fix: prevent presetParameters from being overridden by tool-call input

agentscope-core/src/main/java/io/agentscope/core/tool/ToolExecutor.java

@@ -219,16 +219,15 @@ private Mono<ToolResultBlock> executeCore(ToolCallParam param) {
         // Create emitter for streaming
         ToolEmitter toolEmitter = new DefaultToolEmitter(toolCall, getEffectiveChunkCallback());
 
-        // Merge preset parameters with input
+        // Merge input with preset parameters. Preset values win so framework-controlled
+        // parameters remain immutable from the caller/LLM perspective.
         Map<String, Object> mergedInput = new HashMap<>();
-        if (registered != null) {
-            mergedInput.putAll(registered.getPresetParameters());
-        }
-        if (param.getInput() != null && !param.getInput().isEmpty()) {
+        if (!param.getInput().isEmpty()) {
             mergedInput.putAll(param.getInput());
-        } else if (toolCall.getInput() != null) {
+        } else if (!toolCall.getInput().isEmpty()) {
             mergedInput.putAll(toolCall.getInput());
         }
+        mergedInput.putAll(registered.getPresetParameters());
 
         // Build final execution param
         ToolCallParam executionParam =

agentscope-core/src/test/java/io/agentscope/core/tool/ToolExecutorTest.java

@@ -271,6 +271,82 @@ public Mono<ToolResultBlock> callAsync(ToolCallParam param) {
         assertEquals(2, successCount, "Exactly two calls should succeed");
     }
 
+    @Test
+    @DisplayName("Should apply preset parameters after explicit ToolCallParam input")
+    void shouldApplyPresetParametersAfterExplicitInput() {
+        class OverrideTool {
+            @Tool(description = "Test preset precedence with explicit ToolCallParam input")
+            public ToolResultBlock testOverride(
+                    @ToolParam(name = "param1") String param1,
+                    @ToolParam(name = "param2") String param2) {
+                return ToolResultBlock.text(
+                        String.format("param1: %s, param2: %s", param1, param2));
+            }
+        }
+
+        toolkit.registration()
+                .tool(new OverrideTool())
+                .presetParameters(
+                        Map.of(
+                                "testOverride",
+                                Map.of("param1", "preset_value1", "param2", "preset_value2")))
+                .apply();
+
+        Map<String, Object> explicitInput = Map.of("param1", "agent_value1");
+        ToolUseBlock toolCall =
+                ToolUseBlock.builder()
+                        .id("call-override")
+                        .name("testOverride")
+                        .input(Map.of())
+                        .content("{}")
+                        .build();
+
+        ToolResultBlock result =
+                toolkit.callTool(
+                                ToolCallParam.builder()
+                                        .toolUseBlock(toolCall)
+                                        .input(explicitInput)
+                                        .build())
+                        .block(TIMEOUT);
+
+        assertNotNull(result, "Result should not be null");
+        String resultText = extractFirstText(result);
+        assertTrue(
+                resultText.contains("param1: preset_value1"),
+                "Preset value should override explicit ToolCallParam input");
+        assertTrue(resultText.contains("param2: preset_value2"), "Preset value should be used");
+    }
+
+    @Test
+    @DisplayName("Should use only preset parameters when both input sources are absent")
+    void shouldUseOnlyPresetParametersWhenInputsAbsent() {
+        class PresetOnlyTool {
+            @Tool(description = "Test preset usage when no explicit inputs are present")
+            public ToolResultBlock presetOnly(@ToolParam(name = "param1") String param1) {
+                return ToolResultBlock.text("param1: " + param1);
+            }
+        }
+
+        toolkit.registration()
+                .tool(new PresetOnlyTool())
+                .presetParameters(Map.of("presetOnly", Map.of("param1", "preset_value1")))
+                .apply();
+
+        ToolUseBlock toolCall =
+                ToolUseBlock.builder()
+                        .id("call-preset-only")
+                        .name("presetOnly")
+                        .content("{}")
+                        .build();
+
+        ToolResultBlock result =
+                toolkit.callTool(ToolCallParam.builder().toolUseBlock(toolCall).build())
+                        .block(TIMEOUT);
+
+        assertNotNull(result, "Result should not be null");
+        assertEquals("param1: preset_value1", extractFirstText(result));
+    }
+
     @Test
     @DisplayName("Should format all error messages consistently")
     void testErrorMessageFormat() {

agentscope-core/src/test/java/io/agentscope/core/tool/ToolkitTest.java

@@ -673,7 +673,7 @@ public ToolResultBlock testWithContext(
     }
 
     @Test
-    @DisplayName("Should allow agent parameters to override preset parameters")
+    @DisplayName("Should keep preset parameters authoritative over agent parameters")
     void testPresetParametersOverride() {
         class OverrideTool {
             @Tool(description = "Test tool for parameter override")
@@ -692,7 +692,7 @@ public ToolResultBlock testOverride(
                         Map.of("param1", "preset_value1", "param2", "preset_value2"));
         toolkit.registration().tool(new OverrideTool()).presetParameters(presetParams).apply();
 
-        // Call with agent providing param1 (should override preset)
+        // Call with agent providing param1 (preset should still win)
         Map<String, Object> overrideInput = Map.of("param1", "agent_value1");
         ToolUseBlock toolCall =
                 ToolUseBlock.builder()
@@ -705,9 +705,10 @@ public ToolResultBlock testOverride(
                 toolkit.callTool(ToolCallParam.builder().toolUseBlock(toolCall).build()).block();
         String resultText = getResultText(result);
 
-        // param1 should be overridden by agent, param2 should use preset
+        // Preset values should not be overridden by agent input
         assertTrue(
-                resultText.contains("param1: agent_value1"), "Agent value should override preset");
+                resultText.contains("param1: preset_value1"),
+                "Preset value should override agent input");
         assertTrue(resultText.contains("param2: preset_value2"), "Preset value should be used");
     }