What causes "Assertion failed" in can1357/oh-my-pi?

Inspect the run's surrounding context to see which assertion tripped; pass a descriptive text argument to assert for diagnosability.

can1357/oh-my-pi · error · ToolError

Assertion failed

Error message

Assertion failed

What it means

The computer-run sandbox exposes an assert(condition, text?) helper to agent scripts; when the condition is falsy it throws ToolError with the provided text or the default 'Assertion failed'. This is an in-script assertion mechanism — the script's own check failed, surfacing as a tool error with the run's context.

Source

Thrown at packages/coding-agent/src/tools/computer/worker.ts:522

			signal,
			readOnly: message.session.readOnly,
			snapshot: message.session,
			output,
			screenshots,
		};
		let returnValue: unknown;
		let failure: { error: unknown } | undefined;
		let completed = false;
		try {
			throwIfAborted(signal);
			const session = this.#ensureSession(message.session);
			const runtime = this.#ensureRuntime(message.session);
			runtime.setCwd(message.session.cwd);
			const desktop = this.#createDesktopScope(session);
			runtime.setRunScope({
				desktop: bindRunFacade(desktop, signal),
				assert: (condition: unknown, text?: string): void => {
					if (!condition) throw new ToolError(text ?? "Assertion failed");
				},
				wait: (msOrPredicate: number | (() => unknown), options?: WaitPredicateOptions): Promise<unknown> => {
					const resolved =
						typeof msOrPredicate === "number"
							? undefined
							: {
									timeout: resolvePredicateTimeout(message.timeoutMs, options?.timeout),
									interval: options?.interval,
								};
					return markHandled(waitForRun(msOrPredicate, signal, resolved));
				},
			});
			const { promise: cancelRejection, reject: rejectCancel } = Promise.withResolvers<never>();
			const onCancel = (): void => {
				const abortError =
					signal.reason instanceof ToolAbortError
						? signal.reason
						: new ToolAbortError(undefined, { cause: signal.reason });

View on GitHub (pinned to 9690622007)

Solutions

Inspect the run's surrounding context to see which assertion tripped; pass a descriptive text argument to assert for diagnosability.
Verify the precondition (app running, window title, expected value) before asserting; use wait(predicate) to await UI state instead of asserting immediately.
Wrap assertions in try/catch inside the script if failure should degrade gracefully rather than fail the run.

Example fix

// inside computer run code
// before
assert(win, "Assertion failed");

// after
const win = await desktop.win({ app: "Notes" });
assert(win, `Notes window not found (visible: ${JSON.stringify(await desktop.windows())})`);

Defensive patterns

Strategy: try-catch

Validate before calling

// inside computer run code: check the precondition before asserting
const win = await desktop.win({ app: "Notes" });
if (!win) throw new Error("Notes window missing — open it before asserting");

Try / catch

// inside computer run code
try {
  assert(condition, "descriptive failure text");
} catch (e) {
  await desktop.screenshot(); // capture state for diagnosis
  throw e;
}

Prevention

Always pass a descriptive second argument to assert() so failures are diagnosable.
Use wait(predicate, options) to await UI state instead of asserting immediately after an action.
Verify apps/windows exist before asserting on their properties.

When it happens

Trigger: Computer-run code calls assert(someCondition) and the condition evaluates falsy (e.g. a window lookup returned nothing, a value didn't change, a UI state wasn't reached).

Common situations: Scripts verify a window exists before interacting (assert(win)) but the app isn't open/titled as expected; polling predicates time out and a later assert trips; agents use assert as a guard and pass undefined when lookups fail.

Related errors

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/ef0818009224d289. Report an issue: GitHub.