fix: send tool_result blocks for skipped tools in native protocol

src/core/assistant-message/__tests__/presentAssistantMessage-images.spec.ts

@@ -202,4 +202,159 @@ describe("presentAssistantMessage - Image Handling in Native Tool Calls", () =>
 		// Should have fallback text
 		expect(toolResult.content).toBeTruthy()
 	})
+
+	describe("Multiple tool calls handling", () => {
+		it("should send tool_result with is_error for skipped tools in native protocol when didRejectTool is true", async () => {
+			// Simulate multiple tool calls with native protocol (all have IDs)
+			const toolCallId1 = "tool_call_001"
+			const toolCallId2 = "tool_call_002"
+
+			mockTask.assistantMessageContent = [
+				{
+					type: "tool_use",
+					id: toolCallId1,
+					name: "read_file",
+					params: { path: "test.txt" },
+				},
+				{
+					type: "tool_use",
+					id: toolCallId2,
+					name: "write_to_file",
+					params: { path: "output.txt", content: "test" },
+				},
+			]
+
+			// First tool is rejected
+			mockTask.didRejectTool = true
+
+			// Process the second tool (should be skipped)
+			mockTask.currentStreamingContentIndex = 1
+			await presentAssistantMessage(mockTask)
+
+			// Find the tool_result for the second tool
+			const toolResult = mockTask.userMessageContent.find(
+				(item: any) => item.type === "tool_result" && item.tool_use_id === toolCallId2,
+			)
+
+			// Verify that a tool_result block was created (not a text block)
+			expect(toolResult).toBeDefined()
+			expect(toolResult.tool_use_id).toBe(toolCallId2)
+			expect(toolResult.is_error).toBe(true)
+			expect(toolResult.content).toContain("due to user rejecting a previous tool")
+
+			// Ensure no text blocks were added for this rejection
+			const textBlocks = mockTask.userMessageContent.filter(
+				(item: any) => item.type === "text" && item.text.includes("due to user rejecting"),
+			)
+			expect(textBlocks.length).toBe(0)
+		})
+
+		it("should send tool_result with is_error for skipped tools in native protocol when didAlreadyUseTool is true", async () => {
+			// Simulate multiple tool calls with native protocol
+			const toolCallId1 = "tool_call_003"
+			const toolCallId2 = "tool_call_004"
+
+			mockTask.assistantMessageContent = [
+				{
+					type: "tool_use",
+					id: toolCallId1,
+					name: "read_file",
+					params: { path: "test.txt" },
+				},
+				{
+					type: "tool_use",
+					id: toolCallId2,
+					name: "write_to_file",
+					params: { path: "output.txt", content: "test" },
+				},
+			]
+
+			// First tool was already used
+			mockTask.didAlreadyUseTool = true
+
+			// Process the second tool (should be skipped)
+			mockTask.currentStreamingContentIndex = 1
+			await presentAssistantMessage(mockTask)
+
+			// Find the tool_result for the second tool
+			const toolResult = mockTask.userMessageContent.find(
+				(item: any) => item.type === "tool_result" && item.tool_use_id === toolCallId2,
+			)
+
+			// Verify that a tool_result block was created (not a text block)
+			expect(toolResult).toBeDefined()
+			expect(toolResult.tool_use_id).toBe(toolCallId2)
+			expect(toolResult.is_error).toBe(true)
+			expect(toolResult.content).toContain("was not executed because a tool has already been used")
+
+			// Ensure no text blocks were added for this rejection
+			const textBlocks = mockTask.userMessageContent.filter(
+				(item: any) => item.type === "text" && item.text.includes("was not executed because"),
+			)
+			expect(textBlocks.length).toBe(0)
+		})
+
+		it("should send text blocks for skipped tools in XML protocol (no tool IDs)", async () => {
+			// Simulate multiple tool calls with XML protocol (no IDs)
+			mockTask.assistantMessageContent = [
+				{
+					type: "tool_use",
+					// No ID = XML protocol
+					name: "read_file",
+					params: { path: "test.txt" },
+				},
+				{
+					type: "tool_use",
+					// No ID = XML protocol
+					name: "write_to_file",
+					params: { path: "output.txt", content: "test" },
+				},
+			]
+
+			// First tool is rejected
+			mockTask.didRejectTool = true
+
+			// Process the second tool (should be skipped)
+			mockTask.currentStreamingContentIndex = 1
+			await presentAssistantMessage(mockTask)
+
+			// For XML protocol, should add text block (not tool_result)
+			const textBlocks = mockTask.userMessageContent.filter(
+				(item: any) => item.type === "text" && item.text.includes("due to user rejecting"),
+			)
+			expect(textBlocks.length).toBeGreaterThan(0)
+
+			// Ensure no tool_result blocks were added
+			const toolResults = mockTask.userMessageContent.filter((item: any) => item.type === "tool_result")
+			expect(toolResults.length).toBe(0)
+		})
+
+		it("should handle partial tool blocks when didRejectTool is true in native protocol", async () => {
+			const toolCallId = "tool_call_005"
+
+			mockTask.assistantMessageContent = [
+				{
+					type: "tool_use",
+					id: toolCallId,
+					name: "write_to_file",
+					params: { path: "output.txt", content: "test" },
+					partial: true, // Partial tool block
+				},
+			]
+
+			mockTask.didRejectTool = true
+
+			await presentAssistantMessage(mockTask)
+
+			// Find the tool_result
+			const toolResult = mockTask.userMessageContent.find(
+				(item: any) => item.type === "tool_result" && item.tool_use_id === toolCallId,
+			)
+
+			// Verify tool_result was created for partial block
+			expect(toolResult).toBeDefined()
+			expect(toolResult.is_error).toBe(true)
+			expect(toolResult.content).toContain("was interrupted and not executed")
+		})
+	})
 })

src/core/assistant-message/presentAssistantMessage.ts

@@ -252,16 +252,25 @@ export async function presentAssistantMessage(cline: Task) {
 
 			if (cline.didRejectTool) {
 				// Ignore any tool content after user has rejected tool once.
-				if (!block.partial) {
+				// For native protocol, we must send a tool_result for every tool_use to avoid API errors
+				const toolCallId = block.id
+				const errorMessage = !block.partial
+					? `Skipping tool ${toolDescription()} due to user rejecting a previous tool.`
+					: `Tool ${toolDescription()} was interrupted and not executed due to user rejecting a previous tool.`
+
+				if (toolCallId) {
+					// Native protocol: MUST send tool_result for every tool_use
 					cline.userMessageContent.push({
-						type: "text",
-						text: `Skipping tool ${toolDescription()} due to user rejecting a previous tool.`,
-					})
+						type: "tool_result",
+						tool_use_id: toolCallId,
+						content: errorMessage,
+						is_error: true,
+					} as Anthropic.ToolResultBlockParam)
 				} else {
-					// Partial tool after user rejected a previous tool.
+					// XML protocol: send as text
 					cline.userMessageContent.push({
 						type: "text",
-						text: `Tool ${toolDescription()} was interrupted and not executed due to user rejecting a previous tool.`,
+						text: errorMessage,
 					})
 				}
 
@@ -270,10 +279,25 @@ export async function presentAssistantMessage(cline: Task) {
 
 			if (cline.didAlreadyUseTool) {
 				// Ignore any content after a tool has already been used.
-				cline.userMessageContent.push({
-					type: "text",
-					text: `Tool [${block.name}] was not executed because a tool has already been used in this message. Only one tool may be used per message. You must assess the first tool's result before proceeding to use the next tool.`,
-				})
+				// For native protocol, we must send a tool_result for every tool_use to avoid API errors
+				const toolCallId = block.id
+				const errorMessage = `Tool [${block.name}] was not executed because a tool has already been used in this message. Only one tool may be used per message. You must assess the first tool's result before proceeding to use the next tool.`
+
+				if (toolCallId) {
+					// Native protocol: MUST send tool_result for every tool_use
+					cline.userMessageContent.push({
+						type: "tool_result",
+						tool_use_id: toolCallId,
+						content: errorMessage,
+						is_error: true,
+					} as Anthropic.ToolResultBlockParam)
+				} else {
+					// XML protocol: send as text
+					cline.userMessageContent.push({
+						type: "text",
+						text: errorMessage,
+					})
+				}
 
 				break
 			}