From d35935200f5e1a28833dad7205d6777f48fe1ac1 Mon Sep 17 00:00:00 2001
From: Matteo Collina <hello@matteocollina.com>
Date: Wed, 4 Mar 2026 08:53:33 +0100
Subject: [PATCH] fix(coding-agent): avoid compaction reasoning for
 non-reasoning models (#1793)

---
 .../src/core/compaction/compaction.ts         |  6 +-
 .../test/compaction-summary-reasoning.test.ts | 78 +++++++++++++++++++
 2 files changed, 83 insertions(+), 1 deletion(-)
 create mode 100644 packages/coding-agent/test/compaction-summary-reasoning.test.ts

diff --git a/packages/coding-agent/src/core/compaction/compaction.ts b/packages/coding-agent/src/core/compaction/compaction.ts
index d59ff0ef..4703de6b 100644
--- a/packages/coding-agent/src/core/compaction/compaction.ts
+++ b/packages/coding-agent/src/core/compaction/compaction.ts
@@ -554,10 +554,14 @@ export async function generateSummary(
 		},
 	];
 
+	const completionOptions = model.reasoning
+		? { maxTokens, signal, apiKey, reasoning: "high" as const }
+		: { maxTokens, signal, apiKey };
+
 	const response = await completeSimple(
 		model,
 		{ systemPrompt: SUMMARIZATION_SYSTEM_PROMPT, messages: summarizationMessages },
-		{ maxTokens, signal, apiKey, reasoning: "high" },
+		completionOptions,
 	);
 
 	if (response.stopReason === "error") {
diff --git a/packages/coding-agent/test/compaction-summary-reasoning.test.ts b/packages/coding-agent/test/compaction-summary-reasoning.test.ts
new file mode 100644
index 00000000..3e8fe66c
--- /dev/null
+++ b/packages/coding-agent/test/compaction-summary-reasoning.test.ts
@@ -0,0 +1,78 @@
+import type { AgentMessage } from "@mariozechner/pi-agent-core";
+import type { AssistantMessage, Model } from "@mariozechner/pi-ai";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { generateSummary } from "../src/core/compaction/index.js";
+
+const { completeSimpleMock } = vi.hoisted(() => ({
+	completeSimpleMock: vi.fn(),
+}));
+
+vi.mock("@mariozechner/pi-ai", async (importOriginal) => {
+	const actual = await importOriginal<typeof import("@mariozechner/pi-ai")>();
+	return {
+		...actual,
+		completeSimple: completeSimpleMock,
+	};
+});
+
+function createModel(reasoning: boolean): Model<"anthropic-messages"> {
+	return {
+		id: reasoning ? "reasoning-model" : "non-reasoning-model",
+		name: reasoning ? "Reasoning Model" : "Non-reasoning Model",
+		api: "anthropic-messages",
+		provider: "anthropic",
+		baseUrl: "https://api.anthropic.com",
+		reasoning,
+		input: ["text"],
+		cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+		contextWindow: 200000,
+		maxTokens: 8192,
+	};
+}
+
+const mockSummaryResponse: AssistantMessage = {
+	role: "assistant",
+	content: [{ type: "text", text: "## Goal\nTest summary" }],
+	api: "anthropic-messages",
+	provider: "anthropic",
+	model: "claude-sonnet-4-5",
+	usage: {
+		input: 10,
+		output: 10,
+		cacheRead: 0,
+		cacheWrite: 0,
+		totalTokens: 20,
+		cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+	},
+	stopReason: "stop",
+	timestamp: Date.now(),
+};
+
+const messages: AgentMessage[] = [{ role: "user", content: "Summarize this.", timestamp: Date.now() }];
+
+describe("generateSummary reasoning options", () => {
+	beforeEach(() => {
+		completeSimpleMock.mockReset();
+		completeSimpleMock.mockResolvedValue(mockSummaryResponse);
+	});
+
+	it("sets reasoning=high for reasoning-capable models", async () => {
+		await generateSummary(messages, createModel(true), 2000, "test-key");
+
+		expect(completeSimpleMock).toHaveBeenCalledTimes(1);
+		expect(completeSimpleMock.mock.calls[0][2]).toMatchObject({
+			reasoning: "high",
+			apiKey: "test-key",
+		});
+	});
+
+	it("does not set reasoning for non-reasoning models", async () => {
+		await generateSummary(messages, createModel(false), 2000, "test-key");
+
+		expect(completeSimpleMock).toHaveBeenCalledTimes(1);
+		expect(completeSimpleMock.mock.calls[0][2]).toMatchObject({
+			apiKey: "test-key",
+		});
+		expect(completeSimpleMock.mock.calls[0][2]).not.toHaveProperty("reasoning");
+	});
+});