feat: malformed tool call recovery for open-weight models

src/core/prompts/responses.ts

@@ -39,12 +39,16 @@ export const formatResponse = {
 			suggestion: "Try to continue without this file, or ask the user to update the .rooignore file",
 		}),
 
-	noToolsUsed: () => {
+	noToolsUsed: (malformedToolCallInfo?: string) => {
 		const instructions = getToolInstructionsReminder()
 
+		const malformedHint = malformedToolCallInfo
+			? `\n\n# Malformed Tool Call Detected\n\nIt looks like you tried to call a tool using XML markup in your text response, but this is not supported. You must use the native/platform tool calling mechanism instead of writing XML tags.\n\nHere is what was detected in your response:\n${malformedToolCallInfo}\n\nPlease retry using the proper native tool calling mechanism with the correct tool name and parameters.`
+			: ""
+
 		return `[ERROR] You did not use a tool in your previous response! Please retry with a tool use.
 
-${instructions}
+${instructions}${malformedHint}
 
 # Next Steps
 

src/core/task/Task.ts

@@ -95,6 +95,7 @@ import { getTaskDirectoryPath } from "../../utils/storage"
 import { formatResponse } from "../prompts/responses"
 import { SYSTEM_PROMPT } from "../prompts/system"
 import { buildNativeToolsArrayWithRestrictions } from "./build-tools"
+import { recoverMalformedToolCall, formatRecoveredToolCall } from "./malformed-tool-call-recovery"
 
 // core modules
 import { ToolRepetitionDetector } from "../tools/ToolRepetitionDetector"
@@ -3604,10 +3605,20 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 							this.consecutiveMistakeCount++
 						}
 
+						// Attempt to detect malformed XML-style tool calls in the text output.
+						// This helps open-weight models self-correct by providing specific feedback.
+						let malformedToolCallInfo: string | undefined
+						if (assistantMessage) {
+							const recovered = recoverMalformedToolCall(assistantMessage)
+							if (recovered) {
+								malformedToolCallInfo = formatRecoveredToolCall(recovered)
+							}
+						}
+
 						// Use the task's locked protocol for consistent behavior
 						this.userMessageContent.push({
 							type: "text",
-							text: formatResponse.noToolsUsed(),
+							text: formatResponse.noToolsUsed(malformedToolCallInfo),
 						})
 					} else {
 						// Reset counter when tools are used successfully

src/core/task/__tests__/malformed-tool-call-recovery.spec.ts

@@ -0,0 +1,169 @@
+import { recoverMalformedToolCall, formatRecoveredToolCall } from "../malformed-tool-call-recovery"
+
+describe("recoverMalformedToolCall", () => {
+	describe("Pattern 1: <function=TOOL_NAME><parameter=PARAM_NAME>VALUE</parameter></function>", () => {
+		it("should recover a basic function-style tool call", () => {
+			const text = `<function=attempt_completion>
+<parameter=result>
+Task completed successfully.
+</parameter>
+</function>`
+
+			const result = recoverMalformedToolCall(text)
+
+			expect(result).not.toBeNull()
+			expect(result!.toolName).toBe("attempt_completion")
+			expect(result!.parameters.result).toBe("Task completed successfully.")
+		})
+
+		it("should recover a function-style tool call with trailing </tool_call>", () => {
+			const text = `<function=attempt_completion>
+<parameter=result>
+LOREM IPSUM DOLOR SIT AMET, CONSECTETUR ADIPISICING ELIT...
+</parameter>
+</function>
+</tool_call>`
+
+			const result = recoverMalformedToolCall(text)
+
+			expect(result).not.toBeNull()
+			expect(result!.toolName).toBe("attempt_completion")
+			expect(result!.parameters.result).toBe("LOREM IPSUM DOLOR SIT AMET, CONSECTETUR ADIPISICING ELIT...")
+		})
+
+		it("should recover a function-style tool call wrapped in <tool_call>", () => {
+			const text = `<tool_call>
+<function=read_file>
+<parameter=path>/src/main.ts</parameter>
+</function>
+</tool_call>`
+
+			const result = recoverMalformedToolCall(text)
+
+			expect(result).not.toBeNull()
+			expect(result!.toolName).toBe("read_file")
+			expect(result!.parameters.path).toBe("/src/main.ts")
+		})
+
+		it("should recover multiple parameters", () => {
+			const text = `<function=write_to_file>
+<parameter=path>/src/test.ts</parameter>
+<parameter=content>console.log("hello")</parameter>
+</function>`
+
+			const result = recoverMalformedToolCall(text)
+
+			expect(result).not.toBeNull()
+			expect(result!.toolName).toBe("write_to_file")
+			expect(result!.parameters.path).toBe("/src/test.ts")
+			expect(result!.parameters.content).toBe('console.log("hello")')
+		})
+
+		it("should recover tool call with surrounding text/reasoning", () => {
+			const text = `I will now complete the task.
+
+<function=attempt_completion>
+<parameter=result>
+Done!
+</parameter>
+</function>
+
+That should do it.`
+
+			const result = recoverMalformedToolCall(text)
+
+			expect(result).not.toBeNull()
+			expect(result!.toolName).toBe("attempt_completion")
+			expect(result!.parameters.result).toBe("Done!")
+		})
+	})
+
+	describe("Pattern 2: XML-style <tool_name><param>value</param></tool_name>", () => {
+		it("should recover an XML-style tool call", () => {
+			const text = `<read_file>
+<path>/src/main.ts</path>
+</read_file>`
+
+			const result = recoverMalformedToolCall(text)
+
+			expect(result).not.toBeNull()
+			expect(result!.toolName).toBe("read_file")
+			expect(result!.parameters.path).toBe("/src/main.ts")
+		})
+
+		it("should recover XML-style tool call with multiple parameters", () => {
+			const text = `<execute_command>
+<command>npm test</command>
+</execute_command>`
+
+			const result = recoverMalformedToolCall(text)
+
+			expect(result).not.toBeNull()
+			expect(result!.toolName).toBe("execute_command")
+			expect(result!.parameters.command).toBe("npm test")
+		})
+	})
+
+	describe("No match cases", () => {
+		it("should return null for plain text without tool call patterns", () => {
+			const text = "I need to think about this problem more carefully."
+			const result = recoverMalformedToolCall(text)
+			expect(result).toBeNull()
+		})
+
+		it("should return null for empty string", () => {
+			const result = recoverMalformedToolCall("")
+			expect(result).toBeNull()
+		})
+
+		it("should return null for random XML that does not look like a tool call", () => {
+			const text = "<div><span>Hello</span></div>"
+			const result = recoverMalformedToolCall(text)
+			// This might match pattern 2, but div/span don't have underscore names
+			// The regex requires [a-z_]+ which matches div, but the inner must also match
+			expect(result).toBeNull()
+		})
+	})
+})
+
+describe("formatRecoveredToolCall", () => {
+	it("should format a simple recovered tool call", () => {
+		const recovered = {
+			toolName: "attempt_completion",
+			parameters: { result: "Task done" },
+		}
+
+		const formatted = formatRecoveredToolCall(recovered)
+
+		expect(formatted).toContain("Tool: attempt_completion")
+		expect(formatted).toContain("result")
+		expect(formatted).toContain("Task done")
+	})
+
+	it("should truncate long parameter values", () => {
+		const longValue = "x".repeat(200)
+		const recovered = {
+			toolName: "write_to_file",
+			parameters: { content: longValue },
+		}
+
+		const formatted = formatRecoveredToolCall(recovered)
+
+		expect(formatted).toContain("...")
+		expect(formatted.length).toBeLessThan(longValue.length + 100)
+	})
+
+	it("should format multiple parameters", () => {
+		const recovered = {
+			toolName: "write_to_file",
+			parameters: { path: "/src/test.ts", content: "hello world" },
+		}
+
+		const formatted = formatRecoveredToolCall(recovered)
+
+		expect(formatted).toContain("path")
+		expect(formatted).toContain("content")
+		expect(formatted).toContain("/src/test.ts")
+		expect(formatted).toContain("hello world")
+	})
+})

src/core/task/malformed-tool-call-recovery.ts

@@ -0,0 +1,90 @@
+/**
+ * Malformed Tool Call Recovery
+ *
+ * Detects common XML-style tool call patterns in assistant text output when no
+ * native tool calls were detected. This is especially common with open-weight
+ * models (e.g., qwen3-coder) that sometimes emit tool calls as plain text
+ * instead of using the native tool calling mechanism.
+ *
+ * IMPORTANT: Recovered information is NEVER auto-executed. It is only used to
+ * provide a clearer retry message to the model so it can self-correct.
+ */
+
+export interface RecoveredToolCall {
+	toolName: string
+	parameters: Record<string, string>
+}
+
+/**
+ * Attempts to recover a malformed tool call from the assistant's text output.
+ *
+ * Supported patterns:
+ * 1. `<function=TOOL_NAME><parameter=PARAM_NAME>VALUE</parameter></function>` (with optional `</tool_call>`)
+ * 2. `<tool_call><function=TOOL_NAME>...</function></tool_call>`
+ * 3. XML-style `<TOOL_NAME><PARAM_NAME>VALUE</PARAM_NAME></TOOL_NAME>`
+ *
+ * @param text - The assistant's text output to scan
+ * @returns A RecoveredToolCall if a malformed tool call is detected, or null otherwise
+ */
+export function recoverMalformedToolCall(text: string): RecoveredToolCall | null {
+	// Pattern 1: <function=TOOL_NAME><parameter=PARAM_NAME>VALUE</parameter></function>
+	// Optionally wrapped in <tool_call>...</tool_call>
+	const functionPattern = /<function=([a-z_]+)>\s*([\s\S]*?)<\/function>/i
+	const functionMatch = text.match(functionPattern)
+
+	if (functionMatch) {
+		const toolName = functionMatch[1]
+		const body = functionMatch[2]
+
+		const parameters: Record<string, string> = {}
+		const paramPattern = /<parameter=([a-z_]+)>([\s\S]*?)<\/parameter>/gi
+		let paramMatch
+
+		while ((paramMatch = paramPattern.exec(body)) !== null) {
+			parameters[paramMatch[1]] = paramMatch[2].trim()
+		}
+
+		return { toolName, parameters }
+	}
+
+	// Pattern 2: XML-style <tool_name><param_name>value</param_name></tool_name>
+	// Common with some models that try to emulate XML tool calling.
+	// Requires at least one underscore in the tool name to avoid matching regular HTML tags.
+	const xmlToolPattern = /<([a-z]+_[a-z_]+)>\s*((?:<[a-z_]+>[\s\S]*?<\/[a-z_]+>\s*)+)<\/\1>/i
+	const xmlMatch = text.match(xmlToolPattern)
+
+	if (xmlMatch) {
+		const toolName = xmlMatch[1]
+		const body = xmlMatch[2]
+
+		const parameters: Record<string, string> = {}
+		const paramPattern = /<([a-z_]+)>([\s\S]*?)<\/\1>/gi
+		let paramMatch
+
+		while ((paramMatch = paramPattern.exec(body)) !== null) {
+			parameters[paramMatch[1]] = paramMatch[2].trim()
+		}
+
+		// Only return if we found at least one parameter
+		if (Object.keys(parameters).length > 0) {
+			return { toolName, parameters }
+		}
+	}
+
+	return null
+}
+
+/**
+ * Formats a recovered tool call into a human-readable summary for the retry message.
+ */
+export function formatRecoveredToolCall(recovered: RecoveredToolCall): string {
+	const paramSummary = Object.entries(recovered.parameters)
+		.map(([key, value]) => {
+			// Truncate long parameter values to keep the message concise
+			const truncated = value.length > 100 ? value.substring(0, 100) + "..." : value
+			return `  - ${key}: "${truncated}"`
+		})
+		.join("\n")
+
+	return `Tool: ${recovered.toolName}\nParameters:\n${paramSummary}`
+}