fix(ai): repair interrupted tool result ordering

packages/ai/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## [Unreleased]
 
+- Fixed interrupted tool turns replaying late tool results after an interposed user message ([#1102](https://github.com/PrimeIntellect-ai/prime-agent/pull/1102) by [@junhoyeo](https://github.com/junhoyeo)).
+
 ## [0.7.1] - 2026-08-07
 
 ## [0.7.0] - 2026-08-05

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

@@ -152,31 +152,40 @@ export function transformMessages<TApi extends Api>(
 		return msg;
 	});
 
-	// Second pass: insert synthetic empty tool results for orphaned tool calls
-	// This preserves thinking signatures and satisfies API requirements
+	// Second pass: pair every emitted tool result with a currently pending tool call.
+	// A persisted user message can race an abort result; recover that result from the
+	// remainder of the same turn before synthesizing anything at the user boundary.
 	const result: Message[] = [];
+	const consumedToolResultIndexes = new Set<number>();
 	let pendingToolCalls: ToolCall[] = [];
 	let existingToolResultIds = new Set<string>();
+	const hasUnresolvedToolCall = (toolCallId: string) =>
+		pendingToolCalls.some((toolCall) => toolCall.id === toolCallId) && !existingToolResultIds.has(toolCallId);
+	const appendRealToolResult = (message: ToolResultMessage): boolean => {
+		if (!hasUnresolvedToolCall(message.toolCallId)) return false;
+		existingToolResultIds.add(message.toolCallId);
+		result.push(message);
+		return true;
+	};
 	const insertSyntheticToolResults = () => {
-		if (pendingToolCalls.length > 0) {
-			for (const tc of pendingToolCalls) {
-				if (!existingToolResultIds.has(tc.id)) {
-					result.push({
-						role: "toolResult",
-						toolCallId: tc.id,
-						toolName: tc.name,
-						content: [{ type: "text", text: "No result provided" }],
-						isError: true,
-						timestamp: Date.now(),
-					} as ToolResultMessage);
-				}
+		for (const toolCall of pendingToolCalls) {
+			if (!existingToolResultIds.has(toolCall.id)) {
+				result.push({
+					role: "toolResult",
+					toolCallId: toolCall.id,
+					toolName: toolCall.name,
+					content: [{ type: "text", text: "No result provided" }],
+					isError: true,
+					timestamp: Date.now(),
+				});
 			}
-			pendingToolCalls = [];
-			existingToolResultIds = new Set();
 		}
+		pendingToolCalls = [];
+		existingToolResultIds = new Set();
 	};
 
 	for (let i = 0; i < transformed.length; i++) {
+		if (consumedToolResultIndexes.has(i)) continue;
 		const msg = transformed[i];
 
 		if (msg.role === "assistant") {
@@ -202,14 +211,20 @@ export function transformMessages<TApi extends Api>(
 
 			result.push(msg);
 		} else if (msg.role === "toolResult") {
-			existingToolResultIds.add(msg.toolCallId);
-			result.push(msg);
+			// Unmatched and duplicate results are invalid at every provider boundary.
+			appendRealToolResult(msg);
 		} else if (msg.role === "user") {
-			// User message interrupts tool flow - insert synthetic results for orphaned calls
+			if (pendingToolCalls.length > 0) {
+				for (let lookahead = i + 1; lookahead < transformed.length; lookahead++) {
+					const later = transformed[lookahead];
+					if (later.role === "assistant") break;
+					if (later.role === "toolResult" && appendRealToolResult(later)) {
+						consumedToolResultIndexes.add(lookahead);
+					}
+				}
+			}
 			insertSyntheticToolResults();
 			result.push(msg);
-		} else {
-			result.push(msg);
 		}
 	}
 

packages/ai/test/transform-messages-copilot-openai-to-anthropic.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from "vitest";
 import { transformMessages } from "../src/providers/transform-messages.js";
-import type { AssistantMessage, Message, Model, ToolCall } from "../src/types.js";
+import type { AssistantMessage, Message, Model, ToolCall, ToolResultMessage } from "../src/types.js";
 
 // Normalize function matching what anthropic.ts uses
 function anthropicNormalizeToolCallId(
@@ -46,6 +46,17 @@ function makeAssistantMessage(content: AssistantMessage["content"]): AssistantMe
 	};
 }
 
+function makeToolResult(toolCallId: string, text: string): ToolResultMessage {
+	return {
+		role: "toolResult",
+		toolCallId,
+		toolName: "read",
+		content: [{ type: "text", text }],
+		isError: text === "Request was aborted",
+		timestamp: 2,
+	};
+}
+
 describe("OpenAI to Anthropic session migration for Copilot Claude", () => {
 	it("converts thinking blocks to plain text when source model differs", () => {
 		const model = makeCopilotClaudeModel();
@@ -188,4 +199,117 @@ describe("OpenAI to Anthropic session migration for Copilot Claude", () => {
 			content: [{ type: "text", text: "No result provided" }],
 		});
 	});
+
+	it("hoists a real abort result across an interposed update-restart user message", () => {
+		const model = makeCopilotClaudeModel();
+		const messages: Message[] = [
+			makeAssistantMessage([
+				{ type: "toolCall", id: "call_1|fc_1", name: "read", arguments: { path: "README.md" } },
+			]),
+			{ role: "user", content: "<prime_agent_update_interrupted>", timestamp: 1 },
+			makeToolResult("call_1|fc_1", "Request was aborted"),
+		];
+
+		const result = transformMessages(messages, model, anthropicNormalizeToolCallId);
+
+		expect(result.map((message) => message.role)).toEqual(["assistant", "toolResult", "user"]);
+		expect(result[1]).toMatchObject({
+			role: "toolResult",
+			toolCallId: "call_1_fc_1",
+			content: [{ type: "text", text: "Request was aborted" }],
+		});
+		expect(result).not.toContainEqual(
+			expect.objectContaining({ role: "toolResult", content: [{ type: "text", text: "No result provided" }] }),
+		);
+	});
+
+	it("uses real results from both sides of a user boundary in a parallel tool batch", () => {
+		const model = makeCopilotClaudeModel();
+		const messages: Message[] = [
+			makeAssistantMessage([
+				{ type: "toolCall", id: "call_1|fc_1", name: "read", arguments: { path: "one" } },
+				{ type: "toolCall", id: "call_2|fc_2", name: "read", arguments: { path: "two" } },
+				{ type: "toolCall", id: "call_3|fc_3", name: "read", arguments: { path: "three" } },
+			]),
+			makeToolResult("call_1|fc_1", "one"),
+			{ role: "user", content: "restart", timestamp: 1 },
+			makeToolResult("call_2|fc_2", "two"),
+		];
+
+		const result = transformMessages(messages, model, anthropicNormalizeToolCallId);
+		const results = result.filter((message): message is ToolResultMessage => message.role === "toolResult");
+
+		expect(result.map((message) => message.role)).toEqual([
+			"assistant",
+			"toolResult",
+			"toolResult",
+			"toolResult",
+			"user",
+		]);
+		expect(results.map((message) => [message.toolCallId, message.content[0]])).toEqual([
+			["call_1_fc_1", { type: "text", text: "one" }],
+			["call_2_fc_2", { type: "text", text: "two" }],
+			["call_3_fc_3", { type: "text", text: "No result provided" }],
+		]);
+	});
+
+	it("still synthesizes a missing result at a user boundary", () => {
+		const model = makeCopilotClaudeModel();
+		const messages: Message[] = [
+			makeAssistantMessage([{ type: "toolCall", id: "call_1|fc_1", name: "read", arguments: {} }]),
+			{ role: "user", content: "continue", timestamp: 1 },
+		];
+
+		const result = transformMessages(messages, model, anthropicNormalizeToolCallId);
+
+		expect(result.map((message) => message.role)).toEqual(["assistant", "toolResult", "user"]);
+		expect(result[1]).toMatchObject({
+			role: "toolResult",
+			toolCallId: "call_1_fc_1",
+			content: [{ type: "text", text: "No result provided" }],
+		});
+	});
+
+	it("drops truly orphaned and duplicate late tool results", () => {
+		const model = makeCopilotClaudeModel();
+		const messages: Message[] = [
+			makeToolResult("orphan", "orphan"),
+			makeAssistantMessage([{ type: "toolCall", id: "call_1", name: "read", arguments: {} }]),
+			makeToolResult("call_1", "real"),
+			{ role: "user", content: "continue", timestamp: 1 },
+			makeToolResult("call_1", "duplicate"),
+		];
+
+		const result = transformMessages(messages, model, anthropicNormalizeToolCallId);
+
+		expect(result.map((message) => message.role)).toEqual(["assistant", "toolResult", "user"]);
+		expect(result[1]).toMatchObject({ content: [{ type: "text", text: "real" }] });
+	});
+
+	it("leaves a well-formed tool turn in source order", () => {
+		const model = makeCopilotClaudeModel();
+		const messages: Message[] = [
+			makeAssistantMessage([{ type: "toolCall", id: "call_1", name: "read", arguments: {} }]),
+			makeToolResult("call_1", "real"),
+			{ role: "user", content: "continue", timestamp: 1 },
+		];
+
+		const result = transformMessages(messages, model, anthropicNormalizeToolCallId);
+
+		expect(result).toEqual(messages);
+	});
+
+	it("is idempotent after repairing a broken tool turn", () => {
+		const model = makeCopilotClaudeModel();
+		const messages: Message[] = [
+			makeAssistantMessage([
+				{ type: "toolCall", id: "call_1|fc_1", name: "read", arguments: { path: "README.md" } },
+			]),
+			{ role: "user", content: "restart", timestamp: 1 },
+			makeToolResult("call_1|fc_1", "Request was aborted"),
+		];
+		const repaired = transformMessages(messages, model, anthropicNormalizeToolCallId);
+
+		expect(transformMessages(repaired, model, anthropicNormalizeToolCallId)).toEqual(repaired);
+	});
 });

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## [Unreleased]
 
+- Fixed update-restored sessions becoming unresumable when a restart marker preceded an aborted tool result ([#1102](https://github.com/PrimeIntellect-ai/prime-agent/pull/1102) by [@junhoyeo](https://github.com/junhoyeo)).
 - Added privacy-safe pseudonymous product analytics for onboarding, command use, execution modes, run outcomes, TTFT, latency, usage, tools, retries, and compactions, with disclosure and opt-out controls ([ENG-4682](https://linear.app/primeintellect/issue/ENG-4682/add-privacy-safe-posthog-analytics-to-prime-agent)).
 - Changed sent agent messages in the IPython cell UI to show only the message text with a `╰─` gutter when expanded, matching received messages, and hid the raw `agent_message.send` receipt dictionary.
 - Fixed Homebrew installs attempting to self-update their versioned Cellar keg instead of directing users to `brew upgrade prime-agent` ([#844](https://github.com/PrimeIntellect-ai/prime-agent/issues/844))