`@posthog/ai` doesn't handle `background: true` and sets cost/token to 0

[maximedupre]

Bug description

If we make a call with background: true, e.g.

	let res = await client.responses.parse({
		background: true,
        ...

1. The initial client.responses.parse() call returns immediately with status: 'queued' and 0 tokens
2. PostHog captures this initial response → logs $ai_generation event with 0 input/output tokens
3. No polling until the actual response is received

Related sub-libraries

• All of them
• posthog-js (web)
• posthog-js-lite (web lite)
• posthog-node
• posthog-react-native
• @posthog/react
• @posthog/ai
• @posthog/nextjs-config
• @posthog/nuxt
• @posthog/rollup-plugin
• @posthog/webpack-plugin

[maximedupre]

If there is a workaround, for example, some helper function that is exported from the @posthog/ai package and that I can use on the actual response (after polling) to send the $ai_generation event, that could be very useful too!

e.g.

	await getClient().captureImmediate({
		distinctId: 'system',
		event: '$ai_generation',
		properties: {
			environment: ENV,
			method: 'analyzeStuff',
			$ai_model: model,
			$ai_provider: 'openai',
			$ai_input_tokens: res.usage?.input_tokens ?? 0,
			$ai_output_tokens: res.usage?.output_tokens ?? 0,
			$ai_total_cost_usd: totalCost // <-------------------------------- what's the total cost?
		}
	});