Is there an existing issue for this?

• I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• I have reviewed the documentation https://docs.sentry.io/
• I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/node - fastify

SDK Version

9.42.0

Framework Version

No response

Link to Sentry event

https://lisa-tk.sentry.io/explore/traces/trace/6dd111760bb8edb07b37883a9d35b9db/?node=span-68cf894ebe343333

Reproduction Example/SDK Setup

Sentry.init({
	tracesSampler: ({ attributes, parentSampled }) => {
		const { removeSample } = attributes ?? {};

		if (removeSample !== undefined && removeSample === true) {
			return false;
		}
	},
});

function cancelSpan() {
	Sentry.getActiveSpan()?.setAttribute('removeSample', true);
}

const data = [];
Sentry.startSpan({
	name: 'Ingester',
	op: 'queue.task',
}, () => {
	if (!data.length) {
		cancelSpan();
	}
});

Steps to Reproduce

Returning false in tracesSampler sends the trace/span to Sentry anyways. In the URL you can see the attribute removeSample set to true. I can confirm that the tracesSampler is being invoked but I'm curious as to why spans are being sent when I explicitly return false.

Expected Result

Should filter out trace

Actual Result

Trace shows up in Sentry