fix(ai): support xhigh for Codex GPT-5.5

packages/ai/test/openai-codex-stream.test.ts

@@ -2,7 +2,10 @@ import { mkdtempSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { afterEach, describe, expect, it, vi } from "vitest";
-import { streamOpenAICodexResponses } from "../src/providers/openai-codex-responses.js";
+import {
+	streamOpenAICodexResponses,
+	streamSimpleOpenAICodexResponses,
+} from "../src/providers/openai-codex-responses.js";
 import type { Context, Model } from "../src/types.js";
 
 const originalFetch = global.fetch;
@@ -403,6 +406,61 @@ describe("openai-codex streaming", () => {
 		await streamResult.result();
 	});
 
+	it("preserves gpt-5.5 xhigh reasoning effort from simple options", async () => {
+		const tempDir = mkdtempSync(join(tmpdir(), "pi-codex-stream-"));
+		process.env.PI_CODING_AGENT_DIR = tempDir;
+		const token = mockToken();
+		const sse = buildSSEPayload({ status: "completed" });
+		const encoder = new TextEncoder();
+		const stream = new ReadableStream<Uint8Array>({
+			start(controller) {
+				controller.enqueue(encoder.encode(sse));
+				controller.close();
+			},
+		});
+		let requestedReasoning: unknown;
+
+		global.fetch = vi.fn(async (input: string | URL, init?: RequestInit) => {
+			const url = typeof input === "string" ? input : input.toString();
+			if (url === "https://api.github.com/repos/openai/codex/releases/latest") {
+				return new Response(JSON.stringify({ tag_name: "rust-v0.0.0" }), { status: 200 });
+			}
+			if (url.startsWith("https://raw.githubusercontent.com/openai/codex/")) {
+				return new Response("PROMPT", { status: 200, headers: { etag: '"etag"' } });
+			}
+			if (url === "https://chatgpt.com/backend-api/codex/responses") {
+				const body = typeof init?.body === "string" ? (JSON.parse(init.body) as Record<string, unknown>) : null;
+				requestedReasoning = body?.reasoning;
+				return new Response(stream, {
+					status: 200,
+					headers: { "content-type": "text/event-stream" },
+				});
+			}
+			return new Response("not found", { status: 404 });
+		}) as typeof fetch;
+
+		const model: Model<"openai-codex-responses"> = {
+			id: "gpt-5.5",
+			name: "GPT-5.5",
+			api: "openai-codex-responses",
+			provider: "openai-codex",
+			baseUrl: "https://chatgpt.com/backend-api",
+			reasoning: true,
+			input: ["text"],
+			cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+			contextWindow: 400000,
+			maxTokens: 128000,
+		};
+		const context: Context = {
+			systemPrompt: "You are a helpful assistant.",
+			messages: [{ role: "user", content: "Say hello", timestamp: Date.now() }],
+		};
+
+		await streamSimpleOpenAICodexResponses(model, context, { apiKey: token, reasoning: "xhigh" }).result();
+
+		expect(requestedReasoning).toEqual({ effort: "xhigh", summary: "auto" });
+	});
+
 	it.each(["gpt-5.3-codex", "gpt-5.4"])("clamps %s minimal reasoning effort to low", async (modelId) => {
 		const tempDir = mkdtempSync(join(tmpdir(), "pi-codex-stream-"));
 		process.env.PI_CODING_AGENT_DIR = tempDir;

packages/ai/test/stream.test.ts

@@ -1135,12 +1135,12 @@ describe("Generate E2E Tests", () => {
 			await handleStreaming(llm, { apiKey: openaiCodexToken });
 		});
 
-		it.skipIf(!openaiCodexToken)("should handle thinking with reasoningEffort high", { retry: 3 }, async () => {
-			await handleThinking(llm, { apiKey: openaiCodexToken, reasoningEffort: "high" });
+		it.skipIf(!openaiCodexToken)("should handle thinking with reasoningEffort xhigh", { retry: 3 }, async () => {
+			await handleThinking(llm, { apiKey: openaiCodexToken, reasoningEffort: "xhigh" });
 		});
 
 		it.skipIf(!openaiCodexToken)("should handle multi-turn with thinking and tools", { retry: 3 }, async () => {
-			await multiTurn(llm, { apiKey: openaiCodexToken, reasoningEffort: "high" });
+			await multiTurn(llm, { apiKey: openaiCodexToken, reasoningEffort: "xhigh" });
 		});
 
 		it.skipIf(!openaiCodexToken)("should handle image input", { retry: 3 }, async () => {
@@ -1164,12 +1164,12 @@ describe("Generate E2E Tests", () => {
 			await handleStreaming(llm, wsOptions);
 		});
 
-		it.skipIf(!openaiCodexToken)("should handle thinking with reasoningEffort high", { retry: 3 }, async () => {
-			await handleThinking(llm, { ...wsOptions, reasoningEffort: "high" });
+		it.skipIf(!openaiCodexToken)("should handle thinking with reasoningEffort xhigh", { retry: 3 }, async () => {
+			await handleThinking(llm, { ...wsOptions, reasoningEffort: "xhigh" });
 		});
 
 		it.skipIf(!openaiCodexToken)("should handle multi-turn with thinking and tools", { retry: 3 }, async () => {
-			await multiTurn(llm, { ...wsOptions, reasoningEffort: "high" });
+			await multiTurn(llm, { ...wsOptions, reasoningEffort: "xhigh" });
 		});
 
 		it.skipIf(!openaiCodexToken)("should handle image input", { retry: 3 }, async () => {

packages/ai/test/supports-xhigh.test.ts

@@ -20,8 +20,8 @@ describe("supportsXhigh", () => {
 		expect(supportsXhigh(model!)).toBe(false);
 	});
 
-	it("returns true for GPT-5.4 models", () => {
-		const model = getModel("openai-codex", "gpt-5.4");
+	it.each(["gpt-5.4", "gpt-5.5"] as const)("returns true for %s models", (modelId) => {
+		const model = getModel("openai-codex", modelId);
 		expect(model).toBeDefined();
 		expect(supportsXhigh(model!)).toBe(true);
 	});