Remove tool calls for which there are no results in subsequent user messages.

packages/ai/src/providers/transorm-messages.ts

@@ -1,40 +1,94 @@
 import type { Api, AssistantMessage, Message, Model } from "../types.js";
 
 export function transformMessages<TApi extends Api>(messages: Message[], model: Model<TApi>): Message[] {
-	return messages.map((msg) => {
-		// User and toolResult messages pass through unchanged
-		if (msg.role === "user" || msg.role === "toolResult") {
-			return msg;
-		}
-
-		// Assistant messages need transformation check
-		if (msg.role === "assistant") {
-			const assistantMsg = msg as AssistantMessage;
-
-			// If message is from the same provider and API, keep as is
-			if (assistantMsg.provider === model.provider && assistantMsg.api === model.api) {
+	return messages
+		.map((msg) => {
+			// User and toolResult messages pass through unchanged
+			if (msg.role === "user" || msg.role === "toolResult") {
 				return msg;
 			}
 
-			// Transform message from different provider/model
-			const transformedContent = assistantMsg.content.map((block) => {
-				if (block.type === "thinking") {
-					// Convert thinking block to text block with <thinking> tags
-					return {
-						type: "text" as const,
-						text: `<thinking>\n${block.thinking}\n</thinking>`,
-					};
+			// Assistant messages need transformation check
+			if (msg.role === "assistant") {
+				const assistantMsg = msg as AssistantMessage;
+
+				// If message is from the same provider and API, keep as is
+				if (assistantMsg.provider === model.provider && assistantMsg.api === model.api) {
+					return msg;
 				}
-				// All other blocks (text, toolCall) pass through unchanged
-				return block;
+
+				// Transform message from different provider/model
+				const transformedContent = assistantMsg.content.map((block) => {
+					if (block.type === "thinking") {
+						// Convert thinking block to text block with <thinking> tags
+						return {
+							type: "text" as const,
+							text: `<thinking>\n${block.thinking}\n</thinking>`,
+						};
+					}
+					// All other blocks (text, toolCall) pass through unchanged
+					return block;
+				});
+
+				// Return transformed assistant message
+				return {
+					...assistantMsg,
+					content: transformedContent,
+				};
+			}
+			return msg;
+		})
+		.map((msg, index, allMessages) => {
+			// Second pass: filter out tool calls without corresponding tool results
+			if (msg.role !== "assistant") {
+				return msg;
+			}
+
+			const assistantMsg = msg as AssistantMessage;
+			const isLastMessage = index === allMessages.length - 1;
+
+			// If this is the last message, keep all tool calls (ongoing turn)
+			if (isLastMessage) {
+				return msg;
+			}
+
+			// Extract tool call IDs from this message
+			const toolCallIds = assistantMsg.content
+				.filter((block) => block.type === "toolCall")
+				.map((block) => (block.type === "toolCall" ? block.id : ""));
+
+			// If no tool calls, return as is
+			if (toolCallIds.length === 0) {
+				return msg;
+			}
+
+			// Scan forward through subsequent messages to find matching tool results
+			const matchedToolCallIds = new Set<string>();
+			for (let i = index + 1; i < allMessages.length; i++) {
+				const nextMsg = allMessages[i];
+
+				// Stop scanning when we hit another assistant message
+				if (nextMsg.role === "assistant") {
+					break;
+				}
+
+				// Check tool result messages for matching IDs
+				if (nextMsg.role === "toolResult") {
+					matchedToolCallIds.add(nextMsg.toolCallId);
+				}
+			}
+
+			// Filter out tool calls that don't have corresponding results
+			const filteredContent = assistantMsg.content.filter((block) => {
+				if (block.type === "toolCall") {
+					return matchedToolCallIds.has(block.id);
+				}
+				return true; // Keep all non-toolCall blocks
 			});
 
-			// Return transformed assistant message
 			return {
 				...assistantMsg,
-				content: transformedContent,
+				content: filteredContent,
 			};
-		}
-		return msg;
-	});
+		});
 }