fix(tui): bounded WSL idle animation CPU

- Removed the Loader backpressure cap so slow ConPTY paints retain the documented proportional duty cycle.

- Made WSL terminal-title working state static to avoid a second periodic OSC write loop.

Fixes #8012

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed terminal-title spinner writes consuming CPU during WSL/ConPTY agent waits by using the same static working separator as native Windows ([#8012](https://github.com/can1357/oh-my-pi/issues/8012)).
+
 ## [17.2.11] - 2026-08-07
 
 ### Added

packages/coding-agent/src/utils/title-generator.ts

@@ -6,6 +6,7 @@ import * as path from "node:path";
 
 import { type Api, type AssistantMessage, completeSimple, type Model } from "@oh-my-pi/pi-ai";
 import { StreamMarkupHealing } from "@oh-my-pi/pi-ai/utils/stream-markup-healing";
+import { isConPTYHosted } from "@oh-my-pi/pi-tui";
 import { isTerminalHeadless, logger, prompt } from "@oh-my-pi/pi-utils";
 import type { ModelRegistry } from "../config/model-registry";
 
@@ -533,6 +534,7 @@ function emitTerminalTitle(): void {
 			terminalTitleRuntime.state,
 			terminalTitleRuntime.frame,
 			terminalTitleRuntime.enabled,
+			isConPTYHosted() ? "win32" : process.platform,
 		);
 	setTerminalTitle(next);
 }
@@ -543,7 +545,7 @@ function stopTerminalTitleSpinner(): void {
 }
 
 function startTerminalTitleSpinner(): void {
-	if (process.platform === "win32" || terminalTitleRuntime.timer || !process.stdout.isTTY) return;
+	if (isConPTYHosted() || terminalTitleRuntime.timer || !process.stdout.isTTY) return;
 	terminalTitleRuntime.timer = setInterval(() => {
 		terminalTitleRuntime.frame = (terminalTitleRuntime.frame + 1) % TITLE_SPINNER_FRAMES.length;
 		emitTerminalTitle();

packages/coding-agent/test/terminal-title-state.test.ts

@@ -5,6 +5,7 @@ import {
 	setSessionTerminalTitle,
 	setTerminalTitleState,
 } from "@oh-my-pi/pi-coding-agent/utils/title-generator";
+import { isConPTYHosted } from "@oh-my-pi/pi-tui";
 import { setTerminalHeadless } from "@oh-my-pi/pi-utils";
 import { mockWindowsConsoleTitle, type WindowsConsoleTitleMock } from "./terminal-title-test-utils";
 
@@ -117,31 +118,28 @@ describe("disposeTerminalTitleState", () => {
 		vi.useRealTimers();
 	});
 
-	it.skipIf(process.platform === "win32")(
-		"stops the spinner so no further OSC-title write fires on a tick after dispose",
-		() => {
-			// CONTRACT (the fix): entering `working` arms the spinner interval; once
-			// `disposeTerminalTitleState()` runs, advancing the clock across many tick
-			// periods must produce ZERO additional OSC-title writes. A pending tick
-			// re-emitting the title after teardown is exactly the shell-tab leak.
-			setTerminalTitleState("working");
+	it.skipIf(isConPTYHosted())("stops the spinner so no further OSC-title write fires on a tick after dispose", () => {
+		// CONTRACT (the fix): entering `working` arms the spinner interval; once
+		// `disposeTerminalTitleState()` runs, advancing the clock across many tick
+		// periods must produce ZERO additional OSC-title writes. A pending tick
+		// re-emitting the title after teardown is exactly the shell-tab leak.
+		setTerminalTitleState("working");
 
-			// Control: BEFORE dispose the interval is live — advancing the clock across
-			// several 80ms tick periods DOES emit further OSC-title writes (proves the
-			// timer was actually running, so the post-dispose silence is meaningful and
-			// not a headless/TTY misconfiguration masking all writes).
-			writes.length = 0;
-			vi.advanceTimersByTime(400);
-			const ticksWhileLive = writes.filter(payload => payload.includes(OSC_TITLE_SEQ)).length;
-			expect(ticksWhileLive).toBeGreaterThan(0);
+		// Control: BEFORE dispose the interval is live — advancing the clock across
+		// several 80ms tick periods DOES emit further OSC-title writes (proves the
+		// timer was actually running, so the post-dispose silence is meaningful and
+		// not a headless/TTY misconfiguration masking all writes).
+		writes.length = 0;
+		vi.advanceTimersByTime(400);
+		const ticksWhileLive = writes.filter(payload => payload.includes(OSC_TITLE_SEQ)).length;
+		expect(ticksWhileLive).toBeGreaterThan(0);
 
-			// The fix under test.
-			disposeTerminalTitleState();
+		// The fix under test.
+		disposeTerminalTitleState();
 
-			// After dispose: advance far past many tick periods. No tick may fire.
-			writes.length = 0;
-			vi.advanceTimersByTime(4000);
-			expect(writes.filter(payload => payload.includes(OSC_TITLE_SEQ))).toEqual([]);
-		},
-	);
+		// After dispose: advance far past many tick periods. No tick may fire.
+		writes.length = 0;
+		vi.advanceTimersByTime(4000);
+		expect(writes.filter(payload => payload.includes(OSC_TITLE_SEQ))).toEqual([]);
+	});
 });

packages/coding-agent/test/title-generator.test.ts

@@ -730,6 +730,28 @@ describe("terminal title runtime", () => {
 		}
 	});
 
+	it("keeps the working title static under WSL", () => {
+		const originalPlatform = process.platform;
+		const originalWslDistro = process.env.WSL_DISTRO_NAME;
+		try {
+			Object.defineProperty(process, "platform", { value: "linux", configurable: true });
+			process.env.WSL_DISTRO_NAME = "Ubuntu";
+			setSessionTerminalTitle("wsl-project");
+			writes.length = 0;
+
+			setTerminalTitleState("working");
+			expect(emittedTitles()).toEqual(["π : wsl-project"]);
+
+			writes.length = 0;
+			vi.advanceTimersByTime(400);
+			expect(writes).toEqual([]);
+		} finally {
+			if (originalWslDistro === undefined) delete process.env.WSL_DISTRO_NAME;
+			else process.env.WSL_DISTRO_NAME = originalWslDistro;
+			Object.defineProperty(process, "platform", { value: originalPlatform, configurable: true });
+		}
+	});
+
 	it("uses SetConsoleTitleW without an OSC write on Windows", () => {
 		const originalPlatform = process.platform;
 		const native = windowsTitleMock;

packages/tui/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed slow Loader paints exceeding their cost-aware CPU duty cycle on WSL/ConPTY when a 200 ms backpressure cap was shorter than the proportional delay ([#8012](https://github.com/can1357/oh-my-pi/issues/8012)).
+
 ## [17.2.11] - 2026-08-07
 
 ### Fixed

packages/tui/src/components/loader.ts

@@ -4,7 +4,6 @@ import { Text } from "./text";
 
 const RENDER_INTERVAL_MS = 1000 / 30;
 const SPINNER_ADVANCE_MS = 80;
-const MAX_RENDER_BACKPRESSURE_MS = 200;
 const RENDER_BACKPRESSURE_MULTIPLIER = 9;
 
 type ColorFn = (str: string) => string;
@@ -144,8 +143,8 @@ export class Loader extends Text {
 			if (this.#intervalId !== timer) return;
 			const cadenceDelayMs = Math.max(0, intervalMs - frameCostMs);
 			// Idle for nine times the paint cost to keep animation at or below
-			// 10% CPU, while cheap frames retain their original cadence.
-			const backpressureDelayMs = Math.min(MAX_RENDER_BACKPRESSURE_MS, frameCostMs * RENDER_BACKPRESSURE_MULTIPLIER);
+			// 10% CPU, even when a slow ConPTY write exceeds the normal cadence.
+			const backpressureDelayMs = frameCostMs * RENDER_BACKPRESSURE_MULTIPLIER;
 			this.#scheduleTick(intervalMs, Math.max(cadenceDelayMs, backpressureDelayMs));
 		}, delayMs);
 		this.#intervalId = timer;

packages/tui/test/loader.test.ts

@@ -140,7 +140,7 @@ describe("Loader component", () => {
 		const ui = {
 			synchronizedOutput: true,
 			requestDirectWrite: vi.fn(() => {
-				now += 20;
+				now += 40;
 			}),
 			requestComponentRender: vi.fn(),
 		};
@@ -153,9 +153,9 @@ describe("Loader component", () => {
 		vi.advanceTimersByTime(34);
 		expect(ui.requestDirectWrite).toHaveBeenCalledTimes(2);
 
-		vi.advanceTimersByTime(170);
+		vi.advanceTimersByTime(200);
 		expect(ui.requestDirectWrite).toHaveBeenCalledTimes(2);
-		vi.advanceTimersByTime(10);
+		vi.advanceTimersByTime(160);
 		expect(ui.requestDirectWrite).toHaveBeenCalledTimes(3);
 
 		loader.stop();