fix(ai): omit copilot responses reasoning default closes #2567

packages/ai/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed GitHub Copilot OpenAI Responses requests to omit the `reasoning` field entirely when no reasoning effort is requested, avoiding `400` errors from Copilot `gpt-5-mini` rejecting `reasoning: { effort: "none" }` during internal summary calls ([#2567](https://github.com/badlogic/pi-mono/issues/2567))
+
 ## [0.62.0] - 2026-03-23
 
 ### Added

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

@@ -220,7 +220,7 @@ function buildParams(model: Model<"openai-responses">, context: Context, options
 				summary: options?.reasoningSummary || "auto",
 			};
 			params.include = ["reasoning.encrypted_content"];
-		} else {
+		} else if (model.provider !== "github-copilot") {
 			params.reasoning = { effort: "none" };
 		}
 	}

packages/ai/test/openai-responses-copilot-provider.test.ts

@@ -0,0 +1,44 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { getModel } from "../src/models.js";
+import { streamOpenAIResponses } from "../src/providers/openai-responses.js";
+
+describe("openai-responses github-copilot defaults", () => {
+	afterEach(() => {
+		vi.restoreAllMocks();
+	});
+
+	it("omits reasoning when no reasoning is requested", async () => {
+		const model = getModel("github-copilot", "gpt-5-mini");
+		let capturedPayload: unknown;
+
+		vi.spyOn(globalThis, "fetch").mockResolvedValue(
+			new Response("data: [DONE]\n\n", {
+				status: 200,
+				headers: { "content-type": "text/event-stream" },
+			}),
+		);
+
+		const stream = streamOpenAIResponses(
+			model,
+			{
+				systemPrompt: "sys",
+				messages: [{ role: "user", content: "hi", timestamp: Date.now() }],
+			},
+			{
+				apiKey: "test-key",
+				onPayload: (payload) => {
+					capturedPayload = payload;
+				},
+			},
+		);
+
+		for await (const event of stream) {
+			if (event.type === "done" || event.type === "error") break;
+		}
+
+		expect(capturedPayload).not.toBeNull();
+		expect(capturedPayload).not.toMatchObject({
+			reasoning: expect.anything(),
+		});
+	});
+});