fix(ai): avoid duplicate Codex replay message ids closes #5148

packages/ai/test/openai-responses-message-id.test.ts

@@ -0,0 +1,48 @@
+import type { ResponseOutputMessage } from "openai/resources/responses/responses.js";
+import { describe, expect, it } from "vitest";
+import { getModel } from "../src/models.ts";
+import { convertResponsesMessages } from "../src/providers/openai-responses-shared.ts";
+import type { AssistantMessage, Context, Usage } from "../src/types.ts";
+
+const usage: Usage = {
+	input: 0,
+	output: 0,
+	cacheRead: 0,
+	cacheWrite: 0,
+	totalTokens: 0,
+	cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+};
+
+describe("OpenAI Responses message ID conversion", () => {
+	it("generates unique fallback message IDs for multiple text blocks in one assistant turn", () => {
+		const model = getModel("openai-codex", "gpt-5.5");
+		const assistant: AssistantMessage = {
+			role: "assistant",
+			content: [
+				{ type: "thinking", thinking: "private reasoning" },
+				{ type: "text", text: "visible answer" },
+			],
+			api: "anthropic-messages",
+			provider: "anthropic",
+			model: "claude-opus-4-8",
+			usage,
+			stopReason: "stop",
+			timestamp: Date.now() - 1000,
+		};
+		const context: Context = {
+			systemPrompt: "You are concise.",
+			messages: [{ role: "user", content: "hello", timestamp: Date.now() - 2000 }, assistant],
+		};
+
+		const input = convertResponsesMessages(model, context, new Set(["openai", "openai-codex", "opencode"]));
+		const messageIds = input
+			.filter(
+				(item): item is ResponseOutputMessage =>
+					item.type === "message" && "id" in item && typeof item.id === "string",
+			)
+			.map((item) => item.id);
+
+		expect(messageIds).toEqual(["pi_msg_1", "pi_msg_1_1"]);
+		expect(new Set(messageIds).size).toBe(messageIds.length);
+	});
+});