fix(ai): drop streaming parse internals before persistence

Addresses review feedback on #1507.

packages/ai/src/providers/openai-codex-responses.ts

@@ -1234,6 +1234,8 @@ function handleToolCallArgumentsDone(
 	if (typeof args === "string") {
 		currentBlock.partialJson = args;
 		currentBlock.arguments = parseStreamingJson(currentBlock.partialJson);
+		delete (currentBlock as { partialJson?: string }).partialJson;
+		delete (currentBlock as { lastParseLen?: number }).lastParseLen;
 	}
 }
 
@@ -1312,6 +1314,10 @@ function handleOutputItemDone(
 			name: item.name,
 			arguments: parseStreamingJson(item.arguments || "{}"),
 		};
+		if (runtime.currentBlock?.type === "toolCall") {
+			delete (runtime.currentBlock as { partialJson?: string }).partialJson;
+			delete (runtime.currentBlock as { lastParseLen?: number }).lastParseLen;
+		}
 		runtime.canSafelyReplayWebsocketOverSse = false;
 		stream.push({ type: "toolcall_end", contentIndex: blockIndex(), toolCall, partial: output });
 		return;

packages/ai/src/providers/openai-responses-shared.ts

@@ -560,6 +560,8 @@ export async function processResponsesStream<TApi extends Api>(
 			if (currentItem?.type === "function_call" && currentBlock?.type === "toolCall") {
 				currentBlock.partialJson = event.arguments;
 				currentBlock.arguments = parseStreamingJson(currentBlock.partialJson);
+				delete (currentBlock as { partialJson?: string }).partialJson;
+				delete (currentBlock as { lastParseLen?: number }).lastParseLen;
 			}
 		} else if (event.type === "response.custom_tool_call_input.delta") {
 			if (currentItem?.type === "custom_tool_call" && currentBlock?.type === "toolCall") {
@@ -625,6 +627,10 @@ export async function processResponsesStream<TApi extends Api>(
 					name: item.name,
 					arguments: args,
 				};
+				if (currentBlock?.type === "toolCall") {
+					delete (currentBlock as { partialJson?: string }).partialJson;
+					delete (currentBlock as { lastParseLen?: number }).lastParseLen;
+				}
 				currentBlock = null;
 				stream.push({ type: "toolcall_end", contentIndex: blockIndex(), toolCall, partial: output });
 			} else if (item.type === "custom_tool_call") {

packages/ai/test/apply-patch-freeform.test.ts

@@ -225,6 +225,56 @@ describe("custom_tool_call stream receive", () => {
 		for (const e of events) yield e as ResponseStreamEvent;
 	}
 
+	test("strips streaming parse bookkeeping from function-call output blocks", async () => {
+		const output: AssistantMessage = {
+			role: "assistant",
+			content: [],
+			timestamp: Date.now(),
+			provider: "openai",
+			model: "gpt-5",
+			api: "openai-responses",
+			usage: {
+				input: 0,
+				output: 0,
+				cacheRead: 0,
+				cacheWrite: 0,
+				totalTokens: 0,
+				cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+			},
+			stopReason: "stop",
+		};
+		const emitted: unknown[] = [];
+		const stream = {
+			push: (e: unknown) => emitted.push(e),
+			end: () => {},
+		} as never;
+		const args = JSON.stringify({ command: "x".repeat(300) });
+
+		await processResponsesStream(
+			makeStream([
+				{
+					type: "response.output_item.added",
+					item: { type: "function_call", id: "fc_1", call_id: "call_1", name: "bash", arguments: "" },
+				},
+				{ type: "response.function_call_arguments.delta", delta: args },
+				{ type: "response.function_call_arguments.done", arguments: args },
+				{
+					type: "response.output_item.done",
+					item: { type: "function_call", id: "fc_1", call_id: "call_1", name: "bash", arguments: args },
+				},
+			]),
+			output,
+			stream,
+			makeModel(),
+		);
+
+		const block = output.content[0] as Record<string, unknown>;
+		expect(block.type).toBe("toolCall");
+		expect(block.arguments).toEqual({ command: "x".repeat(300) });
+		expect("partialJson" in block).toBe(false);
+		expect("lastParseLen" in block).toBe(false);
+	});
+
 	test("aggregates delta events into a ToolCall with input arg", async () => {
 		const output: AssistantMessage = {
 			role: "assistant",