fix(coding-agent): reduce automatic theme detection delay

packages/coding-agent/CHANGELOG.md

@@ -9,6 +9,7 @@
 ### Changed
 
 - Softened the bash tool's `PI_*` environment guideline in an attempt to reduce unnecessary inspection commands ([#7128](https://github.com/earendil-works/pi/issues/7128)).
+- Reduced worst-case automatic terminal theme detection delay from 200 ms to 100 ms by probing color-scheme and background support concurrently.
 
 ### Fixed
 

packages/coding-agent/src/modes/interactive/theme/theme.ts

@@ -793,13 +793,21 @@ export async function detectTerminalThemeForAuto({
 	timeoutMs,
 	env,
 }: TerminalAutoThemeDetectionOptions): Promise<TerminalTheme> {
+	let colorSchemePromise: Promise<TerminalTheme | undefined> | undefined;
 	try {
-		const colorScheme = await ui.queryTerminalColorScheme?.({ timeoutMs });
+		colorSchemePromise = ui.queryTerminalColorScheme?.({ timeoutMs });
+	} catch {
+		// Fall back to OSC 11 / COLORFGBG detection when starting the color-scheme query fails.
+	}
+	const backgroundThemePromise = detectTerminalBackgroundTheme({ ui, timeoutMs, env });
+
+	try {
+		const colorScheme = await colorSchemePromise;
 		if (colorScheme) return colorScheme;
 	} catch {
-		// Fall back to OSC 11 / COLORFGBG detection when color-scheme DSR is unsupported.
+		// Fall back to the concurrently queried OSC 11 / COLORFGBG detection.
 	}
-	return (await detectTerminalBackgroundTheme({ ui, timeoutMs, env })).theme;
+	return (await backgroundThemePromise).theme;
 }
 
 export function getDefaultTheme(): string {

packages/coding-agent/test/theme-detection.test.ts

@@ -3,6 +3,7 @@ import { afterEach, describe, expect, it } from "vitest";
 import {
 	detectTerminalBackgroundFromEnv,
 	detectTerminalBackgroundTheme,
+	detectTerminalThemeForAuto,
 	getThemeByName,
 	getThemeForRgbColor,
 	parseAutoThemeSetting,
@@ -99,6 +100,46 @@ describe("detectTerminalBackgroundTheme", () => {
 	});
 });
 
+describe("detectTerminalThemeForAuto", () => {
+	it("starts both queries and returns the preferred color-scheme result without waiting", async () => {
+		let resolveColorScheme!: (theme: "dark" | "light" | undefined) => void;
+		let backgroundQueryStarted = false;
+		const detection = detectTerminalThemeForAuto({
+			timeoutMs: 100,
+			ui: {
+				queryTerminalColorScheme: () =>
+					new Promise((resolve) => {
+						resolveColorScheme = resolve;
+					}),
+				queryTerminalBackgroundColor: () => {
+					backgroundQueryStarted = true;
+					return new Promise<RgbColor | undefined>(() => {});
+				},
+			},
+		});
+
+		expect(backgroundQueryStarted).toBe(true);
+		resolveColorScheme("dark");
+		await expect(detection).resolves.toBe("dark");
+	});
+
+	it("uses the background result when the color-scheme query fails", async () => {
+		await expect(
+			detectTerminalThemeForAuto({
+				timeoutMs: 100,
+				ui: {
+					async queryTerminalColorScheme(): Promise<undefined> {
+						throw new Error("color-scheme query failed");
+					},
+					async queryTerminalBackgroundColor(): Promise<RgbColor> {
+						return { r: 250, g: 250, b: 250 };
+					},
+				},
+			}),
+		).resolves.toBe("light");
+	});
+});
+
 describe("theme color mode", () => {
 	it("uses terminal capabilities", () => {
 		setCapabilities({ images: null, trueColor: false, hyperlinks: false });