fix(agent): recover tools after stream parse errors

packages/agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Recovered completed tool calls after transient stream JSON parse failures while keeping incomplete, unknown, refused, and sensitive calls non-executable.
+
 ## [17.0.5] - 2026-07-18
 
 ### Added

packages/agent/src/agent-loop.ts

@@ -1629,13 +1629,26 @@ function recoverTransientErrorToolTurn(
 	if (message.stopReason !== "error") return message;
 	const toolCalls = message.content.filter(block => block.type === "toolCall");
 	if (toolCalls.length === 0) return message;
+	const stopDetailType = message.stopDetails?.type;
+	const stopDetailCategory = message.stopDetails?.category;
+	if (
+		stopDetailType === "refusal" ||
+		stopDetailType === "sensitive" ||
+		stopDetailCategory === "refusal" ||
+		stopDetailCategory === "sensitive"
+	)
+		return message;
 	const availableToolNames = new Set<string>();
 	for (const tool of availableTools) {
 		availableToolNames.add(tool.name);
 		if (tool.customWireName !== undefined) availableToolNames.add(tool.customWireName);
 	}
 	if (!toolCalls.every(toolCall => availableToolNames.has(toolCall.name))) return message;
-	if (!AIError.isStreamReadErrorText(`${message.errorMessage ?? ""}\n${message.stopDetails?.explanation ?? ""}`))
+	if (
+		!AIError.isStreamReadErrorText(`${message.errorMessage ?? ""}\n${message.stopDetails?.explanation ?? ""}`) &&
+		!AIError.isTransientStreamParseError(message.errorMessage) &&
+		!AIError.isTransientStreamParseError(message.stopDetails?.explanation)
+	)
 		return message;
 	return {
 		...message,

packages/agent/test/agent-loop.test.ts

@@ -630,7 +630,7 @@ describe("agentLoop with AgentMessage", () => {
 		expect(finalTurn.content).toContainEqual({ type: "text", text: "done after recovery" });
 	});
 
-	it("does not recover completed tool calls after non-stream transient errors", async () => {
+	it("runs completed tool calls after a transient stream JSON parse error", async () => {
 		const executedParams: Array<{ value: string }> = [];
 		const toolSchema = type({ value: "string" });
 		const tool: AgentTool<typeof toolSchema, { value: string }> = {
@@ -652,9 +652,9 @@ describe("agentLoop with AgentMessage", () => {
 				{
 					content: [{ type: "toolCall", id: "tool-1", name: "echo", arguments: { value: "hello" } }],
 					stopReason: "error",
-					errorMessage: "rate_limit_error",
+					errorMessage: "JSON Parse error: Unterminated string",
 				},
-				{ content: ["should not continue"] },
+				{ content: ["done after parse recovery"] },
 			],
 		});
 		const config: AgentLoopConfig = { model: mock.model, convertToLlm: identityConverter };
@@ -667,12 +667,275 @@ describe("agentLoop with AgentMessage", () => {
 			mock.stream,
 		).result();
 
+		expect(executedParams).toEqual([{ value: "hello" }]);
+		expect(mock.calls).toHaveLength(2);
+		expect(messages.map(message => message.role)).toEqual(["user", "assistant", "toolResult", "assistant"]);
+		const recoveredTurn = messages[1] as AssistantMessage;
+		expect(recoveredTurn.stopReason).toBe("toolUse");
+		expect(recoveredTurn.stopDetails?.type).toBe("stream_interrupted_after_content");
+		const finalTurn = messages[3] as AssistantMessage;
+		expect(finalTurn.content).toContainEqual({ type: "text", text: "done after parse recovery" });
+	});
+
+	it("recovers only completed calls when a stream parse error interrupts the next call", async () => {
+		const executedParams: Array<{ value: string }> = [];
+		const toolSchema = type({ value: "string" });
+		const tool: AgentTool<typeof toolSchema, { value: string }> = {
+			name: "echo",
+			label: "Echo",
+			description: "Echo tool",
+			parameters: toolSchema,
+			async execute(_toolCallId, params) {
+				executedParams.push(params);
+				return {
+					content: [{ type: "text", text: `echoed: ${params.value}` }],
+					details: { value: params.value },
+				};
+			},
+		};
+		const context: AgentContext = { systemPrompt: [""], messages: [], tools: [tool] };
+		const completedCall = {
+			type: "toolCall" as const,
+			id: "tool-complete",
+			name: "echo",
+			arguments: { value: "complete" },
+		};
+		const incompleteCall = {
+			type: "toolCall" as const,
+			id: "tool-incomplete",
+			name: "echo",
+			arguments: { value: "incomplete" },
+		};
+		const mock = createMockModel({ responses: [{ content: ["done after partial parse recovery"] }] });
+		let streamCalls = 0;
+		const streamFn: typeof mock.stream = (model, callContext, options) => {
+			streamCalls++;
+			if (streamCalls > 1) return mock.stream(model, callContext, options);
+			const stream = new AssistantMessageEventStream();
+			queueMicrotask(() => {
+				const partial: AssistantMessage = {
+					...createAssistantMessage([completedCall, incompleteCall], "error"),
+					errorMessage: "provider stream parse failed",
+					stopDetails: {
+						type: "parse_error",
+						explanation: "JSON Parse error: Unterminated string",
+					},
+				};
+				stream.push({ type: "start", partial });
+				stream.push({ type: "toolcall_end", contentIndex: 0, toolCall: completedCall, partial });
+				stream.push({ type: "toolcall_start", contentIndex: 1, partial });
+				stream.push({ type: "toolcall_delta", contentIndex: 1, delta: '{"value":"incomplete', partial });
+				stream.push({ type: "error", reason: "error", error: partial });
+			});
+			return stream;
+		};
+		const config: AgentLoopConfig = { model: mock.model, convertToLlm: identityConverter };
+
+		const messages = await agentLoop([createUserMessage("run echo")], context, config, undefined, streamFn).result();
+
+		expect(executedParams).toEqual([{ value: "complete" }]);
+		expect(streamCalls).toBe(2);
+		expect(mock.calls).toHaveLength(1);
+		expect(messages.map(message => message.role)).toEqual(["user", "assistant", "toolResult", "assistant"]);
+		const recoveredTurn = messages[1] as AssistantMessage;
+		expect(recoveredTurn.stopReason).toBe("toolUse");
+		expect(recoveredTurn.content.filter(block => block.type === "toolCall").map(block => block.id)).toEqual([
+			"tool-complete",
+		]);
+		expect(messages.some(message => message.role === "toolResult" && message.toolCallId === "tool-incomplete")).toBe(
+			false,
+		);
+	});
+
+	it("does not recover a wrapped refusal after dropping an incomplete sibling", async () => {
+		const executedParams: Array<{ value: string }> = [];
+		const toolSchema = type({ value: "string" });
+		const tool: AgentTool<typeof toolSchema, { value: string }> = {
+			name: "echo",
+			label: "Echo",
+			description: "Echo tool",
+			parameters: toolSchema,
+			async execute(_toolCallId, params) {
+				executedParams.push(params);
+				return { content: [], details: { value: params.value } };
+			},
+		};
+		const context: AgentContext = { systemPrompt: [""], messages: [], tools: [tool] };
+		const completedCall = {
+			type: "toolCall" as const,
+			id: "tool-complete",
+			name: "echo",
+			arguments: { value: "complete" },
+		};
+		const incompleteCall = {
+			type: "toolCall" as const,
+			id: "tool-incomplete",
+			name: "echo",
+			arguments: { value: "incomplete" },
+		};
+		const mock = createMockModel({ responses: [{ content: ["should not continue"] }] });
+		let streamCalls = 0;
+		const streamFn: typeof mock.stream = (model, callContext, options) => {
+			streamCalls++;
+			if (streamCalls > 1) return mock.stream(model, callContext, options);
+			const stream = new AssistantMessageEventStream();
+			queueMicrotask(() => {
+				const partial: AssistantMessage = {
+					...createAssistantMessage([completedCall, incompleteCall], "error"),
+					errorMessage: "provider refused output",
+					stopDetails: { type: "refusal", explanation: "Unexpected end of JSON input" },
+				};
+				stream.push({ type: "start", partial });
+				stream.push({ type: "toolcall_end", contentIndex: 0, toolCall: completedCall, partial });
+				stream.push({ type: "toolcall_start", contentIndex: 1, partial });
+				stream.push({ type: "toolcall_delta", contentIndex: 1, delta: '{"value":"incomplete', partial });
+				stream.push({ type: "error", reason: "error", error: partial });
+			});
+			return stream;
+		};
+		const config: AgentLoopConfig = { model: mock.model, convertToLlm: identityConverter };
+
+		const messages = await agentLoop([createUserMessage("run echo")], context, config, undefined, streamFn).result();
+
+		expect(executedParams).toEqual([]);
+		expect(streamCalls).toBe(1);
+		expect(mock.calls).toHaveLength(0);
+		const errorTurn = messages[1] as AssistantMessage;
+		expect(errorTurn.stopReason).toBe("error");
+		expect(errorTurn.content.filter(block => block.type === "toolCall").map(block => block.id)).toEqual([
+			"tool-complete",
+		]);
+		expect(errorTurn.stopDetails).toEqual({
+			type: "stream_interrupted_after_content",
+			category: "refusal",
+			explanation: "Unexpected end of JSON input",
+		});
+	});
+
+	it("does not recover a mixed known and unknown completed tool turn", async () => {
+		const executedParams: Array<{ value: string }> = [];
+		const toolSchema = type({ value: "string" });
+		const tool: AgentTool<typeof toolSchema, { value: string }> = {
+			name: "echo",
+			label: "Echo",
+			description: "Echo tool",
+			parameters: toolSchema,
+			async execute(_toolCallId, params) {
+				executedParams.push(params);
+				return { content: [], details: { value: params.value } };
+			},
+		};
+		const context: AgentContext = { systemPrompt: [""], messages: [], tools: [tool] };
+		const mock = createMockModel({
+			responses: [
+				{
+					content: [
+						{ type: "toolCall", id: "tool-known", name: "echo", arguments: { value: "known" } },
+						{ type: "toolCall", id: "tool-unknown", name: "missing", arguments: { value: "unknown" } },
+					],
+					stopReason: "error",
+					errorMessage: "JSON Parse error: Unterminated string",
+				},
+				{ content: ["should not continue"] },
+			],
+		});
+		const config: AgentLoopConfig = { model: mock.model, convertToLlm: identityConverter };
+
+		const messages = await agentLoop(
+			[createUserMessage("run mixed tools")],
+			context,
+			config,
+			undefined,
+			mock.stream,
+		).result();
+
 		expect(executedParams).toEqual([]);
 		expect(mock.calls).toHaveLength(1);
-		expect(messages.map(message => message.role)).toEqual(["user", "assistant", "toolResult"]);
 		const errorTurn = messages[1] as AssistantMessage;
 		expect(errorTurn.stopReason).toBe("error");
-		expect(errorTurn.errorMessage).toBe("rate_limit_error");
+		expect(errorTurn.errorMessage).toBe("JSON Parse error: Unterminated string");
+	});
+
+	it("does not recover content-only transient stream parse errors", async () => {
+		const context: AgentContext = { systemPrompt: [""], messages: [], tools: [] };
+		const mock = createMockModel({
+			responses: [
+				{
+					content: ["partial response"],
+					stopReason: "error",
+					errorMessage: "JSON Parse error: Unterminated string",
+				},
+				{ content: ["should not continue"] },
+			],
+		});
+		const config: AgentLoopConfig = { model: mock.model, convertToLlm: identityConverter };
+
+		const messages = await agentLoop(
+			[createUserMessage("answer once")],
+			context,
+			config,
+			undefined,
+			mock.stream,
+		).result();
+
+		expect(mock.calls).toHaveLength(1);
+		expect(messages.map(message => message.role)).toEqual(["user", "assistant"]);
+		const errorTurn = messages[1] as AssistantMessage;
+		expect(errorTurn.stopReason).toBe("error");
+		expect(errorTurn.errorMessage).toBe("JSON Parse error: Unterminated string");
+	});
+
+	it("does not recover ordinary transient errors or terminal stops quoting parse diagnostics", async () => {
+		for (const stopDetails of [
+			undefined,
+			{ type: "refusal", explanation: "Unexpected end of JSON input" },
+			{ type: "sensitive", explanation: "Unexpected end of JSON input" },
+		]) {
+			const executedParams: Array<{ value: string }> = [];
+			const toolSchema = type({ value: "string" });
+			const tool: AgentTool<typeof toolSchema, { value: string }> = {
+				name: "echo",
+				label: "Echo",
+				description: "Echo tool",
+				parameters: toolSchema,
+				async execute(_toolCallId, params) {
+					executedParams.push(params);
+					return {
+						content: [{ type: "text", text: `echoed: ${params.value}` }],
+						details: { value: params.value },
+					};
+				},
+			};
+			const context: AgentContext = { systemPrompt: [""], messages: [], tools: [tool] };
+			const mock = createMockModel({
+				responses: [
+					{
+						content: [{ type: "toolCall", id: "tool-1", name: "echo", arguments: { value: "hello" } }],
+						stopReason: "error",
+						stopDetails,
+						errorMessage: "rate_limit_error",
+					},
+					{ content: ["should not continue"] },
+				],
+			});
+			const config: AgentLoopConfig = { model: mock.model, convertToLlm: identityConverter };
+
+			const messages = await agentLoop(
+				[createUserMessage("run echo")],
+				context,
+				config,
+				undefined,
+				mock.stream,
+			).result();
+
+			expect(executedParams).toEqual([]);
+			expect(mock.calls).toHaveLength(1);
+			expect(messages.map(message => message.role)).toEqual(["user", "assistant", "toolResult"]);
+			const errorTurn = messages[1] as AssistantMessage;
+			expect(errorTurn.stopReason).toBe("error");
+			expect(errorTurn.errorMessage).toBe("rate_limit_error");
+			expect(errorTurn.stopDetails).toEqual(stopDetails);
+		}
 	});
 
 	it("labels the synthetic tool result for a provider-error turn as not-executed and preserves the upstream error", async () => {

packages/ai/src/error/flags.ts

@@ -505,10 +505,13 @@ export function stringify(id: number | undefined): string {
 
 const STREAM_PARSE_TRUNCATION_PATTERN =
 	/unterminated string|unexpected end of json input|unexpected end of data|unexpected eof|end of file|eof while parsing|truncated/i;
+const STREAM_PARSE_DIAGNOSTIC_PATTERN =
+	/(?:json parse error:\s*(?:unterminated string|unexpected end of json input|unexpected end of data|unexpected eof|end of file|eof while parsing|truncated)|json\.parse:\s*(?:unterminated string|unexpected end of data)|unexpected end of json input|unexpected eof|eof while parsing)/i;
 const STREAM_EVENT_ORDER_PATTERN = /stream event order|before message_start/i;
 
 /** Transient stream corruption where the response was truncated mid-JSON. */
 export function isTransientStreamParseError(error: unknown): boolean {
+	if (typeof error === "string") return STREAM_PARSE_DIAGNOSTIC_PATTERN.test(error);
 	return error instanceof Error && STREAM_PARSE_TRUNCATION_PATTERN.test(error.message);
 }
 

packages/ai/test/error-aierr.test.ts

@@ -135,4 +135,18 @@ describe("aierr flag helpers", () => {
 		expect(AIError.retriable(AIError.create(AIError.Flag.Transient))).toBe(true);
 		expect(AIError.retriable(AIError.create(AIError.Flag.UsageLimit))).toBe(true);
 	});
+
+	it("recognizes explicit transient stream parse diagnostics without broad text false positives", () => {
+		const message = "JSON Parse error: Unterminated string";
+		expect(AIError.isTransientStreamParseError(new Error(message))).toBe(true);
+		expect(AIError.isTransientStreamParseError(new Error("response truncated"))).toBe(true);
+		expect(AIError.isTransientStreamParseError(message)).toBe(true);
+		expect(AIError.isTransientStreamParseError("Unexpected end of JSON input")).toBe(true);
+		expect(AIError.isTransientStreamParseError("JSON.parse: unexpected end of data at line 1 column 8")).toBe(true);
+		expect(AIError.isTransientStreamParseError("Unexpected EOF")).toBe(true);
+		expect(AIError.isTransientStreamParseError("EOF while parsing")).toBe(true);
+		expect(AIError.isTransientStreamParseError("truncated")).toBe(false);
+		expect(AIError.isTransientStreamParseError("end of file")).toBe(false);
+		expect(AIError.isTransientStreamParseError("Unexpected token in JSON")).toBe(false);
+	});
 });