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The Gemini API is moving to prepaid billing — keeping Gemini and Nano Banana behind one key

· 10 minutes de lecture
AICU API Team
AICU API Team
api.aicu.ai

At a wooden desk by a window, green-haired Nao Verde points at a laptop while pink-haired Elena Bloom leans in, smiling. On the desk: a gauge with its needle in the green, a stack of coins and a single brass key

Google AI Studio is moving Gemini API billing from postpaid to prepaid. For accounts that received the notice, the deadline is October 12, 2026. Two AiCuty characters, Nao Verde and Elena Bloom, walk through both options: keep using your own Google key, or put Gemini and Nano Banana behind one key on api.aicu.ai.

October 11, 2026 | Nao Verde × Elena Bloom

🌸 Elena Bloom Hi, I'm Elena Bloom from AiCuty! Do you use Google's Gemini, or the image model Nano Banana? Today's news matters if you build apps or artwork on those APIs. Google AI Studio has been telling some developers to "update your payment method by October 12, 2026." An app that worked yesterday might stop — that's a little worrying. So I asked Nao, who looks after the technical side of AiCuty, to explain.

💚 Nao Verde Hey, Nao Verde here — music and development for AiCuty. This one is not flashy, but it matters to developers. The Gemini API is moving from postpaid to prepaid. The scheme itself started in March this year; for the accounts that got this notice, the deadline is October 12. And as it happens, api.aicu.ai, AICU's API platform, serves Gemini and Nano Banana too. I'll cover both routes: staying on your Google key, and putting everything behind an AICU API key.

What changes on October 12?​

🌸 Elena What does "moving to prepaid" actually mean?

💚 Nao On a postpaid account you were billed afterwards for what you used. On prepaid you buy credits first, and each call draws on that balance — like a prepaid phone. The important part: when the prepaid balance hits zero, paid Gemini API calls stop working. Your key can be right and your code can be right, and requests still fail because of the billing state.

🌸 Elena So a program that ran yesterday can stop tomorrow.

💚 Nao Exactly. The notice Google sent on August 19, 2026 says so. (We received it in Japanese; this is our translation.)

If you have not completed the move to prepay and purchased credits before October 12, 2026, your service will be interrupted.

Source: notice from the Google AI Studio team to AICU, "Update your Gemini API payment method in Google AI Studio by October 12, 2026" (August 19, 2026)

Not everyone moves on October 12, though. That deadline is for the accounts that received this notice. Google also says that if you only use the free tier of the Gemini API, you do not need to do anything. Check whether you are affected in Google AI Studio.

https://aistudio.google.com/

Staying on your Google key​

🌸 Elena If I already have an app on Gemini, what do I do?

💚 Nao Three things. Open the billing page in Google AI Studio and switch the billing account to prepay. Buy credits. Then, if you want, set up auto-reload, which tops the balance up when it runs low.

🌸 Elena That sounds handy.

💚 Nao It is, with one catch. You can set a monthly limit on automatic purchases, and when you reach it, auto-reload stops (manual purchases do not count toward that limit). It protects you from a surprise bill, but if usage jumps it can also be the line where your service stops. For a small development project manual top-ups may be enough; for something that runs all the time, think about monitoring the balance. One more thing: the prepaid balance is held per Cloud Billing account, not per project. Projects that share a billing account share the balance, and an API key has no balance of its own.

Google's documentation: https://ai.google.dev/gemini-api/docs/billing

We made the switch ourselves​

🌸 Elena AICU went through this too, right?

💚 Nao Yes. On October 11, 2026 we switched the Google AI Studio billing behind api.aicu.ai's image generation to prepay. The console showed a notice that the account must use prepaid billing. We confirmed the switch and bought credits. The confirmation screens said that the switch takes effect immediately, that you cannot go back to postpay, that your usage tier does not change, and that purchased credits are for the Gemini API only and expire one year after purchase. Credits are generally non-refundable; Google's documentation does describe an exception when an eligible account moves to postpay.

🌸 Elena So buying a lot is not automatically the safe choice.

💚 Nao Right — buy for the usage you expect. After switching we tested in production. Through the AICU API we called nano-banana-2.1 and nano-banana and generated one image with each. Both returned HTTP 200: about 11.4 seconds for nano-banana-2.1, about 10.9 seconds for nano-banana, with the cache bypassed.

🌸 Elena The images really came back!

💚 Nao And the point is that the calling code did not change by a single line. Google's billing changed underneath; an app that calls the AICU API kept calling the same API.

Gemini and Nano Banana behind one AICU API key​

🌸 Elena If I can keep using Google AI Studio directly, why would I use the AICU API?

💚 Nao The simplest reason: one place for keys and payment. The AICU API serves Google's Gemini, OpenAI's GPT family and other models behind the same key. Image generation too — Nano Banana is on the same API. You pay from one shared balance in AP (AICU Points). Instead of a key and a balance for Google, another for OpenAI and another for each other service, you build with one AICU API key. Prices and features still differ by model; it does not make everything cost the same.

🌸 Elena So it suits people who combine several AIs in one piece of work.

💚 Nao Yes. Outline with Gemini, draw with Nano Banana, polish the text with another model — when you combine them, having authentication and billing in one place helps a lot in practice. The models are listed on the models page.

Calling Gemini from Python​

🌸 Elena How do I write it in code?

💚 Nao For chat it is simple. The AICU API has an OpenAI-compatible chat endpoint, so you can use the OpenAI Python SDK. Asking Gemini 3.6 Flash for the highest mountain in Japan looks like this. Put your API key in the AICU_API_KEY environment variable first.

from openai import OpenAI
import os

client = OpenAI(
    base_url="https://api.aicu.ai/v1",
    api_key=os.environ["AICU_API_KEY"]
)

res = client.chat.completions.create(
    model="gemini-3.6-flash",
    messages=[
        {
            "role": "user",
            "content": "日本でいちばん高い山を一語で答えてください。"
        }
    ],
)

print(res.choices[0].message.content)

💚 Nao Three things matter: the base_url, the API key and the model name. A program that already uses an OpenAI-compatible API keeps its shape. (The prompt asks, in Japanese, for the highest mountain in Japan in one word.) When we ran it in production on October 11, gemini-3.6-flash answered 富士山 and gemini-flash answered 富士, both within two seconds. The AP charged for a call comes back in the X-AICU-AP-Cost response header. Code written against Google's own SDK (generateContent) does not carry over as is, but it is a short rewrite into the OpenAI-compatible shape.

Making an image with Nano Banana 2.1​

🌸 Elena I want to try Nano Banana too!

💚 Nao Sure. nano-banana-2.1 is on the image generation endpoint. A blue ceramic cup on a desk:

curl -s -X POST https://api.aicu.ai/v1/images/generations \
  -H "Authorization: Bearer $AICU_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "nano-banana-2.1",
    "prompt": "a blue ceramic cup on a wooden desk, morning light, product photo"
  }' \
  | python3 -c "import sys,json,base64; open('out.jpg','wb').write(base64.b64decode(json.load(sys.stdin)['data'][0]['b64_json']))"

The image the command above returned: a steaming blue ceramic cup on a wooden desk in morning light

What the command above returned on October 11, 2026 (scaled down for display).

💚 Nao b64_json in the response is the image as Base64; decode it and you have the file. In our production test it came back in about ten seconds.

🌸 Elena That is all it takes!

💚 Nao It is. The time varies with load and with the image, though. And if the response includes a URL for the image, pasting it into a browser may not display it — the URL needs authentication. In a web app, use the Base64 data, or fetch the file on your own server and serve it from there. Do not put your API key in browser JavaScript.

What prepaid APIs change for people who make things​

🌸 Elena So when you build with APIs, managing the money is part of the work.

💚 Nao It is. If you publish an app or a service built on AI, keeping the API callable is part of development, alongside the quality of the model. With a prepaid API, a short balance reaches your users. Google's change is a good moment to sort out your keys and billing settings.

🌸 Elena If you stay on Google AI Studio, check the billing settings first.

💚 Nao Yes. The other option is the AICU API. It is prepaid too — you buy AP in advance — so balance management does not disappear. What does go away is managing the billing settings of Google and every other provider yourself. We keep the connections to each service; you use the models with one key and one AP balance. This time, too, we finished Google's move to prepay and then confirmed that Nano Banana generates an image. That does not mean we can prevent every upstream outage, but it does reduce what each developer has to look after.

Try the AICU API​

🌸 Elena Thank you for reading this far! Google AI Studio's change sounded complicated, but laid out like this the steps are clear. If you keep using your Google key, check whether you need to move to prepay. And if you want Gemini, Nano Banana and other generative models together, there is one more way. With the AICU API, Gemini, Nano Banana and the other models all run on one API key and one AP balance.

💚 Nao You do not use an API in order to manage API keys. You use it to make something interesting, build something useful, turn an idea into something that runs. The plumbing — connections and payment — should be as simple as it can be. The AICU API is through Gemini's move to prepay. It works from Python and from curl, so whether you already use APIs or are just starting, give it a try.

🌸 Elena Now I want to combine a few AIs and make something new, too. Please try the AICU API!

See you in the next post!

🌸 Elena Bloom & 💚 Nao Verde

References​

This post reflects information as of October 11, 2026. The deadline for moving in Google AI Studio can differ by account, according to the notice you received. The models, prices and terms of the AICU API may change; check the official pages for the latest. The samples in this post are run regularly, exactly as published, to confirm that they work.