Workers AI - Reject busy synchronous inference requests

The rejectIfBusy option lets synchronous Workers AI inference requests fail when capacity is unavailable. Use it when your application should not wait in a capacity queue.

Pass the option as the third argument to the Workers AI binding:

const response = await env.AI.run(
	"@cf/google/gemma-4-26b-a4b-it",
	{
		messages: [{ role: "user", content: "Explain capacity queues." }],
	},
	{ rejectIfBusy: true },
);

const response = await env.AI.run(
	"@cf/google/gemma-4-26b-a4b-it",
	{
		messages: [{ role: "user", content: "Explain capacity queues." }],
	},
	{ rejectIfBusy: true },
);

For the native REST API, add the option to the request body:

curl --request POST \
  --url "https://api.cloudflare.com/client/v4/accounts/$ACCOUNT_ID/ai/run/@cf/google/gemma-4-26b-a4b-it" \
  --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
  --header "Content-Type: application/json" \
  --data '{
    "messages": [{ "role": "user", "content": "Explain capacity queues." }],
    "options": { "rejectIfBusy": true }
  }'

Refer to Reject busy requests for OpenAI-compatible usage and error behavior.