT_TRUE(status.ok());
+    const auto& result = std::get<ov::genai::ChatHistory>(req.input);
+    ASSERT_TRUE(result[0]["tool_calls"].is_array());
+    EXPECT_EQ(result[0]["tool_calls"].size(), 1u);
+    EXPECT_EQ(result[0]["tool_calls"][0]["name"].as_string().value_or(""), "get_weather");
+    ASSERT_TRUE(result[0]["tool_calls"][0].contains("parameters"));
+    EXPECT_EQ(result[0]["tool_calls"][0]["parameters"]["city"].as_string().value_or(""), "Szczecin");
+}